HIGH STRENGTH STEELS, PROCESSES FOR MAKING SAME, AND MATERIALS RESULTING THEREFROM

Abstract

A method is disclosed for Flash Process heat treating lean alloyed steels in strips, sheets, bars, plates, wires, tubes, profiles, work pieces and the like which are converted into multi-phase, multi chemistry armor and advanced high strength steel produced with a minimum of cost, time and effort. The resulting material is a high performance armor with the ability to prevent penetration by a 0.30-caliber M2 armor piercing bullet shot at a 30 degree obliquity, from perpendicular to the plate. Stopping velocity of 2232 feet per second.

Claims

1. A method for treating a steel article to form a high tensile strength, high hardness, and ductile alloy comprising: (a) providing a steel article having a material thickness no greater than 1.0 inches (25.4 mm), having an initial microstructure of at least ferrite and/or pearlite and/or spheroidized carbides, being in any condition such as cold rolled to full hard, hard, hard, hard, or annealed, and having a chemistry of, by weight, carbon between 0.08 and 0.55%, manganese up to 35.0%, carbide forming elements such as chromium, molybdenum, silicon, titanium, vanadium, columbium, tantalum, cobalt, aluminum, and tungsten up to 25% total weight in combination, nickel less than 8.0%, phosphorus less than 1.0%, and balance iron and other elements and compounds in making steels; (b) optionally preheating the provided steel article to not more than 700 C. with no temporal limits required on the duration of preheating; (c) heating the provided steel article from its starting temperature below 700 C. to a peak temperature of at least 1000 C., but not more than 1400 C., at a rate of 30 C. to 3000 C. per second, with a total heating time of less than ten seconds employing induction, radiant, conduction, convection, resistance, or other heating methods; (d) holding the heated steel article at the selected peak temperature range for less than ten seconds acknowledging the temperature of the steel may remain constant or decrease due to the lack of further heat input during this time; (e) quenching the heated steel article from the peak temperature range to below 500 C. at a temperature rate reduction of between 100 C. and 3000 C./sec in less than 10 seconds employing quench media such as water, aqueous solutions, oils, molten salts/metals, forced air, or other quenching methods; (f) optionally interrupting the quenching of the steel article and holding the temperature of the quenched steel article at a temperature between 150 C. and 500 C. for less than thirty minutes; (g) further cooling of the steel article to below the steel's bainitic and martensitic finish temperatures to form a steel article having at least 5% bainite and at least 60% martensite by volume fraction, a yield strength of at least 1240 MPa (180 KSl), and a tensile strength of at least 1400 MPa (203 KSl). (h) optionally removing residual quench media from the surface of the quenched steel article; (i) optionally tempering the quenched steel article, by methods individually or in combination of induction, radiant, conduction, convection, resistance, or liquefied solution heating, or other heating methods at a temperature from 100 C. to 300 C. for less than thirty minutes; (j) optionally, the steel article can be controlled to have at least 10% to 25% bainite or more; and (k) resulting in a steel article that must have a velocity 50.sup.th percentile (V.sub.50) protection ballistic limit at 30 obliquity angle at least 2500 feet per second (fps) (762 m/s) with a 0.30 caliber armor piercing round for a thickness of 0.25 inches (6.35 mm) and which other thicknesses will have a passing V50 armor performance velocity as defined by US Army MIL DTL 32332 Class 1.

2. A method for treating a steel article to form a high tensile strength, high hardness, and ductile alloy to produce Ultra Hard Armor Class 1 comprising: (a) providing a steel article having a material thickness no greater than 1.0 inches (25.4 mm), having an initial microstructure of at least ferrite and/or pearlite and/or spheroidized carbides, being in any condition such as cold rolled to full hard, hard, hard, hard, or annealed, and having a chemistry of, by weight, carbon between 0.35 and 0.45%, manganese less than 1.0%, carbide forming elements such as chromium, molybdenum, silicon, titanium, vanadium, columbium, tantalum, cobalt, aluminum, and tungsten up to 2.5% total weight in combination, balance iron and other elements and compounds in making steels; (b) optionally preheating the provided steel article to not more than 700 C. with no temporal limits required on the duration of preheating; (c) heating the provided steel article from its starting temperature below 700 C. to a peak temperature of at least 1000 C., but not more than 1400 C., at a rate of 100 C. to 3000 C. per second, with a total heating time of less than ten seconds employing induction, radiant, conduction, convection, resistance, or other heating methods; (d) holding the heated steel article at the selected peak temperature range for less than ten seconds acknowledging the temperature of the steel may remain constant or decrease due to the lack of further heat input during this time; (e) quenching the heated steel article from the peak temperature range to below 100 C. at a temperature rate reduction of between 100 C. and 3000 C./sec in less than 10 seconds employing quench media such as water, aqueous solutions, oils, molten salts/metals, forced air, or other quenching methods; (f) further cooling of the steel article to below the steel's bainitic and martensitic finish temperatures to form a steel article having at least 5% bainite and at least 60% martensite by volume fraction, a yield strength of at least 1400 MPa (203 KSl), and a tensile strength of at least 1800 MPa (261 KSl); (g) optionally removing residual quench media from the surface of the quenched steel article; (h) optionally tempering the quenched steel article, by methods individually or in combination of induction, radiant, conduction, convection, resistance, or liquefied solution heating or other heating methods, at a temperature from 100 C. to 300 C. for less than thirty minutes; (i) optionally, the steel article can be controlled to have at least 10% to 25% bainite or more; and (j) resulting in a steel article that must have a velocity 50.sup.th percentile (V.sub.50) protection ballistic limit at 30 obliquity angle at least 2500 feet per second (fps) (762 m/s) with a 0.30 caliber armor piercing round for a thickness of 0.25 inches (6.35 mm) and which other thicknesses will have a passing V50 armor performance velocity as defined by US Army MIL DTL 32332 Class 1.

3. A method for treating a steel article to form a high tensile strength, high hardness, and ductile alloy to produce Ultra Hard Armor Class 2 comprising: (a) providing a steel article having a material thickness no greater than 1.0 inches (25.4 mm), having an initial microstructure of at least ferrite and/or pearlite and/or spheroidized carbides, being in any condition such as cold rolled to full hard, hard, hard, hard, or annealed, and having a chemistry of, by weight, carbon between 0.43 and 0.53%, manganese less than 1.0%, carbide forming elements such as chromium, molybdenum, silicon, titanium, vanadium, columbium, tantalum, cobalt, aluminum, and tungsten up to 1.5% total weight in combination, balance iron and other elements and compounds in making steels; (b) optionally preheating the provided steel article to not more than 700 C. with no temporal limits required on the duration of preheating; (c) heating the provided steel article from its starting temperature below 700 C. to a peak temperature of at least 1000 C., but not more than 1400 C., at a rate of 100 C. to 3000 C. per second, with a total heating time of less than ten seconds employing induction, radiant, conduction, convection, resistance, or other heating methods; (d) holding the heated steel article at the selected peak temperature range for less than ten seconds acknowledging the temperature of the steel may remain constant or decrease due to the lack of further heat input during this time; (e) quenching the heated steel article from the peak temperature range to below 100 C. at a temperature rate reduction of between 100 C. and 3000 C./sec in less than 10 seconds employing quench media such as water, aqueous solutions, oils, molten salts/metals, forced air, or other quenching methods; (f) further cooling of the steel article to below the steel's bainitic and martensitic finish temperatures to form a steel article having at least 5% bainite and at least 60% martensite by volume fraction, a yield strength of at least 1400 MPa (203 KSl), and a tensile strength of at least 1800 MPa (261 KSl); (g) optionally removing residual quench media from the surface of the quenched steel article; (h) optionally tempering the quenched steel article, by methods individually or in combination of induction, radiant, conduction, convection, resistance, or liquefied solution heating or other heating methods, at a temperature from 100 C. to 300 C. for less than thirty minutes; (i) optionally, the steel article can be controlled to have at least 10% to 25% bainite or more; and (j) resulting in a steel article that must have a velocity 50.sup.th percentile (V.sub.50) protection ballistic limit at 30 obliquity angle at least 2700 feet per second (fps) (762 m/s) with a 0.30 caliber armor piercing round for a thickness of 0.25 inches (6.35 mm) and which other thicknesses will have a passing V50 armor performance velocity as defined by US Army MIL DTL 32332 Class 2.

4. A method for treating a radially symmetric steel article to form a high tensile strength, high hardness, and ductile alloy, comprising: (a) providing a radially symmetric steel article in a bowl-like shape having a material thickness no greater than 0.5 inches (12.7 mm), having an initial microstructure of at least ferrite and/or pearlite and/or spheroidized carbides, being in any condition such as cold rolled to full hard, hard, hard, hard, or annealed, and having a composition of, by weight, carbon between 0.05 and 0.55%, manganese up to 35.0%, carbide forming elements such as chromium, molybdenum, silicon, titanium, vanadium, columbium, tantalum, cobalt, aluminum, and tungsten up to 25% total weight in combination, nickel less than 8.0%, phosphorus less than 1.0%, and balance iron and other elements and compounds in making steels; (b) placing, fixturing, and holding the radially symmetric steel article in a rotating heat/quench apparatus with integral induction heating coils and quench apparatus; (c) rotating the steel article at a rate of at least 6 revolutions per minute (d) optionally preheating the provided rotating radially symmetric steel article to not more than 700 C. with no temporal limits on the duration of preheating in the rotating heat/quench apparatus; (e) heating the provided rotating radially symmetric steel article from its starting temperature below 700 C. to a peak temperature of at least 1000 C., but not more than 1400 C., at a rate of 30 C. to 3000 C. per second, with a total heating time of less than ten seconds employing induction, radiant, conduction, convection, resistance, or other heating methods known to those skilled in the art; (f) holding the rotating heated radially symmetric steel article at the selected peak temperature range for less than ten seconds acknowledging the temperature of the steel may remain constant or decrease due to the lack of further heat input during this time; (g) quenching the rotating heated radially symmetric steel article, while it rotates or remains in a static position after ceasing rotation, from the peak temperature range to below the steel's bainitic and martensitic finish temperatures at a temperature rate reduction of between 100 C. and 3000 C./sec in less than 10 seconds employing quench media such as water, aqueous solutions, oils, molten salts/metals, forced air, or other quenching methods known to those skilled in the art to form a radially symmetric steel article having at least 5% bainite and at least 60% martensite by volume fraction, a yield strength of at least 600 MPa, and a tensile strength of at least 800 MPa. (h) removing residual quench media from the surface of the quenched radially symmetric steel article; (i) optionally rotating the steel article at a rate of at least 6 revolutions per minute (j) optionally tempering the quenched steel article, by methods individually or in combination of induction, radiant, conduction, convection, resistance, or liquefied solution heating, at a temperature from 100 C. to 300 C. for less than thirty minutes; (k) optionally, the steel article can be controlled to have at least 10% to 25% bainite or more (l) optionally performing secondary forming operations such as stamping, flanging, trimming, piercing, and other methods of forming steel known to those skilled in the art to create a finished Flash Process heat/quenched steel article.

5. A method for treating a stainless steel article to form a high tensile strength, high hardness, and ductile alloy to produce stainless High Hard Armor comprises: (a) providing a stainless steel article having a material thickness no greater than 1.0 inches (25.4 mm), having an initial microstructure of at least ferrite and/or pearlite and/or spheroidized carbides, being in any condition such as cold rolled to full hard, hard, hard, hard, or annealed, and having a chemistry of, by weight, carbon between 0.10 and 0.40%, manganese less than 1.0%, chromium between 12.0 and 14.0%, other carbide forming elements such as molybdenum, silicon, titanium, vanadium, columbium, tantalum, cobalt, aluminum, and tungsten up to 5% total weight in combination, balance iron and other elements and compounds in making steels; (b) optionally preheating the provided stainless steel article to not more than 700 C. with no temporal limits required on the duration of preheating; (c) heating the provided stainless steel article from its starting temperature below 700 C. to a peak temperature of at least 1000 C., but not more than 1400 C., at a rate of 100 C. to 3000 C. per second, with a total heating time of less than ten seconds employing induction, radiant, conduction, convection, resistance, or other heating methods known to those skilled in the art; (d) holding the heated stainless steel article at the selected peak temperature range for less than ten seconds acknowledging the temperature of the steel may remain constant or decrease due to the lack of further heat input during this time; (e) quenching the heated stainless steel article from the peak temperature range to below 100 C. at a temperature rate reduction of between 100 C. and 3000 C./sec in less than 10 seconds employing quench media such as water, aqueous solutions, oils, molten salts/metals, forced air, or other quenching methods known to those skilled in the art; (f) further cooling of the stainless steel article to below the steel's bainitic and martensitic finish temperatures to form a stainless steel article having at least 5% bainite and at least 60% martensite by volume fraction, a yield strength of at least 1400 MPa (203 KSl), and a tensile strength of at least 1800 MPa (261 KSl). (g) optionally removing residual quench media from the surface of the quenched stainless steel article; (i) optionally tempering the quenched stainless steel article, by methods individually or in combination of induction, radiant, conduction, convection, resistance, or liquefied solution heating or other heating methods known to those skilled in the art, at a temperature from 100 C. to 300 C. for less than thirty minutes; (j) optionally, the stainless steel article can be controlled to have at least 10% to 25% bainite or more (k) resulting in a stainless steel article that must have a velocity 50.sup.th percentile (V.sub.50) protection ballistic limit at 30 obliquity angle at least 2197 feet per second (fps) (762 m/s) with a 0.30 caliber armor piercing round for a thickness of 0.245 inches (6.25 mm) and which other thicknesses will have a passing V50 armor performance velocity as defined by US Army MIL DTL 46100E.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is butt joint weld seam made of Flash Ultra Hard Class 1 Armor plate. The consumable welding rod is a coat hanger as shown.

[0025] FIG. 2 is weldment made of Flash Ultra Hard Class 1 Armor plate and mild steel welding rod. The weldment has been shot by a 0.30-cal M2 armor piercing round traveling at 2622 feet per second as evidenced by the splatter remains of the bullet.

[0026] FIG. 3 is a plate of Flash Ultra Hard Class 1 Armor Plate. The required V50, at 0.260 thick, is 2554 feet per second. Flash UHA Class 1 having stopped (4) shots above the minimum V50 insures a passing V50 result.

[0027] FIG. 4 is a plate of Flash Ultra Hard Class 2 Armor Plate. The required V50, at 0.260 thick, is 2754 feet per second. Flash UHA Class 2 having stopped (3) shots at 2687, 2725, and 2771 feet per second, the next (3) shots above 2754fps and averaging only 2783 feet per second would result in a passing V50 of 2754 feet per second.

[0028] FIG. 5 is hardness map comparing relative levels of hardness of typical High Hard Armor produced to US Army MIL DTL 46100E, Flash High Hard Armor produced to US Army MIL DTL 46100E made from A1514130 steel and its weld seam, and Flash Ultra Hard Armor produced to US Army MIL DTL 32332 made from A1514140 steel and its weld seam

[0029] FIG. 6 details the steps, equipment and steel article necessary to produce a radially symmetric bowl-like heat treated steel article using the Flash Process thermal cycle.

[0030] FIG. 7 details the steps to stamping press transform a radially symmetric high strength heat treated steel bowl-like article to have non-radial symmetry in the shape of a helmet with a hole pierced into its shape for attachment to receive monitoring sensors and/or visor attachment hardware. This figure also could represent a steel automotive wheel that maintains radial symmetry and has holes pierced into it for various mechanical or design reasons.

[0031] FIG. 8 is a plate of Flash Stainless High Hard Armor Plate. The required V50, at 0.245 thick, is 2197 feet per second. Flash Stainless Armor having stopped (3) shots at 2302, 2307, and 2369 feet per second, the next (3) shots above 2300 feet per second will result in a passing V50 velocity about 125 feet per second above the required V50 as specified in US Army MIL DTL 46100E.

DETAILED DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1, as shown in 1a) is butt joint weld seam made of Flash Ultra Hard Class 1 Armor plate. The consumable welding rod, shown in 1b) is a coat hanger made of mild steel.

[0033] FIG. 2 is weldment, noted as 21, made of Flash Ultra Hard Class 1 Armor plate. The weldment was constructed with mild steel welding wire showing a weld seam, 22, at the points of plate contact. The weldment has been shot by a 0.30-cal M2 armor piercing round traveling at 2622 feet per second, noted as 23, as evidenced by the splatter remains of the bullet. This bullet was shot at a 30 degree obliquity to the perpendicular of the plate per US Army MIL DTL 32332.

[0034] FIG. 3 is a plate of Flash Ultra Hard Class 1 Armor Plate. This plate was tested, per US Army MIL DTL 32332, against 0.30-cal M2 armor piercing bullets. The plate was held at 30 degree obliquity to the entry trajectory of the bullet per MIL DTL 32332 at SFP Works, LLC internal testing facility. The required V50, at 0.260 thick, is 2554 feet per second. Flash UHA Class 1 having stopped (4) shots above the minimum V50, noted as 31, and averaging 2610 feet per second insures a passing V50 result when bullet velocities would be increased further to achieve (3) penetrations.

[0035] FIG. 4 is a plate of Flash Ultra Hard Class 2 Armor Plate. This plate was tested, per US Army MIL DTL 32332, against 0.30-cal M2 armor piercing bullets. The plate was held at 30 degree obliquity to the entry trajectory of the bullet per MIL DTL 32332 at SFP Works, LLC internal testing facility. The required V50, at 0.260 thick, is 2754 feet per second. Flash UHA Class 2 having stopped (3) shots at 2687, 2725, and 2771 feet per second, noted as 41, 42, and 43, the next (3) shots above 2754fps, and averaging only 2783 feet per second, would result in a passing V50 of 2754 feet per second. If faster velocities than 2771 feet per second in any subsequent bullet shots were to stop the bullet from penetrating, the V50 would increase further above the passing V50 required at 2754.

[0036] FIG. 5 is micro-hardness map comparing relative levels of Vickers hardness findings after six passes of gas metal arc welding of typical High Hard Armor produced to US Army MIL DTL 46100E, noted in 5a, Flash High Hard Armor produced to US Army MIL DTL 46100E and made from A1514130 steel, noted in 5b, and Flash Ultra Hard Armor produced to US Army MIL DTL 32332 and made from A1514140 steel, noted in 5c. Micro-hardness mapping is used to identify variances in local hardness of a steel article after applications of heat that occur in welding or other processes. It is understood by those skilled in the art that fresh embrittlement in a weld's heat affected zone will have a higher hardness than tempered regions.

[0037] It can be seen in 5a on the right side of the weld that fresh embrittlement exceeding 500 Vickers exists. This is actually harder than the base armor metal and is a sign that fresh, un-tempered embrittlement has occurred after weld seam cooling. Un-tempered embrittlement can lead to weld performance failures.

[0038] It can be seen in 5b on the right side of the weld that fresh embrittlement approaching 400 Vickers exists. With a maximum hardness in the weld seam of 400 Vickers, the weld seam is softer and more ductile than the base Flash Armor High Hard plate at 500 hardness. It was this discovery that led to the understanding that Flash Armor has non-brittle weld heat affected zones after weld seam cooling.

[0039] It can be seen in the Flash Ultra Hard 600 Armor plate shown in 5c that the weld fresh embrittlement is generally near 400 Vickers. With a maximum hardness in the weld seam near 400 Vickers, the weld seam is softer and more ductile that the base Flash Armor Ultra Hard plate at 600 hardness. It was this discovery that led to the understanding that Flash Ultra Hard Armor has non-brittle weld heat affected zones after weld seam cooling. It should be pointed out that the Flash 600 weld seam has a less brittle weld heat affected zone than the conventional High Hard armor weld seam shown in 5a. This is a significant improvement as Flash Ultra Hard 600 is 12% higher performing against armor piercing bullets than typical High Hard 500. The better weldability of Flash Ultra Hard 600 will allow armored vehicles to be built with less brittle weld seams and 12% higher performing Flash 600 Ultra Hard Armor.

[0040] Shown in 5d is the MIG welding of Flash High Hard armor made to US Army MIL DTL 46100E. This is a single pass MIG weld that demonstrates minimal fresh hardening above 400 Vickers indicating a non-brittle weld seam.

[0041] Shown in 5e is the MIG welding of Flash Ultra Hard armor made to US Army MIL DTL 32332. This is a single pass MIG weld that demonstrates minimal fresh hardening above 400 Vickers indicating a non-brittle weld seam. Approximately 75% of the weld seam is non-brittle. Further, the fresh embrittlement runs parallel to the surface of the plate and not through the thickness leaving the plate's performance more structurally sound.

[0042] FIG. 6 details the steps, equipment, and steel article necessary to produce a bowl-like heat treated steel article using the Flash Process thermal cycle. The first step is to provide a non-heat treated, radially symmetric steel article in a bowl-like shape shown as 61 in FIG. 6a. The second step, 6b, shows an induction heating fixture that attaches to the induction power supply at points 62 and 63. The fixture is designed to rotate the steel article 61 while heating and quenching. 6c shows steel article clamped into the fixture and rotating. 6d shows the rotating steel article having electrical current induced in the heating coil, 64, creating a magnetic field which will heat the radially symmetric steel article. 6e shows the rotating steel article having the heating turned off and the quenchant, 65, water in this example, being sprayed on the rotating steel article. 6f shows the Flash heat treated radially symmetric steel article 66. Note that the microstructure of the steel article has changed its microstructure based on the changed shading of the steel article picture. The steel article is now harder and stronger.

[0043] FIG. 7 details the steps to stamping press transform a radially symmetric high strength heat treated steel article to have non-radial symmetry in the shape of a helmet with a hole pierced in for attachment to receive monitoring sensors. 7a shows the previously made, in FIG. 6, radially symmetric Flash heat treated steel article noted as 71. 7b shows a stamping press tool with the shape of a helmet machined into the male punch side of the tool 72. 7c shows the steel article in its final geometric shape noted as 73. 7d shows a helmet, 74, about to be pierced by a punch, 75, along a path of motion 76 to create hole in the helmet. 7e shows the helmet 77 with a hole 78 pierced through the surface to allow that attachment of monitoring sensors or other apparatus such as a visor. FIG. 7 is demonstrated for the shape of a helmet that changes the radially symmetric steel article. Similarly, a steel automotive wheel could be produced in the same manner specified in FIG. 6 but then in which holes are pierced in the central region for lug nut attachment to the vehicle or decorative regions. Additional forming operations could be performed on the steel wheel to change the shape to be aesthetically pleasing or more functional for aspects such as directing airflow.

[0044] The present invention discloses a method for treating a steel article to form a high tensile strength, high hardness, and ductile alloy, including providing a steel article having a material thickness no greater than 1.0 inches (25.4 mm), having an initial microstructure of at least ferrite and/or pearlite and/or spheroidized carbides, being in any condition such as cold rolled to full hard, hard, hard, hard, or annealed, and having a chemistry of, by weight, carbon between 0.08 and 0.55%, manganese up to 35.0%, carbide forming elements such as chromium, molybdenum, silicon, titanium, vanadium, columbium, tantalum, cobalt, aluminum, and tungsten up to 25% total weight in combination, nickel less than 8.0%, phosphorus less than 1.0%, and the balance being comprised of iron and other elements and compounds in making steels. Prior to Flash process heat treating, and optional step of preheating the provided steel article to not more than 700 C. with no temporal limits required on the duration of preheating may be performed.

[0045] After the optional preheat step, the provided steel article is heated from its starting temperature below 700 C. to a peak temperature of at least 1000 C., but not more than 1400 C., at a rate of 30 C. to 3000 C. per second, with a total heating time of less than ten seconds employing induction, radiant, conduction, convection, resistance, or other heating methods, and then holding the heated steel article at the selected peak temperature range for less than ten seconds acknowledging the temperature of the steel may remain constant or decrease due to the lack of further heat input during this time.

[0046] This heating step is followed by quenching the heated steel article from the peak temperature range to below 500 C. at a temperature rate reduction of between 100 C. and 3000 C./sec in less than 10 seconds employing quench media such as water, aqueous solutions, oils, molten salts/metals, forced air, or other quenching methods.

[0047] An optional step of interrupting the quenching of the steel article and holding the temperature of the quenched steel article may be performed at a temperature between 150 C. and 500 C. for less than thirty minutes.

[0048] Then, further cooling of the steel article to below the steel's bainitic and martensitic finish temperatures forms a steel article having at least 5% bainite and at least 60% martensite by volume fraction, with a yield strength of at least 1240 MPa (180 KSl), and a tensile strength of at least 1400 MPa (203 KSl).

[0049] Residual quench media may be then removed from the surface of the quenched steel article. This method also contemplates an optional step of tempering the quenched steel article, by methods individually or in combination of induction, radiant, conduction, convection, resistance, or liquefied solution heating, or other heating methods at a temperature from 100 C. to 300 C. for less than thirty minutes. The steel article can be controlled to have at least 10% to 25% bainite or more.

[0050] Following these steps has experimentally resulted in a steel article having a velocity 50.sup.th percentile (V.sub.50) protection ballistic limit at 30 obliquity angle at least 2500 feet per second (fps) (762 m/s) with a 0.30 caliber armor piercing round for a thickness of 0.25 inches (6.35 mm) and which other thicknesses will have a passing V50 armor performance velocity as defined by US Army MIL DTL 32332 Class 1.

[0051] Another method in the present invention includes treating a steel article to form a high tensile strength, high hardness, and ductile alloy to produce Ultra Hard Armor Class 1 by following the steps of providing a steel article having a material thickness no greater than 1.0 inches (25.4 mm), having an initial microstructure of at least ferrite and/or pearlite and/or spheroidized carbides, being in any condition such as cold rolled to full hard, hard, hard, hard, or annealed, and having a chemistry of, by weight, carbon between 0.35 and 0.45%, manganese less than 1.0%, carbide forming elements such as chromium, molybdenum, silicon, titanium, vanadium, columbium, tantalum, cobalt, aluminum, and tungsten up to 2.5% total weight in combination, with the balance of the chemistry being iron and other elements and compounds in making steels.

[0052] An optional step of preheating the provided steel article to not more than 700 C. with no temporal limits required on the duration of preheating may be beneficially performed before Flash processing by heating the provided steel article from its starting temperature below 700 C. to a peak temperature of at least 1000 C., but not more than 1400 C., at a rate of 100 C. to 3000 C. per second, with a total heating time of less than ten seconds employing induction, radiant, conduction, convection, resistance, or other heating methods.

[0053] The heated steel article is held at the selected peak temperature range for less than ten seconds, acknowledging that the temperature of the steel may remain constant or decrease due to the lack of further heat input during this time.

[0054] Thereafter, the heated steel article is quenched from the peak temperature range to below 100 C. at a temperature rate reduction of between 100 C. and 3000 C./sec in less than 10 seconds employing quench media such as water, aqueous solutions, oils, molten salts/metals, forced air, or other quenching methods. Further cooling of the steel article to below the steel's bainitic and martensitic finish temperatures will form a steel article having at least 5% bainite and at least 60% martensite by volume fraction, a yield strength of at least 1400 MPa (203 KSl), and a tensile strength of at least 1800 MPa (261 KSl).

[0055] Residual quench media may then be removed from the surface of the quenched steel article. This may be followed by an optional step of tempering the quenched steel article, by methods individually or in combination of induction, radiant, conduction, convection, resistance, or liquefied solution heating or other heating methods, at a temperature from 100 C. to 300 C. for less than thirty minutes. The steel article can be controlled to have at least 10% to 25% bainite or more.

[0056] This modified Flash process heat treatment results in a steel article having a velocity 50.sup.th percentile (V.sub.50) protection ballistic limit at 30 obliquity angle at least 2500 feet per second (fps) (762 m/s) with a 0.30 caliber armor piercing round for a thickness of 0.25 inches (6.35 mm) and which other thicknesses will have a passing V50 armor performance velocity as defined by US Army MIL DTL 32332 Class 1.

[0057] In yet another aspect of the present invention, disclosed is a method for treating a steel article to form a high tensile strength, high hardness, and ductile alloy to produce Ultra Hard Armor Class 2, including certain steps with optional additional treatments. Such a method begins with providing a steel article having a material thickness no greater than 1.0 inches (25.4 mm), having an initial microstructure of at least ferrite and/or pearlite and/or spheroidized carbides, being in any condition such as cold rolled to full hard, hard, hard, hard, or annealed, and having a chemistry of, by weight, carbon between 0.43 and 0.53%, manganese less than 1.0%, carbide forming elements such as chromium, molybdenum, silicon, titanium, vanadium, columbium, tantalum, cobalt, aluminum, and tungsten up to 1.5% total weight in combination, with the balance being iron and other elements and compounds in making steels.

[0058] Prior to Flash process heat treating as described hereinabove, an optional step of preheating the provided steel article to not more than 700 C. with no temporal limits required on the duration of preheating has proved to be beneficial.

[0059] Flash processing of the abovementioned steel article is heated from its starting temperature below 700 C. to a peak temperature of at least 1000 C., but not more than 1400 C., at a rate of 100 C. to 3000 C. per second, with a total heating time of less than ten seconds employing induction, radiant, conduction, convection, resistance, or other heating methods, and holding the heated steel article at the selected peak temperature range for less than ten seconds, while acknowledging the temperature of the steel may remain constant or decrease due to the lack of further heat input during this time.

[0060] Thereafter, the heated steel article is quenched from the peak temperature range to below 100 C. at a temperature rate reduction of between 100 C. and 3000 C./sec in less than 10 seconds by employing quench media such as water, aqueous solutions, oils, molten salts/metals, forced air, or other quenching methods. Further cooling of the steel article is performed to below the steel's bainitic and martensitic finish temperatures to form a steel article having at least 5% bainite and at least 60% martensite by volume fraction, a yield strength of at least 1400 MPa (203 KSl), and a tensile strength of at least 1800 MPa (261 KSl).

[0061] In most instances, it may also be preferable to remove residual quench media from the surface of the quenched steel article.

[0062] Post Flash processing, an optional step of tempering the quenched steel article, by methods individually or in combination of induction, radiant, conduction, convection, resistance, or liquefied solution heating or other heating methods, at a temperature from 100 C. to 300 C. for less than thirty minutes may be beneficial.

[0063] The steel article can be controlled to have at least 10% to 25% bainite or more to provide great strength and anti-ballistic properties.

[0064] This process results in a steel article that has a velocity 50.sup.th percentile (V.sub.50) protection ballistic limit at 30 obliquity angle at least 2700 feet per second (fps) (762 m/s) with a 0.30 caliber armor piercing round for a thickness of 0.25 inches (6.35 mm) and which other thicknesses will have a passing V50 armor performance velocity as defined by US Army MIL DTL 32332 Class 2.

[0065] Yet another aspect of this invention results in high strength steel component for items such as steel wheels, containers, and helmets to name a few, all being primarily circular or bowl-shaped. This embodiment transforms a preformed bowl-like component using the Flash Process thermal cycle of heating and quenching as previously described. Precursor steel of the required chemistry to attain the desired strength is first formed into a circular bowl-like article with typical current industry practices such as stamping, hydroforming, drawing, spin forming, or other means used to create articles with radial symmetry. For example, spin forming could be used to create an automotive steel wheel but at a significantly reduced thickness. The thinner steel wheel is then Flash Processed heat and quenched to near net shape. While a current wheel could be 2.7 mm thick, a Flash heat treated steel wheel could have more strength at 1.8 mm thick. Such a process will allow strengths in excess of 900 MPa up to over 2000 MPa in shapes that would have otherwise been very difficult, if not impossible, to form. Being bendable and non-brittle is very important for steel wheels that may encounter road hazards. While aluminum automotive wheels have increased in popularity for being lightweight, Flash steel wheels could be significantly lighter than aluminum ones. Additionally aluminum wheels often crack when encountering road hazards and are discarded. Flash steel wheels could be bent back to original shape and continue to be used safely. If one tried to make wheels from a martensite microstructure steel, the steel wheel would likely crack while in use just like aluminum ones.

[0066] Upon the transformation to the Flash Bainite microstructure, the steel wheel, or other similar bowl-like workpiece would possess unique properties and forming ability into other shapes. For example, flanges or other locally formed regions of the steel article could be further shaped, relying on Flash Bainite's high bendability and formability, to create geometries desired.

[0067] Military armor helmets in the mid-1900's were primarily made from steel. As decades passed, steel was replaced by other materials because stronger, non-brittle, low elongation martensitic steel simply could not be formed into the bowl-like shape required by the helmet's form. In order to make a Flash Bainite steel helmet, soft untreated steel could be formed into a bowl near the size of the desired helmet, similar to how an untreated steel wheel could be made. The bowl shaped, pre-helmet blank could be heated and quenched following the Flash Process heating/cooling cycle on a rotational induction heating fixture. This Flash Processed bowl could then be shaped into the proper contours of a helmet to fit the head of the wearer. Since a finished helmet is bowl-like but not radially symmetric, a stamping press forming operation can be performed to change the shape of the steel article to the final shape of the helmet more appropriate to fit the head of the wearer. In the mid-1900's, the relatively weaker grades of steel used to create a helmet led to low performance that was surpassed by other composite materials in recent decades. The advent of a Flash helmet would allow the benefits of Flash Bainite's extreme formability and very high armor performance. A Flash helmet with high energy absorbing capacity could outperform the current military helmets made of brittle ceramics and composites at a fraction of the cost.

[0068] A shape such as a helmet could not be formed from very strong steel at strengths over 800 MPa because the steel would not have enough elongation to form the bowl-like shape required. By using conventional steel with greater elongation, the helmet, steel wheel, or other shapes can be formed nearly to net shape, Flash heat treated, and then finish formed to the shape desired with far less forming effort to get to final design dimensions.

[0069] The equipment to create a Flash Processed steel wheel or helmet would be a rotational based fixture for induction heating. The fixture could hold the steel article from the inside or outside of the general shape. As an example, a 33% reduced thickness wheel, at 1.8 mm thick instead of 2.7 mm thick, would be placed on a rotational fixture that spins the part within the induction coil's magnetic field. Rotational speed should be sufficient to allow an even heating of the steel workpiece, wheel, or helmet. As before, the required heating to peak temperature of 1000 C or higher in less than 10 seconds. Given that the rotating steel article should at least make one revolution around the heating coil equates to at least a rotational speed of 6 revolutions per minute (rpm). In the instance of a 2 second heating time, a rotational speed of 30rpm is required just to make a single revolution during the heating time. In practice of this invention, rotational speeds are not limited but speeds of 240 to 480 revolutions per minute would be practical to allow 8 to 16 revolutions of the steel article in the brevity of a 2 second heat treating rise to above 1000 C. Further, limited benefit is likely achieved by rotational speeds of 1000 rpms or more and could actually create added levels of complexity in the rotational equipment to hold the steel article at such elevated revolutions per minute. An induction coil would be custom designed to heat the steel article as it rotates, either from the inside, outside, or both. The rotating part would be rapidly heated according to the aforementioned heating rates used in Flash Processing. The rotating part would then be quenched substantially immediately after achieving peak temp by employing quench media such as water, aqueous solutions, oils, molten salts/metals, forced air, or other quenching methods. The resulting Flash steel wheel would be of significantly higher strength than current steel wheels due to being made of Flash Processed steel and could be significantly lighter based on the performance desired. As shown in Table 1, various strengths are attainable by varying the carbon content of the precursor steel used to create the bowl-like steel article.

TABLE-US-00001 TABLE 1 Approximate strength of Flash Processed Steel based on carbon content Flash Yield Tensile Processed Carbon Strength Strength Hardness Alloy Weight % (MPa) (MPa) Brinell AlSI1010 0.08-0.13 900 1100 340 AlISI1020 0.18-0.23 1200 1500 440 AlSI4130 0.28-0.33 1400 1800 500 AlSI4140 0.38-0.43 1500 2000 600 AlSI4150 0.48-0.53 1700 2100 650

[0070] A preferred method for treating a radially symmetric steel article, such as a military type helmet for the protection of the head of a soldier, to form a high tensile strength, high hardness, and ductile alloy includes providing a radially symmetric steel article in a bowl-like shape having a material thickness no greater than 1.0 inches (25.4 mm), optionally with holes in the bowl shape, having an initial microstructure of at least ferrite and/or pearlite and/or spheroidized carbides, being in any condition such as cold rolled to full hard, hard, hard, hard, or annealed. This steel article has a chemistry of, by weight, carbon between 0.05 and 0.55%, manganese up to 35.0%, carbide forming elements such as chromium, molybdenum, silicon, titanium, vanadium, columbium, tantalum, cobalt, aluminum, and tungsten up to 25% total weight in combination, nickel less than 8.0%, phosphorus less than 1.0%, and the balance being iron and other elements and compounds in making steels.

[0071] This steel article is treated by placing, fixturing, and holding the radially symmetric steel article in a rotating heat/quench apparatus with integral induction heating coils and quench apparatus, and rotating the steel article at a rate of at least 6 revolutions per minute. Optionally, preheating may be performed on the provided rotating radially symmetric steel article to not more than 700 C. with no temporal limits required on the duration of preheating in the rotating heat/quench apparatus, and then followed by heating the provided rotating radially symmetric steel article from its starting temperature below 700 C. to a selected peak temperature of at least 1000 C., but not more than 1400 C., at a rate of 30 C. to 3000 C. per second, with a total heating time of less than ten seconds employing induction, radiant, conduction, convection, resistance, or other heating methods.

[0072] The heated steel article is held at the selected peak temperature range for less than ten seconds, while acknowledging the temperature of the steel may remain constant or decrease due to the lack of further heat input during this time.

[0073] Thereafter, the rotating heated radially symmetric steel article is quenched, while it rotates or remains in a static position after ceasing rotation, from the peak temperature range to below the steel's bainitic and martensitic finish temperatures at a temperature rate reduction of between 100 C. and 3000 C./sec, preferably in less than 10 seconds while employing quench media such as water, aqueous solutions, oils, molten salts/metals, forced air, or other quenching methods to form a radially symmetric steel article having at least 5% bainite and at least 60% martensite by volume fraction, a yield strength of at least 600 MPa, and a tensile strength of at least 800 MPa.

[0074] Following the quench step, an addition optional step may include removing residual quench media from the surface of the quenched radially symmetric steel article by forced air, rotational forces, or other methods and optionally rotating the steel article at a rate of at least 1 revolution per minute.

[0075] Furthermore, yet another additional optional step may be utilized including tempering the quenched steel article, by methods individually or in combination of induction, radiant, conduction, convection, resistance, or liquefied solution heating, or other heating methods at a temperature from 100 C. to 300 C. for less than thirty minutes.

[0076] The steel article can be controlled to have at least 10% to 25% bainite or more in order to provide the strength desired for ultra hard applications, such as anti-ballistic military helmet protection gear.

[0077] In order to achieve desirable shapes of steel articles, performing secondary forming operations such as stamping, flanging, trimming, piercing, and other methods of forming steel will create a finished Flash Process heat/quenched steel article.

[0078] In other words, the steel article may be heat treated first in accordance with the preferred methods of the present invention, and then stamped and treated as a near net shape workpiece to produce a final desired shape that has already been Flash process heat treated.

[0079] It is another aspect of the present invention to use low cost, commercially available input stainless steels such as 13-Chrome also known as a hardenable 400 series stainless steel (0.10 to 0.40% wt carbon, maximum 1.0% wt manganese, 12.00 to 14.0% wt chromium, and other elements but typically about 85% wt iron balance) to create a stainless steel High Hard armor to US Army MIL DTL 46100E certification. The non-iron balance elements can be substituted with other alloys, lowered in concentration, or removed.

[0080] FIG. 8 is a plate of Flash Stainless Steel Armor Plate noted as 81. This plate was tested, per US Army MIL DTL 46100E, against 0.30-cal M2 armor piercing bullets. The plate was held at 30 degree obliquity to the entry trajectory of the bullet per MIL DTL 46100E at SFP Works, LLC internal testing facility. The required V50, at 0.245 thick, noted as 82, is 2197 feet per second. Flash Stainless Armor having stopped (3) shots at 2302, 2307, and 2369 feet per second, noted as 83, 84, and 85, are well above the required 2197 feet per second required. The next (3) shots of higher velocity would result in a passing V50 more than 125 feet per second above the required 2197 feet per second velocity.

[0081] Regarding yet a final aspect of the present invention, disclosed is a method for treating a stainless steel article to form a high tensile strength, high hardness, and ductile alloy to produce stainless High Hard Armor by providing a stainless steel article having a material thickness no greater than 1.0 inches (25.4 mm), having an initial microstructure of at least ferrite and/or pearlite and/or spheroidized carbides, being in any condition such as cold rolled to full hard, hard, hard, hard, or annealed, and having a chemistry of, by weight, carbon between 0.10 and 0.40%, manganese less than 1.0%, chromium between 12.0 and 14.0%, other carbide forming elements such as molybdenum, silicon, titanium, vanadium, columbium, tantalum, cobalt, aluminum, and tungsten up to 5% total weight in combination, with the balance being of iron and other elements and compounds in making steels. The method may optionally include a step of preheating the provided stainless steel article to not more than 700 C. with no temporal limits required on the duration of preheating.

[0082] To effect the preferred heat treatment of the stainless steel article, the stainless steel article is heated from its starting temperature below 700 C. to a peak temperature of at least 1000 C., but not more than 1400 C., at a rate of 100 C. to 3000 C. per second, with a total heating time of less than ten seconds employing induction, radiant, conduction, convection, resistance, or other heating methods. The heated stainless steel article is held at the selected peak temperature range for less than ten seconds acknowledging the temperature of the steel may remain constant or decrease due to the lack of further heat input during this time.

[0083] The heated stainless steel article is then quenched from the peak temperature range to below 100 C. at a temperature rate reduction of between 100 C. and 3000 C./sec in less than 10 seconds employing quench media such as water, aqueous solutions, oils, molten salts/metals, forced air, or other quenching methods, followed by further cooling of the stainless steel article to below the steel's bainitic and martensitic finish temperatures to form a steel article having at least 5% bainite and at least 60% martensite by volume fraction, a yield strength of at least 1400 MPa (203 KSl), and a tensile strength of at least 1800 MPa (261 KSl).

[0084] An optional step of removing residual quench media from the surface of the quenched steel article may be desirable, as well as an optional step of tempering the quenched steel article, by methods individually or in combination of induction, radiant, conduction, convection, resistance, or liquefied solution heating or other heating methods, at a temperature from 100 C. to 300 C. for less than thirty minutes.

[0085] The stainless steel article can be controlled to have at least 10% to 25% bainite or more.

[0086] This method results in a stainless steel article having a velocity 50.sup.th percentile (V.sub.50) protection ballistic limit at 30 obliquity angle at least 2197 feet per second (fps) (762 m/s) with a 0.30 caliber armor piercing round for a thickness of 0.245 inches (6.25 mm) and which other thicknesses will have a passing V50 armor performance velocity as defined by US Army MIL DTL 46100E.

[0087] The foregoing description of a preferred aspect of the inventions have been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings with regards to the specific aspects. The aspect was chosen and described in order to best illustrate the principles of the invention and its practical applications to thereby enable one of ordinary skill in the art to best utilize the invention in various aspects and with various modifications as are suited to the particular use contemplated.

INDUSTRIAL APPLICABILITY

[0088] The present invention finds applicability in the metal treatment industry and finds particular utility in steel treatment applications for the processing and manufacture of high strength steels, armor plate, and bowl-like shapes in high volume processing with minimal equipment CAPEX.