SPREADERS FOR DIE CASTING AND METHODS OF MAKING THE SAME

Abstract

A spreader configured to be implemented in a die of a die casting system is disclosed. The spreader includes: a substrate; a hardening layer and an oxide layer. The hardening layer includes: a nitride and carbide layer disposed on the substrate and increasing hardness; and a white layer disposed on the nitride and carbide layer. The oxide layer includes: an inner transition layer disposed on the white layer and increasing resistance to oxidation; and an outer iron oxide layer disposed on the inner transition layer and increasing resistance to soldering during die casting of a part in the die casting system.

Claims

1. A spreader configured to be implemented in a die for a die casting system, the spreader comprising: a substrate; a hardening layer comprising a nitride and carbide layer disposed on the substrate and increasing hardness, and a white layer disposed on the nitride and carbide layer, wherein the white layer has been transformed into pearlite comprising alternating layers of ferrite and cementite; and an oxide layer comprising an inner transition layer disposed on the white layer and increasing resistance to oxidation and enriched with at least one of nickel and copper, and an outer iron oxide layer disposed on the inner transition layer and increasing resistance to soldering during die casting of a part in the die casting system, wherein the outer iron oxide layer comprises at least one external guide surface i) upstream from the die in which a part is formed, and ii) guides molten metal from a sprue bush into a gate system area of the die.

2. The spreader of claim 1, wherein the substrate comprises at least one of martensite, bainite, and ferrite.

3. The spreader of claim 1, wherein the substrate comprises nanoprecipitation having size less than 50 nm.

4. The spreader of claim 1, wherein thermal conductivity of the substrate is greater than 38 W/mK.

5. The spreader of claim 1, wherein the hardening layer has a hardness of greater than or equal to 65 HRC.

6. The spreader of claim 1, wherein the spreader comprises a body comprising: a first disc; a second disc; and a channel cut into the first disc and the second disc, wherein the channel comprises a guide surface for guiding molten metal during a die casting process of the part.

7. The spreader of claim 1, wherein a thickness of the outer iron oxide layer is 0.5-10.0 m.

8. The spreader of claim 1, wherein a thickness of the inner transition layer is 0.1-5.0 m.

9. The spreader of claim 1, wherein the outer iron oxide layer mainly comprises by weight 70-74% iron, 25-30% oxygen, and 1-5% aluminum.

10. (canceled)

11. The spreader of claim 1, wherein metal in the inner transition layer comprises by weight 4-20% nickel and 1-5% copper.

12. The spreader of claim 1, wherein: a thickness of the white layer is 0.5-2.0 m; and a thickness of the nitride and carbide layer is 80-300 m.

13. The spreader of claim 1, wherein a chemical composition of the substrate comprises by mass 0-0.2% carbon, 0.2-6% copper, 3-10% nickel, 0.5-3% aluminum, 0.2-1.5% manganese, 0-1.5% chromium, 0-2.5% molybdenum, 0-1.5% tungsten, and 0-0.2% vanadium.

14. The spreader of claim 1, wherein the inner transition layer comprises a sawtooth structure.

15. A die casting system comprising: the spreader of claim 1; and the die comprising a first half and a second half, wherein the spreader is attached to the first half and guides molten metal from a sprue bush into a gate system area and a cavity of the die during a die casting process.

16. A method of forming a spreader for a die casting system, the method comprising: providing a forged block of tool steel; machining the block of tool steel to form a preliminary spreader; austenitizing the preliminary spreader; subsequent to austenitizing preliminary spreader, cooling the preliminary spreader to room temperature; subsequent to cooling the preliminary spreader, machining the preliminary spreader to form a final spreader; and subsequent to machining the preliminary spreader, form a hardening layer and an oxide layer by i) nitrocarburizing the spreader and oxidizing the nitrocarburized spreader or ii) oxy-nitrocarburizing the spreader, wherein the hardening layer comprises a nitride and carbide layer disposed on a substrate, and a white layer disposed on the nitride and carbide layer, and wherein the oxide layer comprises an inner transition layer disposed on the white layer, an outer iron oxide layer disposed on the inner transition layer, and at least one external guide surface i) upstream from a die in which a part is formed, and ii) guides molten metal from a sprue bush into a gate system area of the die.

17. The method of claim 16, further comprising, subsequent to machining, nitrocarburizing the preliminary spreader and oxidizing the nitrocarburized spreader to form the hardening layer and the oxide layer.

18. The method of claim 16, further comprising, subsequent to machining, oxy-nitrocarburizing the preliminary spreader to form the hardening layer and the oxide layer.

19. The method of claim 16, further comprising, subsequent to forming the oxide layer, machining the final spreader.

20. The method of claim 16, wherein a chemical composition of the block of tool steel comprises by mass 0-0.2% carbon, 0.2-6% copper, 3-10% nickel, 0.5-3% aluminum, 0.2-1.5% manganese, 0-1.5% chromium, 0-2.5% molybdenum, 0-1.5% tungsten, and 0-0.2% vanadium.

21. The spreader of claim 1, wherein the spreader comprises: a first disc; a second disc disposed on the first disc, having a smaller outer diameter than the first disc, and having a notched side to provide the at least one external guide surface; the at least one external guide surface comprises a plurality of adjacent planar guide surfaces that are recessed in the second disc; and a plurality of side surfaces extending inward from an outer surface of the second disc to the plurality of adjacent planar guide surfaces.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0028] FIG. 1 is a side perspective view of a die casting system including a spreader to guide molten metal into a cavity of a die in accordance with the present disclosure;

[0029] FIG. 2 is a perspective view of an example spreader in accordance with the present disclosure;

[0030] FIG. 3 is a perspective view of a gate system;

[0031] FIG. 4 is a perspective view of another example spreader in accordance with the present disclosure;

[0032] FIG. 5 is a plot of resistance versus cooling rate for different spreader materials;

[0033] FIG. 6 is a side cross-section view of an example portion of a spreader in accordance with the present disclosure;

[0034] FIG. 7 is a scanning electron microscope (SEM) image of a cross-section of a portion of a spreader in accordance with the present disclosure.

[0035] FIG. 8 is a plot of hardness versus immersion time for two spreaders formed of different materials;

[0036] FIG. 9 is a plot of temperature versus time for an example method of forming a spreader including performing an age hardening operation in accordance with the present disclosure;

[0037] FIG. 10 is a plot of temperature versus time for another example method of forming a spreader including combining age hardening, nitrocarburizing and oxidizing operations in accordance with the present disclosure; and

[0038] FIG. 11 illustrate an example method of forming a spreader in accordance with the present disclosure; and

[0039] FIG. 12 is a functional block diagram of a spreader manufacturing system in accordance with the present disclosure.

[0040] In the drawings, reference numbers may be reused to identify similar and/or identical elements.

DETAILED DESCRIPTION

[0041] During each time die casting a part, a surface layer of a spreader of a die is contacted with high temperature molten metal. The same die and spreader are used to die cast multiple parts. This causes a surface layer of the spreader to softened because of increasing temperature, which reduces erosion resistance. Each time after opening the mold, it is needed to blow and spray compressed air and lubricating coating on the surface of the spreader to rapidly cool the spreader. As such, the surface layer of the spreader is subjected to periodic thermal stress and corrosion action, formation and expansion of surface microcracks are caused, and finally, a thermal fatigue phenomena of cracking and stripping occurs. At high temperatures, iron is easy to be corroded by molten metal. The chemical and mechanical reaction between molten metal and substrate of the spreader can induce surface corrosion and soldering on the spreader. For the above reasons, the sprue spreader will be scrapped due to hot melting loss.

[0042] Die casting is performed at high temperatures, for example, the molten metal that is pushed into a die to form a part can be at temperatures greater than 500 C. As an example, the molten metal may be molten aluminum (Al). A spreader of the die is exposed to the molten metal and can thermally fatigue failure, erode and/or washout over time. The spreader is exposed to consistently high temperatures, periodic thermal stress and is flushed by molten metal at excessive velocities. The spreader can also experience soldering/or corrosion, where tiny portions (or bits) of the molten can harden onto the spreader and thus alter the shape and degrade the performance of the spreader. The spreader can be referred to as a sprue spreader and a distributor. The spreader may be in the form of a single unitary structure and/or include multiple distributor rings. During operation, molten metal is pushed towards the spreader from a sprue bush, fills a biscuit area, and is guided to and through a gate system area and into a die cavity. The molten metal in the biscuit area, the gate system area, and the die cavity are cooled during a cooling stage to form a biscuit, a gate system and a part.

[0043] The resultant biscuit, which is formed due to solidification of molten metal in the biscuit area, can have a thickness of 20-35 millimeters. The biscuit is designed to ensure the flow of molten (or liquid) metal (e.g., aluminum alloy) and to ensure integrity and mechanical properties of parts. Due to the size and thickness of the biscuit, the biscuit last to solidify during the cooling stage. The solidification rate of the biscuit thus determines the corresponding ejection time and production time of the part being formed. The cooling of the biscuit tends to be the bottleneck in the production process.

[0044] The examples set forth herein include spreaders and methods of forming the same. The spreaders have improved thermal fatigue resistance, wear resistance, and corrosion resistance. The spreaders have high thermal conductivity properties and thus fast cooling rates. The spreaders have a fast heat removal rate and thus a shorter total cycle time for improved production efficiency and reduced corresponding costs. The spreaders also have high hardness levels and are resistant to erosion/or washout. The spreaders are less susceptible to corrosion and soldering during molten metal filling operations. The spreaders are thermal fatigue, corrosion, erosion and washout resistant and thus have a higher service life expectancy.

[0045] In some embodiments, spreaders are provided for high pressure aluminum die casting that exhibit improved cooling and solidification rates as well as tool service life. The spreaders are made of a tool steel having a unique composition, as disclosed herein, that provides particular attributes including a fast-cooling rate and high resistance to corrosion, erosion, washout, and soldering. The spreaders also exhibit high thermal conductivity, which is attributed to their nano-copper (Cu) particles and coherent interfaces between precipitates and substrate matrices. This facilitates a reduction in surface temperatures of the spreaders and an increase in heat removal rates of the spreaders and biscuits being formed. The increase in heat removal rates of the biscuits increases the corresponding solidification rates and thus shortens the solidification times of the biscuits. Each of the spreaders includes i) an anti-sticking iron oxide layer that enhances corrosion and soldering resistance from molten Al, and ii) a hardening layer formed of carbides and nitrides and is disposed between the anti-sticking iron oxide layer and a substrate and improves surface hardness of the spreader. The spreaders increase production efficiency, reduce cost of applications and maintenance, and have a longer service lifetime than traditional spreaders.

[0046] FIG. 1 shows a die casting system 100 that includes a die 102 having a first half 104 and a second half 106. The die 102 sits in and is held by a mold base set 108. Portions of the mold base set 108 are held by a movable platen 110 and a fixed platen 112. The movable platen 110 is moved by a first motor assembly 114 via a control module 116. The first motor assembly 114 includes a motor 115 that moves a shaft 117 connected to the movable platen 110. The movable plate 110 moves on rails 111. A parting line 118 between the die halves 104, 106 and portions of the mold base set 108 is shown. A sprue bush 120 extends through the fixed platen 112 and towards a spreader 122, which is attached and/or held by the die half 104. Molten metal 124 is supplied to the sprue bush 120 via a ladle 126 or other device.

[0047] A plunger (or piston) 128 pushes the molten metal 124 towards the spreader 122, which guides the molten metal into runner channels 130 in a gate system area 132, which has a gate 134. The molten metal fills a die cavity 135. Depending on an amount of molten metal supplied, the molten metal may at least partially fill an overflow area 136. A plunger 128 is moved by a shaft 137, which is driven by a second motor assembly 138 via the control module 116. The second motor assembly 138 includes a motor 139 that moves the shaft 137.

[0048] The die casting system 100 further includes an ejector back plate 140, an ejector plate 142, and ejector pins 144. The plates 140, 142 and ejector pins 144 are moved via a third motor assembly 146 via the control module 116. The third motor assembly 146 includes a motor 147 that moves a shaft 149 that is connected to the back plate 140.

[0049] The die casting system 100 may perform various operations during a die casting process, which may include the use of one of the spreaders disclosed herein. The operations may include opening the die 102 (separating the die halves 104, 106), lubricating the die halves 104, 106, closing the die 102 (bringing the die halves 104, 106 together), supplying molten metal at high pressure (e.g., 20-120 mega-pascals (Mpa)) and filling the die cavity 135 with the molten metal, cooling the molten metal in the die cavity 135 to form a part, and releasing the part from the die cavity 135. The supplying of the molten metal may be done manually or automatically by a robot or machine. The molten metal may include Al and/or one or more other nonferrous metals, such as magnesium (Mg), zinc (Zn), and Cu. The molten metal may include one or more alloys of Al, Mg, Zn, and Cu. The die halves 104, 106 may have cooling channels extending though the die halves 104, 106 for cooling the part. Cooling fluid is circulated through the channels.

[0050] Subsequent to solidification, the die 102 is opened and the die halves 104, 106 are separated and the solidified shot including the casted part, the gate system and the biscuit are ejected from the die 102 at the same time by the ejector pins 144. The gate system and biscuit are formed in the gate system area 132 and a biscuit area, which is between the spreader 122 and the plunger 128 when the plunger 128 is fully deployed (or pused) into the sprue bush 120. The shot is then removed from the die cavity area by hand or robot. The gate system and the biscuit are removed from the part. This may also include removal of one or more other unwanted portions, such as an overflow portion formed in the overflow area 136.

[0051] Examples of the spreader 122 and methods of forming the same are described below with respect to FIGS. 2 and 4-11. Two example spreaders are shown in FIGS. 2 and 4. These spreaders and other spreaders may be formed using the methods disclosed herein.

[0052] FIG. 2 shows a spreader 600 that includes a body 602. The body 602 may be a solid body or a hollow body. The body 602 may include an outer (or base) ring or disc 604, an inner ring or disc 606, a planar surface 608, and a guide surface 610. When the body 602 is solid, the guide surface 610 may be notched into the discs 604, 606, as shown. The guide surface 610 extends along a notched side 612 of the inner disc 606 and into an end portion 614 of the outer disc 604. The guide surface 610 guides molten metal into runner channels (or areas) of a gate system area. The guided surface 610 is a complex surface that may direct molten metal in multiple directions, for example, towards and into two runner areas. FIG. 3 shows a gate system 700 including a biscuit 702 and two runners 704.

[0053] FIG. 4 shows another spreader 800 that includes a body 802. The body 802 may be a solid body or a hollow body. The body 802 may include an outer (or base) ring or disc 804, an inner ring or disc 806, and a guide surface 810. When the body 802 is solid, the guide surface 810 may be notched into the discs 804, 806 including into an end surface 812 of the inner disc 806, as shown. The guide surface 810 includes three portions 820, 822, 824. Each of the portions 820, 822, 824 includes a bottom surface and side surfaces to guide molten metal. The first portion 820 extends along an end surface (or ledge) 826 of the base disc 804. The second portion 822 extends along a portion 828 of the inner disc 806. The third portion 824 extends along the top surface 812. The guide surface 810 guides molten metal into one or more runner areas of a gate system area. The guide surface 810 is a complex surface that may direct molten metal in one or more directions, for example, towards one or more runner areas.

[0054] The spreaders disclosed herein are formed using the methods disclosed herein and have chemical compositions disclosed herein. FIG. 5 shows a plot of resistance versus thermal conductivity for different spreader materials. A first region 900 is associated with spreader H13 steel, a second region 902 is associated with three-dimensional (3D) printed spreader material, and regions 904, 906 are associated with spreader tool steel for examples disclosed herein. The region 904 is associated with spreaders formed of tool steel disclosed herein that has been austenitized and age hardened. The region 906 is associated with spreaders formed of tool steel disclosed herein that has been surface treated after austenitized and age hardened.

[0055] Spreaders associated with regions 904 and 906 have a higher thermal conductivity (or cooling rate) than spreaders associated with region 900. Spreaders associated with region 906 are more resistive to corrosion, erosion, washout and soldering than spreaders associated with regions 900 and 902. Spreaders associated with region 900 may have a hardness Rockwell C (HRC) scale rating of 45-48. Spreaders associated with region 902 may have a HRC scale rating of 43-45. Spreaders associated with region 904 have a HRC scale rating of greater than or equal to 42. Spreaders associated with region 906 may have a HRC scale rating of greater than or equal to 65. The region 904 is associated with the herein disclosed tool steel without surface treatment. The region 906 is associated with the herein disclosed tool steel with surface treatment as disclosed herein. The surface treatment includes i) nitrocarburizing and oxidizing, or ii) oxy-nitrocarburizing.

[0056] FIG. 6 shows a portion 1000 of a spreader. The spreader includes a substrate 1002 into which and on which multiple layers are formed. The substrate is a steel substrate. An example chemical composition of the steel substrate is provided below. A hardening layer 1004 is formed on the substrate 1002. The hardening layer 1004 includes a white layer 1006 and a nitride and carbide layer 1008. The white layer 1006 may be dissociated into the substrate 1002 and pearlite (N) formation occurs during the casting process to provide a resulting substrate 1010. The white layer 1006 may be discomposed into matric and transformed into pearlite to increase hardening depth. Pearlite is a two-phased, lamellar (or layered) structure composed of alternating layers of ferrite (87.5% by weight) and cementite (12.5% by weight). The white layer 1006 dissociates into substrate 1002 and transforms into pearlite to increase the hardness of the material to resist high temperature softening. The hardening layer 1004 provides nanoprecipitation nitride/carbide strengthening. The hardening layer 1004 is formed by nitrocarburizing, which increases a high hot hardness level of the material and enhances erosion and washout resistance.

[0057] The hardening layer 1004 undergoes an oxidizing treatment to form an oxidizing structure 1020 including an inner transition layer 1022 and an outer layer 1024. The oxidizing structure (or oxidizing layers) improves soldering and corrosion resistance of the spreader. The outer layer 1024 is an outer iron oxide layer. The inner transition layer 1022 has a sawtooth structure, which is represented by jagged line 1032 in FIG. 6 and is enriched with Ni and/or Cu metal. The enrichment of Ni and Cu and sawtooth structure improve the bonding between i) oxidizing structure 1020 including the outer oxide layer, and ii) the hardening layer 1004 of the resulting substrate 1010 and inhibits internal oxidation.

[0058] The spreaders disclosed herein have high thermal conductivity, which is attributed to low carbon, chromium, silicon content and the coherence interface between precipitate and matrix of the corresponding substrates. A coherent interface is formed when there is a good match between lattices of the precipitate and the matrix to provide a continuous structure across the interface. The spreaders have high hardness levels and are highly resistive to corrosion and soldering and high temperature softening.

[0059] The substates have a micro-structure that may include martensite, bainite, and/or ferrite. The substrates include nanoprecipitation having a size less than 50 nanometers (nm) with austenite (e.g., less than 2% by volume). After austenitizing spreaders as described herein at high temperatures, the substrate material is quenched and has a hardness of less than or equal to 30 HRC. In an embodiment, the hardness is less than or equal to 28 HRC. After age hardening and surface treatment of the spreaders, surface hardness is greater than or equal to 65 HRC. Thermal conductivity at temperatures of 200-500 Celsius (C) is greater than or equal to 38 watt per meter-kelvin (W m.sup.1 K.sup.1).

[0060] The outer layer 1024 is referred to as an anti-sticking layer that is formed on a steel surface (or surface 1030). The inner transition layer 1022 has a sawtooth shape and is at an interface between the outer layer 1024 and the hardening layer 1004. The inner transition layer provides interpenetration of the outer layer 1024 (or iron oxide layer) and the hardening layer 1004.

[0061] In an embodiment, a thickness T1 of the outer layer 1024 is 0.5-10 micrometers (m) and a thickness T2 of the inner transition layer 1022 is 0.1-5 m. In an embodiment, the outer layer 1024 includes by weight 70-74% Fe, 25-30% oxygen (O), and 1-5% Al. In an embodiment, the chemistry of oxide in the inner transition layer 1022 includes by weight 70-78% Fe, 20-25% O, and 1-5% Al. In an embodiment, the chemistry of metal in the inner transition layer 1022 includes by weight 4-20% Ni and 1-5% Cu. In an embodiment, the white layer 1006 has a thickness T3 of 0.5-2 m and the nitride and carbide layer 1008 has a thickness T4 of 80-300 m.

[0062] In an embodiment, the chemical composition of the tool steel used to form the substrate 1010, by mass, includes 0-0.2% carbon (C), 0.2-6% copper (Cu), 3-10% nickel (Ni), 0.5-3% aluminum (Al), 0.2-1.5% manganese (Mn), 0-1.5% chromium (Cr), 0-2.5% molybdenum (Mo), 0-1.5% tungsten (W), 0-0.2% vanadium (V), and other chemical elements for the remaining balance of the chemical composition. This composition is different than the composition of H13 steel, which by mass, includes 4.75-5.5% Cr, 1.1-1.75% Mo, 0.8-1.2% Si, 0.8-1.2% V, 0.32-0.45% C, 0.3% Ni, 0.25% Cu, and 0.2-0.5% Mn. The carbon is included to promote the formation of a hard martensitic microstructure during austenitizing. The chromium is included to provide the steel with high oxidation resistance. For H13 steel, chromium, molybdenum, tungsten, vanadium, and/or manganese may be included to promote the formation of carbide particles within the martensitic microstructure during tempering to increase the hardness and strength of the steel.

[0063] In an embodiment, Al content of the tool steel used is greater than or equal to 2% to assure full precipitation of Al and reduce the interstitial Al that cause lattice distortion and reduce thermal conductivity and induced internal oxides during service.

[0064] FIG. 7 shows a SEM image of a cross-section of a portion 1100 of another example spreader. The spreader includes a substrate 1102, a nitride and carbide layer 1103, a white layer 1104 and an iron oxide layer 1106.

[0065] FIG. 8 shows a bar graph of hardness versus immersion time for two spreaders formed of different materials. The first spreader is formed of H13 steel (referred to as the baseline). Bars 1200 are associated with the H13 spreader. The second spreader is formed of tool steel as disclosed herein. Bars 1202 are associated with the spreader formed of the tool steel disclosed herein. The disclosed nitrocarburizing improves hardness and resistance to erosion and washout by nanoprecipitation strengthening in the spreader substrate and adding a white layer and nitride and carbide hardening layer near the surface. The white layer dissociates into the substrate and pearlite (N) formation occurs during casting process to provide a spreader with a high hot hardness level that is resistant to high temperature softening and has increased tooling service life. As an example, the spreader hardness after surface treatment is 65 HRC. After immersing at 500 C. for 2 hours (h), the hardness is 57 HRC. After immersing at 550 C. for 2 h, the hardness is 56.8 HRC. After immersing at 600 C. for 2 h, the hardness is 56.4 HRC.

[0066] The second spreader formed of the tool steel disclosed herein has approximately a 35-40% higher thermal conductivity than the H13 spreader over at least a temperature range of 10-600 C. to realize faster cooling and solidification rates. The tool steel disclosed thus has a shorter part cycle time (time to produce and cool part, gate system and biscuit) and lower surface temperatures (temperatures of surface of spreader decrease quicker than a H13 spreader due to the high thermal conductivity of disclosed spreader).

[0067] FIG. 9 shows a plot of temperature versus time for a method of forming a spreader including performing an age hardening operation. After a block of tool steel is forged having the chemical composition disclosed herein, the block of tool steel is machined to form a spreader (preliminary or final) before austenitizing. The machining may include, for example, CNC machining or other type of machining process. The machining is represented at 1302. Then an austenitizing operation is performed, where temperature of the preliminary spreader is increased above a first predetermined temperature (e.g., 930 C.) for a first predetermined period of time and then quenched to reduce the temperature of the preliminary spreader to room temperature. Austenitization includes heating the steel to a temperature at which it changes crystal structure from ferrite to austenite. Dashed line 1300 represents the predetermined temperature threshold. The temperature increase operation is represented by line 1304. The quenching operation is represented by line 1306. In an embodiment, the austenitizing may include isothermal soaking at 900-1000 C. for 0.5-48 h followed by quenching to room temperature.

[0068] After quenching, an age hardening operation is performed, where the temperature of the preliminary spreader is increased to a second predetermined temperature (line 1308) for a second predetermined period of time. The temperature of the preliminary spreader is then reduced to room temperature. This is represented by line 1310. In an embodiment, the age hardening includes isothermal holding the formed spread at 400-650 C. for 0.1-48 h and then cooling to room temperature.

[0069] After age hardening, the preliminary spreader is machined to provide a final spreader. The machining is represented at 1312. The machining may include, for example, computer numerical control (CNC) machining or other type of machining process. After machining, the spreader may be surface treated and the temperature of the spreader is increased to a third predetermined temperature for a third predetermined period of time. The surface treatment may include forming a nitride coating on the surface of the spreader. The increase in temperature is represented by line 1314. The cooling is represented by line 1316. In an embodiment, the surface treatment includes the spreader being nitrocarburized and post oxidized. Nitrocarburizing is performed to improve resistance to erosion and washout during die casting of a part using the spreader. Nitrocarburization is a thermochemical diffusion process. Nitrogen, carbon, and a very small number of oxygen atoms diffuse onto the surface of steel or other ferrous alloys. This forms a surface compound layer and a diffusion layer. In an embodiment, nitrocarburizing is performed at 400-650 C. for 0.1-48 h. In another embodiment, nitrocarburizing is performed at 450-600 C. for 1-24 h. Nitrocarburizing includes introducing a constant gas mixture composition of ammonia (NH.sub.3), hydrogen (H.sub.2), nitrogen (N.sub.2), and/or carbon monoxide (CO) gas mixtures).

[0070] Oxidizing may be performed subsequent to nitrocarburizing and may include increasing temperature of the spreader to a fourth predetermined temperature for a fourth predetermined period. The associated increase and decrease in temperature are represented by lines 1318, 1320. In an embodiment, oxidizing is performed at 380-600 C. for 0.1-48 h. In another embodiment, oxidizing is performed at 400-560 C. for 1-24 h. Oxidizing includes introducing a constant gas mixture composition of steam (H.sub.2O) and oxygen (O.sub.2). Oxidizing is performed to improve resistance to corrosion and soldering during die casting of a part using the spreader. The oxidizing process includes forming a two-layer structure on the surface of the spreader. In an embodiment, iron oxide (Fe.sub.3O.sub.4) in the outer layer of the spreader is less wettable to molten Al and thus resistant to corrosion and soldering when being exposed to molten Al. The Ni and Cu enriched inner transition layer of the spreader is less prone to react with oxygen and is resistant to further internal oxidation. The sawtooth structure of the inner transition layer improves the connection between outer layer and the substrate of the spreader.

[0071] The method of FIG. 9 does not include an annealing step, a stress relief step, and/or a double tempering steps, which are typically performed when forming traditional spreaders.

[0072] The method of FIG. 9 can be simplified to provide the method of FIG. 10. FIG. 10 shows a plot of temperature versus time for another method of forming a spreader including combining age hardening, nitrocarburizing, and oxidizing operations into an oxy-nitrocarburizing operation. In an embodiment, surface treatment process operations are integrated with an age hardening heat treatment process to reduce time for integrating surface treatment due to quick nitrocarburizing and oxidation.

[0073] After a block of tool steel is forged having the chemical composition disclosed herein, an austenitizing operation is performed, where temperature of the block of tool steel is increased above a first predetermined temperature (e.g., 930 C.) for a first predetermined period of time followed by a quenching operation. Dashed line 1400 represents the predetermined temperature threshold. These operations are represented by lines 1402, 1404. In an embodiment, the austenitizing may include isothermal soaking at 900-1000 C. for 0.5 to 48 h followed by quenching to a room temperature.

[0074] After quenching, the block of tool steel is machined to form a spreader (preliminary or final). The machining may include, for example, CNC machining or other type of machining process. The machining is represented at 1406. After machining, the oxy-nitrocarburizing operation is performed, where the temperature of the block of tool steel is increased to a second predetermined temperature (line 1408) for a second predetermined period of time. The temperature of the spreader is then reduced to room temperature. This is represented by line 1410.

[0075] In an embodiment, oxy-nitrocarburizing is performed at 400-600 C. for 0.1-48 h. In another embodiment, oxy-nitrocarburizing is performed at 450-550 C. for 1-24 h. Oxy-nitrocarburizing includes introducing a constant gas mixture composition of ammonia (NH.sub.3), hydrogen (H.sub.2), nitrogen (N.sub.2), and/or carbon monoxide (CO) gas mixtures) in combination with water (H.sub.2O) and oxygen (O.sub.2).

[0076] FIG. 11 shows a method of forming a spreader. At 1500, a forged block of tool steel having the chemical composition as disclosed herein is provided. At 1501, the block of tool steel is machined to provide a preliminary spreader, as described herein.

[0077] At 1502, the preliminary spreader is austenitized as described herein. At 1504, the preliminary spreader is cooled to room temperature.

[0078] At 1506, it is determined whether a distinct age hardening operation is to be performed. If yes, operation 1508 is performed, otherwise operation 1510 is performed.

[0079] At 1508, the preliminary spreader is age hardened, as described herein. At 1510, the preliminary spreader is machined to provide a final spreader, as described herein.

[0080] At 1512, it is determined whether nitrocarburizing and post oxidation operations are to be performed. If not, operation 1514 is performed, otherwise operation 1515 is performed. At 1514, oxy-nitrocarburizing is performed as described herein.

[0081] At 1515, nitrocarburizing is performed, as described herein. At 1516, post oxidizing is performed, as described herein.

[0082] At 1518, is determined whether additional machining is to be performed. If not, the method ends, otherwise operation 1522 is performed. At 1522, the spreader further machined.

[0083] The methods of FIGS. 9-11 may be implemented by the system of FIG. 12 or by another spreader manufacturing system.

[0084] FIG. 12 shows a spreader manufacturing system 1600 that may include a robot 1602, a treatment station and/or oven 1604, and a machining tool 1606. The robot 1602 may include a control module 1610, a memory 1612, actuators 1614, and a power source 1616. The actuators 1614 may include motors 1618 and other items such as grippers, linkages, brackets, rollers, wheels, arms, joints, etc. The robot 1602 may move blocks of tool steel and spreaders to and from the oven 1604 and the machining tool 1606.

[0085] The treatment station and/or oven 1604 may include a control module 1620, fluid sources and flow controllers 1622, a chamber 1624, and heaters 1626. The fluid sources may include gas sources and liquid sources to supply the gases and liquids referred to herein. The chamber 1624 may be used to increase temperatures of the blocks of tool steel and spreaders. Although not shown in FIG. 12, a quenching station may be included for quickly cooling blocks of tool steel and spreaders.

[0086] The machining tool 1606 may include a control module 1630, a memory 1632, a robot 1634, a table 1636, and drilling, milling, and turning tools 1638. The robot 1634 may be used to hold, move, and rotate blocks of tool steel and spreaders on the table 1636. The machining tool 1606 may be used to machine steel and spreaders.

[0087] As an example, the operations 1500, 1501, 1502, 1504, 1506, 1508, 1510, 1512, 1514, 1515, 1516, 1518, and 1522 of FIG. 11 may be performed by the control modules 1610, 1620, 1630. The control modules 1610, 1620, 1630 may be in wireless communication with each other. As an example, operations 1500 and 1518 may be performed by control module 1610. Operations 1502, 1506, 1508, 1512, 1514, 1515, and 1516 may be performed by control module 1620. Operation 1504 may be performed by control module 1620 or another control module of a quenching station. Operation 1501, 1510, and 1522 may be performed by control module 1630.

[0088] The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.

[0089] Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including connected, engaged, coupled, adjacent, next to, on top of, above, below, and disposed. Unless explicitly described as being direct, when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean at least one of A, at least one of B, and at least one of C.

[0090] In the figures, the direction of an arrow, as indicated by the arrowhead, generally demonstrates the flow of information (such as data or instructions) that is of interest to the illustration. For example, when element A and element B exchange a variety of information but information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B may send requests for, or receipt acknowledgements of, the information to element A.

[0091] In this application, including the definitions below, the term module or the term controller may be replaced with the term circuit. The term module may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

[0092] The module may include one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces that are connected to a local area network (LAN), the Internet, a wide area network (WAN), or combinations thereof. The functionality of any given module of the present disclosure may be distributed among multiple modules that are connected via interface circuits. For example, multiple modules may allow load balancing. In a further example, a server (also known as remote, or cloud) module may accomplish some functionality on behalf of a client module.

[0093] The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, data structures, and/or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple modules. The term group processor circuit encompasses a processor circuit that, in combination with additional processor circuits, executes some or all code from one or more modules. References to multiple processor circuits encompass multiple processor circuits on discrete dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple modules. The term group memory circuit encompasses a memory circuit that, in combination with additional memories, stores some or all code from one or more modules.

[0094] The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory, tangible computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).

[0095] The apparatuses and methods described in this application may be partially or fully implemented by a special purpose computer created by configuring a general purpose computer to execute one or more particular functions embodied in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer.

[0096] The computer programs include processor-executable instructions that are stored on at least one non-transitory, tangible computer-readable medium. The computer programs may also include or rely on stored data. The computer programs may encompass a basic input/output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0097] The computer programs may include: (i) descriptive text to be parsed, such as HTML (hypertext markup language), XML (extensible markup language), or JSON (JavaScript Object Notation) (ii) assembly code, (iii) object code generated from source code by a compiler, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. As examples only, source code may be written using syntax from languages including C, C++, C #, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java, Fortran, Perl, Pascal, Curl, OCaml, Javascript, HTML5 (Hypertext Markup Language 5th revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash, Visual Basic, Lua, MATLAB, SIMULINK, and Python.