SAFETY STEEL OR WEAR-RESISTANT STEEL, AND USE

Abstract

The invention relates to a ballistic steel or wear-resistant steel (1) made up of a multilayer steel materials composite comprising a first layer (1.1) composed of a steel which in the hardened or tempered state has a hardness of >350 HBW and at least one second layer (1.2) which is composed of a steel which is softer compared to the first layer (1.1) and is joined by substance-to-substance bonding to the first layer (1.1), wherein the second layer (1.2) has a hardness which is at least 20% lower than that of the first layer (1.1) in the hardened or tempered state. The invention further relates to a corresponding use of the ballistic steel or wear-resistant steel (1).

Claims

1. A ballistic steel or wear-resistant steel made up of a multilayer steel materials composite comprising a first layer composed of a steel which in the hardened or tempered state has a hardness of >350 HBW and at least one second layer which is composed of a steel which is softer compared to the first layer and is joined by substance-to-substance bonding to the first layer, wherein the second layer has a hardness which is at least 20% lower than that of the first layer in the hardened or tempered state, wherein the first layer comprises, in addition to Fe and production-related unavoidable impurities, in % by weight, C: from 0.1 to 0.6%, Mn: from 0.1 to 2.5%, Cr: from 0.05 to 1.5%, S: up to 0.03%, Sn: up to 0.05%, As: up to 0.02%, Co: up to 0.02%, O: up to 0.005%, H: up to 0.001% and the second layer comprises, in addition to Fe and production-related unavoidable impurities, in % by weight, C: from 0.001 to 0.15%, S: up to 0.03%, Sn: up to 0.05%, As: up to 0.02%, Co: up to 0.02%, H: up to 0.001%, O: up to 0.005%.

2. The ballistic steel or wear-resistant steel as claimed in claim 1, wherein the second layer has an alloying content in respect of at least one of the elements Si, Ni, Cr, Mo and/or Mn which is at least 10% lower compared to the first layer.

3. The ballistic steel or wear-resistant steel as claimed in claim 2 wherein the ballistic steel or wear-resistant steel comprises a third layer composed of a steel which is softer than the first layer and harder than the second layer and is joined by substance-to-substance bonding to the first layer.

4. The ballistic steel or wear-resistant steel as claimed in claim 2 wherein the ballistic steel or wear-resistant steel comprises two second layers which are arranged on the two sides of the ballistic steel or wear-resistant steel and are joined by substance-to-substance bonding to the first layer.

5. The ballistic steel or wear-resistant steel as claimed in claim 2 wherein the ballistic steel or wear-resistant steel comprises two second layers which are arranged on the two sides of the ballistic steel or wear-resistant steel, a third layer as middle layer and two first layers as intermediate layers which are in each case arranged between the middle layer and the second layers.

6. The ballistic steel or wear-resistant steel as claimed in claim 2 wherein the second layer has a thickness of material in the range from 1% to 12% based on the total thickness of the material of the ballistic steel or wear-resistant steel.

7. The ballistic steel or wear-resistant steel as claimed in claim 2 wherein the ballistic steel or wear-resistant steel has been produced by means of cladding or by means of casting.

8. The ballistic steel or wear-resistant steel as claimed in claim 2 wherein the ballistic steel has a surface having a surface roughness Ra in the range from 0.5 to 3 μm on one or both sides.

9. The ballistic steel or wear-resistant steel as claimed in claim 2 wherein the ballistic steel or wear-resistant steel is provided on one or both sides with at least one of a metallic anticorrosion coating and organic coating and paint or varnish.

10. (canceled)

11. (canceled)

12. The ballistic steel or wear-resistant steel as claimed in claim 1 wherein the first layer further comprises: N: from 0.003 to 0.01% and Si: from 0.05 to 1.5%.

13. The ballistic steel or wear-resistant steel as claimed in claim 1 wherein the first layer further comprises: Al: from 0.01 to 2.0%.

14. The ballistic steel or wear-resistant steel as claimed in claim 1 wherein the first layer further comprises: B: from 0.0001 to 0.01%, at least one element selected from the group consisting of Nb, Ti, V and W: in total from 0.005 to 0.2%, Mo: from 0.1 to 1.0%, Cu: from 0.05 to 0.5%, and P: from 0.005 to 0.15%.

15. The ballistic steel or wear-resistant steel as claimed in claim 1 wherein the first layer further comprises: Ca: from 0.0015 to 0.015% and Ni: from 0.1 to 5.0%.

16. The ballistic steel or wear-resistant steel as claimed in claim 1 wherein the second layer further comprises: N: from 0.001 to 0.01%, Si: from 0.03 to 0.7%, Mn: from 0.05 to 2.5%, P: from 0.005 to 0.1%, Mo: from 0.05 to 0.45%, Cr: from 0.1 to 0.75%, Cu: from 0.05 to 0.75%, Ni: from 0.05 to 0.5%, Al: from 0.005 to 0.5%, and B: from 0.0001 to 0.01%.

17. The ballistic steel or wear-resistant steel as claimed in claim 1 wherein the second layer further comprises: at least one element selected from the group consisting of Nb, Ti, V and W: from 0.001 to 0.3%.

18. The ballistic steel or wear-resistant steel as claimed in claim 1 wherein the second layer further comprises: Ca: from 0.0015 to 0.015%.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0111] The invention is illustrated in more detail below with the aid of a drawing depicting working examples. The drawing shows

[0112] FIG. 1) a schematic section through a first working example of a ballistic steel or wear-resistant steel,

[0113] FIG. 2) a schematic section through a second working example of a ballistic steel or wear-resistant steel and

[0114] FIG. 3) a schematic section through a third working example of a ballistic steel or wear-resistant steel.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0115] Ballistic steels or wear-resistant steels according to the invention consist of a multilayer steel materials composite which is composed essentially of commercial steels. They are preferably produced by means of hot rolling cladding. For this purpose, pieces of sheets of different steels of the first, second and optionally third layer are, depending on the application and use, respectively stacked on top of one another and are, at least in part, joined to one another by substance-to-substance bonding along their edges, preferably by means of welding, to give a precomposite. The precomposite is brought to a temperature of >1100° C. and hot rolled in a plurality of steps to give a materials composite having a desired total thickness of material as semifinished part in the form of a strip, plate or sheet and can optionally be processed further by after-rolling or skin-passing to produce a defined surface texture.

[0116] Plates are generally parted from the semifinished part and optionally cut to size to give shaped plates. The plates/shaped plates are heated to austenitizing temperature, in particular above A.sub.c3 based on the first layer, in a furnace for in each case >10 minutes depending on the thickness and heated through, and are subsequently quenched to set the desired hardness in the first layer. After-rolling or skin-passing to set a targeted surface roughness, in particular on the side of the ballistic steel or wear-resistant steel on which the second layer is arranged can preferably be carried out. If the second layer is applied on only one side, the side facing away from the second layer remains essentially uninfluenced by the after-rolling or skinpassing. The ballistic steel or wear-resistant steel can optionally also be subjected to annealing (tempering). Finally, the ballistic steel or wear-resistant steel can be coated on one or both sides with a metallic anticorrosion coating, preferably based on zinc, and/or an organic coating and/or paint or varnish. The ballistic steel or wear-resistant steel of the invention is finished and can subsequently be employed or used for protecting living beings in vehicles or buildings or in construction, agricultural, mining or transport machines.

[0117] As an alternative, the hardened or tempered state can also be set in a ballistic steel or wear-resistant steel according to the invention made up of a multilayer steel materials composite in the form of a strip-like semifinished part, continuously by suitable means in continuous passage, provided the ballistic steel or wear-resistant steel according to the invention is coilable. In particular, continuous coating of the strip can also be implemented economically thereby. However, this is only possible at a total thickness of the material of <10 mm.

[0118] FIG. 1) shows a schematic sectional view through a first working example of a ballistic steel or wear-resistant steel according to the invention (1). The ballistic steel or wear-resistant steel according to the invention (1) comprises a first layer (1.1) composed of a steel having a predominantly martensitic and/or bainitic microstructure in the hardened or tempered state, which has a hardness of >350 HBW, in particular >400 HBW, preferably >450 HBW, more preferably >500 HBW, more preferably >550 HBW, particularly preferably >600 HBW, and a second layer (1.2) which is joined by substance-to-substance bonding to the first layer (1.1) and is composed of a steel which is softer than the first layer (1.1), where the second layer (1.2) has a hardness which is at least 20% lower, in particular at least 50% lower, than that of the first layer (1.1) in the hardened or tempered state. The hardness of the second layer (1.2) is <250 HBW, in particular <200 HBW, preferably <175 HBW, particularly preferably <150 HBW.

[0119] The first layer (1.1) consists of, in addition to Fe and production-related unavoidable impurities, in % by weight, [0120] C: from 0.1 to 0.6%, [0121] optionally N: from 0.003 to 0.01% [0122] optionally Si: from 0.05 to 1.5%, [0123] Mn: from 0.1 to 2.5%, [0124] optionally Al: from 0.01 to 2.0%, [0125] Cr: from 0.05 to 1.5%, [0126] optionally B: from 0.0001 to 0.01%, [0127] optionally one or more elements selected from the group consisting of Nb, Ti, V and W: in total from 0.005 to 0.2%, [0128] optionally Mo: from 0.1 to 1.0%, [0129] optionally Cu: from 0.05 to 0.5%, [0130] optionally P: from 0.005 to 0.15%, [0131] S: up to 0.03%, [0132] optionally Ca: from 0.0015 to 0.015%, [0133] optionally Ni: from 0.1 to 5.0%, [0134] Sn: up to 0.05%, [0135] As: up to 0.02%, [0136] Co: up to 0.02%, [0137] O: up to 0.005%, [0138] H: up to 0.001%. [0139] The first layer (1.1) is preferably formed by a very hard and sufficiently tough steel alloy having the trade name “Secure” and a hardness of 600 HBW or “XAR®” and a hardness of 600 HBW in the hardened or tempered state.

[0140] The second layer (1.2) consists of, in addition to Fe and production-related unavoidable impurities, in % by weight, [0141] C: from 0.001 to 0.15%, [0142] optionally N: from 0.001 to 0.01%, [0143] optionally Si: from 0.03 to 0.7%, [0144] optionally Mn: from 0.05 to 2.5%, [0145] optionally P: from 0.005 to 0.1%, [0146] optionally Mo: from 0.05 to 0.45%, [0147] optionally Cr: from 0.1 to 0.75%, [0148] optionally Cu: from 0.05 to 0.75%, [0149] optionally Ni: from 0.05 to 0.5%, [0150] optionally Al: from 0.005 to 0.5%, [0151] optionally B: from 0.0001 to 0.01%, [0152] optionally one or more elements selected from the group consisting of Nb, Ti, V and W: from 0.001 to 0.3%, [0153] S: up to 0.03%, [0154] optionally Ca: from 0.0015 to 0.015%, [0155] Sn: up to 0.05%, [0156] As: up to 0.02%, [0157] Co: up to 0.02%, [0158] H: up to 0.001%, [0159] O: up to 0.005%. [0160] The soft steel alloy is, for example, formed by a soft, unalloyed steel having the trade name “DD14” and a hardness of 105 HBW after heat treatment of the materials composite (hardening or tempering).

[0161] The thickness of the material of the second layer (1.2) is, for example, 10% based on the total thickness of material of the ballistic steel or wear-resistant steel (1). Since the second layer (1.2) can be coated simply and without a great outlay compared to the first layer (1.1) of the ballistic steel (1) or wear-resistant steel, the ballistic steel or wear-resistant steel (1) has an anticorrosion coating (1.4) based on zinc on one side, preferably an electrolytic zinc coating having a thickness of, for example, 8 μm. The ballistic steel or wear-resistant steel (1) has, for example, been subjected to after-rolling or skin-passing before coating, in order to satisfy, in particular, the new requirements in surface quality and surface roughness for ballistic steels or wear-resistant steels. As a result of the after-rolling or skin-passing, the second layer (1.2) can be plastically deformed at a significantly greater thickness than the first layer. The pronounced yield point which may occur in the second layer can therefore be removed by cold strengthening which is beneficial for the surface appearance after any cold forming required during further processing. The ballistic steel or wear-resistant steel (1) preferably has a surface roughness Ra in the range from 0.7 to 1.6 μm on one side, namely the side on which the second layer (1.2) is arranged. The bombardment resistance or wear resistance is ensured essentially by the thickness of material of the first layer (1.1) having 90% of the total thickness of material of the ballistic steel or wear-resistant steel

[0162] FIG. 2) shows a schematic sectional view through a second working example of a ballistic steel or wear-resistant steel (1) according to the invention. The ballistic steel or wear-resistant steel (1) according to the invention differs from the first working example in that two second layers (1.2), which are arranged on the two sides of the ballistic steel or wear-resistant steel (1) and are joined by substance-to-substance bonding to the first layer (1.2), thus give a three-layer steel materials composite which in this example is coated on both sides with an anticorrosion coating (1.4). The first layer (1.1) is preferably formed by a very hard steel having the trade name “Secure” and a hardness of 600 HBW or “XAR®” and a hardness of 600 HBW. As second layers (1.2), it is possible to use soft bake-hardening steels having the trade name “HX260” and a hardness of 125 HBW after heat treatment of the materials composite (hardening or tempering).

[0163] The bombardment resistance or wear resistance is ensured essentially by the thickness of material of the first layer (1.1) of 90% of the total thickness of material of the ballistic steel or wear-resistant steel (1). The thicknesses of material of the two second layers (1.2) are 5% per side, based on the total thickness of material of the ballistic steel or wear-resistant steel (1). The sandwich configuration gives the ballistic steel or wear-resistant steel (1) additional stability and the soft second layer (1.2) on the side facing away from the impact can decrease detached splinters caused by impulse impact, for example in the first layer (1.1), and has a positive influence on the wear application. The ballistic steel or wear-resistant steel (1) preferably has a surface roughness R.sub.a in the range from 0.9 to 1.8 μm, which has been produced by skin-passing of the ballistic steel or wear-resistant steel (1), on both sides. After skin-passing, the ballistic steel or wear-resistant steel (1) has preferably been coated on both sides with a metallic anticorrosion coating (1.4) based on zinc by hot dip coating, in each case with a thickness of 20 μm. As a result of heating of the ballistic steel or wear-resistant steel (1) to the coating temperature, the ballistic steel or wear-resistant steel (1) experienced an annealing treatment which had advantageously dissipated stresses within the steel materials composite and reduced its hardness by about 100 HBW, and the yield strengths in the two layers (1.2) were able to be increased by the bake-hardening properties, as a result of which the yield strength difference between the first layer (1.1) and second layers (1.2) was able to be reduced by about 30 MPa.

[0164] FIG. 3) shows a schematic sectional view through a third working example of a ballistic steel or wear-resistant steel according to the invention (1). The ballistic steel or wear-resistant steel (1) comprises two second layers (1.2), which are arranged on the two sides of the ballistic steel or wear-resistant steel (1) as outer layers, a third layer (1.3) as middle layer and two first layers (1.1) as intermediate layers which are in each case arranged between the middle layer (1.3) and the second layers (1.2). The ballistic steel or wear-resistant steel (1) is coated on both sides with a metallic anticorrosion coating (1.4). The two first layers (1.1) are preferably formed by a very hard steel having the trade name “Secure” and a hardness of 650 HBW or “XAR®” and a hardness of 650 HBW in the hardened or tempered state. As second layers (1.2), it is possible to use soft IF steels having the trade name “DX54” and a hardness of 90 HBW after the heat treatment of the materials composite (hardening or tempering). The third layer (1.3) is preferably formed by a hard steel which is at the same time tougher than the first layer and has the trade name “Secure” and a hardness of 450 HBW or “XAR®” and a hardness of 450 HBW in the hardened or tempered state. The difference in C content between the first layers (1.1) and the third layer (1.3) is at least 0.02% by weight. The combination of first layers (1.1) and third layer (1.3) gives the ballistic steel or wear-resistant steel (1) a high hardness with satisfactory toughness. The thicknesses of material of the first layers (1.1) are 30% per side and the thickness of the third layer (1.3) is 36%, based on the total thickness of material of the ballistic steel or wear-resistant steel (1). The second layers (1.2) give the ballistic steel or wear-resistant steel (1) made up of a five-layer steel materials composite additional stability and also the advantages mentioned in the second working example, for example the impulse reduction, with the steels having a thickness of material per side of 2% based on the total thickness of the ballistic steel or wear-resistant steel (1). The ballistic steel or wear-resistant steel (1) is preferably coated on both sides with a metallic anticorrosion coating (1.4) based on zinc and having a thickness of 6 μm in each case, which has been applied by electrolytic coating. The ballistic steel or wear-resistant steel (1) can preferably have a surface roughness Ra in the range from 1.1 to 1.6 μm on both sides.

[0165] The invention is not restricted to the working examples depicted in the drawing or to the statements in the general description. The individual abovementioned features can also be combined with one another. A metallic anticorrosion coating and/or organic coating and/or paint or varnish is not absolutely necessary. The ballistic steel or wear-resistant steel of the invention can also be produced from a tailored product, for example a tailored welded blank and/or tailored rolled blank.