HIGH STRENGTH, AIR HARDENING STEEL FOR USE AS WELD FILLER

Abstract

A high strength, air hardening steel includes the following contents in mass-%: C: 0.07 to 0.16, Si: 0.12 to 0.80, Mn: 1.00 to 2.20, Cr: 0.50 to 1.60, Mo: 0.10 to 1.00, Al: 0.010 to 0.060, N: 0.0020 to 0.0150, Ti: 0.010 to 0.050, V+2Nb of 0.030 to 0.200, B: 0.0008 to 0.0050, P: 0.020, S: 0.10, remainder iron, including common steel-incidental elements, for use as weld filler in wire and/or powder form.

Claims

1.-13. (canceled)

14. A high strength, air hardening steel, comprising the following contents in mass-%: C 0.07 to 0.16 Si 0.12 to 0.80 Mn 1.00 to 2.20 Cr 0.50 to 1.60 Mo 0.10 to 1.00 Al 0.010 to 0.060 N 0.0020 to 0.0150 Ti 0.010 to 0.050 V+2Nb 0.030 to 0.200 B 0.0008 to 0.0050 P0.020 S0.010 remainder iron, including common steel-incidental elements, for use as weld filler in wire and/or powder form.

15. The steel of claim 14, wherein the C content is 0.07 to 0.12%.

16. The steel of claim 14, wherein the Si content is 0.20 to 0.40%.

17. The steel of claim 14, wherein the Mn content is 1.60 to 2.10%.

18. The steel of claim 14, wherein the N content is 0.0030 to 0.0125%.

19. The steel of claim 14, wherein the N content of 0.0030 to 0.0080%.

20. The steel of claim 14, wherein the Cr content is 0.70 to 0.85%.

21. The steel of claim 14, wherein the Mo content is 0.20 to 0.35%.

22. The steel of claim 14, wherein the Ti content is 0.02 to 0.04%.

23. The steel of claim 14, wherein the steel has a total content of vanadium and niobium in the form of V+2Nb of 0.05 to 0.12%.

24. The steel of claim 14, wherein the B content is 0.0020 to 0.0040%.

25. The steel of claim 14, for use as weld filler for joint welding, build-up welding or three-dimensional printing of components made from said steel.

26. The steel of claim 14, for use as weld filler for arc welding, in particular inert gas metal arc welding and for laser fusion welding and laser sintering.

Description

[0016] The invention is therefore based on the object to use another alloying concept in order to provide a high strength, air hardening steel for use as weld filler for the production of joint and build-up welds, which alloying concept is cost-effective, while at the same time ensuring superior overall weldability. In addition, the weld filler should be particularly suitable for three-dimensional printing of components made of this steel using laser fusion welding or laser sintering.

[0017] According to the teaching of the invention, this object is achieved by a high strength, air hardening steel with the following contents in mass-%:

C 0.07 to 0.16

Si 0.12 to 0.80

Mn 1.00 to 2.20

Cr 0.50 to 1.60

Mo 0.10 to 1.00

Al 0.010 to 0.060

N 0.0020 to 0.0150

Ti 0.010 to 0.050

B 0.0008 to 0.0050

P0.020

S0.010

V+2Nb 0.030 to 0.200

[0018] remainder iron, including common steel-incidental elements, for use as weld filler in wire and/or powder form.

[0019] The high strength, air hardening weld filler according to the invention is characterized by the realization of a cost-effective alloying concept as a result of the omission of nickel and reduced molybdenum content, and realization of a reduced content of C and Mn in comparison to the known air hardening weld fillers so as to achieve superior general weldability with superior forming properties at the same time.

[0020] The weld filler according to the invention is moreover well suitable for all fusion welding processes, in particular inert gas metal arc welding, for the production of components using three-dimensional printing, for example using the laser fusion or laser sintering process.

[0021] 3D printing of components or application of reinforcements to three-dimensionally shaped components by build-up welding using the air hardening weld filler according to the invention also eliminates advantageously fluctuations in the material properties in the heat impact zone due to the air hardening effect as a result of the very good hardenability and relatively slow cooling.

[0022] Tests have shown that the Cr content decisive for the air hardening effect can be lowered to a value which is noncritical for avoiding chromium carbide precipitations during welding, when at the same time the air hardenability of the steel is improved again using a complex alloying concept based on CrMoTiB.

[0023] According to the invention, the alloying concept is based on the recognition that in contrast to the known steel for seamless tubes, in which nitrogen has to be completely bound by titanium in order to avoid boron nitride precipitations and thus to ensure the effectiveness of the added boron, the nitrogen is also bound by other alloying elements such as Cr or Mo.

[0024] The determination of an overstoichiometric titanium addition in relation to nitrogen is therefore no longer necessarily required. By adding vanadium, precipitates of vanadium carbon nitrides of type V(C,N) are released at higher tempering temperatures and counteract a decrease in strength by a secondary hardening.

[0025] Similar to vanadium, niobium also forms precipitates in the form of carbides or carbon nitrides. In addition to a grain refinement, these precipitations can also contribute to improving tempering resistance.

[0026] When both elements are added to the alloy, a range of 0.030 to 0.200 has proven beneficial for the sum of V+2Nb in mass-%.

[0027] On the basis of this knowledge, the afore-described alloying concept according to the invention has been determined, wherein the following analysis range for the weld filler has been found to be particularly advantageous for a combination of cost-effective alloying concept, good weldability and good air hardenability:

C 0.07 to 0.12

Al0.05

Si 0.20 to 0.40

Mn 1.60 to 2.10

P0.020

S0.010

[0028] N 0.0030 to 0.0125, advantageously 0.0030 to 0.0080

Cr 0.70 to 0.85

Mo 0.20 to 0.35

Ti 0.02 to 0.04

V+2Nb 0.05 to 0.12

B 0.0020 to 0.0040

[0029] remainder iron including common steel-incidental elements.

[0030] As further tests on the weld filler according to the invention have shown, this steel is not only advantageously usable in the automotive sector for joining high strength steels, but also for 3D printing of components made of this steel material. The steel according to the invention is hereby used as a powder, for example for laser sintering or as wire for build-up welding using laser.

[0031] The advantages of this air hardening weld filler according to the invention are listed again hereinafter: [0032] very good general weldability for joint and build-up welding [0033] use for welded, statically and dynamically highly stressed components, [0034] more cost-effective than comparable alloying concepts [0035] excellent suitability for 3D printing of components using arc or fusion welding