Welding additive for electric arc welding and laser beam welding of mixed joins made of austenitic and ferritic steel

Abstract

A welding additive for electric arc welding and laser beam welding of mixed joins composed of austenitic and high-manganese-containing and ferritic steel, where the high-manganese-containing steel has a manganese content of at least 7-30% by weight includes the following alloy elements in % by weight: C 0.04-1.0; Mn 7-30; Si≦6; Al≦4; Mo≦2; Ti≦0.5; Zr 0.01-01; B 0.001-0.01; P<0.005; S<0.002; N<0.008; balance iron and unavoidable steel accompanying elements.

Claims

1. A welding additive for electric arc welding and laser beam welding of mixed joints made of austenitic high-manganese-content steel and ferritic steel having a strength opposing a break when at least maximal forces of more than 25 kN are applied, wherein the high-manganese-content steel has a manganese content of at least 7-30 weight percent, and wherein the welding additive does not include Chromium and Nickel, is configured as a solid wire and comprises the following alloy elements in weight percent: TABLE-US-00003 C 0.04-1.0  Mn  7-30 Si ≦6 Al ≦4 Mo ≦2 Ti ≦0.5 Zr 0.01-0.1  B 0.001-0.01  P <0.005 S <0.002 N <0.008 remainder iron and unavoidable steel accompanying elements.

2. The welding additive of claim 1, having the following composition in weight percent: TABLE-US-00004 C 0.1-0.7 Mn 15-26 Si ≦2.5 Al ≦2.5 Mo ≦1 Ti ≦0.1 Zr 0.01-0.08 B 0.001-0.008 P <0.005 S <0.002 N <0.008 remainder iron and unavoidable steel accompanying elements.

3. The welding additive of claim 2, having the following composition in weight percent: TABLE-US-00005 C 0.1-0.3 Mn 18-20 Si ≦1 Al ≦0.5 Mo ≦1.0 Ti ≦0.1 Zr 0.01-0.04 B 0.004-0.006 P <0.005 S <0.002 N <0.008 remainder iron and unavoidable steel accompanying elements.

4. The welding additive of claim 1, for producing welding joints on uncoated or coated materials.

5. The welding additive of claim 4, for use in conjunction with materials having a metallic coating.

6. The welding additive of claim 5, for use in conjunction with materials with a metallic coating in the basis of zinc and/or aluminum and/or silicone and/or magnesium.

7. A steel alloy for use as a solid welding filler wire for electric arc welding and laser beam welding of mixed joints from austenitic high-manganese-content steel and ferritic steel having a strength opposing a break when at least maximal forces of more than 25 kN are applied, wherein said steel alloy does not include Chromium and Nickel and is composed of the following alloy elements in weight %: TABLE-US-00006 C 0.04-1.0  Mn  7-30 Si ≦6 Al ≦4 Mo ≦2 Ti ≦0.5 P <0.005 S <0.002 N <0.008, remainder iron and unavoidable steel accompanying elements, with a combined addition of Zr at contents of 0.01-0.1 weight % and B at contents of 0.001-0.01 weight percent.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 shows the materials used in various tests along with their microstructures;

(2) FIG. 2 shows a transverse micro-section of a hollow seam welding using the filler wire according to the invention.

(3) FIG. 3 shows the achieved maximal force in a quasi static sheer load test performed on probes produced with different filler wires.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(4) A primary goal of the present invention is to produce mixed joints of high-manganese-content austenitic steel with a conventional steel so that the properties of the joint match those of the used basic materials.

(5) For this purpose, tests were performed with the goal to adjust in the weld metal of such a joint a homogenous transition between ferritic and also martensitic microstructure regions from the ferritic side toward the austenitic microstructure regions of the austenitic side, wherein the microstructures were to be as fine grained as possible.

(6) The tests were performed with an un-galvanized HSDR steel in a sheet thickness of t=1.50 mm and with a hot galvanized micro-alloyed fine grained steel of the grade H340LAD also with a sheet thickness of t=1.50.

(7) The basic materials had the following chemical composition in weight percent:

(8) TABLE-US-00001 HSD ® (Austenite) H340LAD (Ferrite) C 0.7 0.064 Mn 15 0.652 Si 2.5 0.01 Al 2.5 0.038 Mo — 0.003 Ti — 0.0085 Nb — 0.0477 V — 0.003 P <0.005 0.01 S <0.02 0.004 N <0.008 0.0041

(9) For the tests, metal protective gas welding was used, wherein the following process parameters have proven advantageous in pre-tests:

(10) TABLE-US-00002 Welding stream 76-115 A Voltage 17.5-19 V Welding speed 0.7-1 m/min Wire feed rate 0.7-1.2 m/min Gas Corgon 10 (15 l/min) Burner angle β 60° Burner angle α 13° Free wire length 10 mm

(11) Based on the determined welding parameters, the different welding additives listed in table 1 were used. The alloy compositions of the tested filler wires 1-4 have in contrast to the additional wire 5 no added boron and zirconium. Within the scope of a suitability test, samples were produced for the metallographic analysis, for the quasi-static test and for the dynamic vibration test in the time strength range.

(12) FIG. 1 shows the materials used for the tests with their microstructures. The photograph of the microstructure in the image on the bottom left shows the microstructure of the high strength high-manganese-content austenitic steel of the grade HSD® belt with a tensile strength of up to R.sub.m-1000 MPa. An austenitic basic microstructure exists due to the high carbon and manganese content (grain size characteristic number 10).

(13) As ferritic joint partner a micro-alloyed fine grained construction steel of the grade H340LA with a tensile strength of up to 550 MPa was used for which the basic microstructure is shown in the upper right hand side of the image. Finely distributed carbides and nitrides of the micro alloying elements Ti and Nb can be clearly seen.

(14) The material HC340LAD is in the present case hot galvanized with a zink layer Z100. The presence of zink during welding of joints with HSD® was intentionally selected in order to test the welding of strip galvanized material in conjunction with the development of a welding filler wire. The austenitic basic material HSD® was used in the un-galvanized state.

(15) FIG. 2 shows the transverse micro-section of a hollow seam welding with the filler wire 5 according to the invention. In the heat influence zone on the HSD® side, an austenitic microstructure is present.

(16) In the HC340LAD a purely bainitic microstructure is present in the heat influence zone. In the weld metal is also very fine grained in comparison with the joints with the aforementioned alloy concepts, and austenitic and martensitic microstructure phases coexist homogenously distributed.

(17) Expectedly, the hardness of the HSD® slightly decreases compared to the basic hardness of the HSD® of 300 HV0.5 in the heat influence zone. In the weld metal on the other hand similar hardness values are achieved as in the basic material of the HSD® steel.

(18) In the heat influence zone on the side of the HC340LAD the hardness steadily decreases down to the basic hardness of the material. Also this course of hardness has a relatively steady hardness decrease starting form the basic material hardness of the HSD® across the welding joint up to the basic material hardness of the HC340LAD.

(19) FIG. 3 shows eh achieved maximal forces derived from a quasi static shear load test. In the samples produced with the addition wire 1 maximal forces of more than F.sub.max=25 kN are achieved. Hereby the break occurs along the melting line of the seam on the upper sheet metal on the side of the HC340LAD. In the joints produced with the addition wire 2 slightly lower maximal forces are achieved compared to the joints produced with the HSD wire, wherein hereby also individual samples also failed in the unaffected basic material of the HC340LAD. In the joints which were produced with the addition wire 3 maximal forces of more than F.sub.max=25 kN are measured again. The position of the break can in this case be observed in the non-affected basic material of the HC340LAD in all samples. In comparison thereto, in the joints with the addition wires 4 and 5 higher maximal forces are achieved (addition wire 4, F.sub.max=27 kN, addition wire 5, F.sub.max=30 kN) wherein the position of the breaks in most of the samples are along the melting line of he seam on the upper sheet metal of he HC340LAD.

(20) The tests for verifying essentially include tests regarding the bearing properties under dynamic vibrating load on the standardized H-sample-shape. The Woehler diagram (force controlled) determined hereby of the metal protective gas welded mixed joints is at a high level. So called fatigued specimens without rupture at a withstood number of cycles of 2 Mio. load changes were achieved at a load horizon of 40 kN. The slope of the Woehler diagram at a k-value close to k=5 represents a value which reflects a high bearing property under dynamic vibrating load.

(21) The test results show that with the alloy composition according to the invention of the welding additive, the required properties of the welding connection can be safely achieve.