Method for welding metal-based materials

Abstract

The invention relates to a method of welding of at least two metal-based materials (5, 7), non-weldable directly to each other with resistance welding. At least one spacer (6) is joined by welding on at least one of the two surfaces of a material (5) in every interstice between two surfaces of materials to be welded. The welded spacer (6) is utilized so that resistance welding is focused to the surface of the material (5) with the spacer (6) to melt at least one spacer (6) located on the heat affecting zone in order to achieve a weld between the metal-based materials (5, 7).

Claims

1. A method for welding at least two metal-based materials, non-weldable directly to each other with resistance welding, comprising: welding, in a first joining step, at least one spacer to at least one surface of a first metal-based material; providing a second metal-based material; and resistance welding, in a second joining step, the first material to the second material, wherein, during the resistance welding, the at least one spacer is melted in order to achieve a weld between the first metal-based material and the second metal-based material.

2. The method according to claim 1, wherein the spacer is welded to the first metal-based material by arc welding.

3. The method according to claim 1, wherein the spacer is welded to the first metal-based material by plasma welding.

4. The method according to claim 1, wherein the spacer is welded to the first metal-based material by gas metal arc welding.

5. The method according to claim 1, wherein the spacer is welded to the first metal-based material by beam welding.

6. The method according to claim 1, wherein the spacer is welded to the first metal-based material by laser beam welding.

7. The method according to claim 1, wherein the spacer is welded to the first metal-based material by electron beam welding.

8. The method according to claim 1, wherein the resistance welding is carried out by spot welding.

9. The method according to claim 1, wherein the resistance welding is carried out by roller seam welding.

10. The method according to claim 1, wherein the resistance welding is carried out by projection welding.

11. The method according to claim 1, wherein the resistance welding is carried out by weldbonding.

12. The method according to claim 1, wherein the first metal-based material is a steel comprising more than 0.25 weight % C, more than 3 weight % Mn, more than 0.1 weight % N and more than 3 weight % Mo.

13. The method according to claim 1, wherein a composition of the spacer is calculated in accordance with a Schaeffler diagram.

14. The method according to claim 1, wherein the spacer is welded on the surface of steel having a carbon equivalent (CEV) greater than 0.65%, where the CEV is calculated using a formula CEV=C+Mn/6+(Cu+Ni)/15+(Cr+Mo+V)/5, where C, Mn, Cu, Ni, Cr, Mo, and V are a content of each of these elements in the steel in weight %.

15. The method according to claim 1, wherein the first metal-based material is aluminium.

16. The method according to claim 1, wherein the spacer is made of a filler material.

17. The method according to claim 1, wherein the spacer is made of a braze material.

18. The method according to claim 1, wherein, after resistance welding, a gap defined by the spacer is provided between the first metal-based material and the second metal-based material.

19. The method according to claim 18, wherein a proportion of a diameter of the spacer to a height of the spacer is at least five.

20. The method according to claim 1, wherein crevice conditions are prevented between the materials to be welded by coating the surfaces of the materials and the spacer.

21. The method according to claim 1, wherein a spacer controls and directs the welding heat from the resistance welding.

22. The method according to claim 1, wherein the resistance welding is focused on the first metal-based material and the second metal-based material in an area corresponding to the spacer.

Description

(1) The invention is described in more details in the following referring to the drawings, wherein

(2) FIG. 1 illustrates one preferred embodiment of the invention schematically from the side view,

(3) FIG. 2 illustrates another preferred embodiment of the invention schematically from the side view,

(4) FIGS. 3a, 3b and 3c illustrates a preferred embodiment of the invention schematically from the side view,

(5) FIGS. 4a and 4b illustrates a preferred embodiment of the invention schematically from the side view,

(6) FIG. 5 illustrates still one preferred embodiment of the invention schematically in cross-section,

(7) FIG. 6 shows an example to use the Schaeffler diagram in accordance with the invention, and

(8) FIG. 7 illustrates, as described in the prior art of the invention, Schaeffler diagram with an example of problems in the prior art.

(9) The materials, non-weldable directly together with the resistance welding, to be used in the method of the present invention can be for instance steels which are out of the Schaeffler diagram. In general, the steels containing more than 0.25 weight % C, more than 3 weight % Mn, more than 0.1 weight % N and more than 3 weight % Mo are out of the Schaeffler diagram. Furthermore it is possible with the invention to avoid areas of the Schaeffler diagram which are classified with welding problems as illustrated in FIG. 7. The manner to avoid these problems is to use the spacer in a kind of an alloying element. By using the spacer on that manner it is possible to calculate and to choose the material for the spacer with the Schaeffler diagram.

(10) Further, the materials also used in the method of the present invention are the steels having the carbon equivalent (CEV) more than 0.65%, where CEV is calculated using a formula (element contents by weight %):
CEV=C+Mn/6+(Cu+Ni)/15+(Cr+Mo+V)/5.

(11) Also other metal materials, such as aluminium, can be treated in accordance with the present invention.

(12) In FIG. 1 the first welded material 5 provided with a spacer 6 has been welded by resistance welding to the second material 7. The spacer 6 has achieved a gap 8 between the welded materials 5 and 7. The gap 8 prevents a direct contact between the welded materials 5 and 7. Based on the gap 8 defined by the spacer 6 the welded materials 5 and 7 can have different electrochemical potentials without any contact corrosion.

(13) FIG. 2 illustrates cathodic dip coating in connection with the present invention. The first welded material 11 provided with a spacer 12 has been welded by resistance welding to the second material 13. The welded structure 14 is further treated in a coating process to have a coating layer 15, thanks to the spacer 12, on the surface of the first material 11, on the surface of the spacer 12 and on the surface of the second material 13, because the spacer 12 achieves a gap 16 between the welded materials 11 and 13.

(14) The present invention is applied for weldbonding in accordance with FIGS. 3a, 3b and 3c. In FIG. 3a the first material 31 to be welded is provided with a spacer 32 and with an adhesive material 33 for weldbonding. The FIG. 3a also shows the welding area 34 between the first material to be welded and the spacer 32. In FIG. 3b the second material 35 to be welded is added on the adhesive material 33, and the welding electrodes 36 and 37 are ready to start welding between the materials 31 and 35. FIG. 3c illustrates the result of the weldbonding, a nugget weld 38, between the spacer and the second welded material 35. Because the adhesive material 33 was not splashed out, there is no stream channel between the materials 31 and 35.

(15) FIG. 4a illustrates an embodiment where spacers 23 and 24 are welded to the first material 21, and spacers 25 and 26 are welded to the second material 22. As illustrated in FIG. 4b the material 21 and 22 are spot welded in order to have a weld nugget 28 using the spacers 23 and 24 and respectively 25 and 26. Based on the spacers 23 and 25 and respectively 24 and 26 on the both materials 21 and 22 the gap 27 is thus larger than in the embodiment of FIG. 1 that makes better to avoid contact corrosion between the materials 21 and 22.

(16) FIG. 5 illustrates the present invention applied for a tube after resistance welding. The inner tube 41 is first provided with a spacer 43 and then the outer tube 42 is imposed around the inner tube 41. The inner tube 41 and the outer tube 42 are resistance welded to each other to achieve the weld nugget 45. Thus a gap 44 caused by the spacer 43 is formed between the inner tube 41 and the outer tube 42.

(17) FIG. 6 illustrates an example for the use of the Schaeffler diagram according to the invention. In the example the same steels as in the prior art FIG. 7, a martensitic stainless steel 1.4034 being as the first metal 1 and an unalloyed carbon steel being as a second metal 2 shall be welded together. For the spacer material S it is selected a CrNi filler metal which microstructure consists of austenite and about 20 vol % ferrite. The spacer material S is welded with the metal 1 by arc welding, and a resultant alloy S1 is achieved between the first metal 1 and the spacer S. When the second metal 2 is then welded by the resistance welding with the spacer S, the final resultant alloy S2 between the second metal 2 and the spacer S is outside all the areas problematic for resistance welding. Thus a desired weld result is achieved.