阅读说明：本技术 镀锌钢电阻焊中减轻液态金属脆化开裂的焊接凸缘预处理 (Weld flange pretreatment to mitigate liquid metal embrittlement cracking in galvanized steel resistance welding ) 是由 P·王 M·J·卡拉高利思 S·P·梅勒斯 Z·邓 于 2019-05-07 设计创作，主要内容包括：一种减轻镀锌钢电阻焊接中液态金属脆化裂纹的方法,包括：通过以下方式改性钢构件的至少一个面以形成第一工件：将第一层中的含锌材料施加到钢构件的至少一个面上；以及在第一含锌材料层上喷涂第二含铜材料层。使第一工件的该至少一个面与钢材料的第二工件邻接。执行焊接操作以将第一工件接合到第二工件。电阻焊接操作的温度使含锌材料与含铜材料局部熔化以形成含锌材料和含铜材料的黄铜合金。(A method of mitigating liquid metal embrittlement cracks in galvanized steel resistance welding, comprising: modifying at least one face of a steel member to form a first workpiece by: applying the zinc-containing material in the first layer to at least one face of the steel member; and spraying a second copper-containing material layer on the first zinc-containing material layer. The at least one face of the first workpiece is brought into abutment with a second workpiece of steel material. A welding operation is performed to join the first workpiece to the second workpiece. The temperature of the resistance welding operation causes the zinc-containing material to locally melt with the copper-containing material to form a brass alloy of the zinc-containing material and the copper-containing material.)

1. A method of mitigating liquid metal embrittlement cracks in the welding of coated steels including galvanized, galvannealed, and ZAM steels, the ZAM representing a zinc, aluminum, magnesium alloy, the method comprising:

laminating a zinc-containing material and a copper-containing material on at least one face of a steel member to form a first workpiece;

abutting the at least one face of the first workpiece with a second workpiece of steel material; and

performing a welding operation to join the first workpiece to the second workpiece, wherein a temperature of the welding operation produces an alloy of the zinc-containing material and the copper-containing material.

2. A method according to claim 1, wherein in the step of laminating, the zinc-bearing material is applied directly onto the steel member and the copper-bearing material is subsequently applied onto the zinc-bearing material.

3. A method according to claim 1, wherein in the step of laminating, the copper-containing material is applied directly onto the steel member and subsequently the zinc-containing material is applied onto the copper-containing material.

4. The method of claim 1, further comprising applying the copper-containing material with a thermal spray device.

5. The method of claim 1, further comprising applying the copper-containing material at a temperature greater than 400 degrees celsius.

6. The method of claim 1, further comprising selecting the copper content of the copper-containing material such that the melting temperature of the alloy of the zinc-containing material and the copper-containing material is greater than or equal to 400 degrees celsius.

7. The method of claim 1, further comprising selecting substantially pure copper as the copper-containing material.

8. The method of claim 1, further comprising selecting silicon bronze as the copper-containing material.

9. The method of claim 1, wherein the temperature of the resistance welding operation causes the zinc-containing material to alloy with the copper-containing material to form brass or other alloys containing copper and zinc.

10. A method according to claim 1, wherein the steel member defines a coated steel selected from any one of medium strength steels, high strength steels and advanced high strength steels including 3 rd generation high strength steels.

Technical Field

The present disclosure relates to welding, including resistance welding of galvanized steel of ferritic, austenitic, or complex multi-phase microstructure.

Background

Automotive vehicles use High Strength Steel (HSS), such as 3 rd generation HSS, as structural members, such as load beam reinforcements, B-pillar reinforcements, roof rail inner reinforcements, front roof and roof rail members, panel body side rail reinforcements, reinforcing front and rear rails, and reinforcing floor rails. The use of an HSS in these applications allows predetermined deformations to occur during impacts, for example during collisions. HSS generation 3 is defined herein as a steel having a tensile strength (MPa) x elongation ≧ 25,000. High strength steels, including 3 rd generation HSS, are typically coated with a coating such as zinc as a plating protective layer to minimize oxidation of the steel. It is desirable to join steel components including a 3 rd generation HSS using a rapid welding technique, such as resistance welding, which is capable of locally raising the temperature of the weld site to about 1500 degrees celsius or higher. When welding galvanized HSS parts, liquid zinc, which melts at about 400 degrees celsius, interacts with the steel, which, together with strains and stresses generated by heating and cooling of the workpiece during resistance welding, can cause Liquid Metal Embrittlement (LME) cracking.

Liquid metal embrittlement (also known as liquid metal induced embrittlement) refers to the phenomenon in which the tensile ductility of certain ductile metals decreases dramatically or brittle fracture occurs upon exposure to a particular liquid metal. LME actually occurs for several steels that suffer from ductility loss and cracking during hot dip galvanization or during subsequent manufacturing (e.g., during welding). For example, when molten zinc of the electroplated protective coating acts to cause cracks in the base steel material, cracks may occur near or in the weld joint of HSS galvanized steel during resistance welding.

Thus, while the current galvanized 3 rd generation HSS components achieve their intended purpose of improving formability and energy absorption, there is a need for a new and improved pretreatment system and method to mitigate liquid metal embrittlement cracks in galvanized steel resistance welding.

Disclosure of Invention

According to several aspects, a pretreatment method for reducing liquid metal embrittlement cracks in coated steel (including galvanized, galvannealed, and ZAM (zinc, aluminum, magnesium alloy) steel) welds includes laminating a zinc-containing material and a copper-containing material on at least one face of a steel member to form a first workpiece. The at least one face of the first workpiece is brought into abutment with a second workpiece of steel material. A welding operation is performed to join the first workpiece to the second workpiece. The temperature of the welding operation produces an alloy of the zinc-containing material and the copper-containing material.

In another aspect of the present disclosure, in the step of laminating, the zinc-containing material is applied directly to the steel member, and the copper-containing material is subsequently applied to the zinc-containing material.

In another aspect of the present disclosure, in the lamination step, the copper-containing material is applied directly to the steel component and the zinc-containing material is subsequently applied to the copper-containing material.

In another aspect of the disclosure, the method further comprises applying the copper-containing material with a thermal spray device.

In another aspect of the present disclosure, the method further comprises applying the copper-containing material at a temperature greater than 400 degrees celsius.

In another aspect of the disclosure, the method further includes selecting the copper content of the copper-containing material such that the melting temperature of the alloy of the zinc-containing material and the copper-containing material is greater than or equal to 400 degrees celsius.

In another aspect of the present disclosure, the method further comprises selecting substantially pure copper as the copper-containing material.

In another aspect of the present disclosure, the method further comprises selecting silicon bronze as the copper-containing material.

In another aspect of the present disclosure, the temperature of the resistance welding operation causes the zinc-containing material to alloy with the copper-containing material to form a brass material alloy.

In another aspect of the present disclosure, the steel member is defined as a coated steel selected from any one of medium strength steels, high strength steels, and high grade high strength steels including 3 rd generation high strength steels.

According to several aspects, a method of mitigating liquid metal embrittlement cracks in resistance welding of coated steels, including galvanized, galvannealed, and ZAM (zinc, aluminum, magnesium alloy) steels, comprises: modifying at least one face of a steel member by applying a zinc-containing material in a first layer to the at least one face of the steel member and spraying a second copper-containing material layer over the first zinc-containing material layer to form a first workpiece; abutting the at least one face of the first workpiece with a second workpiece of steel material; and performing a resistance welding operation to join the first workpiece to the second workpiece, wherein a temperature of the resistance welding operation locally melts the zinc-containing material and the copper-containing material to produce a brass alloy of the zinc-containing material and the copper-containing material.

In another aspect of the disclosure, the first layer of zinc-containing material is defined as a zinc alloy that further includes at least one of: antimony, aluminum, bismuth, cobalt, gold, iron, lead, magnesium, mercury, nickel, silver, sodium, tellurium, and tin.

In another aspect of the disclosure, the method further comprises adding to the first layer of zinc-containing material at least one of: gunmetal, including copper, tin and zinc; bronze, defined as one of gold-imitation copper and gold-plated bronze with copper and zinc; alloys comprising copper, aluminum, and zinc; alloys of copper, aluminum, zinc, and tin; nickel alloys including nickel, copper, and zinc; a solder having zinc, lead, and tin; and zinc alloys with zinc, aluminum, magnesium and copper.

In another aspect of the disclosure, the method further includes modifying at least one face of the second workpiece prior to the adjoining step by: applying the zinc-containing material in the first layer to at least one side of a second workpiece; and spraying a second copper-containing material layer on the first zinc-containing material layer;

in another aspect of the disclosure, the method further includes orienting the second copper-containing material layer of the second workpiece to face the at least one face of the first workpiece during the adjoining step.

In another aspect of the present disclosure, the second copper-containing material layer is applied to a thickness ranging from about 0.01 millimeters to about 0.5 millimeters, inclusive.

In another aspect of the present disclosure, the copper-containing material has a copper content of greater than 90% by composition.

According to several aspects, a welded assembly pretreated to mitigate liquid metal embrittlement cracks in resistance welding of coated steels, including galvanized, galvannealed, and ZAM (zinc, aluminum, magnesium alloy) steels, includes: a first workpiece having a steel member; a zinc-containing material defining a first layer applied to at least one face of the steel member; and a copper-containing material defining a second layer applied to the first zinc-containing material layer. A second workpiece of a steel material is adjacent the at least one face of the first workpiece. A resistance weld joint joining a first workpiece to a second workpiece has a brass alloy of a zinc-containing material and a copper-containing material formed proximate the weld joint by a temperature of a resistance welding operation.

In another aspect of the present disclosure, a steel component is defined as a 3 rd generation high strength steel.

In another aspect of the disclosure, the copper content of the copper-containing material is selected such that the melting temperature of the alloy of the zinc-containing material and the copper-containing material is greater than or equal to 400 degrees celsius.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

Drawings

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

FIG. 1 is a top view of a known resistance weld assembly;

FIG. 2 is a side view of the resistance weld assembly of FIG. 1;

FIG. 3 is a top view of a weld joint of the resistance weld assembly of FIG. 1 illustrating a liquid metal embrittlement crack;

FIG. 4 is a cross-sectional elevation view taken along section 4 of FIG. 1;

FIG. 5 is a diagram of a copper-zinc binary phase diagram;

FIG. 6 is an assembly flow diagram of the disclosed pretreatment method to mitigate liquid metal embrittlement cracks in galvanized steel resistance welding;

FIG. 7 is an assembly flow diagram according to the modification of FIG. 6;

FIG. 8 is a top view of an electrical resistance weld head using the method of the present disclosure; and

fig. 9 is a cross-sectional elevation view taken along section 9 of fig. 8.

Detailed Description

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

Referring to fig. 1-4, a known assembly 10 is shown having a first metal flange 12 secured to a second metal flange 14 with a resistance weld joint 16. With particular reference to fig. 2, either or both of the first metal flange 12 and the second metal flange 14 may have a pre-set coating of an electroplated material, such as zinc. Prior to the welding operation, a first zinc layer 18 is applied to the first metal flange 12 and an opposing second zinc layer 20 is applied to the second metal flange 14. With particular reference to fig. 3 and 4, the plan view and cross-section of the weld joint 16 illustrate a liquid metal embrittlement crack 22 that forms at a boundary 24 of the weld joint 16.

Referring to fig. 5, a binary phase diagram 26 illustrates the relationship between the melting temperature difference in the celsius range 28 and the composition percentage range 30 that varies between pure copper 32 and pure zinc 34. The binary phase diagram 26 also shows the same data over the Fahrenheit range 36. Curve 38 represents the change in melting temperature, which ranges from a first point 40 at about 400 degrees celsius (pure zinc melting at 419.5 degrees celsius) to a second point 42 at about 1100 degrees celsius (pure copper melting at 1085 degrees celsius).

In accordance with the present disclosure, it has been found that by adding a copper-containing layer on a zinc layer of a galvanized steel material prior to soldering, the "free zinc" coating of the zinc layer melts at about 400 degrees celsius and alloys with the copper in the copper alloy layer during subsequent soldering. This alloying process draws the zinc coating away from the surface of the steel material before the molten zinc has a chance to crack the steel by a Liquid Metal Embrittlement (LME) mechanism. According to the present disclosure, zinc and copper are alloyed together to form brass which is one of a number of possible brass phases, which raises the melting point from that of zinc to above the first point 40 (about 400 degrees celsius). The increase in melting point, in conjunction with the alloying process, acts to draw zinc material away from the surface of the steel and either prevent or significantly reduce the LME of the steel. The present method effectively prevents or significantly reduces LME in associated automotive steels, including when used in coating (e.g., galvanizing and galvannealing) HSS steels, such as 3 rd generation HSS.

Referring to fig. 6 and again to fig. 5, a method of mitigating liquid metal embrittlement cracks in resistance welding of coated steels, including galvanized, galvannealed, and ZAM (zinc, aluminum, magnesium alloy) steels, is performed on a first workpiece 46. According to several aspects, the first workpiece 46 includes a metal plate 48 made, for example, from a 3 rd generation HSS. A coating 50 of a material such as zinc is pre-applied to the metal sheet 48 for galvanically protecting the steel substrate. The zinc material coating 50 has a thickness of about 0.005 mm to about 0.08 mm, inclusive.

In an application step 52, molten droplets of a copper-containing material 54 are sprayed or applied onto the coating 50 of the workpiece 46 to form a first deposited layer 56. The copper-containing material 54 may be applied by additive manufacturing (e.g., by a thermal spray device 58) or may be applied using mechanical methods. The copper-containing material 54 may be, for example, a pure copper material or a copper-containing material, such as silicon bronze. According to aspects, a second deposited layer 60 may be similarly formed on the face of the plate 48 opposite the first deposited layer 56. The thickness of each of first deposit 56 and second deposit 60 ranges from about 0.01 mm to about 0.5 mm, inclusive, although the thickness of copper-containing material 54 added as first deposit 56 and second deposit 60 is not limited. According to several aspects, the thermal spray application of the copper-containing material 54 is performed at an elevated temperature above the first point 40 of about 400 degrees celsius to improve adhesion of the copper or silicon bronze material to the zinc and to initiate the bonding process of the zinc to the copper or silicon bronze prior to the welding operation.

In a subsequent assembly operation, a welded subassembly 62 is formed, and the workpiece 46 is positioned such that the first deposited layer 56 (or the second deposited layer 60) is in direct contact with the zinc coating 64 of the second workpiece 66. According to several aspects, the second workpiece 66 includes a metal plate 68, and the metal plate 68 may be steel, such as, but not limited to, a 3 rd generation HSS, or a low strength steel that may or may not be affected by LME mechanisms. If the first and second workpieces 46, 66 are both high strength steels, such as a 3 rd generation HSS material, and are susceptible to LME during welding, the outermost layers of the zinc or copper material of the two workpieces are aligned to oppose each other to promote alloying of the zinc and copper materials of the two workpieces. In a subsequent pre-weld operation 70, a first electrode 72 is brought into direct contact with an outer surface 74 of the first workpiece 46 and a second electrode 76 is brought into direct contact with an oppositely directed second surface 78 of the second workpiece 66. A first force 80 is then applied by the first electrode 72 and an oppositely directed second force 82 is applied by the second electrode 76 to force the first workpiece 46 into abutment with the second workpiece 66.

In a welding step 84, a resistance welding current is applied by the first electrode 72 and flows through the second electrode 76 through the first and second workpieces 46, 66 to form a weld joint 86. During formation of the weld joint 86, the zinc in the coating 50 melts and alloys with the copper material of the copper-containing material 54 to form a bronze alloy. To minimize the possibility of liquid metal embrittlement as the molten zinc material remains in contact with the steel material, it is desirable that the melting point of the alloyed bronze material in the welding step 84 be as close as possible to the second point 42 of about 1100 degrees celsius of pure copper discussed with reference to fig. 5. It is therefore advantageous for the copper-containing material 54 to have a high copper content, defined as a copper content of more than 90% by composition, for example in the case of silicon bronze. After the welding step 84 and after cooling the weld joint 86, the resistance weld assembly 88 is complete.

According to several aspects, in addition to pure copper and silicon bronze, the copper-containing material 54 may also include the following exemplified metals, which may be combined alone or with the zinc of the coating 50 to make the "zinc alloy" of the present disclosure: antimony, aluminum, bismuth, cobalt, gold, iron, lead, magnesium, mercury, nickel, silver, sodium, tellurium, and tin. Other acceptable zinc-containing alloys include: bronze-gunmetal (copper, tin, zinc); bronze-gold imitation copper (gold-plated bronze) (copper, zinc); devada alloy- (copper, aluminum, zinc); northern euro gold- (copper, aluminum, zinc, tin); nickel alloy-german silver (nickel, copper, zinc); solder- (zinc, lead, tin); and zinc alloy-Zamak (Zamak) (zinc, aluminum, magnesium, copper). The composition of the silicon bronze as described herein is about 96% copper, 3% silicon and 1% manganese.

Referring to fig. 7 and again to fig. 6, it is noted that the material layers used to produce workpiece 90 are modified from workpiece 46 by reversing the layers. For example, starting with a metal sheet 48 'made, for example, from the 3 rd generation HSS, molten droplets of the copper-containing material 54 are sprayed or applied directly onto the metal sheet 48' such that the first deposited layer 56 'directly contacts the metal sheet 48'. Subsequently, in a coating step 92, a coating 50 'of zinc material is applied to the copper-containing material of the first deposited layer 56'. A similar assembly operation forms a welded subassembly 94 similar to welded subassembly 62. The welded subassembly 94 is formed with its metal plate 48 'positioned such that the coating 50' (or, alternatively, the outwardly facing coating 96) is in direct contact with the zinc coating 98 of the second workpiece 100. According to several aspects, the second workpiece 100 includes a metal plate 102, and the metal plate 102 may be, for example, steel, such as, but not limited to, a 3 rd generation HSS, a low strength steel, or a carbon steel. A pre-welding operation similar to pre-welding operation 70, and a welding operation similar to welding step 84 described with reference to fig. 6, are then performed to form a resistance welded assembly (not shown).

Referring to fig. 8 and 9, and again to fig. 5-7, a weld joint 104 is shown, the weld joint 104 being formed using the disclosed method of mitigating liquid metal embrittlement cracks in resistance welding of coated steels, including galvanized, galvannealed, and ZAM (zinc, aluminum, magnesium alloy) steels 44. The weld joint 104 does not exhibit LME cracking in the weld zone 106, but LME cracking is prevalent in weld joints formed using known welding processes (e.g., as shown with reference to fig. 3).

The disclosed method of mitigating liquid metal embrittlement cracks in coated steels (galvanized, galvannealed, and ZAM (zinc, aluminum, magnesium alloy) steels 44) resistance welding provides several advantages. These advantages include the beneficial effect of alloying the zinc coating with another material (e.g., silicon bronze, copper, etc.) so that the zinc element does not penetrate into the grain boundaries of the steel during resistance welding of galvanized steel to form LME cracks. The alloying process can also advantageously start between zinc and silicon bronze in the zinc-plated coating, or between zinc and copper in the zinc-plated coating in a thermal spraying process prior to resistance welding. During resistance welding, an alloying process also occurs between the zinc in the zinc-plated coating and the silicon bronze or copper alloy.

Although the present disclosure is described with reference to resistance welding, the methods of the present disclosure may also be applied to all fusion welding processes, including arc welding processes, laser welding processes, and the like. The method of the present disclosure is also applicable to fusion welding a plurality of workpieces.

The description of the disclosure is merely exemplary in nature and variations that do not depart from the gist of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.