JP2004181473A - Projection welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding method that prevents generation of cracks in a projection weld zone which is joined by flowing a welding current in the projection of an object to be welded. <P>SOLUTION: In the projection welding of high carbon steel to low carbon steel, a projection is prepared in the low carbon steel, i.e., a material having less tendency to cause cracks, thereby suppressing concentration of breaking stress in a plastic deformation part of a weld zone. As a result, conventional temper current supply for crack prevention is no longer required, saving plenty of time to be spent on the temper condition setting and enabling productivity to be greatly improved. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

上記の実験値による従来方法によれば，図５の写真に示すように，円筒状チューブの高炭素鋼側つまり低合金鋼の突起溶接部の塑性変形部に破壊応力が集中し溶接部の変形部にワレが生じた。
【０００７】
本発明の方法は，ワークの材質のみ変更した場合，円筒状チューブを軟鋼材とし，フランジを低合金鋼とした。前記チューブ側に外側バリ防止の突起を設ることによって同様の条件により検証した。図１〜図２の写真に示すように，溶接部の塑性変形部に破壊応力は発生せず，これによって問題のワレの発生場所は溶接動作中の材料変化によるものと判明した。
【０００８】
ワレ防止用のテンパ条件はクールタイムとテンパ電流の両者の組み合わせを求めなければならないため，その条件出しに時間がかかる。また電極の水冷の度合いにより溶接部の温度が変化するため結果的に溶接品質のバラツキが出やすくなるなどの問題が残る。
【０００９】
【発明の効果】
本発明では上記に説明したように，高炭素鋼と低炭素鋼をプロジェクション溶接する場合に，ワレの発生しにくい材料つまり低炭素鋼側に突起を設ることによって溶接部の塑性変形部に集中する破壊応力を発生させないようにしたから，従来から行なわれてきたワレ防止用のテンパ通電が要らなくなり，そのためのテンパ条件出しに多くの時間を費やすことがなくなり生産性を一段と向上させることができる。またワレの発生しやすい材料として，たとえばクロム銅（ＳＣｒ），クロムモリブデン（ＳＣＭ）などがあるが，これらの溶接電流の大きさをコントロールするための条件出しも容易になる。
【図面の簡単な説明】
【図１】本発明方法により破断試験前のマクロ試験（片側）
【図２】破断試験後のマクロ試験
【図３】被溶接物の外観図
【図４】軟鋼製の円筒状チューブの突起形状
【図５】従来方法による破断試験後のマクロ試験[0001]
Field of application belonging to the present invention
The present invention relates to a projection welding method in which a projection (projection) is formed on an object to be welded, and a welding current is concentrated on a point-like or linear portion by the projection to heat and weld.
[0002]
[Prior art]
In projection welding, cracks occur when stress concentrates on the plastic metal in the weld. In order to prevent this cracking, a small current called cracking current for tempering after welding is generally applied to prevent cracking.
[0003]
2. Description of the Related Art Conventionally, rotating parts and the like built in an engine of an automobile or an automatic transmission are problems that metal fatigue and fracture must be avoided. In the case of this type of rotating parts, cracks in the welded portion and the generation of burrs during welding lead to destruction, which is fatal.
[0004]
[Problems to be solved by the invention]
As for the tempering condition for preventing cracking by the conventional projection welding, a combination of both the cool time and the tempering current must be obtained, so that it takes time to find out the condition. In addition, since the temperature of the weld changes depending on the degree of water cooling of the electrode, there remains a problem that variations in welding quality tend to occur as a result.
[0005]
[Means for solving the problem]
Therefore, in order to solve the above-mentioned problems, the present invention provides a method for projecting welding high carbon steel and low carbon steel, by providing a projection on the low carbon steel side to generate a fracture stress generated in the plastically deformed portion of the weld. Provided is a projection welding method characterized by suppressing concentration.
[0006]
In order to compare the present invention with the conventional method, the occurrence of cracks was verified by projection welding experiments using the following experimental values.
-Work (Fig. 3): One of the workpieces is a cylindrical tube made of low alloy steel, and the other is a flange made of mild steel.
・ Projection shape (Fig. 4): Ring projection (prevention of burrs outside cylindrical tube)

According to the conventional method based on the above experimental values, as shown in the photograph of FIG. 5, the fracture stress is concentrated on the plastically deformed portion of the high carbon steel side of the cylindrical tube, that is, the projection welded portion of the low alloy steel, and the deformation of the welded portion Cracks occurred in the part.
[0007]
In the method of the present invention, when only the material of the work is changed, the cylindrical tube is made of mild steel and the flange is made of low alloy steel. The same conditions were verified by providing a projection for preventing external burrs on the tube side. As shown in the photographs of FIGS. 1 and 2, no fracture stress was generated in the plastically deformed portion of the welded portion, and it was found that the location where the problem occurred was caused by a change in the material during the welding operation.
[0008]
As for the tempering condition for crack prevention, a combination of both the cool time and the tempering current has to be obtained, so that it takes time to determine the condition. Further, since the temperature of the welded portion changes depending on the degree of water cooling of the electrode, there remains a problem that variations in welding quality tend to occur as a result.
[0009]
【The invention's effect】
In the present invention, as described above, when projection welding is performed on high-carbon steel and low-carbon steel, the projection is provided on a material that is unlikely to crack, that is, on the low-carbon steel side, thereby concentrating on the plastically deformed portion of the weld. Since no destructive stress is generated, it is no longer necessary to energize the temper to prevent cracks, which is conventionally done, and it is not necessary to spend a lot of time to determine the tempering conditions, thereby further improving productivity. . Further, as a material in which cracks are easily generated, there are, for example, chromium copper (SCr), chromium molybdenum (SCM), etc., and it is easy to determine conditions for controlling the magnitude of the welding current.
[Brief description of the drawings]
FIG. 1 shows a macro test (one side) before a fracture test according to the method of the present invention.
[Fig. 2] Macro test after fracture test [Fig. 3] External view of workpiece to be welded [Fig. 4] Projection shape of cylindrical tube made of mild steel [Fig. 5] Macro test after fracture test by conventional method

Claims (1)

A projection welding method characterized in that when high-carbon steel and low-carbon steel are subjected to projection welding, a projection is provided on one of the low-carbon steel sides to suppress the concentration of fracture stress caused by plastic deformation of a welded portion.

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