JPS6057423B2 - Arc stud welding method of stainless steel bolts to pure copper and low alloy steel mother plates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention utilizes pure copper or low alloy copper with high thermal conductivity and electrical conductivity, such as silver-containing deoxidized copper, Cr copper, Zr-Cr copper, etc.
This relates to a method for stud welding stainless steel bolts to a mother plate made of copper or the like.

In general, the stud welding method is known as a method in which studs (bolts) are directly planted into a structure without drilling or tapping.

Conventionally, when such a stud welding is performed on a mother plate made of pure copper or low-alloy copper, the following problems have occurred.

That is, j, ι-&- 40, 11 IΛ8 yoichi, ne, fEΠζ八sha, = [゜ and because the electrical conductivity is very high, it occurs at the contact area between the mother plate and the stud. Arc heat rapidly diffuses to the base plate, and molten metal is not formed on the base plate side of the contact area with the stud.

(2) In order to increase the amount of arc heat generated at the contact area between the base plate and the stud, increasing the amount of current or the duration of the current used will cause the stud to overheat, resulting in buckling or buckling of the stud. Burn-through occurs and welding becomes impossible.

(3) Even if molten metal is formed on the base plate, because the base plate has good thermal conductivity and the molten metal has very good fluidity, if the base plate is thin, holes will form and welding will not be possible. A heat-affected zone with local deformation and softening is formed on the opposite side of the base plate from the welded part, which impairs the properties of the base plate.

Such problems can be solved by replacing studs (bolts) made of stainless steel (IACS; 1% or less), which has low thermal and electrical conductivity, with oxygen-free copper (IACS; which has very high thermal and electrical conductivity). This is especially noticeable when stud welding is performed on a thick plate (base plate) of 102%).Therefore, arcstat welding between a stainless steel stud and a copper base plate has not yet been fully put into practical use. .

The present inventors have conducted research to solve the problems shown in items (1) to (3) above and to obtain a good weld joint when stud welding stainless steel bolts to a copper mother plate. , pure copper and low alloy copper mother plate (hereinafter abbreviated as copper mother plate)
The weldability of stainless steel bolts (hereinafter referred to as stainless steel bolts) is determined by the ratio of the diameter of the stainless steel bolt to the copper base plate, the energization time, and the ratio of the energization time to the diameter of the stainless steel bolt and the welding current. From the results of various experiments, we have come to understand that this value has a large influence, and that if this value is selected to a specific value, it is possible to perform good static welding.

Therefore, this invention was made based on the above knowledge, and the diameter of the stainless steel bolt is twice the thickness of the copper mother plate, the energization time is 0 seconds or less, and the welding current is 1 (A). By welding within a range where the welding current 1 satisfies , where the diameter of the stainless steel bolt is D (WfL) and the energization time is T (seconds), the copper base plate in contact with the stainless steel bolt can be sufficiently heated. This method is characterized by forming a molten metal pool, preventing buckling or melting of stainless steel bolts, and forming a heat-affected zone on the back surface of the base metal to obtain a good arc stud weld.

Next, in the welding method of the present invention, the reason why the ratio of the diameter of the stainless steel bolt to the copper base plate, the current application time, and the range of the welding current are limited as described above will be explained.

(a) The reason why the diameter of the stainless steel bolt should be less than twice the thickness of the copper mother plate is due to item (3) of the above problem. Under the conditions necessary to solve this problem, if the diameter of the stainless steel bolt is made larger than twice that of the copper base plate, a weld heat-affected zone will form on the back side, causing deformation and softening of the base plate. be.

(b) Current application time is 0. The reason for this is that arc stand welding is carried out in the atmosphere, so if the energizing time exceeds 0 seconds, oxygen and nitrogen will enter the molten pool, making it easy for blowholes to form, resulting in poor fusion welding. This is because they will not be able to obtain the same amount of money.

(c) The reason why IT/D is set to 28 or more is that there are conditions necessary to solve the problem (1) above, and even if the generated arc heat diffuses into the copper base plate, This is to supply sufficient arc heat to form a molten pool on the copper mother plate.

(d) The reason for setting IT/D to 30 or less is that it is a necessary condition to solve the problem (2) above, so that the stainless steel bolt does not burn through and the copper base plate does not melt. This is to form a sufficient molten pool. Next, the welding method of the present invention will be explained using examples.

Tables 1 to 3 are some of the experimental data that were variously studied prior to this invention.

In these tables, the O symbol shown in the welding result indicates sufficient joint strength, and the Δ symbol indicates that although it appears to be jointed from the outside, there is not sufficient joint strength. The x mark indicates that a suitable nugget was not formed and the tensile test could not be performed. Figure 1 is the first
The table is summarized as a graph, and 28≦IT/D≦
In the range of 30, the tensile strength of the joint exceeds the copper mother plate (softened material) strength of 20 to 22 kg/i, indicating that the joint has sufficient joint strength. In addition, in the figure, t indicates the plate thickness (Tn!n) of the copper mother plate, but when D/t is 2
For those with D/t=3, for example, 2
Even within the range of 8≦IT/D≦30, the strength of the joint is equivalent to that of the softened material of the copper base plate, and the weld heat affected zone is as shown in Figure 2b.
As shown in , it shows that it was also formed on the back side of the copper mother plate.

The reason why the tensile strength decreases when the heat-affected zone is formed all the way to the back surface is that the fracture forms are different, as shown in FIG. In other words, when D/t=1 as shown in FIG. In the tensile test, the fracture occurs along the boundary (bond) between the molten metal 3 and the heat-affected zone 4, resulting in so-called tensile fracture. On the other hand, when D/t=3 as shown in Fig. 2b, 28≦IT/D≦
Even if the conditions of 30 are satisfied, the fracture occurs in the thickness direction of the copper mother plate 1, which is a so-called shear fracture. Therefore, it is necessary to select conditions that will not cause shear rupture. Note that 2 indicates a stainless steel bolt. Figure 3 summarizes the results of Table 2 in a graph, and in this case also D/t
It can be seen that the bonding strength is sufficient in the range of ≦2, 28≦IT/D≦30.

Furthermore, Table 3 shows similar results to those shown in Tables 1 and 2.

As mentioned above, according to the welding method of the present invention, it is possible to weld dissimilar metals of stainless steel bolts to a copper base plate, which has not been put into practical use to date. It is possible to secure sufficient bonding strength such that the bonding strength becomes extremely high, and this brings about industrially useful effects such as extremely high reliability.

[Brief explanation of drawings]

Figures 1 and 3 are graphs showing the relationship between IT/D and tensile strength with respect to D/t, and Figures 2 a and b are graphs showing the relationship between IT/D and tensile strength.
FIG. 3 is a longitudinal cross-sectional view showing a formation mode and a fracture mode of a heat-affected zone when is 1 and 3, respectively. In the drawings, 1... copper mother plate, 2... stainless steel bolt, 3... molten metal, 4... heat affected zone, D...
Diameter of stainless steel bolt, t...Thickness of copper mother plate.

Claims (1)

[Scope of Claims] 1. In the arcstat welding method of stainless steel bolts to a mother plate made of pure copper or low alloy copper, the diameter D (mm) of the bolt is not more than twice the thickness of the mother plate, and the current application time T is 0.5 seconds or less, and the welding current I (A) is within a range that satisfies the following formula: 28≦IT/D≦30. Arcstat welding of stainless steel bolts to plates.