JPS61273268A - Resistance welding method for steel material - Google Patents

Abstract

PURPOSE:To prevent the generation of defect on welding zone by providing a jet nozzle toward the welding position and by performing the welding with feeding directly a combustible substance from the nozzle to the material under welding. CONSTITUTION:The resistance welding is performed by bringing respectively electrodes 2, 2' into contact with two sheets of steel plates 1, 1' and by applying a voltage between the electrodes 2, 2'. The combustible substance 5 of oil, etc. is then dropped by providing the jet nozzle 4 of the liquid combustible substance toward the lower part from the immediately above the welding position. Or by arranging two jet nozzle 10 of gaseous combustible substance at the lower part of the welding position the cumbustible gas of hydrogen gas, etc. is spouted. The fed combustible substance is thus burnt by the welding heat to reduce the oxygen quantity in the air close to the welding zone. The mixture of the oxide on the welding zone is therefore eliminated and the defect due to the oxidation is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a welding method for reducing weld defects by supplying a combustible substance to a welding site in resistance welding of steel materials.

(Prior Art) Resistance welding is a widely used technique in which a current is applied to a polymerized steel material while applying pressure, and the resulting resistance heat is used to bathe the steel material.

For example, in a steel mill, hot rolled steel strips that have not yet been cold rolled are connected by this resistance welding, and then cold rolled. However, in the case of resistance welding, when welding in normal atmosphere, molten or high-temperature steel and oxygen in the air spread and form oxides, which enter the molten metal of the weld. This has the disadvantage that welding defects remain in the welded area.

In order to solve this drawback, for example, the following method is known.

One method is to apply a liquid flammable substance to the area to be welded and its vicinity with a brush in advance when manufacturing steel pipes by electric resistance welding, and then use the heat generated during welding to burn the flammable substance. This removes oxygen from the air and suppresses the generation of oxides (Japanese Patent Laid-Open No. 58-2858)
No. 2).

Another method is to heat and evaporate organic liquid below the welding area to create a flammable atmosphere around the welding area when manufacturing steel pipes using electric resistance welding. (Japanese Unexamined Patent Publication No. 59-225890)
.

(Problems to be Solved by the Invention) However, in these known methods, the area around the welding area is coated with a flammable substance by brushing or completely heated to evaporate the liquid combustible substance before resistance welding. Since all of these methods were indirect methods, such as creating a flammable atmosphere, the ability to remove oxygen from combustion was weak. In other words, if brush coating of flammable material is done before resistance welding, the flammable material will evaporate before resistance welding, and if liquid flammable material is heated and evaporated, the flammable atmosphere near the welding area will be diluted. It becomes. Furthermore, the range of resistance welding was limited to steel pipes.

The present invention maintains the welding area under a strong flammable atmosphere by directly supplying flammable substances to the welding area during resistance welding, thereby preventing welding defects as much as possible. The purpose is to provide a resistance welding method.

(Means for Solving the Problems) That is, the present invention provides an injection nozzle μ for a flammable substance toward the welding position in resistance welding of steel materials, and injects the flammable substance from the nozzle into the joining area of the materials in the i-liquid. The gist of this invention is a method for resistance welding steel materials, which is characterized by directly supplying and performing bath welding.

Hereinafter, the method of the present invention will be explained in detail in the case of butt welding of steel plates with reference to the drawings.

In the butt resistance welding method, as shown in Fig. 8, two steel plates (1) to be welded are butt-butted, and in this state, an electric current is applied to each steel plate (IXI). (2X2) and contact the electrodes (2
By applying a voltage between 25 and 25, two steel plates (1) (
1) A current is passed between the steel plates (1) (1)
Welding is performed using the heat generated at the butt part of the weld and the foam.

The method of the present invention involves directly supplying a combustible substance in the form of liquid, gas, or mist to the welding area (3) during welding, and causing heat generated during welding to be applied to the welding area and its vicinity. Welding is performed by burning flammable substances and depriving the air of the welding area of oxygen.

In Fig. 1, a liquid combustible material injection nozzle (4) is provided from just above the welding position downward, and this nozzle /l/(4
) to the welding area during welding (5)
This shows an example of dripping.

Further, FIG. 2 shows an example in which two gaseous combustible substance injection nozzles A10Oαa are provided from below the welding position toward the bath contact position. These injection nozzles (41QO (1
0 is connected to a combustible material supply source (not shown) such as a pump. Furthermore, when supplying combustible material in the form of mist, a gas-liquid mixing nozzle is used as the injection nozzle.

According to the method of the present invention, the supplied combustible material is immediately combusted by welding heat, and not only is there no loss due to evaporation from supply to combustion, but there is also no loss due to diffusion, and almost the entire amount of the supplied amount is combusted. used for. As a result, the amount of oxygen in the air around the weld area is reduced, which prevents oxidation of the molten steel or high-temperature steel, prevents weld defects due to oxides entering the weld area, and The amount of combustible material needed to provide a certain prevention effect can be reduced.

In the method of the present invention, the flammable substance may be any substance as long as it combines with oxygen and burns, and suitable liquid substances include, for example, organic combustible substances such as oil and paint.
Hydrogen gas, hydrocarbon gas, etc. are suitable as gaseous substances.

The amount of combustible material supplied is 1.0 in the case of liquid flammable material.
"" 5.0 cc/sec-m is suitable, and in the case of gas, 0.5 to 5.04' sec-m is suitable. The reason for this is that if it is too small, combustion will be insufficient and a sufficient reducing atmosphere will not be formed, and if it is too large, the effect will not change and the amount of combustible material used will be wasted.

The present invention is not only applicable to butt resistance welding of steel materials shown in FIG. 8, but also to butt welding of steel bars, and can also be applied to lap resistance welding shown in FIG. 4.

(Example) Next, an example will be explained.

Example 1 0.05χO-1,5%5i-0,80% forward electrical steel sheet (
A plate thickness of 2.8mm and a plate width t, ooom) was butt welded in the manner shown in FIG. 1 under the welding conditions shown in Table 1. Mineral oil was used as the flammable substance supplied. In addition, the supply figure was set at 1 meter for 4 marks.

Table 1 For comparison, we show an example (Comparative Example 1) in which mineral oil was applied to the welding area of the same steel plate with a brush barrel (applied amount: 4 g/In) and then butt welded under the conditions in Table 1 (Comparative Example 1). An example (Comparative Example 2) was carried out in which the same steel plates were butt welded under the conditions in Table 1 in the atmosphere without using the welding method.

In order to measure the decrease in tensile strength and elongation of the obtained material due to welding defects, a bulge test shown in FIG. 5 was conducted. That is, the steel plate (1) after welding is passed through a die with a hole (6
) from above and below, press the punch (7) into the hole while applying the tip to the welding part (8) of the steel plate, and press the welding part (8) into the hole.
) The relationship between the change in the amount of indentation (9) of the purge and the degree of cracking was investigated.

The results of this puff resi test are shown in Table 2.

Table 2 O cracks, △ cracks (IW or less)
Cracking had already occurred in Brtts, and cracking had occurred in Comparative Example 1 at 1 oai despite the large amount of combustible material used, but in the method of the present invention, cracking appeared for the first time at 15 days, Comparative Example 1 and Comparative Example 2. It can be said that the occurrence of cracks is extremely low compared to that of the welding process, and there is little decrease in tensile strength or elongation due to welding defects.

Further, Table 8 shows the working time required from the application of oil to the completion of welding for the method of the present invention and Comparative Example 1, respectively.

Table 8 As shown in Table 3, it can be seen that the method of the present invention takes much less time.

As shown in Tables 2 and 8, the method of the present invention can perform resistance welding with fewer weld defects in a shorter time than in Comparative Examples 1 and 2.

Example 2 0.05XC-1,5%S:L-0.80%Mn steel plate (
Board thickness 2-4M, board width 1. OOOXm) were butt-welded in the manner shown in FIG. 2 under the welding conditions shown in Table 4. The combustible material supplied was hydrogen gas, and the amount supplied was 3 + 306 m each.
And so. As a comparative method, butt welding was performed in the same manner in the atmosphere without using flammable materials.

JISI from the welded steel plate with the welded area at the center
All tensile tests were carried out on all test pieces of No. A test pieces.

The results are shown in FIGS. 6 and 7. In Figure 6, the thickness of the steel plate is 2.
．． Tensile strength for OJEm and 4.0mm”-7/
g4k, Figure 7 also shows elongation (X),
It can be seen that the welding method of the present invention marked with ○ is superior to the comparative welding method marked with O in terms of both tensile strength and elongation.

Example 8 0.05% C-1, 5% 51-o, ao% Mn steel hot rolled steel plate (plate thickness 2.3 m, plate width 1,000 to 1,214E
IE) +7): Ia) After the coils were butt welded together in the manner shown in FIG. 2 and under the conditions shown in Table 5, they were cold rolled in a normal cold rolling mill. The flammable material supplied is H.
J gas, the amount of which was 0.5 Km-m. In addition, as a comparative method, butt welding was performed in the same manner in the atmosphere without using flammable materials.

Table 6 shows the fracture rate of the welded area due to cold rolling for the method of the present invention and the comparative method. The rate is low;
It is clear that the properties of the welded area are good.

Table 6 (Effects of the Invention) As is clear from the above explanation, the present invention greatly reduces defects caused by oxidation in the welded part in resistance welding, and has the great advantage of requiring only a small amount of combustible material to be used to suppress oxidation. It has a benefit.

[Brief explanation of drawings]

Figures 1 and 2 are schematic diagrams showing aspects of the present invention, Figure 8 is an explanatory diagram of butt resistance welding, Figure 4 is an explanatory diagram of lap resistance welding, and Figure 5 is a diagram showing a page test. A vertical cross-sectional view, FIG. 6 is a graph showing the relationship between plate thickness and tensile strength, and FIG. 7 is a graph showing the relationship between plate thickness and elongation. 1.1: Steel plate, 2.2: Electrode, 8: Welding part, 4: Oil dripping nozzle, 5: Drop, 6: Dynu, 7: Punch, 8: Welding part, 9: Indentation amount, 1o: Hydrogen blowing nozzle 111: Hydrogen. Figure s1 Figure 2 Figure 1s3 Figure 4 Tsumugi No. 6 WA

Claims (1)

[Claims] (1) In resistance welding of steel materials, a flammable substance injection nozzle is provided toward the welding position, and welding is performed while the flammable substance is directly supplied from the nozzle to the part of the material being welded. Resistance welding method.