JPH03128166A - Arc welding method for steel sheet - Google Patents

Abstract

PURPOSE:To form a weld zone which is free from the generation of strains and has an excellent property to maintain airtightness by using a wire essentially consisting of Cu as a brazing material and to increase the surface roughness of joint surfaces at the time of brazing steel sheets with an arc welding machine. CONSTITUTION:The wire consisting of alumina bronze, phosphorus bronze, silicon bronze, etc., having the compsn. of >90% Cu is used as the brazing material 2 and the surface roughness of the joint part 4 is specified to >=25S; in addition, arc welding is executed at a high temp. of 1500 deg.C in the atm. at the time of arc 3 welding the weld zone 4 of the steel sheets 1, 1 by using the brazing material 2. The molten brazing material 5 shrinks on cooling and since the coefft. of thermal expansion of the brazing material 2 is larger than the coefft. of thermal expansion of the base metals 1, 1, the welding by diffusion joining is executed in the butt parts of the base metal steel sheets 1, 1 roughened in surface by the large shrinking force of the brazing material. The weld zone which is free from strains and has an excellent airtightness is thus formed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Field of Industrial Application) The present invention relates to joining thin steel plates by arc welding, and is used for joining heat exchangers that can withstand high temperatures and exhaust manifolds of engines. Ru.

(Prior art) A heat exchanger for a high temperature section, for example, a heat exchanger for a Stirling engine, is composed of three steel plates, and the joining method is TIG.
Welding methods are used. (Literature National, Technical Report ■○L23No, 2 Apr1977
).

(Problems to be Solved by the Invention) The TIG welding method uses a simple device, but when welding is repeatedly used at high temperatures, there is a risk of distortion, and there is also a problem with the airtightness of the joint. The present invention provides a joining method that can be used in heat exchangers, etc. made of steel plates that are repeatedly used at high temperatures, so that there is no distortion in the joined parts, airtightness is maintained, and the joining method is easy and can be performed at low cost. is a technical issue.

(Structure of the invention) [Means for solving the problem] The technical means taken to solve the problem are as follows. In other words, as a method of brazing thin steel sheets with an arc welder, a wire containing 90% or more of copper, such as aluminum bronze, phosphor bronze, or silicon bronze, is used as the brazing material, and the surface roughness of the joint surface is 253 or higher, and 150 in the atmosphere
This is a thin @temporary arc welding method that joins by diffusion bonding by arc welding at a high temperature of 0 ''C or higher.

(Function) When joining 7IV steel plates by arc welding with a wire containing 90% or more of Cu, 1500% by arc welding.
If heated above ℃, the surface of the base metal will melt and the molten part will be filled with filler metal, but when the molten part cools, if the coefficient of thermal expansion of the wire is larger than that of the base metal, the wire will have a strong The phenomenon of diffusion bonding occurs at the joint when the force contracts, and the bond is made using the strength of the base metal or a strength close to it, rather than the strength of the brazing filler metal.This diffusion bonding allows for repeated use at high temperatures. However, there will be no distortion of the joint or leakage of airtightness.

(Example) Examples will be described below.

Figure 1 is an explanatory diagram of the joining method by arc welding, where 1 is a steel plate, 2 is a wire containing 90% or more of copper such as algo bronze, phosphor bronze, or silicon bronze, which has a large coefficient of thermal expansion. 3 is an arc, and 4 is a joint between steel plates.

In Fig. 1, (a) shows the timing of starting welding, (b) shows the state where part of the copper plate is melted by the arc and the brazing filler metal 5 has expanded, and (C)
(d) shows a state in which the brazing material has cooled and started to shrink, (d) shows a state in which further shrinkage has occurred, and (e) shows a state in which the temporarily abutted surfaces are joined under the brazing material.

Figure 2 is an enlarged explanatory diagram of the diffusion bonded state under the filler metal when welded using the arc welding method, and as shown in (a) to (d), the coefficient of thermal expansion of the filler metal is FIG. 2 is an enlarged explanatory view of an example in which the abutting portions of steel plates are joined by diffusion bonding because the contraction force of the brazing filler metal is large when the base material contracts because it is larger than the expansion coefficient.

Diffusion bonding is difficult when the surface roughness of the abutted portion of the steel plates in FIG. 2 is rough as cut by the press (surface roughness 25S or less), and the bonding surface must be smoothed by cutting or the like.

Further, when the base material is a steel plate, the arc welding temperature needs to be higher than 1500"C, which is the melting temperature of the steel plate, and diffusion bonding cannot be performed at the conventional brazing temperature of about 900 to 1000C.

In addition, since shrinkage bonding occurs during cooling, the brazing filler metal must have a larger coefficient of expansion than the base steel plate.

(effect) The present invention has the following effects.

(1) Diffusion bonding is performed in vacuum at 10-' Torr and 0.
5-1kg/K2, temperature 800℃ or higher, holding time 3
Although more than 0 minutes are required and expensive equipment is required for this purpose, diffusion bonding can be performed in the atmosphere rather than in a special atmosphere using an arc welding machine as in this embodiment.

(2) The left and right steel plates are joined by brazing, but due to diffusion bonding, strength greater than brazing strength can be ensured.

(3) Since it can withstand high temperatures higher than the heat resistance temperature of brazing, it is suitable for joining the outer panels of a Stirling engine that has a combustion chamber inside.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of this embodiment, and (, a) shows the welding start state;
(b) shows the state in which the filler metal has expanded, (C) shows the state in which the filler metal has cooled and started to contract, (d) shows the state in which the shrinkage has progressed further, and (e) shows the state where the mating surface of the plates under the filler metal is Shows the state of diffusion bonding. Figure 2 (a) to (d) are enlarged explanatory diagrams of the state of diffusion bonding using arc welding, and Figure 3 (a) to (・) are enlarged explanatory diagrams of the joints made using the conventional method. FIG. 3 is an enlarged explanatory diagram showing a state where no bonding is performed. 1...Thin steel plate. 2.5... Brazing material. 4...Joint part.

Claims (1)

[Claims] As a method of brazing thin steel plates with an arc welder, a wire containing 90% or more of copper, such as aluminum bronze, phosphor bronze, or silicon bronze, is used as the brazing material, and the surface roughness of the joint surface is 25S. A method for arc welding thin steel plates, which is performed by arc welding at a high temperature of 1500° C. or higher in the atmosphere and by diffusion bonding.