JPS61286076A - Press joining method for iron pipe and copper pipe - Google Patents

Abstract

PURPOSE:To join both materials in short time with the surface activation by the destruction of oxide film and resistance heating due to the press fitting by press-fitting an iron pipe to the end part of a copper pipe and by pressing the press-fitting part with heating by electrification. CONSTITUTION:The oxide films on the inner face of a copper pipe and the outer face of an iron pipe are destroyed by forcibly pushing the iron pipe 2 in the copper pipe 1 expanding its end part. In this case the copper pipe 1 may not be expanded in case of the press-fitting being enabled without buckling and the destruction of the oxide film makes the adhesion by the following stage easy by exposing the neo-surfaces of both materials. The resistance welding machine provides to electrodes 5, 6 the resistance plates 3, 4 having high electric resistance and semi-circular shape on the contact face. The oxidation of the both materials 1, 2 under joining is reduced with the efficient work of the resistance heating by the destruction of the oxide film and the use of resistance plate and the joining is therefore performed without brazing filler metal nor flux.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pressure welding method for iron pipes and copper pipes, and particularly to a pressure welding method consisting of two steps of press fitting and resistance heating.

[Background of the invention]

Conventionally, when joining iron pipes and copper pipes, the end of the copper pipe is generally expanded or contracted, the end of the iron pipe is fitted into this part, and the brazing material is applied while heating that part with a gas burner. The method used was to melt it and then pour it into the fitted gap and fix it, but it had the following drawbacks.

(1) Since silver solder is used as the brazing material and flux is used, a large number of man-hours are required to remove the flux.

(2) It requires a lot of manual work and takes a long time to join.

(3) Requires worker skills and is difficult to automate.

(4) The cost of silver solder is high, and the use of silver solder hinders automation.

For example, examples related to this type of pressure welding method include JP-A-54
-133450 publication is mentioned.

[Purpose of the invention]

An object of the present invention is to provide a method for pressure welding iron pipes and copper pipes using an automatic machine that does not require brazing filler metal, 7 lacs, or operator skill.

[Summary of the invention]

A feature of the present invention is that in the first step, the end of the iron pipe to be joined is press-fitted into the copper pipe or its expanded or contracted part, thereby destroying the oxide film on the surface that contacts the art material and making it easier for the new surface to come into contact with it. Then, in the next step, they are joined by heating and pressurizing them with electrodes each having a half groove that matches the circular shape of the outer surface of the joining part using a resistance welding machine. .

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

The figure shows an example of joining an iron pipe and a copper pipe of the same diameter. Figure 1 shows an example of joining an iron pipe 2 to a predetermined length to a copper pipe 1 whose end has been expanded to, for example, 85% of the diameter of the iron pipe. This shows the case in which the material is press-fitted as shown by the arrow in the figure. The purpose is to destroy the oxide film on the inner surface of the copper pipe and the outer surface of the iron pipe by forcing it in. If it is possible to press fit without buckling, the copper pipe does not need to be expanded. In other words, the larger the difference between the outer diameter of the iron pipe to be press-fitted and the inner diameter of the copper pipe, the more effective it is.

The destruction of the oxide film promotes the exposure of both new surfaces, and the subsequent pressurization facilitates the adhesion of the new surfaces to each other.

FIG. 2 shows a state in which a press-fitted part is pressed into contact with an electrode using a resistance welding machine, and shows a resistive plate 3.4 having a semicircular contact surface with high electrical resistance or a counter electrode 5.4. 6. Copper has an extremely high electrical conductivity, so it is difficult to concentrate resistance heat, and since the necessary temperature at the joint does not rise when electricity is passed through a common copper electrode, heat can be reduced by attaching an iron-based resistance plate. concentrate.

FIG. 3 shows a cross section of the heat generating plate and the pipe press-fit part, and the 0 dimension is important. By heating and pressurizing with electricity, both pipes are slightly contracted in the press-fitting part, and the outside diameter of the press-fitting part is approximately 90 to 9,596 mm. At the interface, when electricity is applied, the new surfaces of both metals become high temperature for a short time and are chemically activated, so that they can be brought into close contact with each other by applying pressure.

-For example, if the diameter of both pipes is 4.76, the inner diameter is 5.2
Press fit the iron pipe into the copper pipe expanded to 0 dimension 5.4
As a result of joining with an electrode of 18,000 A, a current application time of 507, and a pressure of 500, a joint was obtained that did not break from the copper pipe base material and did not leak.

According to this example, resistance heating is efficient due to the destruction of the oxide film by press-fitting and the use of a resistive plate. , there is little oxidation of the materials being joined (it is possible to join without brazing filler metal or flux).

Effects of the invention] According to the present invention, by setting pressure welding conditions, it is possible to join iron pipes and copper pipes in a constant and reliable manner in a short time, unlike brazing work that was conventionally performed mainly by hand. can be done. Material costs and man-hours are significantly reduced, and this operation can be automated, resulting in significant quality and economic effects.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the main part press-fitted into an iron pipe and a copper pipe, and FIGS. 2 and 3 are cross-sectional views of the main part illustrating the state in which the press-fit parts are pressed together by resistance heating. 1... Copper pipe, 2... Iron pipe, 3.4... Resistance plate, 5.6... Electrode. Stem 1 mouth'$2 Japanese tea 3 lo

Claims (1)

[Claims] 1. A method of pressure welding an iron pipe and a copper pipe, which comprises press-fitting an iron pipe into the end of the copper pipe, and pressurizing the press-fitted part between the copper pipe and the iron pipe while applying electricity and heating.