JPS6330182A - Upset butt welding method - Google Patents

Abstract

PURPOSE:To decrease the discarding quantity at a joint end part and to improve the mechanical strength of a joint part by cutting the ends of steel strips in the transverse direction so as to make complemental coupling, fitting the ends to each other and welding the joint part by pressurizing and energizing under specific conditions. CONSTITUTION:The ends of the steel strips are transversely cut (A) to make the complemental coupling, for example, to a wave shape and the cut ends are fitted (B) to each other. Such ends are clamped by electrodes and are butted (C) under 1-100kg/mm<2> pressurizing force. A non-oxidative atmosphere is maintained (D) at said butt part by blowing an inert gas thereto at about 10-300l/min injecting flow rate. The butt part is subjected to upset butt welding (E) by conducting 5-300A/mm<2> current for 0.1-3sec to the butt part. The weld beads generated in the joint part are then removed (F) by a cutter by which the joined steel strip is obtd. (G). The discarding quantity of the joining material is thereby decreased and the sectional area of joining is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an upset butt welding method in which ends of steel strips are pressed together and joined by electrical heating.

(B) Prior Art Conventional methods for joining the ends of steel strips to each other include the following.

A mechanical pressure welding method in which the ends of the materials to be joined are overlapped and joined by pressing or rolling, or a mechanical method in which the ends of the materials are formed into a jigsaw shape to increase the joint cross-sectional area. There is mating, etc. However, these mechanical methods require complicated forming training because it is necessary to increase the joint area of the material ends.
Further, even if the bonding is performed by pressing or rolling, sufficient bonding strength cannot be obtained if an oxide layer remains at the bonding interface.

Therefore, in addition to the above-mentioned mechanical methods, joining methods have been proposed that include arc bath welding, seam welding, and the like. However, this joining method also takes a relatively long time to weld, as it is necessary to weld the entire top and bottom surfaces along the joining line of the materials.
Oxide may be drawn into the joint interface due to burn-through or scattering of the weld bead, and indentation flaws may occur over a wide range of material surfaces during pressure welding.

In order to improve this method, a method of joining using flash butt welding has also been proposed. However, this method also requires a relatively long time to melt the joint, and oxides generated at the melted part tend to get caught up in the joint interface, which causes a decrease in breaking strength. Problems to be Solved by the present invention The problems to be solved by the present invention are to reduce the amount of cutting off of the joining material as much as possible, to maximize the overall joint cross-sectional area, and to easily perform welding.
The purpose is to obtain a butt welding method.

(d) Means for Solving All Problems The upset butt welding method of the present invention involves pressing the ends of steel strips together and joining them by applying 710 volts of heat. cutting in the width direction so as to make a complementary connection; fitting the cut ends of the steel strips together and abutting them with a pressing force of 1 to 100 Kq/ma; and applying a current of 5 to 300 A/- to the abutted portions. 01～
By applying electricity for 3 seconds, all of the above problems are solved.

The method of the present invention can more effectively solve the above problem by placing the abutting portion in a reducing atmosphere during the abutting and energization.

(E) Embodiment An embodiment of the absent butt welding method of the present invention will be described with reference to the drawings.

FIGS. 1A to 1G schematically illustrate the steps of the method of the invention. First, as shown in Figure (A), the ends of the copper strip are cut in the width direction so as to be complementary to each other. Examples of this complementary cutting are shown in FIGS. 2A to 2D. It is preferable that this complementary cutting is made in a shape that allows the total cross-sectional area of the joint to be relatively large, and that the amount of cutting of the joint portion in the post-joining process can be reduced. Typical examples include a waveform (A), a sawtooth shape (B), a gear shape (C), and a jigsaw shape (D), as shown in FIG. The number, pitch, and amplitude of waves are determined by the material, dimensions, etc. of the steel strip.

As shown in FIG. 1, after complementary cutting, the ends of the steel strips are fitted together (I3) and butted against each other with a cutting edge pressure of 1 to 100' K9/mIj (C). In this step, the ends of the copper strip are clamped with electrodes and pressure is applied so that the end surfaces are all in contact.

This fitting and butting process is important for making the @plane current density uniform at the joint of the materials to be joined, eliminating molten layer oxide, and improving the weld structure and mechanical properties due to the hot forging effect. be. When the pressing force is less than IKq/+n++, the contact resistance of all the butt cross sections of the materials to be joined becomes non-uniform, the current density distribution becomes non-uniform, and as a result, non-uniform heating phenomenon occurs in all the butt cross sections. In addition, a cast structure remains due to insufficient forging effect, resulting in a decrease in joint performance. on the other hand,
If the cutting edge pressure exceeds 100 Kq/rra, the force is excessive, resulting in poor bonding such as excessive deformation of the bonded portion or displacement of the bonded surface due to slippage.

Place the butt part in a reducing atmosphere (D). For example, an inert gas such as N2 gas may be sprayed onto the joint. This step is not mandatory.

The injection flow rate of the inert gas is preferably in the range of 10 to 300 e/min. If the flow rate is less than 101/γnin,
The effect of non-oxidizing atmosphere is insufficient. Flow rate is 3001
If it exceeds 7 m1n, no further effect can be expected.

A current of 5 to 300 A/+ol'f 0.1 at the butt part
Apply electricity for ~3 seconds.

This step is necessary to properly adjust the thermal temperature of the cutting edge in order to obtain a molten layer with a uniform thickness with little oxide formation on the joint surface. If the current density is less than 5 A/-, the thickness of the molten layer may become uneven due to insufficient heat input, the finished film layer formed on the molded end surface may not be melted and finely dispersed, and may remain at the bonding interface, or the bonded area may become uneven. Cracks may occur in the rolling direction, leading to a decline in joint performance. Current density is 30 OA
/M or more, excessive heat input causes problems such as burn-through of the molten layer and excessive deformation of the bonded portion, leading to defective bonding.

The energization time is one of the conditions that determines the amount of heat input, and
It is also a condition that affects bonding efficiency. If the energization time is 01 seconds, the heating area will be narrow because the time is too short.
Due to insufficient heat input, a molten layer necessary for pressure welding is not formed, resulting in poor bonding. If the energization time is 3.0 seconds or more, the heating area becomes too wide because the time is too long, and also causes coarsening of crystal grains in the hot part, leading to a decrease in joint performance. When joining hot materials, the problem of temperature drop due to time loss arises.

Finally, as shown in FIG.
).

(f) Effects According to the method of the present invention, the amount of cutting off of the joint end is small;
The mechanical strength of the joint has also been further improved.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the steps of the welding method of the present invention. FIG. 2 is a plan view showing an example of complementary cutting of the end of the steel strip. Patent applicant: Sumitomo Metal Industries, Ltd. (5 other people) (A) (B) figure (C), (O)

Claims (2)

[Claims] (1) In the upset butt welding method in which the ends of the steel strip are pressed together and joined by electrical heating, the ends of the steel strip are cut in the width direction so as to be complementary to each other, and the cut end of the steel strip is Fit them together and butt them with a pressure of 1 to 100 Kg/mm^2, and apply a pressure of 5 to 300 A/m to the butt portion.
An upset butt welding method consisting of applying a current of m^2 for 0.1 to 3 seconds. (2) In the upset butt welding method in which the ends of the steel strip are pressed together and joined by electrical heating, the ends of the steel strip are cut in the width direction so as to be complementary to each other, and the cut end of the steel strip is Fit them together and butt them with a pressure of 1 to 100 Kg/mm^2, and apply a pressure of 5 to 300 A/m to the butt portion.
An upset butt welding method comprising applying a current of m^2 for 0.1 to 3 seconds and placing the abutted portion in a reducing atmosphere.