DE3102732A1 - METHOD AND DEVICE FOR ELECTRIC PRESSURE WELDING - Google Patents

Description

Hamburg, January 26th, 1981

Method and device for electric pressure butt welding

The invention relates to a method for electric pressure butt welding, in particular of Workpieces with a large weld cross-section, e.g. sheet metal or pipes.

That is to say, it is primarily workpieces whose cross-sectional shape largely deviates from that of a circle or a square with the smallest circumference in relation to the area, ie with the same cross-sectional area, it has large outer dimensions.

In the case of an electric press butt weld, the sheet metal ends to be welded should pass through current heated to welding temperature and then welded by pressing them together. the A prerequisite for a press butt weld is the uniform heating of both workpiece ends the entire welding cross-section. This is where the real problem lies. Besides, the warming must be like this done quickly that there is no

Scale forms, which then remains in the weld seam when it is pressed against one another or upsets. Only a very small amount of scale is produced when upsetting pressed out of the seam.

For uniform heating, a uniform contact resistance over the entire welding cross-section is required and an even power distribution is required. By always existing bumps of the abutting cross-sectional areas, there is no uniform contact. One possibility to achieve a uniform contact of the abutting cross-sectional areas; consists in removing the unevenness of the surfaces to be welded by passing current until they are doughy to be heated and then pressed wide, so that an even contact of the two to be welded Cross-sectional areas comes about. Then the heating and the pressing together would then take place or upsetting the workpieces, i.e. the actual welding process takes place. But also this procedure leads - as was found in the context of the present invention - not to a satisfactory one Result.

Because the initially protruding bumps, which are then pressed wide in a doughy state, have then already such a high temperature that during the subsequent heating over the entire welding cross-section these points reach the welding temperature much sooner than the other points. Uniform heating is therefore not achieved.

The invention is based on the object of proposing a method with the aid of which the described Disadvantages are avoided and a perfect butt weld is achieved with simple means.

The solution to this task is the actual welding program, consisting of heating and Upsetting, a separate contact program to achieve a uniform over the entire weld cross-sectional area Upstream contact.

Due to the temporal separation of the contact program preparing the welding from the following one Welding program are on the one hand excessive pressure forces when pushing the bumps wide and on the other hand unequal temperatures avoided during the actual welding process.

In a further embodiment of the invention, the contact program consists of a high contact force and a large amperage, as a result of which bumps in the contact plane are heated and pressed wide will. The contact program is then made up of a short, currentless cooling and heat equalization period completed. In this way there is an even contact over the entire cross-sectional area of the weld and a uniform starting temperature and a uniform contact resistance for the subsequent Welding program achieved.

Finally, according to the invention for carrying out the method according to the invention, the to be welded Workpieces must be clamped very briefly between well-cooled electrodes.

The invention makes it possible to keep the contact program so short in time that the risk of a Scale formation is avoided.

For this purpose, the two ends, e.g. of a rim ring, are placed in two opposing clamping devices a butt welding machine, each with a water-cooled electrode and a clamping jaw.

One clamping device is arranged on a carriage which is driven so that the Sheet edges are pressed against each other with a preselected force program. One electrode the preselectable current is supplied, which is fed via the sheet metal edges and the other electrode to the power source flows back.

In order to be largely independent of external influences and to ensure a uniformly reproducible welding temperature To obtain a further embodiment of the method according to the invention is that the end of the heating within the actual welding program by running through an adjustable Path is given, the path being a measure of the welding temperature for a given contact force is.

This can also be achieved by another embodiment of the method according to the invention, which is characterized in that the end of the heating within the actual welding program by the Achievement of a given quadratic current narrowing (It) is given,

The welding process according to the invention is now divided into:

1 . Contact time:

During this time, heating and spreading the unevenness creates an even contact across the entire width of the sheet.

2. Cooling down time :

During this time, the uneven heat resulting from the contact time cools down.

3. Heating and upsetting time :

During this time, the sheet metal edges are evenly upset over the entire width brought and compressed.

Only the cooling time brought success.

Claims (5)

NAC H O ε Γ. - *! '■ HT 31Ο27 .. "2 Hamburg, January 26th, 1981 Process and device for electric pressure butt welding. PATENT CLAIMS 1.) Process for electric pressure butt welding, especially of workpieces with a large weld cross-section, e.g. sheet metal or pipes, characterized in that the actual welding program (heating and upsetting) is a contact program upstream to achieve uniform contact over the entire cross-sectional area of the weld will. 2. The method according to claim 1, characterized in that during the contact program by a hthe Contact force and a large current strength Unevenness in the contact plane is heated and pressed wide and that the contact program by means of a short-term, currentless cooling and heat equalization time is terminated. 3. Device for performing the method according to claims 1 and 2, characterized in that that the workpieces to be welded are clamped very briefly between well-cooled electrodes. 4. The method according to claim 1, characterized in that that the end of the heating within the heating within the actual welding program through an adjustable path can be traveled through, the path being a given contact force Measure for the welding temperature is. 5. The method according to claim 1, characterized in that the end of the heating within the actual Welding program by reaching a specified quadratic amount of current (It) given is.