SU904853A1 - Method of preparing metallic billet to electric contact heating - Google Patents

Description

(54) METHOD OF PREPARING FOR ELECTROCONTACT HEATING OF METAL PREPARATION

one

The invention relates to the processing of metals by pressure and can be used when heating blanks of bar, profile and sheet material before forging and hot stamping.

The known method of electrocontact heating of metal blanks by passing an electric current through the blank, as a result of which heat is generated in the blank 1.

The widespread use of this method is limited by the difficulty of ensuring reliable electrical contact with the workpiece.

Even with good quality processing of the surfaces of the contacts and the workpiece, their connection may not be ideal. The contact resistance and current density at the points of contact are greater than in other parts of the workpiece. As a result, local overheating occurs under the contacts.

There is a method of electrocontact heating of metal blanks, in which the indicated disadvantage is eliminated by using contacts from the molten material. In this case, the method of preparing for the electric contact heating of the preform consists in that the conductive capacitance is filled with a melted electrically driven material and placed in it the end of the preform 2.

The disadvantage of this method is increased complexity, since the ends of the workpiece must be bent beforehand, and after heating or after stamping, respectively, straighten or cut off these ends.

The purpose of the invention is to reduce the complexity of the process.

The goal is achieved by the fact that, according to the method of preparing for the electrical contact heating of a metal billet, the conclusion is that the conductive capacitance is filled with molten electrically conductive material and the end of the preform is placed into it, filling the capacitance 20 with an electrically conductive material is formed above the edge of the capacitance of a convex meniscus not less than the thickness of the billet billet and place this end above the edge of the tank.

The physical essence of the method is based on the fact that metal melts have the highest surface tension among liquids, for example, platinum is 1820 DL LH at 2000 ° C, at mercury at 20 ° C - 484 dyn / cm, and for comparison, water at 20 ° C - 72.8 dyn / cm.

This solution allows the billet to contact the liquid metal above the edges of the container in which the liquid metal is located, which eliminates the need to bend the ends of the billet to immerse them in the liquid metal.

The drawing shows a diagram explaining the implementation of the proposed method.

Cups 1 made of copper and connected to the secondary winding 2 of transformer 3 are placed into contacts 4 of a fusible alloy, for example Wood's alloy, the glasses 1 being filled with liquid contacts 4 to form a convex meniscus 5 on which the workpiece 6 is placed. isolating and reducing heat loss, the workpiece rests on ceramic pins 7. Example. In two glasses of red copper, connected to the secondary winding of a transformer with a power of 50 kW, put liquid contacts made from Wood's alloy. The beakers are preheated to the melting temperature of the Wood alloy (tfu, 68 ° C) and 6 of them pour the Wood alloy in a liquid state until a convex meniscus is formed. The inner diameter of the glass is 50 mm, the height of the convex meniscus is 2 mm. On the convex menisci of both contacts lay the workpiece in the form of a strip of titanium alloy with a thickness of 1.5 mm and dimensions in plan of 50x300 mm. Heating is effected up to 900 ° C.

The advantage of the proposed method in comparison with the known one is that it does not require preliminary preparation of the blanks (bending of the ends), which is especially important when heating the core blanks

such as angles, channels, I-beams, etc., i.e., labor intensity is reduced.

In addition, the proposed method allows full use of the workpiece for deforming, since the contact points do not undergo any physical irreversible changes and can move freely, which makes it possible to carry out shaping without stopping the heating.

The advantage of the method consists in the almost complete absence of waste material of the material being heated, since in the known methods, under the contacts on the workpiece, an allowance of 15–20 mm along the length of the workpiece is left to ensure the required current density and uniform heating of the workpiece. In the proposed method, it is sufficient to give an allowance along the length of the workpiece 2-5 mm in the case of heating in the clamp or to warm without allowance in the case of heating separately from the deforming device.

Claims (2)

1. Trofimov N. D., Sokolov V. E. Equipment for hot stamping with electric heating. M., “Mechanical Engineering, 1972, p. nineteen. 2. USSR author's certificate No. 706170, cl. B 21 J 1/06, 10.07.78 (prototype).