JPS647140B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an electrode used in a remelting furnace such as a vacuum arc melting furnace or an electroslag melting furnace in a double melting process for producing an alloy. It is something.

[Conventional technology]

As a melting method for manufacturing alloys, a double melting method has been adopted in recent years for the purpose of reducing segregation, improving hot workability, and reducing nonmetallic inclusions. This double melting method involves first melting the blended raw materials in a vacuum induction furnace, arc furnace, atmospheric high frequency induction furnace, etc., then manufacturing an ingot, and using this ingot as an electrode, it is used in a vacuum arc melting furnace, electroslag melting furnace, etc. The final product, ingot, is produced by remelting the ingot. By the way, the remelting electrode used in the double melting method has been manufactured by simply casting after primary melting as described above.

[Problems to be solved by the present invention] When an electrode is made by casting a high carbon cobalt alloy (components: 1% carbon, 4% tungsten, 30% chromium, residual cobalt), the electrode is There was a problem that part of the liquid fell off, making it impossible to redissolve it. That is, in the electrode used for remelting, a large temperature difference occurs between the melted portion and the solid portion slightly separated from the melted portion, and this temperature difference generates a large thermal stress between them. In this case, there is no problem if the electrode is highly ductile, but if the electrode is simply cast from the above-mentioned high carbon cobalt alloy, the ductility of the electrode is extremely low. For this reason, there was a problem in that the electrodes cracked due to thermal stress during remelting, and a portion of the cracks fell off.

[Means for solving problems]

As a means to solve the above-mentioned problems, this invention produces an ingot after first melting the blended raw materials, hot-forging the ingot, and then
Heat treatment is performed to remove distortion.

〔Example〕

Examples of the present invention will be described below. In this embodiment, in the double melting method shown in the conventional example, the steps of hot forging treatment and strain relief heat treatment are added to the ingot produced after primary melting.

The method of the present invention is similar to the conventional method in that the blended raw materials are first melted to produce an ingot, but the method of the present invention further includes the following steps. That is, first, the ingot is subjected to hot forging treatment. The purpose of this hot forging treatment is to change the forged structure of the ingot to a forged structure and increase the ductility of the ingot. In this case, the training ratio is
The time is determined depending on the type of alloy, and for example, in the case of the above-mentioned high carbon cobalt alloy, it is set to a minimum of about 1.1 s.

Next, the hot forged product is subjected to strain relief heat treatment for the purpose of further increasing ductility. The heat treatment temperature in this case is appropriately determined depending on the type of alloy. For example, in the case of the above-mentioned high carbon cobalt alloy, the temperature is set at 1000°C to 1250°C.

The remelting electrode manufactured by the above process has high ductility; for example, in the case of the above-mentioned high carbon cobalt alloy, the elongation of the ingot after primary melting is about 0.5% or less; The elongation after hot forging and strain relief heat treatment is approximately 7%. Therefore, this remelting electrode can sufficiently cope with the thermal stress generated in the electrode during remelting, and can therefore prevent the electrode from cracking and falling off as a result.

[Experimental example] In order to confirm the effects of the present invention, a high carbon cobalt alloy (component: carbon
1.1%, tungsten 4.5%, chromium 31%, iron 1
%, residual cobalt) was hot forged at 1200℃ with a forging ratio of 1.2S, and then heat-treated at 1200℃ for 1 hour to remove distortion, then air-cooled, and its elongation was measured. However, it was 5.8%.

Next, when remelting was carried out using this ingot as an electrode, the electrode did not crack or fall off at all, and smooth remelting could be carried out.

On the other hand, for comparison, the elongation of an ingot manufactured after primary melting made of a high carbon cobalt alloy with similar components used in the conventional method was measured and found to be 0%.

Next, when the conventional ingot was used as an electrode for remelting, the electrode cracked and part of it fell off.

〔Effect of the invention〕

As explained above, according to the method for manufacturing an electrode for remelting of the present invention, an ingot is manufactured after primary melting of the blended raw materials, and this ingot is hot forged, and then subjected to heat treatment for strain relief and then remelted. Since the melting electrode is manufactured, the ductility of the remelting electrode can be increased, and therefore,
It is possible to prevent the remelting electrode from cracking due to thermal stress during remelting, and it is possible to prevent a part of the electrode from falling off due to this.

Claims (1)

[Claims] 1. A method for producing electrodes used in a remelting furnace in the double melting process in alloy production using the double melting process, in which an ingot is produced after primary melting of the blended raw materials, and this ingot is heated. A method for producing an electrode for remelting, which comprises performing a heat treatment to remove strain after forging.