JPS5942061B2 - Additive for smelting and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a smelting additive containing magnesium metal.

Magnesium metal has been widely used in recent years as a smelting additive, such as a desulfurization additive for hot metal during metal smelting and an additive for producing spheroidal graphite cast iron.

These smelting additives are added to molten metal at high temperatures, so magnesium, which has a relatively high vapor pressure,
When used in the form of pure magnesium, a rapid reaction occurs, which is extremely dangerous, and it is difficult to obtain stable reaction results.

Conventionally, when magnesium is used as a smelting additive, various methods have been proposed for suppressing the reaction when adding magnesium.

For example, impregnated coke or sponge iron with magnesium Fe-8i-Mg, Ni-M
g.

There is a method using a magnesium alloy such as Si-Mg.

However, the method of adding an alloy is not necessarily a preferable method, as unnecessary metals other than magnesium are inevitably added, resulting in contamination of the processed product with impurities.

The present inventors conducted various studies on additives for smelting using magnesium metal, and found that a molded body obtained by molding and heat-treating magnesium metal containing magnesium oxide is an extremely preferable additive for smelting. Ta.

The ratio of magnesium oxide and magnesium metal used in the method of the present invention is not particularly limited, but 9 parts by weight of magnesium oxide to 5 to 90 parts by weight of magnesium metal.
The standard amount is 5 to 10 parts by weight.

The above ratio can be determined as appropriate depending on the amount of sulfur in the molten metal to which it is added.

In the method for producing metallic magnesium, metallic magnesium obtained by the so-called carbon reduction method, which is obtained by reducing magnesium oxide with carbon at high temperature, is collected as dust containing magnesium oxide, carbon, etc., but in the present invention, This dust is used as a raw material for the molded body.

The high-temperature carbon reduction reaction of magnesium oxide proceeds reversibly within a certain temperature range, so in order to efficiently obtain the reaction product, the reaction product must be removed from the temperature range as quickly as possible. Needs to be cooled.

This cooling is carried out, for example, by bringing the reaction product into contact with a water-cooled plate, or by bringing the reaction product into contact with a cooling gas such as nitrogen or argon.

The metallic magnesium in the dust obtained by such a method, especially using a cooling gas, is an ultrafine powder, and the surface of the metallic magnesium is generally coated with magnesium oxide, which further enhances the effects of the present invention. It is something.

The dust is molded using a conventional molding machine in an inert atmosphere such as nitrogen or argon, and then subjected to a subsequent heat treatment.

Molding is carried out into shapes and sizes suitable for handling, such as granules, pellets, spheres, and nodules.

The conditions for heating the molded product are based on the melting point of magnesium metal,
Preferably it is carried out at temperatures up to 1100°C.

When the heating temperature is close to the melting point of metallic magnesium (approximately 650°C), metallic magnesium is dispersed and condensed into particles.
At temperatures between 00°C and 900°C, the metal magnesium condenses into layers and acts as a binder, resulting in a strong molded product.

However, if the temperature is higher than necessary, e.g. 1100℃ or higher,
It is not preferable to carry out the heat treatment in this way because there is a lot of vaporization loss of metallic magnesium.

The heat treatment is performed in an inert atmosphere such as nitrogen or argon.

The additive obtained by the method of the present invention forms an extremely strong molded product because the molten magnesium metal acts as a binder.
Easy to handle.

Further, since the coexisting magnesium oxide acts as a diluent for metallic magnesium, when it is added to molten metal, a rapid reaction of metallic magnesium does not occur, and an extremely stable reaction result can be obtained.

Next, the present invention will be explained with examples.

Example 1 Magnesium oxide was reduced with carbon at 1,850°C, and the resulting product was introduced into a cooling chamber with a nitrogen gas flow and cooled to produce metallic magnesium dust (magnesium oxide 21.5 wt %, magnesium metal 72.0wt%
, 4.7 wt% carbon) was pressure molded (500 kg/cI'It) into a diameter of 30 m/m and a thickness of 10 m/m using a pressure molding machine sealed with nitrogen.

This molded product was heat-treated at 700° C. in an argon atmosphere.

The molded product had strong hardness.

A ductile pig iron desulfurization test was conducted using this molded product.

The desulfurization test device used was one with a carbon plunger.

The magnesium molded product obtained according to the present invention was added to ductile pig iron (2 kg) maintained at 1350 to 1400°C in a nitrogen atmosphere in the proportions shown in the following table.

For comparison, a test was also conducted in which CaC2, which is normally used for desulfurization, was used in the desulfurization of ductile pig iron using the same equipment.

The conditions and results are shown in the table below.

Claims (1)

[Claims] 1 Metallic magnesium containing magnesium oxide obtained by reducing magnesium oxide with carbon and bringing the resulting reaction product into contact with a large amount of inert gas and quenching it is molded and molded in an inert atmosphere. 1. A method for producing an additive for smelting, which comprises heating the additive at a temperature. 2. The method according to claim 1, wherein the heating is performed at a humidity that is higher than the melting point of metal magnesium and lower than 1100°C.