JPS5825737B2 - Tetsu − Kuromugokino Seizouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides Fe-
This invention relates to a method for directly manufacturing Cr alloy.

Conventionally, in order to produce a Fe-Cr alloy, a carbon-based reducing agent and a solvent such as quicklime, silica sand, etc. are added to chromium ore, and the chromium ore is melted and reduced in an electric furnace.

However, smelting reduction using the electric furnace method requires a large amount of electrical energy to reduce chromium and separate gangue accompanying chromium ore as slag, and the high melting point of the Fe-Cr alloy makes it difficult to perform high-temperature smelting. It has drawbacks such as requiring the use of expensive refractories.

In order to lower the processing temperature in this smelting reduction method using an electric furnace, we obtain sintered ore that has been partially reduced as a pretreatment before charging it into the electric furnace. An improved method in which energy is used only for melting and reducing the remaining unreduced chromium is proposed in Japanese Patent Publication No. 36-2153.

However, this improved method also has the disadvantage that the reduction treatment requires a long time, and since slag separation is still performed in an electric furnace, there are the same problems as described above.

Unlike the electric furnace method that uses electrical energy, the present invention directly produces Fe from chromium ore by solid reduction.
-Providing a method for manufacturing a Cr alloy.

Generally, chromium ore is (Mg, Fe)0(Cr, AI
, Fe)20s, and FeO and Cr2O3 are reduced, and its chemical equilibrium equation is expressed by the following two equations.

7Cr203+27 to 2Cr7C3+21CO3FeO
+4C, 1: Fe5c +3CO In order to make this reaction proceed to the right, it is more beneficial to reduce the activity of each component in the production system.

In other words, in carbon (solid) reduction of chromium ore,
It is beneficial to reduce the partial pressure of CO by lowering Pco (equilibrium partial pressure) and to reduce the concentration and activity of the reduction product Cr7C3.

Based on this idea, the present inventors first
As a result of various experimental studies on means of reducing the activity of chromium ore, we have found that Fe-containing substances (iron, iron oxide, iron powder, etc.) are added to chromium ore to reduce the total (Cr+Fe') in the raw material.

Weight ratio of Cr amount to amount Cr/ (Cr + Fe
,' is 0.6 or less, and when a lumpy mixture made by adding a carbonaceous reducing agent to this mixture, pulverizing it into a fine powder, and granulating it is subjected to solid reduction treatment, It is believed that the concentration of Cr7C3 in the production system is kept low and the reaction inevitably proceeds, promoting the reduction of chromium and achieving this reduction in a very short time in a relatively low temperature range even under atmospheric pressure. I found out.

By blending Fe-containing substances (iron and iron oxides) into the raw materials as described above, the obtained solid reduced product becomes a form that is highly suitable for magnetic beneficiation and is used to separate concentrate and gangue. It has been found that magnetic selection can be carried out extremely effectively.

Here, the upper limit of 0.6 for the weight ratio Cr/(Cr+F e ) of the amount of Cr to the total amount of (Cr+Fe) in the raw material is:
This was confirmed experimentally, and as shown in Figure 1, the solid reduction was carried out at 1250°C for 8 hours under normal pressure by changing the Cr/(Cr+Fe) ratio in the raw materials and according to the example below. In processing, iron ore is reduced in Cr content (Cr + Fe) <
This is because it has been found that when added within a range of 0.6, reduction of 90% or more is achieved.

FIG. 1 also plots the case where only chromium ore without iron ore is added, and in this case, the Cr reduction rate is reduced.

Note that the lower limit of the ratio of Cr/(Cr+Fe) is Fe-Cr
Although it is related to the purpose of the alloy, it is approximately 0.15.

Note that the reduction treatment according to this method is preferably carried out at a temperature of 1150°C or higher and lower than the melting point.

As described above, one feature of this method is that an appropriate amount of Fe-containing material such as iron ore is blended with Cr ore and solid reduction treatment is performed at a relatively low temperature. As is clear, the reduction reaction can proceed more advantageously when carried out under reduced pressure.

The magnetic beneficiation treatment after this reduction treatment is also a characteristic step of the present invention, and this magnetic beneficiation has succeeded in extremely effective recovery of concentrate.

In other words, as a result of repeated experiments by the present inventors to improve the efficiency of magnetic beneficiation, we found that chromium ore (chromium oxide)
By adding Fe or Fe oxide to the concentrate, the magnetic properties of the concentrate can be increased, and by pulverizing the raw material and adding boron oxide or a boron oxide-containing substance to the raw material, the efficiency of magnetic separation can be greatly improved. It became clear.

The effect of this addition of boron oxide on magnetic separation is remarkable,
This is thought to be due to the phenomenon that agglomeration into particles of a certain size, which is desirable as concentrate particles, occurs during the solid reduction treatment.

Therefore, in the present invention, the addition of boron oxide is one of the requirements, and Fe is added to the Cr oxide so that the weight ratio Cr/(Cr+Fe) of the amount of Cr to the total amount of (Cr+Fe) in the raw material is 0.6 or less. In addition to adding a carbonaceous reducing agent and, if necessary, a binder, boron oxide or a boron oxide-containing substance is added in an amount of 0.1 to 1 in terms of boron oxide.
0% by weight is added and mixed and granulated into a lump, this lump is heated under atmospheric pressure or reduced pressure to reduce it to a solid, and the obtained solid reduced product is separated by magnetic beneficiation to separate the gangue component. A method for producing an Fe-Cr alloy is provided.

Here, the effect is exhibited when the amount of boron oxide added is 0.1% or more, but since the addition of 10% or more increases the economic burden, it is preferably added in the range of 0.1 to 10%.

Further, when performing the reduction treatment under reduced pressure, it is preferable that the degree of vacuum is approximately 5 Torr, which is the maximum degree of vacuum during heating.

Note that preferable results can be obtained even if the reduction treatment is performed in an inert gas atmosphere.

The effect of adding boron oxide is shown by a test example: Chromium ore (Cr; 39% by weight, Fe; 12% by weight) 104 parts by weight Iron ore (Fe; 67% by weight) 65 parts by weight Carbon
A blended raw material consisting of 32 parts by weight is uniformly mixed in a fine powder state with or without the addition of boron oxide as shown in Table 1, and after granulation, solid reduction is performed under the reduction treatment conditions shown in Table 1 to obtain solid reduced pellets. was crushed into about 100 meshes and subjected to magnetic separation under magnetic separation conditions of 600 Gauss. As a result, Cr was recovered as shown in Table 1, and Fe--Cr alloy concentrate was obtained.

From the results in Table 1, compared to Control Example A without the addition of boron oxide, Example B, in which 10 parts by weight of boron oxide was added and the same reduction treatment was performed, showed an improvement in the Cr reduction rate, and the Cr magnetic separation efficiency. It can be seen that it has increased dramatically.

Even in Example C, in which the reduction treatment time was shortened and the amount of boron oxide added was reduced, the Cr reduction rate and Cr magnetic separation efficiency were greatly improved**.

Further, the present method will be explained by giving specific examples, and its effects will be shown.

Example 1 Table 2 shows the compositions (% by weight) of the chromium ore and iron ore tested.

Other test materials include electrode powder as a carbonaceous reducing agent;
A reagent was used for boron oxide, and these test materials were blended in the amounts shown in Table 3. After adding and mixing 1% by weight of bentonite as a binder, the samples were charged into a ball mill and ground to 250 meshes or less.

This fine powder blended raw material was granulated into green pellets with a diameter of about 10 to 15 mm, kept at 200°C for 3 hours, dried, charged into a carbon resistance heating furnace, and placed in a normal pressure Ar atmosphere. 12
Heating was carried out to 50°C for 2 hours and at 1250°C for 1 hour.

Table 4 shows the pellet analysis values (wt%) after this solid reduction treatment.
Shown below.

The obtained reduced pellets were pulverized to a particle size of 100 mesh or less, and subjected to magnetic separation at 600 Gauss.

The concentrate grade (wt%) after this magnetic separation was analyzed and shown in Table 4.
An e-Cr alloy was obtained.

The Cr magnetic separation efficiency in this example was 91%.

Example 2 The same test materials as in Example 1 were mixed in the amounts shown in Table 5.

This mixed formulation was ground to a particle size of 250 mesh or less using a ball mill and granulated into green pellets having a diameter of about 10 to 15 mm.

After drying the raw pellets by keeping them at 200° C. for 3 hours, they were placed in a resistance heating vacuum furnace and subjected to solid reduction treatment under the following conditions.

Heating conditions: 2 hours to 1250℃ 1 hour at 1250℃ Vacuum degree: 0.4 Torr at the start of heating Maximum 1.7 Torr during heating After cooling 0.3 Torr Table 6 shows the analytical values of this solid reduced pellet.

The reduced pellets were pulverized to a particle size of about 100 mesh or less, and subjected to dry magnetic separation at 600 Gauss.

The obtained concentrate was analyzed and powdered Fe-C of the grade shown in Table 6 was obtained.
An r alloy was obtained.

The Cr magnetic separation efficiency in this example was 89%.

As described above, according to the method of the present invention, reduction treatment is performed at a low temperature and in a short time, and magnetic separation is subsequently performed extremely effectively, so that Fe-Cr alloy can be produced with an energy advantage, and low-grade chromium ore can also be produced. Combined with the advantage of being fully usable, it has a significant economic effect.

The obtained Fe-Cr alloy can be provided at low cost for manufacturing Cr alloy steel and stainless steel.

[Brief explanation of drawings]

FIG. 1 is a graph of experimental results in which the influence of the ratio of Cr/(Cr+Fe) on the Cr reduction rate was investigated.

Claims (1)

[Claims] 1. Carbon is added so that the weight ratio Cr/(Cr + Fe) of the amount of Cr to the total amount of (Cr + Fe) in the raw material is 0.6 or less.
A Fe-containing substance is blended with r-oxide, and in addition to the addition of a carbonaceous reducing agent, boron oxide or a boron oxide-containing substance is added and mixed in an amount of 0.1 to 10% by weight in terms of boron oxide, and the mixture is granulated into a lump. The lumps are heated under atmospheric pressure to reduce them to solids,
A method for producing an Fe-Cr alloy, characterized in that the obtained solid reduced product is subjected to magnetic beneficiation to separate gangue components. 2 C so that the weight ratio Cr/(Cr+Fe) of the amount of Cr to the total amount of (Cr+Fe) in the raw material is 0.6 or less.
A Fe-containing substance is blended with r-oxide, and in addition to the addition of a carbonaceous reducing agent, boron oxide or a boron oxide-containing substance is added and mixed in an amount of 0.1 to 10% by weight in terms of boron oxide, and the mixture is granulated into a lump. A method for producing an Fe-Cr alloy, which comprises heating a lump under reduced pressure to reduce it to a solid, and magnetically sorting the obtained solid reduced product to separate the gangue component.