JPS5952940B2 - Dephosphorization method for high carbon ferromanganese - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for dephosphorizing high carbon ferromanganese, which is the cheapest ferroalloy as a source of manganese.

Generally, manganese is an essential additive element for improving the mechanical properties of steel, and so-called high-grade steels contain 1% or more of manganese.

Furthermore, high manganese nonmagnetic steel, which has recently attracted attention as a nonmagnetic material that is cheaper than stainless steel, has about 18% manganese added.

On the other hand, phosphorus is an element that inhibits the mechanical properties of steel.

For this reason, it is desirable to reduce phosphorus in steel as much as possible, and it is necessary to keep it to at least 0.04% or less.

High carbon ferromanganese is the cheapest ferroalloy used as a manganese additive in the steelmaking process.

This high carbon ferromanganese is mainly produced by an electric furnace method.

In the electric furnace method, manganese ore is produced by carbon reduction in an electric furnace, but at the same time, phosphorus oxides in the raw material are also reduced and enter the ferroalloy, resulting in a phosphorus content of 0.15 to 0. ．．
It reaches as much as 20%.

Therefore, when this ferroalloy with a high phosphorus content is used as a manganese source in the steelmaking process, there is a problem in that phosphorus enters from the ferroalloy and the phosphorus content in the finished high-grade steel increases.

Therefore, if an increase in the phosphorus content in the finished high-grade steel due to this ferroalloy becomes a problem, it is unavoidable to use manganese metal, which contains almost no phosphorus and is produced by an expensive electrolytic method.

Until now, research has been conducted on the dephosphorization of high carbon ferromanganese.

However, the only method that has been found in the laboratory is to apply Ca or Mg to high carbon ferromanganese at about 900°C, and this method requires pulverizing the high carbon ferromanganese to a particle size of about 0.06 mm. However, pulverization and post-processing require a lot of cost and time, and a large amount of Ca or Mg is required to uniformly dephosphorize the entire amount processed, and the dephosphorization efficiency is poor, with zero
．． There was a problem that it contained about 10% phosphorus.

On the other hand, as a method for denitrifying low-carbon ferrochrome,
9-73321 and JP-A-50-143712 disclose that Ca-CaC
A method of dephosphorizing by applying a flux consisting of 1□ or Mg-MgCl° has been proposed.

The present invention relates to a method for dephosphorizing and denitrifying alloys containing alloy components that are easily oxidized, and in which a flux consisting of Ca-CaC1□ or Mg-MgCl2 is applied to Co and low carbon ferromanganese of 12% or less. A method for dephosphorization by dephosphorization is described.

The chemical reaction of the dephosphorization method according to the above conventional invention is, for example, C
When a-CaC1□ is used, it is thought that Ca and P proceed through the reaction of formula A below.

3Ca+2P-→Ca3P2. ．． ．． ．． ．． ．． A However,
In the presence of C, this Ca will generate CaC2 through the reaction of formula B below.

Ca+2(, −→CaC2・−・・−B Therefore,
Conventionally, it was thought that a dephosphorization method using Ca could not be applied to molten iron with a high C content of 5% or more, such as the subject of the present invention.

An object of the present invention is to provide a dephosphorization method that can perform dephosphorization of high carbon ferromanganese on an industrial scale.

This invention contains 2 to 50% of one or both of Mg and Ca.
The remainder is Mgcl.

, a flux consisting of one or two types of Cacl□,
High carbon ferromanganese containing granular or powdered C: 5% or more is treated in a non-oxidizing atmosphere at a temperature above the melting point of the flux and below the melting point of the high carbon ferromanganese. This is a method for dephosphorizing carbon ferromanganese.

The reasons why the flux according to the present invention described above is effective for dephosphorizing high carbon ferromanganese are considered to be the following four points.

The first point is that since the activity of phosphorus in the metal is greatly increased by the presence of carbon, dephosphorization easily progresses in the case of high carbon ferromanganese with C: 5% or more.

To be more specific, the activity of phosphorus P in the metal, that is, aP, is expressed by the formula 0.

ap=fp(%P) ■Here f
p is the activity coefficient, and in the case of a Fe-p ternary dilute solution, fP=1, but when carbon is present, P undergoes an interaction.

The interaction coefficient ec−J′ of C with respect to the activity of P,
! :fP holds the relationship of formula (2).

1ogfP=c-'x (%C) @
here,.

←'=0.079, and when (C) is present at 5% or more like high carbon ferromanganese, from the formula ■, f
P=2.5, and in the case of high-carbon ferromanganese containing a large amount of carbon, the activity of P is more than twice that of low-carbon ferromanganese, and it can be pointed out that dephosphorization progresses more easily.

The second point is as follows.

When dephosphorizing a solid metal by immersing it in a flux, a high diffusion rate of phosphorus in the solid metal is necessary for effective dephosphorization.

Generally, at the same processing temperature, a low melting point alloy exhibits a faster phosphorus diffusion rate than a high melting point alloy, but in the case of high carbon ferromanganese, the melting point is lower due to the iron-manganese alloy and the large amount of carbon it contains. It is pointed out that the melting point of about 1250°C is lower than that of low carbon ferrochrome, which is about 1700°C, and therefore works advantageously for dephosphorization.

The following points can be pointed out as the third point.

Phosphorus in solid high-carbon ferromanganese is not uniformly distributed, and segregated parts containing nearly 2% phosphorus are dispersed in the matrix with an average phosphorus content of 0.01% or less.
It is thought that dephosphorization proceeds more favorably than when phosphorus is uniformly dissolved.

The fourth point is that the lower the temperature, the more easily calcium bonds with phosphorus than with carbon, and dephosphorization progresses more favorably.

Furthermore, there are many cracks in the granular high carbon ferromanganese, and flux easily enters the granules through these cracks, so even if the high carbon ferromanganese is not pulverized and has a large particle size, it is relatively good. It is thought that dephosphorization progresses.

The method of this invention will be explained in detail below.

The high carbon ferromanganese may be of any composition range as long as the carbon content is 5% or more.

Next, it is necessary to make this into granules or powder, but there are various methods, such as crushing or crushing the lumps, using a sieve when sizing a commercially available product, or manufacturing using an atomization method. Available.

The particle size varies depending on the desired dephosphorization level, but for effective dephosphorization, the particle size is 10 mm or less, preferably 5 mm.
It is best to set it to the following.

The flux used contains 2 to 50% of one or both of Mg and Ca, with the remainder being MgCl2. CaCl2-1
It consists of one species or two species.

This flux is Mg, Ca is M, 'p2 and Ca3
Rukoto has the ability to create P2 and dephosphorize, and Mg and Ca are M
Since it can mutually form a melt with MgCl2 at temperatures above 700 to 800°C, dephosphorization proceeds effectively and uniformly even with small amounts of Mg and Ca. CaCl2 is Mg5P2. It is effective in dephosphorizing high carbon ferromanganese because it acts as a solvent for Ca3P2.

At least one of Mg and Ca in the flux is
If it is less than 2%, effective dephosphorization will not proceed, and if it exceeds 50%, the dephosphorization efficiency will not improve any further.
Contains at least one of Mg and Ca in the range of
The rest is Mgcl.

, Cacl. At least one of these constitutes the flux.

The amount of flux used is preferably at least 100 kg or more per ton of high carbon ferromanganese.

However, even if the weight is less than 100 kg, good dephosphorization can be achieved by performing a treatment such as stirring to improve contact between the flux and the high carbon ferromanganese.

In addition, to expect a good dephosphorizing effect, 200
The use of ~400 kg of flux is preferred.

Next, regarding the processing temperature, since the solid metal is dephosphorized, it needs to be higher than the melting point of the above-mentioned flux and lower than the melting point of high carbon ferromanganese.

Note that when Mg is used in the flux, unless it is treated at a temperature below its boiling point, Mg will evaporate and dephosphorization will not proceed effectively.

Therefore, the optimum processing temperature is preferably about 900°C to 1100°C.

Furthermore, since Mg and Ca are used in the flux, the processing atmosphere needs to be a non-oxidizing atmosphere in order to prevent reactions between MgO and CaO. For example, it is preferable to perform the processing in an inert gas such as argon.

Although a long treatment time is preferable in order to obtain high dephosphorization efficiency, sufficient dephosphorization can be achieved with a treatment time of 3 hours or less.

Further, the reaction vessel used for the treatment may be a vessel made of an ordinary oxide refractory such as MgO.

However, since the above-mentioned flux is easily eroded when used, Fe.

A metal container made of a metal or an alloy such as Mo or W and having a melting point higher than the processing temperature is preferable.

However, if Ca is not used in the flux, a graphite container can be used.

In other words, Ca reacts with graphite to form carbide, but Mg
does not produce this, so a graphite container can be used as the reactor.

The ability to use a graphite container in this manner is a feature of the treatment of high carbon ferromanganese according to the present invention.

Finally, to separate the high carbon ferromanganese and flux after dephosphorization, there are methods such as dissolving only the flux with water, or washing with dilute hydrochloric acid to elute the flux even faster, but what other methods are available? Needless to say, any method that allows separation can be used.

Examples according to the present invention will be shown below to clarify its effects.

High carbon ferromanganese consisting of the components shown in Table 1 below was crushed and sieved to obtain samples with two particle sizes: one with a particle size of 0.3 to 1 mm and one with a particle size of 3 to 4 mm.

Dephosphorization was carried out in an Ar atmosphere of 1 atm, using a container made of stainless steel or graphite, by reacting 500 g of high carbon ferromanganese with fluxes having various compositions under the treatment conditions shown in Table 2.

Each sample after treatment was washed with dilute hydrochloric acid after eluting the flux in water, and the phosphorus content was examined.

The results are shown in Table 3 together with the dephosphorization rate.

As is clear from the above results, when the flux according to the present invention is applied to a sample with a particle size of high carbon ferromanganese of 1 mm or less, a dephosphorization rate of 90% or more can be obtained.
It can be seen that even when the particle size is 3 to 4 mm, a high dephosphorization rate of 70% or more can be obtained.

Claims (1)

[Claims] l A flux containing 2 to 50% of one or two of Mg and Ca and the remainder consisting of one or two of Mgcl□ and Cacl□ in granular or powder form C: 5% or more high carbon ferromanganese A method for dephosphorizing high carbon ferromanganese, characterized in that the dephosphorization is carried out in a non-oxidizing atmosphere at a temperature above the melting point of the flux and below the melting point of the high carbon ferromanganese.