JPS629663B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method for dephosphorizing high carbon ferromanganese. Generally, Mn is known as an essential alloying element for improving the mechanical properties of steel, and is usually found in high-grade steels.
The Mn component is added in an amount of 1% or more (hereinafter "%" indicates weight %). Also, these days, much higher than steel
High manganese non-magnetic steel with Mn content (Mn content of approx.
18%) has been developed and is attracting attention as a non-magnetic material that is cheaper than stainless steel. As a method of adding Mn to such steel, the method of adding ferroalloy to molten iron is generally adopted, and as this ferroalloy for adjusting Mn is the cheapest, it is highly priced. Carbon ferromanganese is widely used. This high-carbon ferromanganese is usually manufactured by reducing Mn ore with carbon in an electric furnace, but at this time, the P oxide in the raw material is also reduced and enters the metal, so ordinary raw materials are not used. The high carbon ferromanganese manufactured by
This was a high value. Therefore,
This high carbon ferromanganese with high P content is
When used as a source, this ferroalloy releases P into steel.
This resulted in an increase in the P content of the steel product itself. On the other hand, P in steel is known to be a harmful impurity that reduces the mechanical properties of steel. Therefore, from the perspective of improving steel quality, it is important to reduce the P content as much as possible, and at least quantity
It is necessary to suppress it to 0.04%. Therefore, Mn
In cases where an increase in P in the steel caused by the ferroalloy for adjustment is a problem, electrolytic manganese is currently used to adjust the Mn. However, although this electrolytic manganese contains almost no P, it is very expensive and increases the cost of the steel itself manufactured using it. Several attempts have been made to obtain ferromanganese with a low P content by dephosphorizing carbon ferromanganese. Conventionally, the only known relatively effective method for dephosphorizing high carbon ferromanganese was to treat powdered high carbon ferromanganese with Ca or Mg at a temperature of approximately 900°C. However, this method had the following drawbacks. That is, (a) the high carbon ferromanganese to be dephosphorized needs to be finely reduced to a particle size of about 0.06 mm, which increases the cost of pulverization and requires a great deal of cost and time for post-processing. (b) In order to uniformly dephosphorize the entire amount of ferromanganese to be treated, large amounts of expensive Mg and Ca are required. (c) Dephosphorization efficiency is not very good, and P after treatment
Only products with a content of up to 0.1% can be obtained. Therefore, the above dephosphorization methods have only been tested on a laboratory scale and cannot be implemented on an industrial scale. Therefore, the same applicant first focused on the low price of high carbon ferromanganese, and in order to dephosphorize this high carbon ferromanganese more efficiently and make it a cheap and high quality Mn source. Ferromanganese is made into granules or powder, which contains one or more of Mg and Ca to supplement P, and the rest is
A method for dephosphorizing high carbon ferromanganese, which consists of allowing a flux consisting of one or more of MgCl ₂ and CaCl ₂ to act in an inert gas atmosphere at a temperature above its melting point and below the melting point of high carbon ferromanganese. Furthermore, we have proposed that an alloy containing easily oxidized alloy components such as Cr and Mn be made into granular or powdered form, and a flux containing metal Ca to supplement P, with the remainder being NaCl, is added at a temperature above its melting point. They also proposed a method for dephosphorizing the alloy by operating it in an inert gas atmosphere at a temperature below the melting point of the alloy. These prior inventions were made based on the following findings. That is,
Since Ca easily reacts with C to generate CaC ₂ , for example, even if a flux consisting of Ca and CaF ₂ is added to molten iron with a high carbon content and a high temperature of 1600℃, CaC ₂ will not be generated. dephosphorization does not proceed, and therefore, for example,
Dephosphorization of high-temperature molten iron using a Ca-containing flux such as Ca-CaF ₂ system was limited to the dephosphorization of low-carbon molten iron, but the ambient temperature is approximately 1000℃. At low temperatures, even solid granular carbon-saturated high-carbon ferromanganese
Dephosphorization proceeds with a flux consisting of Ca and CaCl ₂ or MgCl ₂ or NaCl, and in this case, dephosphorization and decarburization proceed simultaneously, that is, high carbon ferromanganese in a solid state at low temperatures. This was based on the discovery that dephosphorization progresses in a dephosphorizing flux containing Ca even if carbon is saturated. However, although this dephosphorization method can perform efficient and good dephosphorization, it still has the problem that the fluxes such as Ca and Mg are expensive and that care must be taken when handling them for safety reasons. was. From the above-mentioned perspective, the present inventors first studied the basics of the Ca dephosphorization mechanism in order to find a flux consisting of an inexpensive and easy-to-handle additive component to replace Ca and Mg, which play the role of supplementing P. As a result of our investigation, we found that in the case of high-carbon ferromanganese that is in a solid state at low temperatures, dephosphorization proceeds with a dephosphorization flux containing Ca, even if it is saturated with carbon. reacts with mode C
It is based on the thermodynamic principle that it is easier to produce CaC ₂ while P is easier to produce Ca ₃ P ₂ at lower temperatures. First, it has a unique structure in which high-P segregation areas are uniformly distributed in a low-P matrix, and there are many cracks that often cut across these segregation areas. They came to the conclusion that the dephosphorizing flux enters into the grains through the cracks, making it easier to preferentially remove P present in a high-activity state. Therefore, the present inventors proposed that at low temperatures,
If Ca binds more easily to P than C, then
Even if CaC ₂ , which is cheap and easy to handle, is used instead of Ca, the Ca generated by the decomposition of CaC ₂ may combine with P and dephosphorization progresses, so further research is needed. As a result of stacking, it contains CaC ₂ ,
If a flux consisting of one of CaCl ₂ , MgCl ₂ , or NaCl is used at a relatively low temperature above the melting point of the flux and below the melting point of high carbon ferromanganese, dephosphorization of high carbon ferromanganese will proceed effectively. I discovered that. Therefore, the present invention has been made based on the above knowledge, and involves making high carbon ferromanganese into granules or powder, and applying it in an inert gas atmosphere.
A flux consisting of one of CaCl ₂ , MgCl ₂ , and NaCl and CaC ₂ is heated above the melting point of the flux,
Moreover, it is characterized in that dephosphorization can be carried out efficiently by operating at a temperature below the melting point of high carbon ferromanganese. Furthermore, the dephosphorization method of this invention will be explained in more detail. The high carbon ferromanganese targeted in this invention has, for example, 6 to 7% C and 60 to 80% Mn.
%, but the ingredients are not limited to these, and may be ones that are outside this ingredient composition range or ones that contain Si, etc. In short, any high carbon ferromanganese is eligible. be. This high carbon ferromanganese needs to be made into granules or powder before dephosphorization treatment, but the usual method of crushing or crushing the lumpy high carbon ferromanganese, or the process of sizing an ingot into a commercially available product, can be done using a sieve. Any method can be adopted, such as the method used or the method of producing grains or powder by an atomization method or the like. The particle size is adjusted depending on the desired level of dephosphorization. That is, the smaller the particle size is, the better the dephosphorization is, but for effective dephosphorization, the particle size is preferably 5 mm or less, preferably 2 mm or less. However, even if it is coarser than this, dephosphorization will proceed, albeit to a lesser extent. The flux used is composed of one of CaCl ₂ , MgCl ₂ , or NaCl and CaC ₂ , of which CaC ₂ is a substance that provides Ca, which is an active ingredient for dephosphorization, and CaCl ₂ , MgCl ₂ , NaCl are
It forms a melt together with CaC ₂ and at the same time serves as a solvent for the dephosphorization product Ca ₃ P ₂ . The proportion of CaC ₂ present in the flux is preferably 3 to 50% of the total flux. This is because when the CaC ₂ present in the flux is less than 3% of the total flux, effective dephosphorization is difficult to proceed, whereas when the CaC ₂ present in the flux is more than 50% of the total flux, the melting point of the flux is This is because it becomes too high and no improvement in dephosphorization can be expected. However, among those used with CaC ₂ , only when using NaCl, it is important to make the amount of CaC ₂ high, for example, 20% or more, if high dephosphorization is desired. Of the flux raw materials, it is natural to use anhydrous CaCl ₂ , MgCl ₂ , or NaCl, but since these substances are highly deliquescent, care must be taken not to absorb moisture. This is because when moisture is present, it reacts with CaC ₂ to produce acetylene, reducing the amount of active ingredients and reducing the dephosphorizing ability. CaC ₂ of flux raw material
The desulfurizing agent may be one commonly used as a desulfurizing agent, but it goes without saying that it may also be a chemical-grade desulfurizing agent with higher purity. The amount of flux to be used is determined based on the amount necessary for the target high carbon ferromanganese to contact the flux. Specifically, it is preferable that the flux is at least 100 kg or more per ton of high carbon ferromanganese, but even if the amount is less than this, it is possible to increase the chance of contact between the flux and high carbon ferromanganese by stirring during the treatment. We can expect great dephosphorization. From the results of various studies, 200
It was concluded that ~300Kg/ton is the best. The contact treatment temperature between the high carbon ferromanganese and the flux must be higher than the melting point of these fluxes and lower than the melting point of the high carbon ferromanganese. Specifically, the temperature is generally in the range of 800 to 1200°C, although it varies depending on the composition of the flux. Preferably, the temperature is about 1000°C for good dephosphorization. Normal oxide refractories (for example, MgO) can be used as reaction vessels for the treatment, but the flux used in this invention tends to corrode refractories, so if this becomes a problem,
A metal container made of metals and alloys such as Fe, Mo, and W and having a melting point higher than the processing temperature is preferable. It is also possible to use a graphitic reaction vessel in the method of the invention using CaC ₂ . Since the processing atmosphere is a reductive dephosphorization using CaC ₂ , it must be non-oxidizing, and Ar
It is important to carry out the process in a reactive gas such as Further, the longer the treatment time, the higher the dephosphorization rate, which is preferable, but a treatment time of 4 hours or less is generally sufficient. The flux can be separated from the high carbon ferromanganese after the dephosphorization treatment by dissolving only the flux with water, but washing with dilute hydrochloric acid allows faster elution of the flux. However, this is just one example of a separation method, and it goes without saying that any method may be used as long as it can separate high carbon ferromanganese and flux. Next, the present invention will be explained by examples. First, high carbon ferromanganese having the composition shown in Table 1 was crushed and separated using a sieve, with a particle size of 0.3 to 1 mm and a particle size of 1 to 2 mm:
500g was subjected to contact treatment with flux using a high frequency furnace (graphite was used as the heating element) in an Ar atmosphere of 1 atm under the condition that a specified amount of the flux composition shown in Table 2 was used. I did this.

[Table] The sample after the contact treatment was immersed in water to elute the flux, washed with dilute hydrochloric acid, and analyzed for components to measure the P content in the high carbon ferromanganese. The results are also shown in Table 2.

[Table] From the results shown in Table 2, it is clear that high carbon ferromanganese can be efficiently dephosphorized by the method of the present invention. As described above, according to the present invention, high carbon ferromanganese can be dephosphorized with high efficiency through relatively simple processing operations, and the properties of steel can be improved without increasing the P content. Industrially useful effects are brought about, such as the ability to obtain ferroalloy for manganese adjustment at low cost.

Claims (1)

[Claims] 1. High carbon ferromanganese is made into granules or powder, and in an inert gas atmosphere, CaCl ₂ ,
1. A method for dephosphorizing high carbon ferromanganese, which comprises applying a flux consisting of MgCl ₂ , one type of NaCl, and CaC ₂ at a temperature above the melting point of the flux and below the melting point of the high carbon ferromanganese.