JPS58171519A - Treatment of molten iron - Google Patents

Abstract

PURPOSE:To efficiently evaporate and remove low b.p. metals such as Cu, Sn, Zn, As, S and Mn from molten iron or molten steel contg. C and S, by keeping the molten metal at a specified temp. above the melting temp. and by holding it in a specified vacuum atmosphere under agitation. CONSTITUTION:Molten iron or molten steel contg. C and Si is kept at a temp. about 50 deg.C above the melting temp., and it is held in a vacuum atmosphere of 10<-1>-10<-4>mm.Hg under agitation. For example, molten cast iron contg. 2.5-4.2% C and 0.5-4% Si is kept at >=1,200 deg.C and subjected to said treatment. By the treatment, only low b.p. metals such as Cu, Sn, Zn, As, S and Mn are evaporated and removed without reducing the C and Si contents.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a treatment method for effectively removing harmful elements from molten iron used in the production of iron castings and steel products.

In general, various industrial metal materials are produced using scrap steel and pig iron as mixed raw materials. In the production of , it is essential to use uncontaminated and pure raw materials. This is due to the fact that the basic constituent elements of these tough materials are Fe and Cl.
In addition to 8i, Nagi, Cu%8n, Zn, Pb%mul,
This is because if a large amount of elements such as 8 are contained, the material properties such as toughness are inhibited, and at the same time it becomes difficult to manufacture. For example, in the case of duct tie 7%/cast iron, Mn, Cu, 8
Elements such as n make it difficult to turn the structure into ferrite even by heat treatment, and elements such as B, 8 and 8 inhibit graphite from becoming spheroidal. Also, in the case of steel materials such as stainless steel, if -1(3u, 8u, S, etc.) are contained in an excess of 9, this will cause problems such as promoting intergranular corrosion and lowering the impact value.

However, due to the problem of resource depletion and the diversification of materials such as alloy steel and plated steel, it has recently become difficult to obtain the necessary melting raw materials such as high-quality scrap, which has forced an increase in manufacturing costs. has been done.

As a countermeasure to this problem, attempts have been made to develop a manufacturing method that does not rely on the availability of pure raw materials, that is, a manufacturing method that involves removing harmful elements such as iron from the molten iron after melting the compound. For example, conventionally known means for removing iron oxide include blowing oxygen or adding iron oxide to remove it by oxidation. However, this method has the problem that not only i but also originally useful 8i, 0, etc. are actively removed, and there are many problems with p1 removal, effectiveness, and economy. 41 known molten iron processing methods near) Teja, Ou, 8n, Zn, ? , 8 The reality is that no means have been found to effectively remove other trace amounts of harmful elements.

In view of such technical problems, the present invention! From Fe-C-8i hot metal or molten steel used for the production of 111 cast iron castings and strong steel materials, there is no loss of the useful C and 8iK that are originally required, and harmful calm, false, 8u% is removed.
We have succeeded in providing Shin-Ku with an innovative method for processing molten iron that can effectively remove only the elements Zn, Mus, and 80%.

The processing method of the present invention uses appropriate temperature control, stirring means, and high vacuum treatment in combination under specific conditions to remove copper, Cu, 8n, and Z from the target #gong or molten steel.
It is preferable to selectively evaporate and remove only low-boiling point metals such as n, mu 3.8, etc. f:R.

The treatment method of the present invention uses a ladle 4 of re-0-8i bath pig iron or molten steel melted in a melting furnace such as a cupola, blast furnace, or electric furnace.
L< is 10-'smHg~ when the hot metal is drawn into an induction furnace, the temperature of the hot metal or molten steel is kept at about 50°C or more higher than the melting temperature in the tube vacuum treatment equipment, and stirring is not added.
This is usually carried out by keeping the IQ--Hg in a vacuum atmosphere for several tens of minutes. At this time, the required stirring is performed by the electromagnetic induction stirring action in the case of an induction furnace.
Separate mechanical stirring means such as external application of rocking or vibration or starvation stirring may also be used.

In the treatment method of the present invention, EI3Fi which maintains the hot metal or molten steel at a temperature higher than its melting temperature by about 50°C or more is used.
This is to promote the evaporation of low-boiling metal elements, as is clear from the rituals described below. To explain this tEK specifically, for example, hot metal for strong cast iron castings, that is, C2,5~4
, 2 notes, 8i 0.5 to 4.0%, it is necessary to maintain the melting temperature of the bath at 1200° C. or more, which is about 1150° C. or more than 50° C.

In addition, whitening in which hot metal or molten steel is stirred in a vacuum atmosphere increases the contact area between the molten iron and the atmosphere and shortens the processing time. In fact, as evidenced by the Examples described below, the effect of stirring is remarkable.

In addition, in the 9 & process method of the present invention, the bath pig iron or molten steel is heated to 10 m! Ig~10--Keep in a high vacuum atmosphere specified by the dog 3! Ji! The purpose of this is to evaporate and remove only the target low-boiling point metal selectively and in a short period of time. As can be understood from the examples described below, even if a pressure atmosphere exceeding the upper limit is effective for degassing, it is not very effective in removing the harmful metal elements by evaporation; This is because the pressure atmosphere below may lead to loss of useful elements such as 81 and C, and at the same time, it is difficult to use equipment. The so-called vacuum degassing process, in which N, O8, etc. are degassed from molten metal in an atmosphere of several hundred centimeters, is well known in the industry and is a well-known technology, but the present invention specifically .8n, MusJl! (3
This is an epoch-making technical idea that is clearly distinguishable from conventional techniques in that it makes it possible to vaporize and remove metal elements such as u.

Next, a 5iilIi example of the present invention will be briefly explained. Tables 1 to 3 below show examples and comparative examples in which cast iron hot metal was treated and treated under various conditions as hot metal. Here, Table 1 is summarized from the viewpoint of the degree of influence of temperature, Table 2 Fi is summarized from the viewpoint of the degree of vacuum, and Table 3 is summarized from the viewpoint of the stirring effect.

(Next '1#) Table 1 Influence of temperature Table 2 Influence of degree of vacuum Temperature constant 1350℃ Table 3 Influence of stirring (straw waste wave induced stirring) effect temperature 1350
~1400℃ constant vacuum degree 9~5x10-temperature constant stirring power is evaluated by the load power size K, both are 30
As is clear from the results shown in Tables 1 to 6 above, the process according to the present invention involves continuously loading hot metal at a constant temperature in a constant temperature range. When method t'' is carried out, the temperature is 8.
．． A very remarkable evaporation removal effect was obtained for 8n, (As), and a considerably large evaporation removal effect was also observed for Cu. On the contrary, C, which is a useful essential component, 8
There was almost no change in iK, confirming that the treatment method of the present invention can selectively evaporate and remove only harmful low-boiling point metals such as O, O, 8n, Zn, and 1% S. can.

According to the molten iron processing method of the present invention, Fe-C-
Regarding 5t series bath pig iron or molten steel, the harmful Mn and Ou
, 8n, Zn, Mu3, S, and other low boiling point metals can be effectively vaporized and removed. Therefore, the treatment method of the present invention can be applied to 5j! If this is done, the restrictions on the quality grades of compounded raw materials that were conventionally imposed on the melting of strong cast iron and steel materials will be greatly eased, the desired products can be manufactured economically, and the industrial value that contributes to the effective use of resources will be enormous. It is something.

Claims (1)

[Claims] lFe-0-8i hot metal or molten steel is heated to a temperature of 10-'-Hg to 10-'-Hg while being stirred, while being maintained at a processing temperature that is approximately 50°C higher than its melting temperature. Ou, 8n, Zm,
A method for producing molten iron characterized by evaporating and removing low boiling point metals such as 1S%i. 2 Processed molten iron-IIXC2,5~4.2 plow, 8i Q,
Cast iron hot metal containing 5 to 4.0% tube metal and processing temperature 1
200℃ or higher, and low boiling point metals such as Cu, 8n, In% 3.8, Nagi, etc. without causing C1Bit loss.
2. The treatment method according to claim 1, wherein t-evaporation is carried out.