JPS63210232A - Manufacture of steel for high-carbon wire rod excellent in wiredrawability - Google Patents

Abstract

PURPOSE:To obtain a steel excellent in wiredrawability, by charging specific amounts of powder consisting of SiO2, CaO, and Na2O into a molten high-carbon steel which is deoxidized by using Si and Mn and in which the value of Mn/Si is regulated so as to prevent the formation of nonmetallic inclusions. CONSTITUTION:A molten steel for wire rod is deoxidized by using no Al but Si and Mn, and C content and the value of Mn/Si are regulated to 0.25-1.00% and >=1.7, respectively. The molten high-carbon steel is tapped into a ladle, etc., into which a powder consisting of 30-45% SiO2, 30-45% CaO, and 10-40% Na2O is charged by >=200g per ton of molten steel. By the above method, the formation of Al2O3 is prevented and nonmetallic inclusions are softened (Si-Mn-Ca-Na-O type) with good reproducibility. Further, the nonmetallic inclusions can surely be controlled into ones having ductile structure. Accordingly, the steel for high-carbon wire rod excellent in wiredrawability can be manufactured with good reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application) The present invention relates to a method for manufacturing a high carbon wire steel having excellent wire drawability among carbon steels used for cord wires, piano wires, and the like.

(Background of the invention and prior art) Ultra-fine wires such as cord wires and piano wires used in radial tires are generally made from hot-rolled high carbon killed steel.
．． It is manufactured by making a 5Wφ wire rod and subjecting it to several cold drawing processes (wire drawing process) while also using patenting in between. One of the causes of wire breakage during wire drawing is at2o3. Nonmetallic inclusions with poor ductility, such as 5in2, are formed and the drawability of steel is inhibited. Therefore, there is a method to make the inclusions harmless by changing the form of the deoxidized product to one that does not have a negative effect on ductility. It was proposed (Japanese Unexamined Patent Publication No. 50-71507) that Si, M for deoxidizing molten steel was used to make the deoxidized product into a spessartite composition.
A method has been used to adjust the amounts of n and At added. This method is excellent in that it focuses on controlling the shape of inclusions, but because it uses At, hard A220. , and the nonmetallic inclusions cannot be completely softened, which poses a problem in terms of accuracy in controlling the shape of the inclusions.

(Summary of the Invention) In order to solve such problems, the present invention aims to prevent the formation of Az=os generated as non-metallic inclusions by deoxidation, and to reliably soften the non-metallic inclusions. It does not use deoxidizing aluminum, which is the source of Az and os, and performs deoxidation with Si and Mn, and is a powder with a low melting point in an amount that sufficiently reacts with the deoxidation products present in molten steel. The present inventors discovered that the formation of At203 can be prevented by adding a material (quadrant having a composition that is ductile during hot rolling) and that nonmetallic inclusions can be reliably controlled to be soft, and the present invention has been completed. It is something.

That is, without using At as a deoxidizing agent, Mn
/ Sin! :30-45 staff, OaO: 30
The method is characterized in that powder consisting of Na2O: 10-45% and A2O: 10-0% is charged at an amount of 2 oor or more per ton of molten steel.

(Detailed Description) As mentioned above, the present invention deoxidizes C1125 by using Si and Mn without using any ht as a deoxidizing agent.
~1°0096, 810230~45% for high carbon steel molten steel adjusted to have an Mn/Si ratio of 1.7 or more
, Oao 30-45%, Nan.

By adding powder consisting of 10 to 40 particles in an amount of 92002 or more per ton of molten steel, which is an amount that sufficiently reacts with non-metallic inclusions in molten steel, the generation of ht, os harmful to wire drawability is prevented, and soft (51-M) with good reproducibility and non-metallic inclusions.
Next, the reason why the amount of C and Mn/S1 are limited as described above in the present invention will be explained.

C should be at least 0.25% to ensure the strength of the product.
However, if it exceeds 1.00%, workability deteriorates, so α is set at 25 to 1.00%.

S10 is difficult to stretch when the nn/s1 ratio is less than 1.7.
! 1 because system inclusions increase and significantly impede wire drawability.
．． Must be 7 or more.

The present invention also regulates the addition of ht and 5i02
- By introducing powder consisting of OaO-5i02, the composition of non-metallic inclusions can be reproducibly determined <Sl-Mn-C!
It controls to a-Na-0, but B10
1- slo, the lowest melting point in the OaO binary system, /
Nano is added to the flux having a composition of OaO == 1 so that inclusions with sufficient ductility are formed at the hot rolling temperature (1000 to 1200°C), and if the mixing ratio is less than 10% Na, inclusions are formed. There is no ductility effect of Nan.

It has been found that at 40% or more, the effect is saturated and the cost increases, so in the present invention, 5i02 3
0-45 qb, OaO50-45%, Na201
By using a powder with a composition of 0 to 40,
It elongates long after hot rolling and produces harmless inclusions during cold wire drawing.

The amount of powder to be added is 2,001 or more per ton of molten steel, preferably 1
-1.500 r or more. Since deoxidation products in molten steel are produced in the range of about 50 to 2002 per ton of molten steel, if the powder is less than 2001, the amount of reaction with the deoxidation products is insufficient and the inclusions are not sufficiently produced. There is no particular upper limit to the amount of input, but excessive input is economically wasteful, so it is generally preferable to set it to 5.000 f or less.

In addition to the method of introducing the powder from the top, it is also possible to inject the powder into the molten steel together with an inert gas such as Ar gas through an immersion lance, and the latter is preferable in order to shorten the reaction time. . In the case of top charging, it is preferable to use inert gas or electromagnetic stirring to stir the molten steel in order to promote the reaction.

Next, embodiments of the present invention will be shown and characteristics will be explained.

Steel having the chemical composition shown in Table 1 is melted in a 70-ton converter to produce Fe-81, which has a low content of ht as an impurity.
After adding Fe-Mn and Fe-Mn as a deoxidizing agent, the steel was tapped in such a way as to suppress the outflow of slag at the end of the tapping process, and the powder was placed in the ladle (powder 1
') 40 qbC! ao -30% 5i02-30
% Nano (see symbols A-E, L-O) powder and (powder 11) 45% OaO-451SiO
, -10 Na2O powder was added in various amounts shown in Table 1. After that, 30017 m of Ar gas was added to the molten steel.
After stirring the molten steel for 7 minutes at a flow rate of 1.5 in., a slab was cast by a continuous casting method.

For comparison, continuous casting was also carried out in the same manner without the addition of powder. The obtained slab was hot rolled to produce a wire rod of 5.5+mφ, and the wire rod was inspected for inclusions by microscopic observation. Inspection area to be measured 4
The number of non-ductile inclusions with an inclusion width of 3 μm or more and the number of ductile inclusions with an inclusion width of 3 μm or less were counted in Circle 2, and the results are shown in Table 1. Next, this 5.5+a+φ wire was cold-worked to 5.5fiφ→2.6■φ and lead patented→1.
3fiφ, lead patenting → [L5mφ → α2wxφ
In the process, the wire was drawn to α2rmφ. The number of wire breaks at this time is also shown in Table 1 as a wire breakage index (=an index expressed by the number of wire breaks when drawing 1 ton of steel, with the maximum value of the comparative steel being 100).

As is clear from the results in Table 1, when 92,009 particles per ton of molten steel or more were introduced by the method of the present invention, the number of non-ductile inclusions decreased significantly and the number of ductile inclusions increased. The composition of the inclusions is 51-Mn-0a-Na-0, and since the inclusions are controlled to be soft, most of the inclusions are drawn into a fine shape with a width of less than 3 μm by hot rolling. This effect was hardly observed when the input amount was less than 2 o o y / ) tons, and a large number of non-ductile inclusions were produced as in the case where no powder was added. The number of non-ductile inclusions is reflected in the number of wire breaks during wire drawing.
In the steel of the present invention, the breakage index is about 0 to 25, whereas
The comparison steel showed a very high result of 80 or more.

As explained above, according to the present invention, the formation of non-ductile non-metallic inclusions that inhibit the wire drawability of steel can be prevented by the simple operation of adding powder, and the non-metallic inclusions can be reliably made ductile. The composition can be controlled. Therefore, high-carbon wire steel with excellent wire drawability can be produced with good reproducibility, and the advantage it brings to actual operations is extremely large.

Claims (1)

[Claims] SiO_230-45%, CaO30-45%, Na
Powder consisting of _2O10-40% per ton of molten steel 200
1. A method for producing high carbon wire rod steel with excellent wire drawability, characterized in that a steel for high carbon wire rods with excellent wire drawability is introduced.