JPS61143511A - Production of steel for high-carbonwire having excellent drawability - Google Patents

Abstract

PURPOSE:To produce a steel for a high-carbonwire having excellent drawability with good reproducibility by charging an adequate amt. of powder consisting of a specific ratio each of SiO2, MnO and Al2O3 to a molten high-carbon steel consisting of a specific compsn. contg. C, Mn,Si, etc. CONSTITUTION:The powder of the spessartite compsn. consisting of 35-55% SiO2, 45-65% Mn and 10-30% Al2O3 is charged at about >=200g, more prefer ably about 500-5,000g for each one ton of the molten steel to the molten high- carbon steel contg. 0.25-1.00wt% C and adjusted to >=1.7 Mn/Si ration. The above-mentioned powder is preferably adjusted to about 200-1,000mum grain size and the timing for the charging is not particularly limited as far as the powder is added after the addition of a deoxidizing agent. The resulted product of deoxidation is adjusted to the spessartite compsn. by the above-mentioned powder charged to the molten steel. The high-carbon steel which can be satisfac torily drawn and prevents snapping during drawing and has good drawability is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing high-carbon wire rods with excellent wire drawability with good reproducibility.

(Prior art) Ultrafine wire rods for cord wires or music wires used in radial tires, conveyor belts, high-pressure hoses, etc. are generally made of high carbon killed steel and hot rolled into wire rods with a diameter of approximately 5.5 mm. It is manufactured by subjecting it to cold drawing (wire drawing) several times, with patenting in between.

One of the causes of wire breakage during wire drawing of high carbon steel is that nonmetallic inclusions with poor ductility such as AQ203.5i02 are formed in the steel due to the addition of deoxidizing agents, which inhibits the wire drawability of the steel. can be mentioned. Therefore, it is possible to reduce the amount of nonmetallic inclusions by adjusting the deoxidizing agent or adjusting other steel components, or by making the inclusions harmless by changing their morphology to one that does not have a negative effect on ductility. Many proposals have been made to prevent disconnections caused by physical objects.
For example, JP-A No. 49-30217, JP-A No. 50-715
No. 07, No. 50-81907, No. 50-117618
No. and No. 51-31612).

Among these conventional techniques, JP-A-50-71507 proposes a carbon steel in which a deoxidizing agent component to be added is adjusted so that nonmetallic inclusions have a subesatite composition. Nonmetallic inclusions with a spessartite composition generated by deoxidation are elongated during rolling and wire drawing processes, so
It exhibits the advantageous property of hardly inhibiting wire drawability. In addition, shesatite is SiO2-AQ203-
Corresponds to the eutectic point of the ternary system of Mn0, and the melting point is approximately 1140°C
Because of its low carbon content, it can easily float and separate during casting in the ingot-forming method. Therefore, nonmetallic inclusions having a spessartite composition are effective in significantly improving the wire drawability of steel from both the standpoint of making inclusions harmless and reducing them.

(Problems to be Solved by the Invention) In order to make the deoxidized product have a composition of spessartite, S1% Mn, A! for deoxidizing molten steel must be used. Conventionally, the method of adjusting the amount of 2 added appropriately has been taken, but the composition of the deoxidized product may vary due to variations in the amount of oxygen in the molten steel before deoxidation or the influence of the refractory lining of the container that receives the molten steel. There was a problem that the accuracy was poor because it often deviated from the target value.

Therefore, if a method for manufacturing high carbon guild steel for wire rods that can reliably and reproducibly convert nonmetallic inclusions generated by deoxidation into a spessartite composition is provided, the wire drawability of the steel will be further improved. It will be.

(Means for Solving the Problems) The present inventors introduced into molten steel an amount of powder having a spessartite composition sufficient to react with the deoxidation products present in the molten steel, that is, nonmetallic inclusions. By doing so, inclusions can be reliably controlled within the spessartite composition range even if there are changes in the molten steel composition or influences from refractories, and even if the amount of inclusions increases, it will remain in spessartite. As long as the inclusions are stretched during rolling and wire drawing, the inventors have discovered that an increase in the amount of inclusions does not impede wire drawability, and have completed the present invention.

Here, the present invention provides high carbon steel molten steel containing 0.25 to 1.00% C and adjusted to a Mn/Si ratio of 1.7 or more, SiO2: 35 to 55%, MnO: 45～
65% and A12203=10 to 30% of spessartite powder in an amount of 200 g or more per ton of molten steel.

(Function) This invention is extremely effective in manufacturing not only the above-mentioned cord wire but also high carbon wire rods that are widely used by wire drawing. is due to the following reason.

C (carbon) is required to be at least 0.25% in order to ensure the strength of the product, but if it exceeds 1.00%, workability deteriorates, so it is set at 0.25 to 1.00%.

The reason why the Mn/Si ratio is set to 1.7 or more is that when the Mn/Si ratio is 1.7 or more, non-metallic inclusions generated during deoxidation during the blooming-wire rolling process are elongated and the product becomes thin. This is because, although the drawability of the wire is significantly improved, when the Mn/Si ratio is less than 1.7, SiO2-based inclusions that are difficult to draw increase, and the drawability is significantly inhibited.

In addition, in this specification, % and ratio are weight % and weight ratio unless otherwise specified.

It is preferable to suppress P and S as impurity elements as much as possible. In particular, for wire rods for cord wires, it is preferable to aim for P: 0.015% or less and S: 0.010% or less.

As mentioned above, in the conventional manufacturing method, the composition is adjusted to the spessartite composition range while minimizing the amount of nonmetallic inclusions produced. The composition of the deoxidized product did not necessarily reach the target value.

According to the present invention, since powder having a spessartite composition is added in an amount sufficient to react with non-metallic inclusions in molten steel, the deoxidized product is reliably adjusted to a spessartite composition without being affected by the above-mentioned effects. can do. As a result, the amount of inclusions increases as a whole, but most of the inclusions with a subesatite composition are caused by hot rolling and wire drawing.
It has a fine fibrous form of less than μm and does not inhibit wire drawability. Furthermore, even if a small number of wires with a diameter of 3 μm or more are observed, most of them exhibit ductility and the drawability is not impaired. As a result, high carbon swi with good wire drawability is obtained despite the increase in the amount of inclusions, and wire breakage during wire drawing is reduced.

The attached drawing shows a ternary phase diagram of MrlO%203SiO2, and spessartite is 5i0 as indicated by diagonal lines in the figure.
2:A(2203:Mn0=5:2:3
It corresponds to the composition range with the lowest melting point in this ternary system centered on (molar ratio), and the hot rolling temperature (1000-1200℃
) and has ductility. SiO2:3 of powder used in the present invention
5-55%, MnO:, 45-65%, AQ203:1
The composition range of 0 to 30% corresponds approximately to the shaded area in the accompanying drawings. Note that the powder used in the present invention does not have to be spessartite itself, and may be a powder of the three types of oxides within the above spessartite composition range, but spessartite is preferable from the viewpoint of shortening the reaction time.

The amount of powder to be added is 200 g or more, preferably 500 g or more per ton of molten steel. Since the amount of deoxidation products in molten steel is about 50 to 200 g per ton of molten steel, the powder
If it is less than g, the amount of reaction with the deoxidized product will be insufficient, and it will not be possible to make all the deoxidized products have the target composition. There is no particular upper limit to the amount of input, but excessive input is economically wasteful and may have negative effects, so it is generally 5000 g.
The following is preferable.

In addition to charging the powder from the top, the powder may also be blown into the molten steel through an immersion lance together with an inert gas such as static gas, and the latter is preferable in order to shorten the reaction time.

In the case of top charging, stirring of the molten steel by inert gas or electromagnetic stirring can also be used to promote the reaction, which is preferable.

The timing of adding the powder is not particularly limited as long as it is after the addition of the deoxidizing agent. For example, a method may be adopted in which a deoxidizing agent is introduced into a ladle during tapping in a converter, and powder having a spessartite composition is introduced into the tapping ladle or blown into the ladle using an immersion lance.

The composition of the powder to be charged may be within the range of the spessartite composition specified in the present invention, but it can also be varied as appropriate within the above range depending on the type and amount of the deoxidizing agent used. For example, when the deoxidizing agent is mainly composed of AQ2o3, powder containing a large amount of MnO or 5i02 can be added. The particle size of the powder is preferably about 200 to 1000 microns.

Generally, wire rods, which are the raw materials for high-grade products such as cord wires, are manufactured using the ingot method, but since the method of the present invention is very effective in preventing deterioration of wire drawability, it is not limited to the ingot method, but is also economically Steel with good wire drawability can be obtained even if the continuous casting method is used, which is advantageous in this regard. According to the agglomeration method, nonmetallic inclusions including added powder float and separate in the mold, and because the amount of inclusions is large, this floatation and separation easily occurs. Therefore, the amount of inclusions in the steel is reduced. In the continuous casting method, nonmetallic inclusions are not separated, but since the cooling rate is fast, the inclusions are finely precipitated in the steel, which is advantageous for wire drawability. As mentioned above, as long as the inclusions have a spessartite composition, the inclusions have ductility and are drawn into a fibrous form during rolling and wire drawing, and become even finer.

The following examples illustrate the method of the invention.

(Example) Steel having the chemical composition shown in Table 1 below was melted in a 707 converter, and the steel was tapped in such a way as to suppress the outflow of slag at the final stage of tapping, and 35% 5i02 50% MnO- was placed in the ladle. 15%A (22
03 or 42%SiO2 42%Mn0-16%AQ2
Powder with a spessartite composition of 03 (average particle size is 5
00 μm) was added in various amounts shown in Table 1. Thereafter, Ar gas was blown into the molten steel at a flow rate of 300 β/min for 7 minutes to stir the molten steel, and then it was cast by a continuous casting method. For comparison, continuous casting was performed in the same manner without adding powder.

The obtained slab was hot rolled to produce a wire rod with a diameter of 5.5 mm, and the wire rod was inspected for inclusions by microscopic observation. The measurement area is 44mm2, and the inclusion width is 3μ.
For wires of m or more, count the number of non-ductile inclusions (alumina type, gear roughsite type) that are considered harmful to wire drawability, and the number of ductile type inclusions (subesatite type) that are considered harmless. Ta. The results are shown in Table 1.

Next, this 5.5 mm φ wire rod was cold-worked to 5.5 mm φ - 2.6 mm φ lead patenting 1
．． 3mmφ lead patenting 0.5mmφ-40,
The wire was drawn to 0.2 mm φ in the 2 mm φ step. The number of wire breaks at this time is also shown in Table 1 as a wire breakage index (=an index representing the number of wire breaks during ml ln wire drawing, with the maximum value of the comparative steel being 100).

As is clear from the results in Table 1, when 200 g or more of powder having a spessartite composition is introduced per ton of molten steel according to the method of the present invention, the number of non-ductile inclusions is significantly reduced. The total number of inclusions, including ductile ones, has also decreased. This is because most of the inclusions have a width of 3 μm due to hot rolling.
It is drawn into a fine form that does not inhibit the drawability at all,
This indicates that inclusions with a width of 3 μm or more are also ductile inclusions. This effect was hardly observed when the amount added was less than 200 g, and a large number of non-ductile inclusions were generated as in the case where no powder was added. The result of the number of non-ductile inclusions is reflected in the result of the number of wire breaks during wire drawing, and while the wire breakage index of the invention steel is about 12 to 30, it is 80 or more for the comparative steel. It was very expensive.

(Effect) As shown above, according to the present invention, 5i02K12
With the simple operation of adding 0s MnO-based powder, it is possible to prevent the formation of non-ductile non-metallic inclusions that inhibit the wire drawability of steel, without worrying about changes in the amount of oxygen in the steel or the effects of refractories. Nonmetallic inclusions can be reliably controlled to have a desired ductile composition. Therefore, it becomes possible to manufacture high-carbon wire rods with excellent wire drawability with good reproducibility, which is a great advantage for actual operations.

[Brief explanation of the drawing]

The attached drawing is a phase diagram showing the spessartite composition range in the MnOpH203SiO2 ternary system. Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent Attorney Hirose Do - (1 other person) iOz

Claims (1)

[Claims] Contains C: 0.25 to 1.00%, and the Mn/Si ratio is 1.
．． SiO_2:3 to high carbon steel molten steel adjusted to 7 or higher
5-55%, MnO: 45-65% and Al_2O_
3: Powder with a spessartite composition consisting of 10 to 30%,
A method for producing a high carbon wire rod with excellent wire drawability, the method comprising adding 200 g or more per ton of molten steel.