JPH06346194A - Stainless steel wire rod excellent in wire-drawability - Google Patents

Abstract

PURPOSE:To produce a stainless steel wire rod which is meltable in the air and has superior wire-drawability without excessive regulation of oxygen content. CONSTITUTION:This stainless steel wire rod excellent in wire-drawability which has a composition consisting of, by weight, <=0.15% C, <=1.0% Si, <=2.0% Mn, <=0.05% P, <=0.03% S, 7-30% Ni, 15-25% Cr, and the balance Fe with impurities and in which the inclusions in the steel exist in the form of multiple inclusions including CaO can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel wire rod having excellent wire drawability, which is less likely to be broken during the wire drawing process when wire is drawn to an extremely fine wire diameter, and has a wire mesh or a filter having good corrosion resistance. The present invention relates to a stainless steel wire rod having excellent wire drawability, which is preferably used as a wire drawing material for an ultrafine stainless steel wire used as a corrosion resistant stainless spring for various precision instruments.

[0002]

2. Description of the Related Art Stainless steel wires are often used as extra fine wires due to the miniaturization of various wire mesh or filter meshes and the miniaturization of springs for various precision equipment. The wire may be drawn up to about 50 μm before use.

[0003]

However, in the process of drawing a stainless steel wire having such an ultrafine wire diameter, a wire breakage may occur, which may deteriorate the workability of wire drawing. There was a point.

It is also possible to improve the wire drawability by reducing the oxygen content in the steel by reducing the amount of inclusions and the diameter of inclusions by performing special melting or repeated deoxidation. However, there was a problem that the dissolution cost would increase. Further, when attempting to reduce the oxygen content in steel by deoxidizing Al, there is a problem that the amount of Al ₂ O ₃ which is a hard inclusion increases and the drawability decreases. .

[0005] Therefore, it was a problem to be able to obtain a stainless steel wire rod having excellent wire drawability without depending on Al deoxidation and by melting in the air at a low melting cost.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has excellent wire drawability not only by Al deoxidation but also by atmospheric melting with low melting cost. The purpose is to be able to obtain stainless steel wire.

[0007]

In the stainless steel wire rod having excellent wire drawability according to the present invention, the inclusions present in the steel are C
It is characterized in that it is configured as a composite inclusion containing aO.

In the embodiment of the stainless steel wire rod excellent in wire drawability according to the present invention, the inclusion has a small diameter or a soft diameter, the size of which is 1/3 or less of the wire diameter after wire drawing. You can

Further, the steel composition, in% by weight, is C:
0.15% or less, Si: 1.0% or less, Mn: 2.0%
Below, P: 0.05% or less, S: 0.03% or less, N
i: 7 to 30%, Cr: 15 to 25%, Mo: 1.0 to 6.0%, Cu: 1.0 to 4.0% in some cases, and the balance Fe and impurities. The steel can contain Total-Ca: 10 to 50 ppm, and the total steel can be regulated to Total-Al: 50 ppm or less.

In the stainless steel wire rod having excellent wire drawability according to the present invention, the inclusions present in the steel are made to be complex inclusions containing CaO. ₂ O ₃ )-(SiO ₂ )-(Mg
O)-(Cr ₂ O ₃ ) -based inclusions can be formed as a composite inclusion to lower the melting point and soften the inclusions, and the large-sized inclusions are reduced and the total number of inclusions is reduced. This is because the large inclusions are reduced and the inclusions are softened, so that, for example, inclusions having a maximum minor diameter that is 1/3 or less of the wire diameter after wire drawing are included. By doing so, it is possible to prevent disconnection during wire drawing.

In order to make the inclusions present in the steel a composite inclusion containing CaO, for example, AO is used.
After melting stainless steel using D furnace and also without deoxidation with Al, transfer the molten steel into a ladle,
Add Ca in the state of a wire to this ladle,
Ca is added by putting Si powder in an iron pipe and adding it.

In the stainless steel wire rod having excellent wire drawability according to the present invention, the steel composition is C: 0.15% or less, Si:
1.0% or less, Mn: 2.0% or less, P: 0.05% or less, S: 0.03% or less, Ni: 7 to 30%, Cr: 1
5 to 25%, balance Fe and impurities, and by adding a small amount of Ca and controlling a small amount of Al, Total-Ca in the steel: 10 to 50 ppm
Together including, Total-Al: by regulating less than 50ppm, control the form of ASTM-A rigid D-type inclusions by method _{(Cr 2 O 3, Al 2} O 3 , etc.) micro inclusions with reducing However, it is preferable that wire breakage due to inclusions during wire drawing can be prevented, and that wire drawing into an ultrafine wire having a wire diameter of about 50 μm can be satisfactorily performed.

In such a steel composition, C is an element effective as a solid solution in the matrix to strengthen the matrix, and when it is used as a wire for spring, it is effective in increasing the strength of the spring. For applications, it is desirable to set the content to 0.06% or more, but if it is too large, the corrosion resistance decreases, so 0.15% or less is preferable.

Si is a high melting point inclusion of Al ₂ O ₃ ,
In order to suppress the formation of Cr ₂ O _3, etc., the basicity (CaO / SiO ₂ ) of the slag is set to an intermediate value around 2.0 or a lower value to obtain a high melting point B according to the ASTM-A method.
Since it is desirable not to use Al as a deoxidizing agent when the steel is melted so as to reduce the amount of system inclusions and D type inclusions, it is added in order to act as a deoxidizer together with Mn. However, if it is too large, ferrite is likely to be generated, so 1.0% or less is preferable.

Mn is added so as to act as a deoxidizing agent as well as a desulfurizing agent together with Si in the case of melting steel, but if it is too much, it lowers the workability and deteriorates the corrosion resistance. So 2.0%
The following is recommended.

Since P deteriorates the corrosion resistance, it is preferable that the amount of P is as small as possible. Therefore, the upper limit is preferably 0.05% or less.

Since S impairs hot workability, it is desirable that the amount is as small as possible. Therefore, the upper limit is preferably 0.03% or less.

Ni is an austenite stabilizing element,
Since it is a main element for improving the corrosion resistance of stainless steel as an austenite phase, and at the same time it is an element useful for suppressing the work-induced martensite, it is preferable to set it to 7% or more. However, in order to stabilize the austenite, it may not be contained more than necessary, and it will rather increase the cost. Therefore, the content is preferably 30% or less.

Cr is an element that contributes to improving the corrosion resistance, and it is preferable to contain Cr by 15% or more in order to obtain such an effect, but if it is contained in a large amount, ferrite will be formed, so it should be 25% or less. Is good.

In addition, Ca is the basicity of slag (CaO
/ SiO ₂ ) is set to an intermediate value of about 2.0 or a value lower than 2.0, and the steel is melted to produce B-based inclusions (Al ₂ O ₃ ) and D in the ASTM-A method. When attempting to suppress the amount of system inclusions (Cr ₂ O ₃ , Al ₂ O ₃ ) produced, a trace amount of Al ₂ O ₃ , MgO, C
By adding a slight amount when the r ₂ O ₃ are generated is a inclusions low-melting CaO- _{(Al 2 O} 3) -
It has a function of controlling the morphology of Al ₂ O ₃ -based inclusions by generating (MgO)-(Cr ₂ O ₃ ) -based composite inclusions, and the low melting point inclusions are in a liquid state at the molten steel temperature. Therefore, it becomes easy to melt and separate into slag when molten steel is stirred,
By reducing the amount of inclusions and contributing to the miniaturization of inclusions, it helps to reduce the maximum minor axis of D-type inclusions by the ASTM-A method to about 16 μm or less, and large inclusions exceeding about 16 μm. Even if there is an object, it is useful for controlling the shape of the object to be softened so that the maximum diameter in the direction orthogonal to the drawing direction is 16 μm or less during drawing.

Therefore, in order to prevent the occurrence of breakage during wire drawing, the size of the inclusions is set to 1 / of the wire material after wire drawing.
In consideration of the fact that it is desirable that the number is 3 or less, in this case, it is possible to smoothly wire up to a wire rod of about 50 μm.

In order to obtain such an effect of addition by Ca, it is preferable that the content of Total-Ca is 10 ppm or more. However, even if a large amount of Ca is added, the effect cannot be improved, so 50 ppm or less is preferable. .

If the Al content is too high, Al ₂ O ₃
Of the B-type inclusions produced by the ASTM-A method, resulting in a decrease in wire drawability.
It is desirable that the total content of the total Al is 50 ppm or less.

The stainless steel wire according to the present invention is not limited to such austenite type, but can be applied to ferrite type, for example, C:
0.12% or less, Si: 1.0% or less, Mn: 1.25
% Or less, P: 0.06% or less, S: 0.03% or less, C
r: 11 to 30%, Mo: 0.7 in other cases
5 to 2.50%, N: 0.015% or less, etc., and it is also possible to apply it to the one consisting of the balance Fe and impurities.

[0025]

In the stainless steel wire rod according to the present invention, the inclusions present in the steel are composite inclusions containing CaO by the addition of a small amount of Ca and the control of a small amount of Al (for example,
_{CaO- (Al 2 O 3) -} (MgO) - (Cr 2 O 3)
Since the inclusions have been controlled and the morphology of the micro inclusions is controlled, the inclusions are softened, resulting in excellent wire drawability. Even if it is about the same as that of the stainless steel wire, the wire drawing property will be good and the melting cost will not increase, and the wire breakage due to inclusions will be prevented during wire drawing of the ultra-fine stainless steel wire, and the stainless steel wire Which contributes to the improvement of fatigue strength of stainless springs when used as a spring material and the downsizing of stainless springs, and can respond to the demand for lighter, thinner, shorter and smaller devices in terms of spring parts. Becomes

[0026]

EXAMPLE Austenitic stainless steel having the chemical composition shown in Table 1 was melted in an electric arc furnace or an AOD furnace, formed into billets, and each billet was flawed and then rolled to a wire diameter of 5. A wire drawing material of 5 mm was obtained.

At this time, during the smelting, the slag basicity CaO / SiO ₂ ratio was set to about 1.9, and the steel was melted. After melting, each basic component of each wire drawing material,
When the Ca content, Al content, and O content were examined, Table 1
It was shown in. In addition, the D-type intervening article position (maximum minor axis, composition of inclusions) in each wire drawing material according to the ASTM-A method is determined by a wire material giant inclusion (≧
The results are shown in Table 2 when examined by a quantitative analysis of 10 μm) and an extraction analysis of inclusions.

Next, each wire drawing material having a diameter of 5.5 mm was subjected to solution heat treatment, pickling and film forming treatment, and then wire drawing, and as shown in Table 2, D-type inclusions were obtained. If the maximum minor axis was 16 μm or less, there was no wire breakage due to inclusions and wire drawing up to a diameter of 50 μm was possible without problems, but among the D-type inclusions whose maximum minor axis exceeds 16 μm, In some cases, wire drawing rupture due to inclusions occurred and wire drawing up to a wire diameter of 50 μm was impossible. For example, in No. 1 in which the maximum minor axis of D-type inclusions was 35 μm. In the case of 4, breakage occurred before the wire diameter reached 100 μm.

Further, a fatigue test was carried out to evaluate the fatigue characteristics, and the fatigue strength was measured. The results are also shown in Table 2. In the case where the maximum minor axis diameter of the D-based inclusions is 16 μm or less, the inclusions are present. The fatigue strength was high due to the miniaturization of the material, but the maximum diameter of the D-based inclusions was 1
If it exceeds 6 μm, the fatigue strength is low.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

INDUSTRIAL APPLICABILITY In the stainless steel wire rod according to the present invention, the inclusions present in the steel are composite inclusions containing CaO due to the addition of a small amount of Ca and the control of a small amount of Al. The morphology is controlled, the inclusions are softened and refined, and the wire drawability is excellent, and the oxygen content in the steel is the same level as before. Since the wire drawability can be improved even if there is, there is no increase in melting cost, and it is possible to prevent disconnection due to inclusions during wire drawing of ultra-fine stainless steel wire. , Thinning of stainless steel wire, improvement of fatigue strength of stainless spring when used as spring material, and contribution to downsizing of stainless spring. Leads to significantly better effect that those that can meet the plane of the spring parts against.

Claims (4)

[Claims] 1. A stainless steel wire rod having excellent wire drawability, wherein the inclusions present in the steel are composite inclusions containing CaO. 2. The stainless steel wire rod having excellent wire drawability as set forth in claim 1, wherein the inclusion has a small diameter or a soft diameter whose size is 1/3 or less of the wire diameter after wire drawing. 3. The steel composition, in% by weight, C: 0.15% or less, Si: 1.0% or less, Mn: 2.0% or less, P:
0.05% or less, S: 0.03% or less, Ni: 7 to 30
%, Cr: 15 to 25%, the balance Fe and impurities, The stainless steel excellent in wire drawability according to claim 1 or 2. 4. Steel-Total: Ca: 10 to 50
The stainless steel wire rod excellent in wire drawability according to claim 3, which contains ppm and is regulated to Total-Al: 50 ppm or less.