JP2003193195A - High-strength steel wire with excellent drawability - Google Patents

Abstract

(57) [Summary] [Problem] Even if the C content is 0.8 mass% or more of the eutectoid composition, since proeutectoid cementite is not generated during patenting, it is excellent in wire drawing workability and after patenting. The present invention provides a method of providing a steel wire rod having excellent drawability due to a finer lamella spacing of the pearlite phase of the present invention with a new component composition. SOLUTION: C: 0.8 mass% or more and 1.5 mass% or less, S
i: 0.05 mass% to 2.00 mass%, Mn: 0.2 mass% to 1.5 mass%, Cr: 0.1 mass% to less than 0.5 mass%, Al: 0.6 mass% to 3.0 mass%, P: 0.02 mass
% And S: 0.02 mass% or less, with the balance having the composition of iron and inevitable impurities, making the structure after patenting substantially a pearlite phase, and having an average lamellar spacing of 0.15 μm or less. .

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a PC steel wire and a PC.
Suitable for producing high strength steel wire by utilizing the wire reinforcement used for manufacturing various wires such as steel stranded wire, wire rope wire, spring and steel cord filament, and especially by strengthening by cold drawing. The present invention relates to a high-strength steel wire rod having excellent wire drawability.

[0002]

2. Description of the Related Art In the field of high-strength steel wire, after eutectoid steel wire is made into a fine pearlite structure by patenting, strong cold wire drawing is carried out by utilizing its good wire drawability. The technology for manufacturing the high-strength steel wire has already been put into practical use. For example, in order to obtain a high-strength steel wire, it is effective to increase the amount of C, and Japanese Patent Application Laid-Open No. 7-179994 discloses a hypereutectoid high-strength steel wire and a manufacturing technique thereof. . That is, by increasing the C content, the amount of cementite is increased, and the lamellar spacing is refined, so that the strength is increased to some extent.

However, in the hyper-eutectoid steel, as is clear from the Fe-C phase diagram, pro-eutectoid cementite is apt to be generated in the former austenite grain boundaries during patenting, which causes deterioration of cold drawability. It is easy and it is difficult to stably obtain a high strength steel wire.

Further, if the lamellar spacing of the high carbon steel wire is further refined, higher wire drawability can be obtained, and as a result, high strength steel wire can be manufactured. Although the heat treatment method and the like have been devised, none of them are said to be sufficient, so that development of a new steel wire rod has been desired.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to perform wire drawing since proeutectoid cementite is not formed during patenting even if the C content is 0.8 mass% or more of the eutectoid composition. It is intended to provide a method of providing a steel wire rod having excellent property and excellent wire drawing workability because the lamellar spacing of the pearlite phase after patenting becomes fine by a new component composition.

[0006]

Means for Solving the Problems The inventors conducted a detailed study on the relationship between the chemical composition of steel and the pearlite structure after patenting and its wire drawability.
We have found a new steel composition that does not generate pro-eutectoid cementite phase even if the amount is 0.8 mass% or more and that the lamellar spacing of the pearlite phase after patenting can be significantly refined.

Further, it has been found that in the steel wire rod according to this steel composition, the average lamellar spacing can be controlled to 0.15 μm or less, and the wire drawing workability and the high strength are remarkably superior to the conventional ones. Came to do.

That is, the gist of the present invention is as follows. (1) C: 0.8 mass% or more and 1.5 mass% or less, Si: 0.05 ma
ss% or more and 2.00 mass% or less, Mn: 0.2 mass% or more and 1.5 mass
% Or less, Cr: 0.1 mass% or more and less than 0.5 mass%, Al: 0.6
mass% or more and 3.0 mass% or less, P: 0.02 mass% or less and S: 0.02 mass% or less, the balance has a composition of iron and inevitable impurities, and the structure after patenting is substantially a pearlite phase. And the average lamellar spacing is 0.15μ
It is a high-strength steel wire rod excellent in wire drawing workability, which is characterized by being m or less.

(2) In the above (1), Cu: 0.
02mass% or more and 1.00mass% or less, Ni: 0.02mass% or more and 1.00
mass% or less, Mo: 0.02 mass% or more and 0.30 mass% or less, V:
0.005 mass% or more and 0.100 mass% or less, Nb: 0.005 mass%
Over 0.100 mass% and Ti: 0.005 mass% over 0.10
A high-strength steel wire rod excellent in wire drawing workability, which has a component composition and contains any one or two or more of 0 mass% or less.

(3) In the above (1) or (2),
Furthermore, Ca: 0.0005 mass% or more and 0.0100 mass% or less, Mg: 0.
0005mass% or more and 0.0100mass% or less and REM: 0.0005ma
A high-strength steel wire rod excellent in wire drawing workability, characterized by having a composition of any one or more of ss% to 0.0100 mass%.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting the component composition of the present invention will be described below. C: 0.8 mass% or more and 1.5 mass% or less C is an important element that controls the strength of the steel wire rod, and the higher the C content, the higher the strength. For that, 0.8 ma
ss% or more is necessary. However, if the content is too large, the ductility decreases and the wire drawability decreases, so the content is 1.5 ma.
The range is ss% or less.

Si: 0.05 mass% or more and 2.00 mass% or less Si is an element necessary for deoxidation and is an important element for strengthening the steel wire rod by solid solution strengthening. For that, 0.05 mass% or more is necessary. However, if the amount is too large, the ductility is lowered and the wire drawing workability is lowered, so the content is made 2.00 mass% or less.

Mn: 0.2 mass% or more and 1.5 mass% or less Mn is an element necessary for deoxidation, and is an important element for strengthening by promoting the formation of cementite. The above is necessary. However, if the amount is too large, the ductility is lowered and the wire drawing workability is lowered, so the content is made 1.5 mass% or less.

Cr: 0.1% by mass or more and less than 0.5% by mass Cr is effective in reducing the lamellar spacing of the pearlite phase after patenting by significantly promoting the formation of cementite. For that, 0.1 mass%
The above is necessary. However, if the content is too large, the effect is saturated, and the ductility is deteriorated to deteriorate the wire drawing workability. Therefore, the content is made less than 0.5 mass%.

Al: 0.6 mass% or more and 3.0 mass% or less Al suppresses the formation of pro-eutectoid cementite during patenting, and therefore increases the amount of C without forming pro-eutectoid cementite that deteriorates wire drawing workability. It is an important element that enables. For that purpose, 0.6 mass% or more is required.
However, if the amount is too large, the ductility is lowered and the wire drawing workability is lowered, so the content is made 3.0 mass% or less.

P: 0.02 mass% or less and S: 0.02 mass%
Hereinafter, P and S segregate at the grain boundaries of the steel and reduce the ductility, so it is necessary to reduce them as much as possible. Therefore, the content is suppressed within the range of P: 0.02 mass% or less and S: 0.02 mass% or less.

Cu, Ni and Mo Cu, Ni and Mo are effective elements for strengthening the steel wire rod by solid solution strengthening. However, if the amount is too large, the ductility is lowered and the wire drawability is lowered. Therefore, the content is Cu: 0.02 mass% or more and 1.00 mass% or less, Ni: 0.02 mass%
% To 1.00 mass% and Mo: 0.02 mass% to 0.30ma
The range is ss% or less.

V, Nb and Ti V, Nb and Ti are elements that contribute to strengthening the strength of the steel wire rod by forming carbonitrides. However, if the content is too large, the ductility is lowered and the wire drawability is lowered, so the content is
V: 0.005 mass% or more and 0.100 mass% or less, Nb:
0.005 mass% or more and 0.100 mass% or less, Ti: 0.005 mass%
The range should be 0.100 mass% or less.

Ca, Mg and REM Ca, Mg and REM have the effects of forming fine oxides in the steel and refining the austenite grains to refine the pearlite structure and improve wire drawability. However, if it is too large, the ductility is lowered and the wire drawing workability is lowered. Therefore, the content is Ca: 0.0005 mass% or more and 0.0100 masss or more.
% Or less, Mg: 0.0005 mass% or more and 0.0100 mass% or less, and
REM: The range is 0.0005 mass% or more and 0.0100 mass% or less.

When the steel material having the above composition is subjected to patenting, the structure after the patenting is substantially a pearlite phase and the average lamellar spacing is 0.15 μm or less. Here, the structure which is substantially a pearlite phase is
It means a structure in which the area fraction of the pearlite phase is 90% or more. Here, a so-called pseudo pearlite phase in which the lamellar morphology of plate-like cementite is broken is also included.

In this pearlite phase structure, it is important that the average lamellar spacing is 0.15 μm or less. This is because when the average lamellar spacing is larger than 0.15 μm, the wire drawing workability becomes poor and the strength increase due to wire drawing also becomes small.

Regarding patenting, it is not necessary to limit the conditions in particular, and the general method for manufacturing a wire using this type of steel material may be used. However, the lamella interval described above is 0.
It is necessary to set the condition to 15 μm or less, and this condition can be appropriately determined.

[0023]

[Examples] Steel billets containing the chemical components shown in Table 1 were produced by melting in a converter, subjecting to RH degassing treatment, continuous casting, and billet rolling.
After heating to 1100 ° C, it was rolled into a 5.5 mmφ steel wire rod. Next, after heating the steel wire rod to 950 ° C. and performing patenting in a lead bath at 650 ° C. (excluding No. 21 in Table 1), the steel wire rod was tested for tensile strength, pearlite phase ratio and pearlite phase. The average lamellar spacing was determined. Further, the steel wire rod after the patenting was subjected to continuous wire drawing with a surface reduction rate of 12% / pass, and the wire drawing limit work ratio until disconnection was obtained. The results of the above measurements are also shown in Table 1.

[0024]

[Table 1]

In Table 1, Nos. 1 and 2 are conventional steels, and No. 1 is a conventional eutectoid steel. Although no proeutectoid cementite is observed, the tensile strength is low due to the large lamellar spacing. Further, No. 2 is a hyper-eutectoid steel, and although the lamellar spacing is small, there is a pro-eutectoid cementite phase, so the wire drawing limit is lowered.

On the other hand, all the steels satisfying the conditions of the composition and lamellar spacing of the present invention have a small lamellar spacing and no proeutectoid cementite phase. Therefore, it is clear that the tensile strength and the wire drawing limit are far superior to those of the conventional steel.

On the other hand, in Comparative Example No. 6, the amount of Cr deviates from the lower limit of the present invention. Therefore, the lamellar spacing becomes large, and both the strength and the wire drawing limit deteriorate. Further, in Comparative Example No. 8, the amount of Cr deviates from the upper limit of the present invention. Therefore, the wire drawing limit is deteriorated. Furthermore, No. 13 which is a comparative example is Al
The amount deviates from the lower limit of the present invention. for that reason,
As the lamellar spacing increases, proeutectoid cementite phase also appears, and both strength and wire drawing limit deteriorate. Further, in Comparative Example No. 14, the amount of Al deviates from the upper limit of the present invention. Therefore, the wire drawing limit is deteriorated.

No. 21, which is a comparative example, is a comparative material in which the lamellar spacing is changed by changing the patenting conditions using the same wire material as No. 4. Therefore, the lamellar spacing becomes large, and both the strength and the wire drawing limit deteriorate.

[0029]

According to the present invention, since a high-strength steel wire rod having excellent cold drawability is provided, it is possible to obtain an excellent quality steel wire by high working using this steel wire rod. If steel wire is applied to various structures, it will contribute greatly to weight reduction and improvement of reliability.

Claims (3)

[Claims] 1. C: 0.8 mass% to 1.5 mass%, Si: 0.05 mass% to 2.00 mass%, Mn: 0.2 mass% to 1.5 mass%, Cr: 0.1 mass% to 0.5 mass%, Al : 0.6 mass% or more and 3.0 mass% or less, P: 0.02 mass% or less and S: 0.02 mass% or less, and the balance having a composition of iron and inevitable impurities,
A high-strength steel wire rod having excellent wire drawability, characterized in that the structure after patenting is substantially a pearlite phase and the average lamellar spacing is 0.15 μm or less. 2. The Cu: 0.02 mass as defined in claim 1.
% Or more and 1.00 mass% or less, Ni: 0.02 mass% or more and 1.00 mass% or less, Mo: 0.02 mass% or more and 0.30 mass% or less, V: 0.005 mass% or more and 0.100 mass% or less, Nb: 0.005 mass% or more and 0.100 mass% or less And Ti: 0.00
Any 1 or 2 from 5 mass% to 0.100 mass%
A high-strength steel wire rod excellent in wire drawing workability, which is characterized by having a component composition containing at least one kind. 3. The Ca or Ca according to claim 1, further comprising:
0.0005 mass% or more and 0.0100 mass% or less, Mg: 0.0005 mass% or more and 0.0100 mass% or less, and REM: 0.
[0005] A high-strength steel wire rod having excellent wire drawability, characterized by having a composition of any one or two or more of at least 0.0100 mass% and not more than 0.0100 mass%.