JPS583928A - Manufacture of steel wire rod - Google Patents

Abstract

PURPOSE:To prevent the breading of a steel wire rod in a drawing stage when the rod is manufactured by hot drawing, by carrying out spheroidizing after hot drawing and finish drawing at specified temps. CONSTITUTION:A steel contg. 0.4-1.5wt% C, 0.1-0.4wt% Si and 0.1-1.5wt% Mn as basic components or contg. further Cu, Ni, Cr, Mo or other element is heated to 900-1,000 deg.C, hot rolled, finish-drawn at the Ar3 transformation point of the rolled steel-900 deg.C, and spheroidized at 750 deg.C for 6hr. By carrying out heating to such a relatively low temp. and working at such a low temp. as mentioned above, the structure is made fine, the rupture deflection is increased, and the breaking of the resulting steel wire rod during drawing is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a steel wire rod with excellent breakage resistance during wire drawing.

There are many types of steel wire rods, ranging from low carbon steel wire rods to medium and high carbon steel wire rods, and even alloy steel wire rods, but these steel wire rods are often made from steel ingots or billets. It is manufactured by hot rolling and then spheroidizing annealing.

Then, this steel wire rod is usually drawn into a steel wire by a wire drawing process. However, in the above wire drawing process,
Breakage may occur due to minute surface flaws that occur during wire transportation, etc., and the occurrence of such breakage significantly reduces efficiency in the wire drawing process. Therefore, conventionally, as a means of improving the above-mentioned surface flaws,
Countermeasures are often taken such as inspecting for surface flaws using eddy current flaw detection or removing surface flaws using a different solvent or surface peeling, but for minute surface flaws, it is necessary to completely remove them. That is difficult. In addition, if such measures are taken, steel wire manufacturing costs will increase, as wire drawing operations will have to be temporarily suspended when surface flaws are discovered, and yields will decrease due to surface solvents. I had a problem. Therefore, it has been desired to develop a steel wire rod that is less prone to breakage during wire drawing even if the degree of surface flaws is the same, but there has been little research into this type of problem, and Few methods have been proposed to reduce the occurrence of breakage during wire drawing in the presence of wire.

Therefore, the present inventors focused on reducing the occurrence of breakage during wire drawing by increasing the toughness of the steel wire rod, and as a result of various experimental studies, the toughness of this type of steel wire rod is as follows.
It was confirmed that the evaluation could be made by measuring the fracture deflection by the press notch bending test as shown in Figures 1 and 2, and further experiments were carried out with the aim of developing a steel wire rod with a larger fracture deflection. It was completed. In addition, in Fig. 1 and Fig. 2,
1 is a test piece, 2 is a pressing tool, 6 is a support, and 4 is a notch formed in the test piece 1.

This invention was made by focusing on the above-mentioned conventional problems, and as described above, a steel wire rod with a larger breaking deflection was developed, and a wire drawing process for drawing this steel wire rod into a steel wire was made. The purpose is to reduce the occurrence of breakage.

In this invention, C: 0.4 to 1.5% by weight, 8i: O01
~0.4% by weight, Mn: 0.1 to 1.5% by weight as a basic composition, and further contains appropriate alloy components as necessary when manufacturing a steel wire rod by hot rolling. Rolling is started after the steel is heated to a relatively low temperature of 900°C or higher and 1000°C or lower, and then passed through the final roll when the rolled material is within a relatively low temperature range of 900°C or higher than the Ar3 transformation point of the rolled material. It is characterized in that the rolling temperature is controlled (7) to perform finish rolling, and then spherical dead annealing is performed in the usual manner.

The steel wire according to the present invention includes C: 0.4 to 1.5% by weight,
Si: 0.1~0.4% by weight, Mn: 0.1~
The basic composition is 1.5% by weight, and additionally contains appropriate alloying elements as necessary.For example, ordinary carbon steel wire rod (hard steel wire rod, spring steel wire rod, carbon steel wire rod for cold heading, etc.) ) and alloy steel wire rods (including spring steel wire rods, heat-resistant steel wire rods, iron-chromium heating wire rods, etc.).

Among the above chemical components, the content of C is 4 layers)
If it is less than that, the necessary strength as a steel wire cannot be expected, and
■. If the content exceeds 1% by weight, a large amount of reticular cementite will be produced and the toughness will be significantly impaired, so the content is set at 0.4 to 1.5% by weight.

Further, in order to sufficiently deoxidize and obtain defect-free steel in steel manufacturing operations, it is necessary to contain 0.1% by weight or more of Sl. However, even if it exceeds 0.4% by weight, the deoxidizing effect reaches a saturated state, so the Si content for the purpose of deoxidizing is 0.1 to 0.4% by weight as a basic component of steel. did.

Limium is an element effective in improving the hardenability of steel and improving its strength and toughness, but if it is less than 0.1% by weight, the effect cannot be obtained. Moreover, if it exceeds 1.5% by weight, there is a risk of uneven strength due to segregation during agglomeration, so the basic component of the steel is set at 0.1 to 1.5% by weight.

In addition to the above basic components, if necessary, S'1CuINi
, Or, Mo, W, CO, kl,
V, Nb, Ti.

One or more types of Zr, B, etc. can also be contained.

Among these, Si is an effective element for increasing the tempering softening resistance and settling resistance of steel, and in particular, in the case of spring steel wire rods, Si cannot be contained in an amount exceeding the amount required for deoxidation. desirable. However, if the content is too large, it becomes extremely brittle, so it is preferable to set the upper limit to 3% by weight.

When Cu is contained in an appropriate amount, it increases the strength of steel through precipitation hardening, but if it is too large, hot workability is significantly impaired, so the upper limit is preferably set to 0.05% by weight.

Ni is an element that helps improve the toughness of steel, but if it is present too much, austenite becomes unstable and yield strength is insufficient, so the upper limit is preferably 3% by weight.

Cr is an effective element for increasing the hardenability and strength of steel, but too much Cr makes the steel brittle and impairs hot workability, so the upper limit is preferably 2% by weight.

MO is an effective element for increasing the hardenability and strength of steel, but its effect reaches a saturated state when it exceeds 1.5% by weight, and containing more than that actually impairs the hot workability of steel. , the upper limit is preferably 1.5% by weight.

W is an effective element for increasing the strength of steel, but too much W impairs hot workability, so the upper limit is set at 1.
The content is preferably 5% by weight.

Co is an effective element for increasing the temper softening resistance of steel, but if it exceeds 2% by weight, its effect reaches saturation, so the upper limit is preferably 2% by weight.

Furthermore, kt and V, Nb, Ti, 'Z
, r are effective elements for promoting spheroidization in the spheroidizing annealing after rolling by refining crystal grains in the rolling process and refining pearlite produced by Ar and transformation. However, if the At content is too large, A, /, and N in the steel will become nuclei and graphitization will easily occur during spheroidizing annealing after rolling, so it is recommended to set the upper limit to 0.03% by weight. good. Also, V, Nb, Tl.

When Zr is contained, it is preferable to contain it within a range where the above-mentioned effects are saturated; therefore, VINb,
The upper limits of Ti and Zr are each 0.1% by weight or less, and V
+ Nb + Tl + Zr (It is good to regulate it at 0.3% by weight.

Next, when manufacturing a steel wire rod by hot rolling using the steel containing the above basic composition and appropriate additive elements as necessary, the steel is heated to a temperature of 900°C or more and 1000°C or less, and then rolled. Finish rolling is performed at a temperature of 900° C. or lower than the Ar transformation point of the rolled material, and then spheroidization is performed.

Here, rolling is started after heating the above-mentioned steel to a relatively low temperature of 900°C or more and 1000°C or less, in order to suppress the growth of crystal grains as much as possible by lowering the heating temperature of the steel before starting rolling. It's for a reason. In addition, in the subsequent rolling, the finish rolling temperature when passing through the final roll of rolling is set to a temperature above the Ar3 transformation point and below 900°C in order to further enhance the effect of microstructural refinement. . That is, if the finish rolling temperature exceeds 900°C, the effect of refining the structure will be weakened and spheroidization will be difficult to proceed in the subsequent spheroidizing annealing, so the upper limit of the finish rolling temperature is set at 900°C. On the other hand, the second rolling temperature change is Ar,
If it is lower than the transformation point, the deformation resistance increases, so Ar3
Above the metamorphosis point.

In addition, in the above finish rolling, the cooling rate after the rolled material passes through the final roll is adjusted so that the metal structure after the temperature of the steel wire reaches room temperature has a total area of ferrite + pearlite of 90 or less. This is more desirable because the toughness of the steel wire rod subjected to the subsequent spheroidizing annealing can be further improved.

Example 1 Steel having the chemical composition shown in Table 1 is melted in a high-frequency induction furnace and then formed into an ingot. After heating these steel ingots to the heating temperature also shown in Table 1, wire rod rolling is started, and the rolled material is the final The finish rolling temperature when passing through the rolls was adjusted to the temperature shown in Table 1, and then air-cooled to obtain a wire material with a diameter of 13 m+l+. Subsequently, spheroidizing annealing was performed at 750° C. for 6 hours to produce a steel wire rod. Next, test pieces 1 shown in FIGS. 1 and 2 were cut out from each steel wire rod. The dimensions of the test piece 1 at this time are diameter CD) of 7 mm, length of 100 + n + n, θ of notch 4 = 60°,
=: 0.2 hearing, R = 0.02 deafness, and a breath notch bending test was conducted using suppressor 2 as specified in L-80. The results are also shown in Table 1.

As shown in Table 1, in the wire rod of test material AI in which both the heating temperature of 11 t and the finish rolling temperature were high, the structure was sufficiently refined and the amount of fracture deflection was small.

On the other hand, the heating temperature is relatively low at 900 to 1000°C, and the finish rolling temperature is also relatively high, above the Ar3 transformation point (the Ar3 transformation point of the sample material shown in Table 1 is about 720°C) and below 900°C. The amount of fracture deflection was large in all of the test materials A2 to 70 wire rods with lower finish rolling temperatures, and the lower the finish rolling temperature, the greater the effect of refining the structure, and the subsequent spheroidization was promoted well, resulting in a lower fracture deflection. are increasing. In addition, in those containing Nb and V, the structure was finely refined and the fracture deflection was more frequent.

Example 2 Steel having the chemical composition shown in Table 2 was melted and made into ingots in the same manner as in Example 1, and after each steel ingot was heated to the heating temperature shown in Table 2, rolling was started, and the finish rolling temperature was The wire material was adjusted to the temperature gvc shown in Table 2, passed through a final roll, and then cooled in air to produce a wire material with a diameter of 10 cm. Next, each wire material was subjected to spherical dead annealing at 750° C. Similarly, Table 2
Shown below. The Ar3 transformation point of the sample materials shown in Table 2 is approximately 7.
It is 29°C.

As shown in Table 2, in the wire rod of specimen A8 in which both the heating temperature and the finish rolling temperature were high, the image fineness of the structure was not sufficient and the amount of deflection at break was small. Furthermore, results were obtained that the amount of fracture deflection was small for the wire rod of sample material A9, which had a high heating temperature, and the wire rod of sample material shop 10, which had a high finish rolling temperature. In contrast, sample material A1
Good results were obtained for all wire rods Nos. 1 to 13. In addition, experiments were also conducted on wire rods containing Cr and Be, and good results were obtained in both cases.

As explained above, according to this invention, C: 0
．． 4-1.5% by weight, Si: 0.1-04% by weight
, Mn: When manufacturing a steel wire rod by hot rolling using steel having a basic composition of 0.1 to 1.5% by weight, the steel f is heated to a temperature of 900°C or more and 1000°C or less, and then rolled. Since finishing rolling is performed at a temperature above the Ar3 transformation point of the rolled material and below 900°C, and then spherical Hokuto annealing is performed, it is possible to refine the structure by low-temperature heating and low-temperature rolling. It is possible to increase the amount of fracture deflection of the steel wire by promoting spheroidization in the subsequent spherical Hokuto annealing, and the increase in the amount of fracture deflection reduces the occurrence of breakage during wire drawing. It has excellent effects.

[Brief explanation of the drawing]

FIGS. 1 and 2 are an explanatory diagram showing the implementation status of the press notch bending test method used for evaluating the toughness of steel wire rods, and an enlarged explanatory diagram of the notch of the test piece. Patent applicant: Daido Steel Co., Ltd.

Claims (1)

[Claims] (1) C: 0°4~1.5% by weight, Si: 0.1~
0.4% by weight, Mn: When manufacturing a steel wire rod by hot rolling using steel having a basic composition of 0°1 to 1.5% by weight, the steel is heated to a temperature of 900°C or higher and 1000°C or lower. 1. A method for manufacturing a steel wire rod, which comprises starting rolling after rolling, performing finish rolling at a temperature of not less than the Ar3 transformation point of the rolled material and not more than 900° C., and then performing spheroidizing annealing.