JPS60149732A - Heat treatment of steel wire rod - Google Patents

Abstract

PURPOSE:To obtain a steel wire rod having improved ductility after patenting by subjecting a steel wire rod contg. C and Al respectively at prescribed ratios to heat treatment for deposition of AlN to fix the N solutionized in said wire rod prior to patenting treatment. CONSTITUTION:A steel wire rod contg. 0.4-1.0% C and >=0.01% Al and having the intermediate size after hot rolling or in the midway of drawing is held for >=10min at 650-950 deg.C to increase the AlN in the steel. The steel wire rod subjected to the above-described heat treatment is subjected to a heat treatment method to dip the same into a lead bath in succession to form pearlite structure, i.e., patenting treatment, or is reheated after cooling by which said steel rod is patented and the solid soln. N in the steel is precipitated as AlN. The reduction of the steel wire rod is thus considerably improved and the ductility is improved. Generation of a trouble such as a disconnection during drawing is thus prevented and working at a high reduction of area is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to, for example, a PC (Prestressed, Conc!J)
-1-) Hot-rolled steel wire rod used in the production of steel wire such as copper wire and hard steel wire, or intermediate-sized steel wire rod in the middle of wire drawing (hereinafter referred to as
The present invention relates to a heat treatment method for wire rods (collectively referred to as wire rods).

(Background Art) Conventionally, hot-rolled brown carbon steel (C0.04 to 0.04.
-9%) wire Aj is continuously heated in a heating furnace at 950 to 1000°C to form an austenitic structure, and then
A heat treatment method (referred to as patenting treatment) in which the material is immersed in a lead bath heated to 0 to 600° C. to form a barlite structure is generally used.

The purpose of this patenting treatment is primarily to obtain a wire rod with excellent wire drawability.In this process, the set temperatures of both the heating furnace for austenitization and the lead bath furnace for rapid cooling transformation to a predetermined temperature are lowered by 1. The tensile strength of the wire is adjusted to a predetermined value. Although the tensile strength can be adjusted in this way, it is difficult to adjust the ductility using conventional methods. Especially eutectoid steel (
In the case of large-diameter wire rods (CO, S%), they lack ductility, which can cause wire breakage during wire drawing and poor drawing, elongation, and twisting in products.

(Disclosure of the Invention) The present invention solves the above-mentioned problems with jQ! It was developed to improve the ductility of steel wire after patenting by applying AfiN precipitation heat treatment to fix the nitrogen solidly dissolved in the steel wire before patenting treatment. The present invention aims to provide a method for heat treatment of wire rods.

In the present invention, a steel wire containing 0.4 to 1.0% of CO and 1.01% or more of Ar is subjected to J-5 heating at a temperature of 650 to 950°C for 10 minutes or more, and then subjected to patenting treatment. Watermelon, or reheat after cooling and patenting! I
! This is a method of heat treatment of steel wire, which is characterized by the following steps:

The wire rod used in the present invention is C0.4-1.0%, A
Made from steel containing #0.01% or more, and added with Si, Ni, Cr, V, and other additives to improve properties.
A small amount of all elements such as Mo and W may be added. The wire rod is a hot-rolled wire rod or an intermediate-sized wire rod that is in the process of being drawn.

The explanation below will mainly take hot rolled wire rods as an example.
Wood brother J is not limited to this.

Hot rolled wire rods are generally heated and rolled to a temperature of 1100 to 1200°C. During billet heating prior to rolling, a reaction of AβN→Aβ+N occurs between Aβ and N in the steel.

Also, when cooling after finishing wire rod rolling, the normal cooling rate is A.
βA-N −+ A (The reaction of IN is hardly adequate.

As a result, in the hot-rolled wire rod, Aβ and N each exist in a solid solution state in the steel.

The present inventor focused on nitrogen present in a solid solution state as a cause of inhibiting the ductility of patented wire rods, and conducted the following autopsy.

(Experimental example 1) C0, 80%, SiO, 26%, Mn 0.69%, A
lO, 021%.

11.5 cm of hot-rolled steel wire rod containing 6a% of No.
After holding for 0 minutes, it was cooled and AβN present in the steel was analyzed. The relationship between the heating temperature and the amount of AβN in steel is the first
As shown in the figure.

From Figure 1, it can be seen that when the wire is heated and held at a temperature of 650 to 950°C, the AI-J-N-*AβN reaction progresses, the solid solution nitrogen in the steel decreases, and the AβN increases. .

Next, using the same wire rod as above, 2
After heating and holding for ~120 minutes, it is cooled and p, (I
An analysis of N was conducted. The relationship between the heating holding time and the amount of AgN in the steel is shown in FIG.

From FIG. 2, it can be seen that when the heating and holding time is 10 minutes or more, the above reaction progresses and the h(IN) in the steel increases, so that a holding time of 10 minutes or more is required.

From the above results, it is necessary to hold the steel at a temperature of 650 to 950°C for more than 10 minutes as a heat treatment for AβN precipitation in steel. Temperature is less than 650°C or 95°C
If the temperature exceeds 0°C, sufficient AaN is not precipitated as shown in FIG. 1, so a large amount of solid solution nitrogen exists in the steel, and the effect of improving ductility cannot be obtained. Also, the time between 11% and 11% is not IO minutes/l! 4, the A side cannot produce a sufficient amount of 4Jτ, and the same effect as above cannot be obtained.

(Experimental Example 2) Using the same wire as used in Experimental Example I, heat and hold at a temperature of 750'C for 2 to 120 minutes, cool and heat to 900'C.
After being reheated to a temperature of .degree. C. and held for 10 minutes to austenitize, the material was immersed in a lead bath kept at a temperature of 560.degree. C. to cause Barley 1-transformation and a patenting treatment was performed.

The relationship between the heating holding time at 750° C. and the tensile strength and drawing strength of the obtained wire is as shown in FIG.

Figure 3 shows that the tensile strength of the wire rod after patenting treatment is almost constant regardless of the length of the heating and holding time, whereas the drawing strength, which indicates ductility, strongly depends on the time, and the At 2 minutes, the aperture is 31%, but at 10 minutes, it is about 36%.
, it becomes 50% in 20 minutes or more, and it can be seen that the drawing strength is greatly improved.

(Experimental Example 3) Using the same wire as used in Experimental Example 1, it was heated and held at a temperature of 750°C for 2 to 80 minutes as shown in the thermal history in Figure 4, and then heated at a temperature of 900°C. After being heated and held for 5 minutes, it was immersed in a lead bath kept at a temperature of 560°C to perform a patenting treatment.

The relationship between the heating holding time at 750°C and the drawing area 9 of the obtained wire is shown in FIG.

From FIG.
It can be seen that the drawing strength is improved by heating and holding at 50° C. for 10 minutes or more.

Second, from the results of Experimental Examples 1, 2, and 3, it was found that heat treatment prior to patenting treatment must be carried out at a temperature of U650 to 950'C for a holding time of 10 minutes or more.

In the present invention, the CM in the steel is specified as 0.4 to 1.0% because the present invention improves the ductility of the pearlite structure. This is because a cementite structure appears at the pearlite grain boundaries when pearlite ferrite is mixed, which impairs wire drawability, making it impossible to obtain the effects of the present invention.

Also, A calli in steel? The reason why i is defined as 0.01% or more is because
Button 1 unavoidably contained in 0.01% less/1171
This is because the fixation of nitrogen in the steel is insufficient, and the crystal grain size during the patenting process becomes coarse due to the lack of AIIN, resulting in a decrease in ductility.

(Example) C0, 82%, SiO, 25%, MnO, 71%,
Jo, 023%.

A hot rolled wire rod of 11.5 ynm containing NO,0059% was heated and held in the form of a coil under the AgN precipitation heat treatment conditions shown in Table 1, air cooled, and then continuously patterned under the conditions shown in Table 1. tinging treatment was applied.

The tensile strength and drawing strength of the obtained patented wire are as shown in Table 2.

Table 1 Table 2 From Tables 1 and 2, it can be seen that the tensile strength of the specimens according to the present invention is not much different from that of the conventional specimens treated only with patenting treatment, but the reduction of area is significantly improved.

This is because the tensile strength of the wire rod is almost determined by the heating temperature and lead bath temperature, which are the patenting treatment conditions, but the reduction of area, which indicates ductility, is significantly affected by the AβN precipitation heat treatment before the patenting treatment, as described above. There is no point in improving.

(Effect of start) The method for heat treating a steel wire rod of the present invention configured as described above has the following effects.

Steel wire containing C004~10% and Ac1.01% or more is held at a temperature of 650~950'C for 10 minutes or more and then subjected to patenting treatment, or after cooling and reheating to patenting treatment. Because of the patenting process, the isothermal nitrogen in the steel is precipitated as AβN, which greatly improves the drawing of the wire.It has excellent ductility, eliminates troubles such as wire breakage during wire drawing, and is highly durable. In addition to being able to process the area reduction rate, the drawing value of the steel wire is high.
Moreover, the twisting characteristics are also improved.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing the relationship between heat treatment conditions and the amount of AEN in the steel after treatment, respectively, and Figure 1 shows the relationship between the heating temperature and the amount of AEN in the steel after treatment.
Figure 2 shows the relationship between the heating holding time and AβN (at). Figure 3 shows the relationship between the heat treatment heating time and the tensile strength and reduction of area of the obtained wire when cooling after heat treatment and applying patenting treatment. Figure 4 is a diagram showing the thermal history of an experimental example in which patenting treatment was subsequently applied after heat treatment. Figure 5 is a diagram showing the heat treatment heating time and the obtained wire rod in the experimental example shown in Figure 4. It is a diagram showing the relationship between the apertures.

Claims (1)

[Claims] (+) After holding a steel wire rod containing CO, 4 to 10%, and 1.01% or more of Ar at a temperature of 650 to 950°C for 10 minutes or more, it is subsequently subjected to a patenting treatment, or it is heated after being cooled. Apply patenting treatment! I
A method of heat treatment of steel wire to give S characteristics.