JPH01255627A - Heat treatment of steel wire - Google Patents

Abstract

PURPOSE:To produce the title homogeneous steel wire with the surface uniformly scaled and having less variations in tensile strength by air-coiling an annular coil of a high-temp. hot-rolled steel wire in a specified temp. range, water- cooling the coil with a water spray, etc., and further cooling the coil in the hot water contg. bubbles. CONSTITUTION:The high-temp. hot-rolled steel wire 2 having an austenitic structure is formed into a non-concentric ring by a loop layer 1, and the ring is developed and rolled down onto a horizontal roller conveyor 3. The ring- shaped steel wire 2 is air-cooled at 720-900 deg.C for 3-20sec so that the temp. of the edge part is made lower than that of the center part to form a thin oxide scale on the surface. The wire is then placed on an inclined conveyor 4, cooled by a mist or sprayed water 5, then dipped in >=70 deg.C hot water or the hot water 7 contg. bubbles, conveyed by a horizontal chain conveyor 8 in a cooling water tank 6, and discharged. A steel wire having an oxide scale uniform in thickness, with the pearlite transformation homogeneized, and having uniform tensile strength is obtained in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat treatment for cooling a high-temperature wire at a predetermined cooling rate during heat treatment of a steel wire, particularly to an improvement in a heat treatment method using hot water.

[Prior art] It does not generate M nucleate boiling, only produces film boiling, obtains the necessary and sufficient cooling rate, is equivalent to lead patenting, has little variation, is homogeneous, and has good wire drawability. A processing method capable of producing carbon steel wire rods is disclosed in Japanese Patent Application No. 10555/1986.
No. 8 (Japanese Unexamined Patent Publication No. Sho GO-248824).

In this method, a non-concentric ring-shaped wire rod of high carbon steel is transferred in an expanded form in a substantially horizontal direction while it is being hot-rolled and the metal structure is at a high temperature exhibiting an austenitic structure. The method comprises: heating the steel in a cypress containing a refrigerant consisting of a gas-water multiphase fluid that is in a strongly disturbed state and maintained at a predetermined temperature of 95° C. or lower in which a large number of oxidizing bubbles are uniformly dispersed. Pass the wire rod through P12 dipping,
This is a method using so-called controlled cooling, in which a refrigerant is flowed in a predetermined direction and at a predetermined speed to the wire rod, and heat treatment is performed by providing uniform cooling conditions over the entire length.

In addition, as shown in Japanese Patent Application Laid-open No. Sho G+-9GO40, the steel wire is rolled down onto the conveyor by a loop layer, and the wire is heated so that the wire is subjected to as uniform heat treatment conditions as possible until the stage of conveyance. A chain conveyor arranged in a multi-stage cascade is used to transfer the refrigerant, and by loosening the shape of the wire at the edge of the concentric ring-shaped wire rod, the flow of the refrigerant is improved. It has been shown that a configuration can be adopted in which the width of the chain conveyors arranged in a cascade is made different from each other, and the contact position between the chain and the wire rod is changed at short intervals to prevent the occurrence of coal spots. .

[Problem to be solved by the invention]! - In order to heat-treat the wire as described above, the wire is dropped onto a horizontal conveyor in a loop layer, passed through an inclined chain conveyor, immersed in a heat treatment bath, and cooled. Since the cane wire rods are transferred one after another, when the wire rods are immersed in the tank, there is a temperature difference such that the ring edge part is high 4 and the center part is low temperature. For this reason, the oxidation scale of the obtained wire becomes non-uniform.

As disclosed in the prior art, ♂t is immersed in a heat treatment tank.
It goes without saying that it is important to proceed with the uniform treatment of the wire rod after the treatment, but as mentioned above, the medium and high carbon steel wire rods are in an austenitic state and before being immersed in the heat treatment bath. If there is a temperature difference between the edge of the ring and the center of the cotton while it is being rolled out and transported in a non-concentric ring shape, it is a big problem that the oxidized scale that forms on the surface of the cotton material becomes non-uniform.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides that wire rods transferred in a non-concentric ring shape are heat-treated while maintaining an equalized temperature state before being immersed in a heat treatment tank. Heat treatment is performed by immersing the steel wire in a tank, and in order to equalize the temperature, the steel wire being transferred is cooled by applying mist or spray water.

The present invention will be explained below with reference to an embodiment shown in FIG.

In the figure, 1 is a loop layer, 3 is a horizontal roller conveyor, 4 is an inclined chain conveyor, 8 is a horizontal chain conveyor, and 9 is a mist or spray water generator installed opposite to the inclined chain conveyor 4.

The steel wire 2 is rolled out in a non-concentric ring shape in a loop layer 1 and rolled onto a horizontal roller conveyor 3 and transferred onto an inclined chain conveyor 4 where it is treated with mist or spray water 5. Continuously immersed in hot water or vapor phase mixed refrigerant.

After the steel wire is spooled, it is necessary to air oxidize it within a range of 3 to 15 seconds in order to achieve stable film boiling for cooling in the hot water tank θ. Therefore, mist spray or spray cooling must be performed after the above-mentioned rolling-off and after air oxidation for 3 to 20 seconds. During this air oxidation time, the wire 2 is cooled by radiation and convection, but at this time, the center portion is cooled more strongly than the edge portions, and the temperature difference between the center and the edges is promoted.

FIG. 2 shows the mist, or the mist of the spray water generator 8,
Or the arrangement of the spray water generating unit C is shown.

The arrow indicates the direction in which the steel wire rod 2 moves. As shown in the figure, the generation unit C is a ring edge portion of the steel wire rod 2 that moves in a non-concentric ring-like unfolded form from upstream to downstream, symmetrical to the center line in the traveling direction of the conveyor, and then the ring edge portion and its inner side. The portions, then the ring edge portions, and the inner portions thereof are disposed in stages opposite the ring edge portions and the inner portions thereof. In the center portion of the steel wire 2 that moves in a non-concentric ring shape, where the wire cross density is low, the cooling capacity is not affected or is arranged to be extremely small.

In order to prevent the steel wire rod 2 from undergoing pearlite transformation at this stage,
The temperature is set at 720℃ or higher and 900℃ or lower.
Cooling is adjusted with mist or spray water so that the steel wire rod 2 has a uniform temperature distribution in the length direction and width direction in the shape of a non-concentric ring, which results in an even temperature distribution. Then, they are sequentially immersed in hot water 7 containing about 6 bubbles, cooled, and transformed into pearlite.

Considering the temperature distribution, even when cooling in hot water or air-water mixed phase refrigerant, the center part is cooled more strongly than the edge part, so the edge part of the steel wire is made to be lower temperature than the center part immediately before immersion. It is desirable to cool the area by spray or mist spray. The temperature of the hot water pipe is set at 70°C or higher.

As a result, the scale thickness of high-temperature oxide scale becomes uniform,
Uniform gloss, color, etc. are achieved, and pearlite transformation during continuous transfer in hot water is also homogenized, resulting in a steel wire rod with uniform tensile strength.

[Example 0.81%C, 0.23%St, 0.49%Mnl
0.011%P, 0.013%S high carbon steel
Wire rods are rolled from X 110-1 square billet, rolled at a finish rolling temperature of 930-91i0℃, rolled off with a roof layer, transferred by a horizontal roller conveyor, and then transferred by an inclined chain conveyor, with an air oxidation time of 13-15 seconds. At this position, cooling was performed by mist from the top of the chain conveyor. Mist is the unit of mist generation as shown in Figure 2! Arranged in two sections, with water pressure of 2k in each unit.
g/cJ 1 Air pressure was 1.3 kg/c-.

The mist cooling time when the ring is deployed is approximately 4 to 5 minutes at the edge.
It is between sec.

The range of the minimum and maximum temperature of the coil ring that passed under this mist generator is within 30℃, and the average value is 825℃.
It was ℃.

The setting conditions for the refrigerant in the heat treatment tank were 93° C. hot water containing fine air bubbles. In addition, the steel wire was cooled and transformed while being transferred on a chain conveyor with steps.

The tensile strength and surface oxidation scale of the obtained steel wire were observed.

On the other hand, as a comparative example, a heat treatment method was used in which the treatment was performed with the mist cooling on the inclined chain conveyor stopped during the above treatment, and other conditions were the same.

Table 1 shows the tensile test results, the appearance observation of the surface scale, and the difference in scale thickness (the difference between the scale thickness at the edge and the scale thickness at the center).

In Table 1, A is a result of the conventional method shown as a comparative example, and B is a result of the method of the present invention.

In the case of the present invention, the deviation in tensile strength is small and improved. Further, in the conventional method, red scale is observed at the edges, but in the method of the present invention, the scale is black and homogeneous. Furthermore, the difference in scale thickness between the edge and center areas is small, indicating that the scale has been homogenized.

Table 1 The present invention can be applied to heat treatment of medium carbon steel wire rods as well as high carbon steel wire rods.

[Effects of the Invention] As explained above, according to the method of the present invention, it is possible to homogenize the surface oxidation scale and reduce the fluctuation width of the tensile strength, thereby obtaining a homogeneous steel wire rod.

[Brief explanation of the drawing]

FIG. 1 shows an example of a device implementing the invention. FIG. 2 shows an example of the arrangement of a mist or spray water generator. 1... Roof layer, 2... Steel wire rod, 3... Horizontal roller conveyor, 4... Inclined chain conveyor,
5... Mist or spray water, 6... Hot water tank, 7
...Hot water containing bubbles, 8.Horizontal chain conveyor, 9.Mist or spray water generator.

Claims (1)

[Claims] (1) A ring-shaped coil of hot-rolled steel wire at a high temperature with an austenant metal structure is continuously transferred in a horizontally expanded form while being heated with hot water of 70°C or higher or an air-water mixed phase refrigerant. In a heat treatment method in which the steel wire rod is immersed in a liquid and subjected to controlled cooling to undergo pearlite transformation, the steel wire rod rolled up in the loop layer is heated 3 times on a dipping conveyor that leads it to a refrigerant tank.
After air oxidation for ~20 seconds, mist or spray water is subsequently applied to the steel wire moving on the conveyor to cool it and bring the temperature of the steel wire just before dipping to 720°C ~ 9.
A method for heat treating a steel wire, characterized by cooling the edge portion to a temperature in the range of 00° C. so that the temperature is lower than the center portion.