JPH06226326A - Cooling method for rolled wire - Google Patents

Abstract

PURPOSE:To uniformly cool a rolled wire by specifying the ring pitch of a wire and a foam injection speed. CONSTITUTION:When a non-concentric ringed hot rolled wire S is cooled with foam fluid, the ring pitch of the wire is >=10mm, the foam injection speed from foam supplying nozzles 11(11a, 11b) is given at 0.1-50m/sec and the wire is cooled directly. When the ring pitch comes below 10mm, though the injection speed is optimized, dispersion of the cooling speed is deteriorated quickly. The reason why the foam injection speed is given by 0.1-50m/sec is that the lower limit capable of reducing the dispersion of the cooling speed in a practical area (20-40mm) of the ring pitch is given by 0.1m/sec and the upper limit 50m/see is an area in which the foam fluid is injected to the ringed wire of the minimum diameter 5mm without disturbing the ringed shape. In this way, uniformity of foam cooling is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method of supplying a foaming fluid to a steel wire rod (hereinafter referred to simply as a wire rod) after final finish rolling to regulate and cool the steel wire rod. In addition, in the present invention, "foam" refers to a state of aggregation of a large number of bubbles separated by thin liquid films.

[0002]

2. Description of the Related Art The applicant of the present invention has proposed a method for cooling a rolled wire rod by a foam fluid capable of controlling a wide range of cooling rates with a single cooling medium (Japanese Patent Application No. 61-206716 and Japanese Patent Application No. 62-206716). 88876). Further, the present applicant has proposed to freely control the cooling rate by changing the gas-liquid mixing ratio of the foam fluid and the foam supply amount per unit area of the material to be cooled (Japanese Patent Application No. 63-256215).

In addition, a method has been proposed in which the foam supplied to the overlapping portion of the wire in the width direction of the non-concentric ring-shaped wire is made larger than that of the single wire to uniformly cool the wire (Japanese Patent Application No. 63-250421).
issue). However, according to the above proposal, even if the amount of foam supplied to the overlapping portion of the wire is increased, the foam is restricted by the side guide of the conveyor, and as a result, the flow to the part in the single wire state at the center of the ring becomes intense and uniform cooling is achieved. No significant improvement effect has been achieved.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved method capable of improving the uniform cooling property in the controlled cooling with the above foam fluid.

[0005]

Means for Solving the Problems As a result of various investigations by the present inventors to achieve the above-mentioned object, when a non-concentric ring-shaped wire was cooled by a foam fluid on a moving conveyor, it was injected from a foam injection nozzle. It is possible to achieve uniform cooling by limiting the ring pitch and the foam injection speed so that the foam flow immediately after is not affected by the foam flowing in the cooling tank. It is confirmed that more uniform cooling can be achieved by changing the spraying speed of the foam so that the passing foam speed becomes constant, which constitutes the present invention, and the gist thereof is as follows. is there.

(1) When cooling a non-concentric ring-shaped hot-rolled wire rod with a foam fluid, the ring pitch of the wire rod is set to 10 mm or more, and the foam injection speed from the foam supply nozzle is set to 0.1 to 50 m / sec. A method for cooling a rolled wire rod, which comprises directly cooling. (2) It is characterized in that foam is sprayed into a gap in the width direction of the non-concentric ring-shaped hot-rolled wire rod, and the foam spray velocity is changed so that the foam velocity passing around the wire rod becomes constant. The method for cooling a rolled wire rod according to item 1 above.

(3) A plurality of nozzles are arranged in the width direction of the non-concentric ring-shaped hot rolled wire rod so that the injection speed of the portion where the overlapping density (gap distribution) of the wire rod is high is higher than that of the portion where the density is low. The method for cooling a rolled wire rod according to the above item 2, characterized by: The reason for limiting the numerical values of the constituent features of the present invention will be described.
The ring pitch is adjusted by changing the rolling speed and the transfer speed ratio of the ring-shaped coil at the stage of forming the rolled wire into the ring-shaped coil.

[0008] Another injection velocity of the foam, shows the ring pitch, the ratio of the mean value X _TS and variation sigma _TS tensile strength of the wire, ie the results of investigating the relationship between the variation rate X _TS / sigma _TS in FIG. As can be seen from FIG. 4, in the present invention, the reason why the ring pitch is set to 10 mm or more is that if the ring pitch is less than 10 mm, the variation in the cooling rate is aggravated even if the injection rate is optimized. The ring pitch is preferably 20 to 40 mm from the viewpoint of shortening the length of the foam cooling zone. Further, the foam jet speed of 0.1 to 50 m / sec is a practical range of the ring pitch (20 to 40 mm).
Thus, the lower limit of the injection speed that can reduce the variation of the cooling speed is 0.1 m / sec, and the upper limit of the injection speed is 50 m / sec.
The sec is defined as such since it is a range in which the ring-shaped wire rod having a minimum diameter of 5 mm is not sprayed and the ring shape is not disturbed.

Next, an embodiment of the present invention will be described with reference to the drawings. 1 to 3 are schematic explanatory views of an apparatus for carrying out the present invention. In the figure, 1 is a laying head, 2 is an atmospheric transportation zone, 3 is a foam cooling zone, 4 is a focusing tab, 5 is a conveyor, 6 is a cooling tank, 7 is a side guide, 8 is a lower nozzle header, and 9 is lateral. Nozzle header, 10 is a lower foam injection port (11a is a single nozzle, 11b is a slit nozzle),
12 is a side foam injection port.

The hot-rolled wire S cooled from the finish rolling mill to a predetermined temperature is wound from the laying head 1 into a non-concentric ring shape with a predetermined ring pitch, and is conveyed in the atmosphere while being conveyed.
After being conveyed at a predetermined conveying speed, while being dropped into the foam cooling zone 3 and being conveyed by the conveyor 5 at a predetermined conveying speed, the inside of the side guide 7 is moved to the lower side of the ring-shaped wire. Foam injection of the foam injection port 10 (single-mouth nozzle 11a or slit nozzle 11b) of the lower nozzle header 8 arranged in the width direction and the longitudinal direction or the side nozzle header 9 arranged laterally in the longitudinal direction. It is directly cooled by the foam sprayed at a predetermined foam spray speed from the mouth 12 or both of the foam spray ports, cooled to a predetermined temperature, and then focused by the focusing tab 4. The spraying speed of foam from the nozzle is determined in consideration of the overlapping density (gap distribution) of the ring-shaped wire. That is, the flow resistance of the portion where the overlapping density is high becomes larger than that of the portion where the overlapping density is low. Assuming that the foam jet velocity of the portion having a high overlapping density is v ₁ , the resistance coefficient is k ₁ , and the portions having a low overlapping density are v ₂ and k ₂ , respectively, the following relationship is established.

[0011]

[Equation 1]

Therefore, in order to make the portion having a high resistance coefficient and a high overlap density faster than the portion having a low overlap density, the foam injection port 10
The uniform convection heat transfer coefficient is made uniform by making the foam velocity passing around the wire constant to be uniform by changing the opening area of the foam or changing the supply pressure of the foam to achieve more uniform cooling. The present invention will be described based on examples.

[0013]

[Example] Finish rolling speed from finishing mill to 80 m / sec
Hot-rolled steel wire rod (non-heat treated high-strength steel wire rod for cold forging (C: 0.18 to 0.25%, Si: 0.15 to 0.3
0%, Mn: 0.70 to 1.70%, P: 0.030%
Hereinafter, S: 0.030% or less, T.I. Al: 0.010 to
(0.050%, wire diameter 5.5 mm) is formed into a non-concentric ring shape with a laying head, and 60 m / mi in the atmospheric transport zone.
After being conveyed at a conveyance speed of n, it is dropped into the foam cooling zone, the foam zone conveyance speed is 30 to 50 m / min, and the ring pitch is 30 to 40 mm.
When the ratio of the average value X _TS of the tensile strength of the steel wire rod obtained by cooling from 800 ° C. to 400 ° C. at 40 m / sec and then allowing it to cool, and the variation σ _TS , that is, the variation rate σ _TS / X _TS, was investigated. As shown in FIG. 4, the value was as small as 0.015 or less.

[0014]

According to the present invention, when the ring-shaped rolled wire is cooled with foam, it is possible to achieve extremely uniform cooling.
It is possible to significantly reduce variations in mechanical properties such as the tensile strength of the wire as compared with the conventional method.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of an implementation device of the present invention.

FIG. 2 is a plan view showing a state where a wire rod wound in a ring shape is being conveyed on a conveyor.

FIG. 3 (a) is a vertical cross-sectional view of the wire rod cooling equipment, and FIG. 3 (b) is an enlarged view of a lower nozzle header portion of the equipment.

[Fig. 4] Ring pitch and average value of tensile strength of wire rod X _TS
FIG. 6 is a diagram showing a relationship between a ratio of the variation σ _TS and a variation rate σ _TS / X _TS .

[Explanation of symbols]

 1: Laying Head 2: Atmospheric Transport Zone 3: Foam Cooling Zone 4: Focusing Tab 5: Conveyor 6: Cooling Tank 7: Side Guide 8: Lower Nozzle Header 9: Side Nozzle Header 10: Lower Foam Jet 11a: Single-mouth nozzle 11b: Slit nozzle 12: Lateral foam jet S: Concentric ring wire

Claims (3)

[Claims] 1. When cooling a non-concentric ring-shaped hot-rolled wire with a foam fluid, the ring pitch of the wire is 10 m.
A method for cooling a rolled wire rod, wherein the cooling rate is not less than m and the rate of foam injection from the foam supply nozzle is 0.1 to 50 m / sec for direct cooling. 2. A non-concentric ring-shaped hot-rolled wire rod is sprayed with a foam in a gap in the width direction, and the foam jet speed is changed so that the foam velocity passing around the wire is constant. The method for cooling a rolled wire according to claim 1. 3. A plurality of nozzles are arranged in the width direction of a non-concentric ring-shaped hot rolled wire rod so that the injection speed of a portion where the overlapping density (gap distribution) of the wire rod is high is higher than that of a portion where the density is low. The method for cooling a rolled wire rod according to claim 2.