JPH0899114A - Froth cooling method for high-temperature steel products - Google Patents

Abstract

PURPOSE: To simultaneously accomplish a wide range of cooling controllability and uniform coolability by specifying the particle diameter of the froth foamed from an aq. soln. contg. a foaming agent, such as surfactant or/and water-soluble polymer which is a cooling medium. CONSTITUTION: While a hot rolled wire S cooled down to a specific temp. from a finishing mill is wound to a nonconcentrical ring form at a specific ring pitch from a laying head 1, the wire is transported at a specific transporting speed in a transporting zone 2 in the atm. The wire is thereafter dropped into a froth cooling zone 3 and while the wire is transported at a specific transporting speed by a conveyor 5 in the cooling zone 3, the wire is directly cooled under the froth of a grain size of <=1mm injected at a specific injection speed from lower supply nozzles 8 arranged along the transverse and longitudinal directions below the annular wire on the inner side of side guides 7 or side direction supply nozzles 9 arranged transvessely in the longitudinal direction and upper supply nozzles 10 arranged in the longitudinal direction. The wire is cooled down to a specific temp. and is ten bundled in a bundling tab 4.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for cooling a high temperature steel material with a foam fluid comprising an aqueous solution containing a foaming agent such as a surfactant or / and a water-soluble polymer as a cooling medium, and in particular, the characteristics of the foam are defined. The present invention relates to the cooling method. In addition, in the present invention, “foam” refers to an aggregated state of a large number of bubbles each separated by a thin liquid film.

[0002]

2. Description of the Related Art The applicant of the present invention has previously proposed a method for cooling a rolled wire rod with a foaming fluid capable of controlling a wide range of cooling rates with a single cooling medium (Japanese Patent Publication No. 4-50370 and Japanese Patent Publication No. 4-26924). Issue). Further, the present applicant has proposed to freely control a wide range of cooling rates 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). However, these methods focus on the cooling rate in the case of cooling with foam, and are unsatisfactory from the viewpoint of the stability of the foam to be supplied and uniform cooling.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to solve these problems of the prior art and to provide a foam cooling method for high temperature steel material capable of simultaneously achieving a wide range of cooling controllability and uniform cooling performance. It is what

[0004]

The present invention provides (1) a method for cooling a high temperature steel product using a foam as a medium, from an aqueous solution containing a cooling medium such as a surfactant or / and a foaming agent such as a water-soluble polymer. A foam cooling method for high-temperature steel material, characterized in that the particle diameter of the generated foam is 1 mm or less. (2) In a method of cooling a high temperature steel material using foam as a medium, a volume immediately after generation of foam generated from an aqueous solution containing a surfactant serving as a cooling medium and / or a foaming agent such as a water-soluble polymer is V _f , foam an elapsed time from generation to reach the vicinity of the high-temperature steel the t (min), the inside of the liquid film between in foam bubbles flows down under the influence of gravity within this time t, the volume of the aqueous solution to drain V _L The method of foam cooling of high temperature steel material is characterized by satisfying the following formula (1). (V _L / V _f ) × 100 / t ≦ 5.0 [% / min] (1) It should be noted that the simultaneous implementation of the method (1) and the method (2) does not hinder at all.

[0005]

In order to achieve the above-mentioned object, the present inventors have made various investigations in the case of foam cooling a non-concentric ring-shaped high-temperature wire on a moving conveyor. As a result, the foam is, for example, below, lateral, or above the material to be cooled. When supplying so as to cover the material to be cooled, the rate of change in the gas-liquid mixing ratio of the foam (foam fluid) near the material to be cooled is small, and the cooling medium penetrates into the parts where the overlapping density of the wire is high. As described above, it was confirmed that a wide range of cooling rate controllability and uniform cooling property could be achieved at the same time by cooling with a particle size of foam of 1 mm or less. Specifically, it is preferable that the particle size of the foam is 0.05 to 0.3 mm.

Further, the foam as a cooling medium is made to have an appropriate water retention property to make the water content in the foam (foam fluid) near the material to be cooled uniform, and the interface between the high temperature steel material and the foam fluid during cooling. In order to make the above-mentioned film thickness generated in a constant _value , _Vf is a constant volume of foam containing the aqueous solution and air immediately after the foam is generated, and the elapsed time from the generation of foam to the vicinity of the material to be cooled is t (minutes), when the volume of the aqueous solution that flows down and drains in the liquid film between the bubbles in the foam due to gravity within this time t is _VL , the volume ratio per unit time ( _VL / V _f )
It was confirmed that uniform cooling was achieved by cooling under a foaming condition in which the drainage rate R was × 100 / t and R was 5.0% / min or less. Specifically, the drainage rate R per unit time is preferably 2.0 to 5.0% / min.

An embodiment of the steel product manufacturing line of the present invention will be described with reference to the drawings. In FIG. 1, 1 is a laying head for paying out a rolled wire rod in a ring shape, 2 is a transport zone in the atmosphere, 3 is a foam cooling zone, 4 is a focusing tab, and S
Is a non-concentric ring-shaped hot rolled wire. Figure 2 shows the foam cooling zone 3
FIG. 5 is a cross-sectional view of the conveyor, 5 is a conveyor, 6 is a cooling tank, 7 is a side guide, 8 is a lower foam supply nozzle, 9 is a side foam supply nozzle, 10 is an upper foam supply nozzle, and F is a foam fluid. The foaming device is located outside the cooling tank 6 (not shown), and is supplied from the foam supplying nozzles 8, 9 and 10 through pipes so as to cover the non-concentric ring-shaped hot rolled wire S.

The hot-rolled wire S cooled to a predetermined temperature from the finish rolling mill is wound in a non-concentric ring shape with a predetermined ring pitch from the laying head 1 while being conveyed in the atmosphere to the conveying belt 2.
Of the ring-shaped wire rod inside the side guide 7 while being transported into the foam cooling zone 3 at a predetermined transport speed after being transported at a predetermined transport speed by the conveyor 5. At a predetermined injection speed from the lower supply nozzle 8 arranged in the width direction and the longitudinal direction, the side supply nozzle 9 arranged laterally in the longitudinal direction and the upper supply nozzle 10 arranged in the longitudinal direction. It is directly cooled by the foam F and is cooled to a predetermined temperature and then focused by the focusing tab 4.

In the present invention, cooling is performed with the particle size of the foam fluid being 1 mm or less. When the particle size of the foam is 1 mm or more, the bubbles are easily broken, and the rate of change in the gas-liquid mixing ratio of the foam fluid increases, and the cooling rate. However, there is a tendency for variations in
This is because when the foam particle size is 1 mm or less, it is difficult for the foam to break, and the cooling medium penetrates into the high-density overlapping portion of the non-concentric ring-shaped wire as well, so that the boiling heat transfer is stable.

Further, in the present invention, the drainage rate R of the foam per unit time is set to 5.0% / minute or less so that the foam has an appropriate water retention property and the water content in the foam of the foam fluid is made uniform. This is to stabilize the boiling heat transfer by making the vapor film thickness generated at the interface between the cooling target material and the foam fluid during cooling constant.

[0011]

[Examples] Steel wire rod hot rolled from a finishing mill at a finishing rolling speed of 80 m / sec (non-heat treated high tensile strength steel wire rod for cold forging, C:
0.18-0.25%, Si: 0.15-0.30%,
Mn: 0.70 to 1.70%, P: 0.030% or less,
S: 0.03% or less, T.I. Al: 0.010 to 0.05
(0%, wire diameter 5.5 mm) is formed into a non-concentric ring shape with a laying head, and is transported in the atmospheric transport zone at a transport rate of 60 m / min, then dropped into the foam cooling zone, and the foam cooling zone transport rate is set. Is 50 m / min, the ring pitch is 40 mm, and the bubble diameter is 0.05 to 1.9 mm, the drainage rate is 2.0 to 20.0% / min per unit time, and the amount of foam is supplied per unit floor area during transportation. 4 from 800 ℃ with 1.2m ³ / min ・ m ² foam fluid
The ratio of the average value X _TS of the tensile strength and the standard deviation σ _TS of the steel wire obtained by cooling to 00 ° C. and then allowing it to cool, that is, the fluctuation rate σ _TS / X _TS was investigated, and as shown in FIG. By setting the foam particle size to 1 mm or less, or by setting the drainage rate R of the supplied foam per unit time to 5.0% / min or less, the above-mentioned fluctuation rate is significantly reduced. By satisfying the conditions at the same time, the same fluctuation rate becomes 0.
It is a very small value of 015 or less, and it can be seen that further uniform cooling can be achieved.

[0012]

According to the present invention, when a high-temperature steel material is cooled with foam, it is possible to cool it extremely uniformly, and it is possible to significantly reduce variations in mechanical properties such as tensile strength of the steel material.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example of an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an example device of an embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a foam particle size, a drainage rate R per unit time, a ratio of an average value X _TS of a wire rod tensile strength and a standard deviation σ _TS , that is, a variation rate σ _TS / X _TS .

[Explanation of symbols]

 1 Laying Head 2 Air Transport Zone 3 Foam Cooling Zone 4 Focusing Tab 5 Conveyor 6 Cooling Tank 7 Side Guide 8 Lower Foam Supply Nozzle 9 Side Foam Supply Nozzle 10 Upper Foam Supply Nozzle S Non-Concentric Ring Wire F Foam Fluid

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[Procedure amendment]

[Submission date] October 5, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art The applicant of the present invention has previously proposed a method for cooling a rolled wire rod with a foaming fluid capable of controlling a wide range of cooling rates with a single cooling medium (Japanese Patent Publication No. 4-50370 and Japanese Patent Publication No. 4-26924). Issue). Further, the present applicant has proposed to freely control a wide range of cooling rates 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 Publication No. 3-22450 ). However, these methods focus on the cooling rate in the case of cooling with foam, and are unsatisfactory from the viewpoint of the stability of the foam to be supplied and uniform cooling.

Claims (2)

[Claims] 1. A method of cooling a high temperature steel material using foam as a medium, wherein the particle diameter of the foam produced from an aqueous solution containing a cooling medium such as a surfactant or / and a foaming agent such as a water-soluble polymer is 1 mm or less. A method for foam cooling of high-temperature steel material, which is characterized in that 2. A method for cooling a high temperature steel material using foam as a medium, wherein the volume immediately after formation of foam generated from an aqueous solution containing a surfactant serving as a cooling medium and / or a foaming agent such as a water-soluble polymer is V _f , T (minutes) is the elapsed time from the generation of foam until reaching the vicinity of the high temperature steel material, and within this time t, the volume of the aqueous solution that flows down in the liquid film between the bubbles in the foam due to the effect of gravity and drains A foam cooling method for a high-temperature steel material, characterized in that the following expression (1) is satisfied when V _L is satisfied. (V _L / V _f ) × 100 / t ≦ 5.0 [% / min] (1)