JPS6362824A - Heat treatment of rolled wire rod - Google Patents

Abstract

PURPOSE:To decrease the dispersion in cooling rate and to cool steel material at a desired cooling rate in a stable state by immersing a high-temp. rolled wire rod into bubbles of a controlled moisture content. CONSTITUTION:A floor plate 4 provided with many fine holes 3 is installed to the inside on the bottom side of a cooling tank 1. An aq. soln. 5 contg. a surface active agent and water soluble polymer is stored between the floor plate 4 and the floor plate 2 of the cooling tank 1 and a filter 6 is immersed therein. Gas is blown to the filter 6 to bubble the aq. soln. 5. The bubbles 8 are blown from the fine holes 3 of the floor plate 4 into the cooling tank 1 until the inside of the tank 1 is filled with the bubbles 8. The high-temp. wire rod 7 is immersed into the bubbles 8 and is thereby cooled. The water content in the bubbles 8 is adjusted to a 0.01-80g/100ml range. The cooling rate of the wire rod 7 is freely controllable if the water content in the bubbles 8 and the temp. of the aq. soln. 5 are adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a wire heat treatment method in which a high-temperature wire immediately after hot rolling is immersed in a foam made of a surfactant or a water-soluble polymer.

(Prior technology) As a heat treatment method by rapidly cooling or slowly cooling a high-temperature wire rod immediately after hot rolling, a method of blowing air, mist, water, etc., and a method of immersion in a metal bath of salt, lead, etc. are disclosed in Japanese Patent Publication No. Showa 57-9
Methods such as immersion in a hot liquid in a fluidized agitation state as shown in No. 8213 are used depending on the purpose. Most of these cooling technologies have excellent features despite having a single function, but in order to support the high-mix, small-lot production, which is a trend in recent steel manufacturing technology, it is necessary to install multiple cooling devices. As a countermeasure to this problem, a multi-Jlj! method is introduced in 1 Bulletin of the Japan Institute of Metals, Vol. 25, No. 6 (198B), p. 559. This led to the creation of the heat treatment system.

The feature of this system is that it uses an air cooling method for cooling rates below 10℃/S, and an immersion method for cooling rates higher than that.The equipment has a two-line structure (upper and lower), and the immersion line uses fluidized stirring for cooling. It has a refrigerant circulation system etc. for this purpose. Furthermore, the air cooling line is equipped with a heat insulating cover and a blower, and is designed to obtain a desired cooling rate of 2 to 100°C/S.

tΔI Drunk Course tag koh+ ←Yushine 1 ■ Crystal; 1 However, the cooling rate is too fast for adjusting cooling of spring steel and high carbon steel wire, especially for spring steel, if immersed in hot water near the boiling point. However, if the material is simply allowed to cool naturally in the atmosphere, the cooling rate will be non-uniform, causing the problem of ferrite decarburization occurring in areas where the cooling rate is slow. For this reason, a cooling method in which air is applied is generally used as a means of achieving a cooling rate intermediate between immersion cooling in hot water and natural cooling in the atmosphere. However, when the continuous non-concentric wire rings are coiled in a laying head and cooled on a conveyor, the degree of overlapping of each ring changes from the center of the ring to both sides, so the amount of air blast is Measures are taken such as changing the amount depending on the degree of ring overlap. However, the conventional method of applying air from below to the overlapping portions of the rings is insufficient and uniform cooling is difficult, and the variation in the cooling rate within the ring is greater than in materials immersed in hot water. Therefore, variations in mechanical properties such as tensile strength become large, causing problems such as tool wear during secondary machining, which impairs dimensional accuracy and also causes bending during straightening. .

In addition, as a cooling method for homogeneous patenting, there is an immersion cooling method in a strongly agitated fluid refrigerant of gas and hot water. Wire rods are placed on a conveyor and shake during the overloading process, causing trouble during conveyance, partial peeling of scale, and mechanical descaling before secondary processing and during pickling. In addition to causing rough skin, blowing in a large amount of air requires running costs such as blowers and refrigerant circulation equipment, which leads to larger and more complex equipment, and extremely high equipment costs. was there.

(Means for Solving the Problems) The present invention provides a completely new cooling method for improving the above-mentioned drawbacks. In other words, the cooling state is between the range of air cooling and the range of immersion cooling with strong stirring of the refrigerant, and the water content obtained by adding a foaming agent to water is 0.01 g to 80 g.
/10h+ foam, which provides a method for cooling steel in a stable state.Furthermore, by making the foam from a surfactant or water-soluble polymer, the desired cooling can be achieved. This method improves not only the speed but also the variation in cooling rate compared to other cooling methods.

Hereinafter, the present invention will be explained in detail based on the drawings.

In the equipment shown in FIG. 1, a floor plate 4 with a large number of pores 3 is installed inside the bottom side of the cooling tank l, and between the floor plate 4 and the bottom plate 2 of the cooling tank 1, a surfactant or a An aqueous solution 5 containing a water-soluble polymer is stored, and a filter 6 is immersed therein.

By blowing gas (air) into this filter 6, the aqueous solution 5 is foamed, and bubbles 8 are blown out from the pores 3 of the floor plate 4 into the cooling tank 1, and the tank is filled with bubbles. In this bubble, wire rod 7
The following results were obtained by immersing and cooling.

That is, 0.5 liters of anionic surfactant is added to 1fL of water at room temperature.
wtl and higher alcohol 0. A wire rod with a diameter of 9.5 amφ containing 0.4z C was heated to 800° C. and cooled by immersion in foam generated by pouring water into which OEi wt$ was added, and the cooling rate was measured. As a result, as shown in FIG. 2, as the amount of water in the bubbles increases, the cooling rate increases. It can also be seen that the lower the temperature of the aqueous solution containing the blowing agent (surfactant or water-soluble polymer), the higher the cooling rate (in the figure, the solid line marked with . is 40°C, and the dashed line marked with Δ is 95°C).
(aqueous solution temperature), such an effect is thought to be due to a combination of cooling due to the latent heat of vaporization of water in the bubbles, boiling heat transfer, and further radiation heat transfer.

Therefore, by adjusting the water content in the foam and the temperature of the aqueous solution containing the foaming agent, the cooling rate can be freely controlled, and the mechanical properties such as the tensile strength of the wire can be controlled.

In the present invention, the lower limit water content in foam is 0.01g/10
0■I is the limit water content that allows continuous cooling of a high-temperature wire rod by immersing it in foam. In other words, when the water content in the foam is less than 0.01 g/100ml, the cooling rate is 1fI: 100g/100ml. , the temperature of an aqueous solution containing a blowing agent is lowered to below room temperature to generate bubbles, and the cooling rate obtained when cooling with the bubbles is exactly the amount of water that exceeds the cooling rate obtained by cooling with conventional wind. .Also,
The upper limit of 80 g/100 m1 is the cooling rate lθ obtained by immersion in a strongly agitated refrigerant in a conventional multifunctional system.
The water content was selected with a slight margin to the water content required to clear the temperature of ~30°C/sec. Here, the amount of water in the foam is controlled by the type of foaming agent, the distance from the surface of the aqueous solution containing the foaming agent at a concentration of 1 to the material to be cooled, the height of the foam, the amount of air supplied, the type of filter, etc.

The foam used to cool the wire is made from surfactants and water-soluble polymers, allowing stable and continuous cooling. That is, it is possible to easily control the particle size, water content, etc. of the foam, and the variation in cooling rate is improved compared to immersion cooling in hot water. As a foaming agent, the foam made from surfactants and water-soluble polymers completely surrounds the coil even in areas where wire rings overlap and have a high density, so the foam responds to the amount of heat dissipated by the wire. This is because the evaporation rate of water inside changes. That is, in areas where the wire rings have a high overlap density, the evaporation rate of water in the bubbles becomes faster and the amount of heat removed increases. The reason why the bubbles still did not disappear is thought to be because the bubble generation rate sufficiently compensated for this.

Next, the necessity of surfactants and water-soluble polymers will be explained.

This is because when a surfactant is used as a foaming agent, the surfactant adsorbs onto the surface of the gas and liquid, lowering the surface tension and increasing the surface viscosity. , stability, etc., and when water-soluble polymers are used, they mainly improve the surface viscosity or surface viscoelasticity of the gas-liquid surface and form stable bubbles.

In this way, when a surfactant or a water-soluble polymer is used as a foaming agent, the generated foam becomes uniform and stabilized, and a uniform layer of foam with a water content of 0.01 to 80 g/100 m1 can be arbitrarily created. I can do it. When this foam is used to cool high-temperature wire rods, the cooling atmosphere can be easily controlled, making it possible to stably produce wire rods of targeted quality with less quality fluctuations and loft fluctuations.

On the other hand, it is also possible to form foam using only mechanical force such as forced extraction without using these foaming agents, but the foam formed in this way has high surface energy and low surface viscosity. As a result, the cooling atmosphere for the wire is not constant, resulting in loft fluctuations and quality fluctuations, making it difficult to stably produce wire rods of the desired quality.

The blowing agents used in the present invention are surfactants and water-soluble polymers, which will be described in detail below.

The surfactant referred to here is a water-soluble organic compound that adsorbs to the surface of gas and liquid and reduces surface activity.
More specifically, fatty acid salts, higher alcohol sulfate ester salts, liquid fatty oil sulfate ester salts, aliphatic amines and aliphatic flaxes, sulfone salts of dibasic fatty acid esters, fatty acid amide sulfonates, and alkylaryls. 7-ion activators such as sulfone ugly salts, formalin-condensed naphthalene sulfonic acid salts 9, and aliphatic amine salts,
Cationic activators such as quaternary ammonium salts, alkylpyridinium salts, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxysorbitan alkyl esters 1 nonionic surfactants such as alkyl betaines, alkyl dimethylamine oxides, etc.

Main examples include amphoteric active agents such as alkylalanine, but are not limited thereto.

When generating foam, one or both of these surfactants are used.
It is preferable to use a mixture of more than one species by adding it to the tree in an amount of o, oot to 40%.

In addition, water-soluble polymers include natural 9 synthetics, half-combined starch, starches, funori, agar, sodium alginate, gum arabic, gum tragacanth, trolo alloy, konjac, glue, casein, gelatin, egg white, plasma protein, pullulan. , dextrin, carboxy starch, pritesh gum, dialdehyde starch, cationic starch.

Viscose, methylcellulose, ethylcellulose, carboxymethylcellulose, methylcellulose, polyvinyl alcohol, polyethylene glycol, polyalkylene glycol.

Main examples include polyacrylamide, polyacrylic acid, polyvinylpyrrolidone, aqueous alkyd polyvinyl ether, polymaleic acid copolymer, polyethyleneimine, saponin, etc., but are not limited thereto.

When generating foam, it is preferable to use one or more of these water-soluble polymers in an amount of 0.01 to 3 oz to water.

The surfactants and water-soluble polymers mentioned below may be mixed in any proportion. Further, in order to improve the properties and stability of the foam, an appropriate amount of a chelating agent, builder, higher alcohol, etc. may be added to the aqueous surfactant solution or the mixture of the surfactant and water-soluble polymer.

Examples of chelating agents include aminocarboxylate salts such as dihydroxyethylglycine, hydroxyethyliminodiacetic acid, nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and the like.

Oxycarboxylic acids such as sodium citrate, sodium gluconate, and sodium tartrate, polycarboxylic acids, hydroxyethane diphosphonic acid, nitrilotrismethylenephosphonic acid,
There are phosphonic acids such as ethylenediaminetetramethylenephonic acid, condensed phosphates such as sodium tripolyphosphate, sodium birophosphate, etc., and one or more of them can be used at 0.0
It is preferable to use 0.01 to 20%.

Further, the higher alcohol is preferably a primary or secondary alcohol having 6 to 36 carbon atoms, and hexanol.

One or more types of octatool, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, oleyl alcohol, Guerbet alcohol with a carbon number of 18,24,38, etc., are added to the surfactant in an amount of 0.5 to 100%. You may add 30%.

In addition, builders such as sodium silicate, sodium sulfate, and soda carbonate may be added in an amount of 0.1 to 30% to the above formulation.

(Example) Next, an example in which cooling is performed using the cooling device shown in FIG. 1 will be described in detail.

Between the floor plate 4 and the bottom plate 2 of the cooling tank 1, an anionic surfactant 0.
An aqueous solution 5 at about 95° C. to which $5 wt. This filter 6 to 7
Send fl/win air to reduce particle size from 1 to 3cm inside the cooling tank.
Fill to a height of about 250cm with bubbles of 8 degrees.

After this preparation was completed, 9.5■ heated to about 900℃
A bundle 7 of φ wire rods was immersed and cooled. Here, in order to reduce the variation in cooling rate, the distance from the surface of the aqueous solution containing the foaming agent to the wire is approximately 50i + st.
At the same time, a certain amount of air was continuously sent to the filter to keep the high-temperature wire completely immersed in the bubbles.

As a result, cooling with the foam of the present invention results in a cooling curve (■) shown in Figure 3, which is between the cooling curve (■) obtained by immersion cooling in hot water and the cooling curve (■) obtained by natural cooling in the atmosphere. can be easily controlled.

In the above explanation, air is generally used as the gas to be blown in, but from the viewpoint of preventing surface oxidation of the cooling wire, N2
Inert gases such as gases or reducing gases can also be used.
In addition, in this experiment, bubbles were generated using the so-called air supply method, in which air is introduced into a filter with holes of a certain diameter.
Another method is stirring.

Shaking method. There are boiling methods, depressurization methods, solubility reduction methods, or a combination thereof, and the present invention does not limit the foam generation method. In addition, it is also possible to generate the desired foam outside the cooling tank and then feed it into the cooling tank.1 Usually, the temperature of the aqueous solution containing the foaming agent is between 0°C and 100°C, but it can be used at room temperature. A method of controlling the amount of water in the foam to obtain a desired cooling rate is desirable from the viewpoint of energy saving, and it is also possible to preheat the temperature of the blown gas before use.

(Effects of the Invention) As explained in detail below, the present invention is a cooling method that controls the cooling rate by controlling the moisture content and temperature of bubbles for cooling the wire, which is different from the conventional method of cooling by blowing air. Uniform cooling is possible compared to other methods. In addition, compared to the method of cooling by immersing in hot liquid under strong agitation, the suitable material resistance is smaller, and the material properties are good even with a small diameter wire material such as 5.5 cmφ, and the peeling of scale is also possible. Furthermore, the present invention does not require refrigerant treatment, evaporation equipment, refrigerant circulation equipment, etc., and the equipment cost in the structural cylinder is very low.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing an example of equipment for carrying out the present invention, and Figures 2 and 3 are graphs showing the cooling rate and cooling curve when heat treated by the method of the present invention.・Cooling tank, 2...bottom plate, 3...pores, 4...
・Floor plate, 5...aqueous solution, 6...filter, 7...
・Bundle of wire rod, 8... bubble.

Claims (2)

[Claims] (1) Water content 0.01 obtained by adding a foaming agent to water
A heat treatment method for a rolled wire rod, which comprises immersing a high-temperature wire rod in bubbles of g to 80 g/100 ml and cooling it. (2) The method for heat treatment of rolled wire rod according to claim 1, characterized in that the blowing agent is made from a surfactant or a water-soluble polymer.