JPH0322450B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for cooling hot wire rods following a hot rolling process, and in particular to a method for cooling hot wire rod rings following a hot rolling process, in particular rolling successive groups of overlapping hot wire rings with offset centers on a conveyor. The present invention relates to a method of cooling by supplying a refrigerant while being transported.

(Prior art) As a method of heat-treating a high-temperature wire rod by rapidly or slowly cooling it after hot rolling, air, mist,
A method of spraying water, etc., a method of immersion in a metal bath such as salt or lead, a method of immersion in a liquid such as hot water, cold water, or oil, or a method of hot liquid in a fluidized stirring state as shown in JP-A No. 57-9826. There are methods such as immersion.
Each of these methods is used depending on the purpose, and most of them have excellent features even though they have a single function. However, in order to cope with high-mix, small-lot production, which is a recent trend in steel manufacturing technology, multiple cooling devices must be installed, which complicates the manufacturing process and increases equipment costs.

As a countermeasure to these problems, we have developed a multifunctional heat treatment system as introduced in the Bulletin of the Japan Institute of Metals, Vol. 25, No. 6 (1986), page 559. The feature of this system is that it uses an air cooling method for cooling speeds of 10℃/s or less, 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. In addition, a heat insulating cover and blower are attached to the air cooling line to achieve the desired cooling rate of 2~
It is designed to obtain 100°C/s.

Furthermore, Japanese Patent Application Laid-open No. 60-248824 proposes a heat treatment method using an air-water multiphase fluid in which many bubbles are dispersed in water, but since the basic form of the refrigerant is liquid, there is a limit to the ability to adjust the cooling rate. can be seen. In addition, JP-A-57-140834 and the above-mentioned JP-A-60-
An example of adding a surfactant can be seen in Publication No. 248824, but these are added to lower the transition temperature from film boiling heat transfer to transition boiling (nucleate boiling) heat transfer defined by the boiling curve. has been done.

However, in the case of controlled cooling of spring steel and high carbon steel wire, especially in spring steel, if immersion cooling is performed in hot water near the boiling point, the cooling rate is too fast and a supercooled structure is generated. If this happens, the cooling rate will be non-uniform, leading to the problem of ferrite decarburization occurring in areas where the cooling rate is slow. From this,
Blast cooling is generally used as a means of achieving a cooling rate between immersion cooling in hot water and natural cooling in the atmosphere.

In the above-mentioned blast cooling method, when the non-concentric wire rings are coiled in the coiling head and are continuously placed on the conveyor and cooled, the degree of overlap of each wire ring is as follows: from the center of the wire ring to both sides. Therefore, measures are taken such as changing the amount of air blast depending on the degree of overlapping of the wire rings.

When cooling a wire rod formed into a non-concentric wire ring shape while being conveyed on a conveyor, the overlapping density of the wire rods at both ends of the wire ring is large and the refrigerant is in sufficient contact with the wire rod shape compared to the single wire-shaped portion in the center of the wire ring. The disadvantage is that cooling becomes weaker.

Further, as a cooling method for homogeneous patenting, there is an immersion cooling method in a strongly agitated fluid refrigerant of gas and hot water.

(Problems to be Solved by the Invention) However, in the blast cooling method, conventionally, air is applied from below to the overlapping portion of the wire rings, making uniform cooling difficult, and variations in the cooling rate within one wire ring result in heat loss. It is larger than that of materials treated by immersion cooling in water. Therefore, variations in mechanical properties such as tensile strength become large, causing problems such as tool wear during secondary processing, adversely affecting dimensional accuracy, and causing bending during straightening. .

In addition, in the method of immersion cooling in a strongly agitated fluid refrigerant of gas and hot water, since the refrigerant is in a strongly agitated state, small diameter wire rods around 5.5 mmφ are placed on a conveyor and passed through the process. This causes vibrations, causing trouble during transportation, and partial peeling of scale, which causes rough skin during mechanical descaling and pickling before secondary processing. Furthermore, since a large amount of air is blown into the system, running costs such as a blower and a refrigerant circulation device are required, which leads to larger and more complicated equipment, as well as extremely high equipment costs.

SUMMARY OF THE INVENTION The present invention aims to improve the above-mentioned drawbacks and provides a method for cooling a hot-rolled wire rod, which can cool the hot-rolled wire rod uniformly over its entire length and at a cooling rate within a wide range.

(Means for Solving the Problems) The wire cooling method of the present invention includes forming a continuous group of overlapping high-temperature wire rings on a conveyor so that their centers are shifted, and transporting the wire ring group by the conveyor. In the method of cooling by supplying a refrigerant, the refrigerant is foam, and more foam is supplied to a portion of the wire ring where the overlap density is high than to a portion where the overlap density is low. Here, foam refers to a group of single bubbles that exist outside of water and are separated by a thin film of liquid. Therefore, it is essentially different from the conventionally known gas-water multiphase fluid in which bubbles are dispersed in water, which is obtained by blowing gas into water. The foam is formed by a thin film of an aqueous solution containing at least one of a surfactant or a water-soluble polymer.

To form a group of wire rings, the wire rings are fed out from the winding head of a winder onto a conveyor as is conventionally done.

Foam can be generated by an air supply method, a stirring method, a shaking method, a boiling method, a pressure reduction method, a solubility reduction method, or the like. In the air supply method, air, an inert gas such as _N2 , or a reducing gas is blown into an aqueous solution containing a blowing agent. For example, a spray nozzle is used to supply the foam to the wire ring. The foam injection nozzle may be placed on either the upper or lower side of the wire ring,
Further, the cold water supply nozzle for quenching may also be used. In order to supply more foam to a portion of the wire ring with a high overlap density than to other portions, the foam is supplied from, for example, a foam injection nozzle that is concentrated on the portion of the wire ring with a high overlap density. Alternatively, foam having a higher moisture content may be supplied to a portion of the wire ring where the overlap density is higher than to other portions.

The amount of water in the foam is controlled by the ratio of the foaming agent to water in the aqueous solution containing the foaming agent, the type and concentration of the foaming agent, or the amount of air blown into the aqueous solution containing the foaming agent.

The lower limit water content in foam is 0.01g/100ml (foam 100
0.01g of water per ml) is desirable. This 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 amount of water in the foam is less than 0.01 g/100 ml, the amount of water is such that the foam hardly plays a role in influencing the cooling rate. In addition, the temperature of an aqueous solution containing a blowing agent is lowered to below room temperature to generate foam, and the cooling rate obtained when cooling with the foam is just the amount of water that exceeds the cooling rate obtained by cooling with conventional air. be. Further, it is desirable that the upper limit water content in the foam is 80 g/100 ml. This water content was selected with a slight leeway over the water content required to clear the cooling rate of 10 to 30°C/sec obtained by immersing in a strongly agitated refrigerant in a conventional multifunctional system. .

As mentioned above, foams are created from aqueous solutions containing surfactants and water-soluble polymers.

The surfactant here refers to a water-soluble organic compound that adsorbs to the surface of gas and liquid to reduce surface activity.More specifically, it refers to fatty acid salts, higher alcohol sulfate ester salts, and liquid fatty oils. Sulfate ester salts, sulfates of aliphatic amines and aliphatic amides, fatty alcohol phosphate ester salts, sulfone salts of dibasic fatty acid esters, fatty acid amide sulfonates, alkylaryl sulfonates, naphthalene sulfonates of formalin condensation anionic activators such as aliphatic amine salts, quaternary ammonium salts, alkylpyridinium salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenol ethers, polyoxyethylene alkyl Main examples include nonionic surfactants such as esters, sorbitan alkyl esters, polyoxysorbitan alkyl esters, and amphoteric surfactants such as alkyl betaines, alkyl dimethylamine oxides, and alkylalanines. It is not limited.

When generating foam, one or a mixture of two or more of these surfactants is added at a rate of 0.001 to 40% based on water.
It is preferable to add and use it so that

Water-soluble polymers include natural, synthetic, and semi-synthetic water-soluble polymers, including cornstarch, starches, funori, agar, sodium alginate, gum arabic, gum tragacanth, troloalloy, konnyaku, glue, and casein. , gelatin, egg white, plasma protein, pullulan, dextrin, carboxy starch, gum brite, dialdehyde starch, cationic starch,
Viscose, methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, polyvinyl alcohol, polyethylene glycol, polyalkylene glycol,
Main examples include polyacrylamide, polyacrylic acid, polyvinylpyrrolidone, water-soluble alkyd polyvinyl ether, polymaleic acid copolymer, polyethyleneimine, sabonin, 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 30% based on water.

The above-mentioned surfactant and water-soluble polymer may be mixed and used 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 dihydroxyethylglycine, hydroxyethyliminodiacetic acid,
Aminocarboxylic acid salts such as nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, oxycarboxylic acids such as sodium citrate, sodium gluconate, and sodium tartrate, polycarboxylic acids,
There are phosphonic acids such as hydroxyethane diphosphonic acid, nitrilotrismethylenephosphonic acid, and ethylenediaminetetramethylenephonic acid, and condensed phosphates such as sodium tripolyphosphate and sodium pyrophosphate, and one or more of them can be used in an amount of 0.001 to 20%.
It is preferable to use

Further, the higher alcohol is preferably a primary or secondary alcohol having 6 to 36 carbon atoms, such as hexanol, octanol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, oleyl alcohol, 18 carbon atoms,
One or more types of Guerbet alcohols such as 24 and 36 may be added in an amount of 0.5 to 30% based on the surfactant.

In addition, builders, such as sodium silicate, sodium sulfate, and soda carbonate, may be added to the above formulation at a rate of 0.1 to
You may add 30%.

Usually, the temperature of the aqueous solution containing the blowing agent is between 0℃ and 100℃.
Although it is used at temperatures up to 100°C, it is preferable to use it at room temperature and control the amount of water in the foam to obtain the desired cooling rate in terms of energy savings. It is also possible to preheat the temperature of the blown gas before use.

(Function) The foam supplied to the wire ring group enters between the rings and adheres to the wire surface. The aqueous foam film adhering to the wire surface evaporates due to the heat retained in the wire and is cooled by a combination of boiling heat transfer and radiation heat transfer.

The surfactant in the foam adsorbs to the surface of the gas and liquid, lowering the surface tension, and increasing the surface viscosity to improve the foamability during foam formation, the size or uniformity of the foam diameter, stability, etc. Furthermore, the water-soluble polymer in the foam improves the surface viscosity or surface viscoelasticity of the gas-liquid surface, forming a stable foam.

Since more foam is supplied to the portion of the wire ring where the overlap density is high than to the portion where the overlap density is low, the foam sufficiently surrounds the ring. Therefore, even if the evaporation rate of the aqueous solution in the foam increases and the amount of heat removed increases in areas where the wire rings overlap and have a high density, the foam will not disappear because the foam will be sufficiently replenished. As a result, the portions with high overlap density are cooled in the same way as the portions with low overlap density, and the wire is cooled uniformly over the entire length.

The cooling ability of foam changes depending on the amount of water in the foam.
Also, the moisture content can be adjusted over a wide range. Therefore, in one cooling facility, the cooling rate of the wire can vary over a wide range (from cooling with cooling water to natural cooling in the atmosphere, for example, 1 to 120°C/sec for a wire diameter of 10 mm). controlled.

(Example) Figures 1 and 2 show examples of the present invention, respectively. Figure 1 is a plan view showing a group of wire rings being conveyed on a conveyor, and Figure 2 is a cooling equipment. FIG.

The hot-rolled wire is sent out in a ring shape onto a conveyor 1 from a rolling head (not shown) of a winding machine, and a wire ring group S is formed on the conveyor 1. In the wire ring group S, the wire rings overlap closer to the side edge A than in other parts B.

The conveyor 1 is housed in a channel 2, and side guides 3 are provided on both sides.
A header 5 is arranged directly below the conveyor 1, and foam injection nozzles 6 are attached to both ends of the header 5, respectively. Foam injection nozzle 6
are directed toward both ends A of the wire ring group S. Further, an aqueous solution tank 8 storing an aqueous solution containing a foaming agent and an air tank 9 are connected to the header 5 to a foamer 10 via a supply pipe 7.

In the cooling equipment configured as described above, when an aqueous solution is blown into the foamer 10 together with air, the aqueous solution is foamed, and foam F is ejected from the foam injection nozzle 6 toward both ends A of the wire ring group S. . The ejected foam F spreads not only to both ends A of the wire ring group S but also to the entire channel 2, and the inside of the channel is filled with the foam F. The wire ring group S is immersed in this foam F and is cooled.

To give a specific example of wire cooling, the aqueous solution was water 1 at room temperature and 2.5 wt % of an anionic surfactant added thereto. Approximately 10/min of air is added to this aqueous solution.
200/min was introduced into the foamer to generate foam.
In such a foam, the diameter containing 0.4% C
A wire rod with a diameter of 9.5 mm was heated to 900°C and cooled by immersion.
As a result, the wire rod was cooled uniformly, and it was possible to stably manufacture a wire rod of the target quality with less quality fluctuation and lot fluctuation.

FIGS. 3 and 4 each show other examples of cooling equipment implementing the present invention. In the following embodiments, members similar to those shown in FIG. 2 are given the same reference numerals, and detailed explanations thereof will be omitted. In addition, the aqueous solution tank shown in Figure 2,
The air tank and foamer are omitted and not shown.

In FIG. 3, the header 5 is arranged directly above the channel 2, and the foam injection nozzle 6 is inclined so as to point toward the side end A of the wire ring group S. The foam F is supplied only into the side guide 3. In FIG. 4, the header 5 is placed directly above the channel 2, similar to the cooling equipment shown in FIG. The foam injection nozzle 6 is oriented between the side end A of the wire ring group S and the side guide 3.

This invention is not limited to the above embodiments. For example, when generating foam, an inert gas such as N ₂ gas or a reducing gas may be used instead of air from the viewpoint of preventing surface oxidation of the cooling wire.

(Effects of the Invention) In this invention, foam made from an aqueous solution containing a surfactant and a water-soluble polymer is used as a refrigerant, so the foam produced is uniform and stabilized, and the foam has a uniform water content. Layers can be created arbitrarily. This makes it easier to control the cooling atmosphere, and it is possible to stably produce wire rods of targeted quality with less quality fluctuation and lot fluctuation.

Compared to the conventional method of applying wind to cool the wire, the present invention can uniformly cool the wire over its entire length. In addition, compared to the conventional method of cooling by immersing in a hot liquid under strong stirring, the wire threading resistance is smaller, and the threading property is good even with a small diameter wire such as 5.5 mmφ, and scale peeling is also prevented. There are no problems such as rough skin caused by acid washing. Furthermore, it does not require refrigerant treatment, evaporation equipment, refrigerant circulation equipment, etc., has a simple structure, and has very low equipment costs.

Further, in the present invention, the cooling rate can be controlled over a wide range by controlling the water content and temperature of the foam. Therefore, compared to conventional methods, the mechanical properties such as tensile strength of the wire can be reduced by 1.
It can be adjusted over a wide range depending on the base cooling equipment.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a group of wire rod rings being conveyed on a conveyor, FIG. 2 is a longitudinal sectional view showing an example of cooling equipment for carrying out this invention, and FIGS. 3 and 4 are FIG. 7 is a vertical cross-sectional view showing other examples of cooling equipment. DESCRIPTION OF SYMBOLS 1... Conveyor, 2... Channel, 3... Side guide, 5... Header, 6... Foam injection nozzle, 7... Supply pipe, 8... Aqueous solution tank, 9... Air tank, 10
... Foaming machine, A... side end of wire ring group, B... central part of wire ring group, F... foam, S... wire ring group.

Claims (1)

[Scope of Claims] 1. A method in which a continuous group of high-temperature wire rings overlapping with their centers shifted is formed on a conveyor, and the group of wire rings is cooled by supplying a refrigerant while being conveyed by the conveyor. The refrigerant is foam formed by a thin film of an aqueous solution containing at least one of a surfactant and a water-soluble polymer, and is characterized by supplying more foam to areas of the wire ring that overlap and have a higher density than areas that overlap and have a lower density. A method for cooling wire rods. 2. The method for cooling a wire rod according to claim 1, characterized in that foam is supplied from a foam injection nozzle that is concentrated in a portion of the wire rod ring where the overlap density is high. 3. The method of cooling a wire rod according to claim 1, characterized in that the amount of moisture in the foam supplied to the portion of the wire rod ring with a high overlapping density is greater than that supplied to the portion with a low overlapping density.