KR100797303B1 - Method for producing wire rod of tire cord treated with mechanical descaling having good scale adhesivity - Google Patents

Abstract

A method for producing a tire cord wire rod having excellent scale adhesion is provided, wherein the method is suitable for eliminating surface scales by mechanical descaling. A method for producing a tire cord wire rod for mechanical descaling having excellent scale adhesion comprises: extracting a billet from a reheating furnace in a temperature range of 950 to 1050 deg.C; hot rolling the extracted billet; cooling the hot rolled wire rod in a cooling rate of 120 to 190 deg.C/sec; and coiling the cooled wire rod in a temperature range of 890 to 930 deg.C. The billet has a composition comprising, by weight percent, 0.65 to 0.88% of C, 0.15 to 0.30% of Si, 0.4 to 0.8% of Mn, 0.02% or less of P, 0.02% or less of S, and the balance of Fe and other inevitable impurities. The composition further comprises 0.23% or less of Cr by weight percent.

Description

METHOD FOR PRODUCING WIRE ROD OF TIRE CORD TREATED WITH MECHANICAL DESCALING HAVING GOOD SCALE ADHESIVITY}

1 is a conceptual diagram showing that the scale is dropped when the shrinkage rate of the wire rod and the scale is different in the cooling process,

2 is a process flowchart showing a process of manufacturing a tire cord wire rod;

3 is a photograph showing whether or not the surface scale of the tire cord wire rod is removed; and

4 is a photograph illustrating the degree of scale dropout rate of the tire cord wire rod.

The present invention relates to a method for manufacturing a tire cord wire for mechanical peeling having excellent scale adhesion, and more particularly, to a tire cord wire manufactured for the purpose of removing the scale formed on the surface before drawing by a mechanical method. The present invention relates to a method for manufacturing a tire cord wire rod having a thick scale so that it can be easily applied to a mechanical peeling method and can be maintained until the peeling process.

A tire cord is a material that is inserted into a belt or a carcass position of a car in a thin line to improve durability of a tire. These tire cords are made in the fine wire state through the wire processing and heat treatment process in the wire state, and because it is subjected to extreme work hardening as the fine wire is characterized in that the strength is much higher than 3000MPa compared to the general steel. The tire cord as described above may be easily disposed in the tire due to the characteristic of the high strength thin wire, thereby effectively reinforcing the tire.

As described above, the tire cord manufacturing process is a process in which the wire diameter gradually decreases through extreme processing, and thus provides a cause for the wire to be broken by providing a stress concentration point when the wire surface has a flaw during the drawing process. . Therefore, these defects need to be removed as much as possible. The defect is often caused by the scale generated by oxidation of the wire surface in the wire manufacturing process.

Therefore, the scale removal process is necessarily accompanied before the wire drawing process of manufacturing the steel wire for tire cords.

The descaling process can be divided into two types according to the removing method. One of them is a chemical removal process, in which a scaled wire is placed in a container containing hydrochloric acid or nitric acid to dissolve and remove only the scale. Recently, the method of dissolving scale using acid has a tendency to decrease the frequency of use gradually because a large amount of waste water is generated, causing environmental pollution.

As another mechanical peeling method, a wire is passed between rollers, which are mechanical peeling equipments, to cause cracks in the scale structure to remove scales. Since the mechanical peeling method does not cause much environmental problems due to the above-described chemical peeling method, its usage is gradually increasing.

The key to such a mechanical peeling method is that when passing the wire between the rollers, the scale should be well broken and removed, and after removal, only the wire with a good surface should remain.

In order to satisfy this condition, it is necessary to form a scale having a relatively thick thickness of a certain level or more. In other words, sufficient thickness is required in order to be sufficiently crushed by the roller. Moreover, the composition of the said scale needs to be a composition which is favorable for peeling.

However, even if this type of scale is formed during the wire fabrication process, if the scale has already fallen off before undergoing mechanical exfoliation in the subsequent process, the scale falls off and reacts with oxygen in the atmosphere on the newly exposed surface, creating a new scale. Since the scale is not suitable for mechanical peeling and is hardly removed by the mechanical peeling method, it is important to maintain the scale formed during the wire manufacturing process until the drawing process.

Therefore, it is important to secure good adhesion of the manufactured scale. Japanese Unexamined Patent Publication No. 2005-281793 discloses a method for producing a wire rod for steel wire and an invention relating to wire rod for steel wire, which has the best adhesion and peelability. The present invention relates to a method for producing a steel wire having a scale on its surface and a steel wire produced therefrom. The present invention is to control the components of the steel in the appropriate range and to change the winding temperature in accordance with the relationship between Si, S and Cr to form a scale having a thickness of 5 ~ 15㎛ on the wire surface, the scale has the best adhesion and peelability The idea is to have However, the known technique is insufficient to control the phenomenon of causing scale desorption of the surface when the wire is wound even when the coiling temperature is changed according to a chemical component to ensure scale adhesion and peelability, or even under the conditions of the component. The scale thickness of the wire rod manufactured by this is in the range of 5-15 micrometers, and it is not enough considering that the scale thickness suitable for the mechanical peeling method is 10 micrometers or more normally.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to provide a method for producing a wire cord for a tire cord having good scale adhesion suitable for removing surface scale by a mechanical peeling method.

One embodiment of the production method of the tire cord wire for mechanical peeling with excellent scale adhesion of the present invention for achieving the above object is to extract the billet at a temperature of 950 ~ 1050 ℃ in a heating furnace and then hot rolled and cooled and wound It is characterized by taking.

At this time, the cooling rate at the time of cooling after the hot rolling is preferably 120 ~ 190 ℃ / sec.

In addition, the winding temperature at the time of winding is preferably 890 ~ 930 ℃.

Another embodiment of the method for producing a mechanical peeling tire cord wire having excellent scale adhesion of the present invention is the cooling rate is 120 ~ 190 ℃ / sec when the billet is extracted in a heating furnace and hot rolled after cooling It is characterized by that.

At this time, the coiling temperature during the winding is preferably 890 ~ 930 ℃.

Another embodiment of the method for producing a mechanical peeling tire cord wire having excellent scale adhesion of the present invention is to extract the billet in the temperature range of 950 ~ 1050 ℃ in a heating furnace, after hot rolling to 120 ~ 190 ℃ / sec Cooling at a cooling rate, and then wound in a temperature range of 890 ~ 930 ℃.

Billet used in the production method of the present invention advantageous as described above in weight% C: 0.65-0.88%, Si: 0.15-0.30%, Mn: 0.4-0.8%, P: 0.02% or less, S: 0.02% or less, It is more preferable to have the composition which consists of remainder Fe and other unavoidable impurities.

In addition to the above composition, Cr: 0.23% by weight or less may further be included.

Hereinafter, the present invention will be described in detail.

The present inventors carefully examined the condition of the wire for tire cords for mechanical peeling having excellent scale adhesion. Even if a thick scale is formed on the surface of the wire, the stress on the scale is different when the shrinkage of the wire and the scale is different during the cooling of the wire. This has resulted in the discovery that the scale can be pre-crushed and detached from the wire rod and has led to the present invention.

That is, as shown in FIG. 1, the scale generally exhibits a much lower shrinkage rate when cooling than that of the steel. If the shrinkage difference is reduced to minimize the rapid contraction of the steel during cooling, less stress is generated at the interface between the scale and the steel, thereby preventing the scale from crushing and detaching. In this case, the stress is largely applied to the interface between the scale and the steel, and the scale is crushed and detached.

Therefore, the present invention is to improve the adhesion of the scale by reducing the difference in shrinkage between the scale and the wire formed on the surface of the wire in the wire manufacturing process, the whole process from the extraction from the heating furnace to winding and cooling the wire It is an invention which further improves the adhesiveness of a scale by setting careful conditions with respect to.

Wire rod for tire cords targeted by the present invention is by weight% C: 0.65-0.88%, Si: 0.15-0.30%, Mn: 0.4-0.8%, P: 0.02% or less, S: 0.02% or less, balance Fe and It has a composition composed of other unavoidable impurities. The composition may contain up to 0.23% Cr in weight percent.

The reason for limiting the composition of the target wire is described below. The following composition is only described as the most preferable composition for applying the present invention, tire tire wire rod even if deviating to some extent the composition prescribed in the present invention as long as the tire cord wire by the excellent manufacturing method of the present invention described below. If it is in the composition range of the advantageous production method of the present invention can be applied.

C: 0.65-0.88% by weight (hereinafter referred to as '%' only)

The C is the most effective element to increase the strength to the lower limit of 0.65% in consideration of the strength of the final tire cord, it is preferable to limit the upper limit to 0.88% in consideration of the generation of cornerstone cementite due to the cooling rate decrease.

Si: 0.15-0.30%

Since Si is an element necessary for deoxidation of steel, if the content thereof is too small, the deoxidation effect is not sufficient, so 0.15% or more should be added. In addition, as the effective ferrite solid solution strengthening element, the continuous spacing of the pearlite layer becomes fine during the continuous cooling, and there is an effect of reducing the strength during the heat treatment of the new wire. However, when excessively added in excess of 0.30%, it is difficult to generate decarburization and to remove scale for drawing during heating for hot rolling. Therefore, it is preferable to limit the content to 0.15 to 0.30%.

Mn: 0.4 ~ 0.8%

The Mn forms a manganese emulsifier (MnS) together with sulfur in the material as well as deoxidation effect in the production of steel, thereby preventing red brittleness by sulfur, so 0.4% or more should be added. In addition, Mn is a very effective element to increase the strength of the material and to refine the pearlite interlayer spacing, but when it is added in excess of 0.8%, Mn is more likely to cause segregation and lowers the critical cooling rate at which martensite occurs. The limit is significantly reduced compared to other elements. Therefore, it is desirable to limit the content to 0.4 to 0.8%.

P: 0.02% or less, S: 0.015% or less

P is an impurity, the lower the content is better, but if controlled too extreme, the cost for removing impurities in the steelmaking process increases. Therefore, it is usually preferable to manage the P and S contents at 0.02% or less and 0.015% or less, respectively.

When the composition of the steel is controlled by the above composition, a tire cord having sufficient freshness and strength can be manufactured. In addition to the above composition, Cr may be further added within the range of 0.23% or less.

Cr: 0.23% or less

The Cr is an element that is very effective in increasing the hardenability of the steel to refine the pearlite to increase the strength and ductility, but when it is added in excess of 0.23%, the content of the Cr may be less than 0.23% since martensite may be generated during material cooling. It is preferable to limit to.

It is preferable that the tire cord is manufactured by the following manufacturing conditions for the tire cord having the above advantageous composition.

That is, as shown in FIG. 2, after reheating the billet having the composition in a heating furnace, the wire rod for the tire cord of the present invention may be manufactured through a process of extracting, rolling and cooling and winding at a predetermined temperature. The key part of the invention is the extraction temperature in the reheating furnace, the cooling rate during cooling and the coiling temperature. Other manufacturing conditions are similar to those for manufacturing a tire cord wire in general, and those skilled in the art can easily modify them to suit the conditions of the present invention.

Hereinafter, the core conditions of the present invention will be described in detail.

Furnace Extraction Temperature: 950 ~ 1050 ℃

It is preferable that the temperature which reheats a billet and extracts it from a heating furnace is 950-1050 degreeC. Since the billet is cooled after casting and then rolled again, the billet is reheated to prepare the billet at a temperature suitable for rolling. In the present invention, the billet temperature may be a very important factor controlling the scale adhesion. That is, in general, the extraction temperature after the reheating of the billet is often increased to 1250 ° C. In the present invention, when the billet is reheated at a high temperature as described above, a decarburized layer is developed on the surface, and as a result, the adhesion to the scale is adversely affected. The reason for this is that steels with a low carbon content have a large shrinkage rate upon cooling, and as a result, the stress acting on the scale becomes large and the scale easily falls off. Therefore, it is preferable to suppress a furnace extraction temperature to 1050 degrees C or less. However, if the extraction temperature is less than 950 ℃, the load acting on the roll during rolling may not only cause problems in the process but also satisfy the subsequent winding temperature conditions, the extraction temperature is above 950 ℃ It is limited.

Cooling Speed: 120 ~ 190 ℃ / sec

After rolling, ie, passing through the final rolling mill and then winding up, water cooling is performed, but the cooling rate in the water cooling section is preferably 120 to 190 ° C / sec. If the cooling rate exceeds 190 ° C / sec, the shrinkage rate of the wire rod is excessively increased while the scale shrinkage rate does not show a large difference according to the cooling rate. Promotes elimination. Therefore, the cooling rate is preferably maintained at 190 ° C / sec or less. In terms of scale adhesion, it is preferable to keep the cooling rate as low as possible, but when the cooling rate is low, the rolling speed of the final rolling mill should be lowered and the number of water cooling units should be adjusted smaller. In this case, the productivity decreases rapidly. The cooling rate is preferably at least 120 ° C / sec.

Winding Temperature: 890 ~ 930 ℃

The winding temperature is also an important condition for securing scale adhesion. Winding temperatures of conventional wire rods for tire cords range from about 830 ° C to 930 ° C. However, when winding the wire for tire cord in a wide range as described above, it is difficult to expect the improvement of scale adhesion. When the coiling temperature exceeds 930 ℃ scale component phenomenon called blistering occurs on the scale and scale adhesion decreases, on the contrary, when the coiling temperature is less than 890 ℃ can be obtained a scale of sufficient thickness Not. Therefore, it is preferable that a coiling temperature is 890-930 degreeC.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are only intended to illustrate the present invention by way of example, not intended to limit the scope of the present invention, the scope of the present invention to the matters described in the claims and reasonably inferred therefrom. It is important to note that this is determined by.

(Example)

The tire cord billet having the composition shown in Table 1 was prepared under the conditions shown in Table 2, and if the scale was dropped, the scale was visually observed, and if the scale was well attached as shown in FIG. 3 (b), FIG. 3 (b) As described above, when the scale was dropped and the surface of the smooth wire rod was exposed, it was indicated by x. The scale dropout rate was calculated as the scale dropout rate by calculating the area ratio of the portion of the wire rod surface not covered by the scale, and the results are also shown in Table 2. 4 shows the wire surface shape for each scale dropout rate obtained in the present invention.

number C (% by weight) Si (% by weight) Mn (wt%) P (% by weight) S (% by weight) One 0.822 0.206 0.503 0.005 0.0148 2 0.826 0.189 0.499 0.005 0.0134 3 0.802 0.208 0.538 0.005 0.0125 4 0.802 0.182 0.518 0.004 0.0140 5 0.810 0.188 0.507 0.005 0.0147 6 0.810 0.202 0.501 0.006 0.0091 7 0.826 0.190 0.487 0.004 0.0110 8 0.816 0.203 0.512 0.004 0.0114 9 0.802 0.182 0.518 0.004 0.0140 10 0.819 0.221 0.511 0.004 0.0110 11 0.816 0.196 0.511 0.005 0.0150 12 0.816 0.205 0.510 0.005 0.0103 13 0.814 0.201 0.511 0.005 0.0110 14 0.830 0.196 0.517 0.005 0.0133 15 0.827 0.195 0.506 0.004 0.0120 16 0.810 0.195 0.480 0.006 0.0080 17 0.817 0.211 0.504 0.005 0.0084 18 0.829 0.196 0.492 0.005 0.0140 19 0.816 0.180 0.494 0.004 0.0140 20 0.822 0.201 0.515 0.003 0.0160 21 0.816 0.180 0.494 0.003 0.0090 22 0.822 0.201 0.515 0.005 0.0090 23 0.820 0.200 0.496 0.002 0.0080 24 0.820 0.201 0.500 0.004 0.0100 25 0.812 0.195 0.510 0.004 0.0074 26 0.819 0.190 0.499 0.003 0.0089

number Furnace Extraction Temperature (℃) Finishing mill exit temperature (℃) Winding temperature (℃) Finishing rolling ~ winding cooling rate (℃ / sec) Scale dropout Scale dropout rate (%) One 1080 1030 900 265.3 × 55 2 1080 1030 900 265.3 × 50 3 1070 1020 900 244.9 × 60 4 1100 1040 900 285.7 × 70 5 1090 1030 900 265.3 × 60 6 1030 1000 900 204.1 × 40 7 1050 1020 900 244.9 × 40 8 1020 1000 900 204.1 × 30 9 1030 1010 900 224.5 × 40 10 1010 1030 900 265.3 × 50 11 1030 980 900 163.3 ○ 5 12 1050 990 900 183.7 ○ 3 13 1040 960 900 122.4 ○ 7 14 1050 980 900 163.3 ○ 5 15 1010 960 900 122.4 ○ 5 16 1030 970 900 142.9 ○ One 17 1030 980 900 163.3 ○ 5 18 1080 1030 900 160.2 × 50 19 1100 1050 900 170.0 × 40 20 1090 1040 900 155.2 × 50 21 1180 1030 900 180.3 × 50 22 1030 1000 850 190 ○ 5 23 1040 1020 860 185.1 ○ 5 24 1030 1010 870 180.6 ○ 3 25 1020 1000 850 175.2 ○ 5 26 1040 1030 850 174.3 ○ 5

As described above, the numbers 1 to 5 denote not only the extraction of the billet at a temperature higher than the heating furnace extraction temperature specified in the present invention, but also the cooling rate cooled at a rate higher than 190 ° C / sec. Even when visually observed, a large amount of scale was dropped out, and the scale dropout ratio obtained by the area ratio was also high, which is higher than 50%. In addition, the numbers 6 to 10 satisfy the extraction temperature specified in the present invention, but the cooling rate is excessively high. In this case, the dropout rate was slightly lower than that of the numbers 1 to 5, but the dropout rate was about 30 to 50%. It can be seen that it represents.

On the other hand, in the case of Nos. 11 to 17, which are manufactured by heating furnace extraction temperature, winding temperature, and cooling rate under the conditions specified in the present invention, the scale is well attached as shown in FIG. It was found that the scale dropout rate determined by the area ratio was also 7% or less, indicating that a good scale was formed for mechanical peeling.

In addition, in the case of No. 18 to 21, all other conditions satisfy the range specified in the present invention, but the furnace extraction temperature is higher than that specified in the present application, and as a result, the furnace extraction temperature and Although the cooling rate shows better results than the case where all of the cooling rates are not satisfied, it was confirmed that the scale dropout rate is higher than the most preferable case that satisfies all the conditions defined in the present invention as shown in Nos. 11 to 17.

In addition, in the case of Nos. 22 to 26, the coiling temperature is lower than the conditions specified in the present application. In this case, the dropout of the scale is not observed. However, when the winding temperature is excessively low as in the case of Nos. 22 to 26, the scale thickness is about 6 to 8 μm, which is not suitable for use in mechanical peeling. In other cases, a scale thickness of about 10 to 13 μm was confirmed.

As described above, according to the present invention, a tire cord wire rod having excellent scale adhesion can be produced with high productivity.

Claims (8)

The billet is extracted at a temperature of 950 to 1050 ° C. in a heating furnace, hot rolled, cooled to a cooling rate of 120 to 190 ° C./sec, and wound. Way. delete delete When the billet is extracted in a heating furnace, hot rolled, cooled, and wound, the cooling rate is 120 to 190 ° C / sec. The method of claim 4, wherein the winding temperature at the time of winding is 890 to 930 ° C. After the billet is extracted in a heating furnace at a temperature range of 950 to 1050 ° C., hot rolled and cooled at a cooling rate of 120 to 190 ° C./sec, it is then wound in a temperature range of 890 to 930 ° C. A method for producing this excellent mechanical stripping tire cord wire. The billet according to any one of claims 1 and 4 to 6, wherein the billet is C: 0.65-0.88%, Si: 0.15-0.30%, Mn: 0.4-0.8%, P: 0.02% or less. , S: 0.02% or less, residue Fe and other unavoidable impurities, characterized in that the composition of the tire cord wire for mechanical peeling excellent scale adhesion, characterized in that the composition. The method of manufacturing a tire cord wire for mechanical peeling excellent in adhesion to scale according to claim 7, further comprising Cr: 0.23% by weight or less in addition to the composition.

Images