KR101351946B1 - Cold-rolled steel sheet having excellent formability, heat resistance, surface properties for working and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a cold rolled steel sheet for processing and a method of manufacturing the same having excellent heat resistance and discoloration resistance, and include C: 0.01 to 0.10%, Ti: 0.07 to 0.15%, Sn: 0.05 to 0.25%, and Mn: 0.10 to 0.35 by weight. Cold rolled steel for processing and excellent in heat resistance and discoloration, including%, Al: 0.02% to 0.08%, P: 0.003% to 0.020%, N: 0.002% to 0.006%, S: 0.015% or less, balance Fe and other unavoidable impurities The manufacturing method is a technical subject matter.
According to the present invention, it can be manufactured at low cost compared to the existing stainless steel sheet, and has various processing characteristics of elongation flangeability, bending property and deep drawing property, which is excellent at room temperature workability, and yield resistance is increased due to the increase in the aging resistance by precipitation of solid elements. The phenomenon does not occur, not only excellent moldability, but also excellent in high temperature strength to secure the shape freezing properties of high-temperature applications, the life of the equipment is extended, it is possible to manufacture a cold-rolled steel sheet for high temperature processing excellent in discoloration resistance at high temperatures.

Description

COLD-ROLLED STEEL SHEET HAVING EXCELLENT FORMABILITY, HEAT RESISTANCE, SURFACE PROPERTIES FOR WORKING AND MANUFACTURING METHOD THEREOF}

The present invention relates to a cold-rolled steel sheet for high-temperature processing used in automobiles, home appliances, boilers, and the like, and to a method for manufacturing the same, and more particularly, to cold-rolled steel sheet having excellent heat resistance and discoloration resistance by optimizing steel components and process conditions. It relates to a manufacturing method.

In the past, cast iron was generally used in parts of products such as automobile exhaust systems, home communication systems, ovens, boilers, etc., but high heat resistance is required because it is continuously exposed to a high temperature environment of several hundred degrees (° C.) or more, so as to secure such high temperature characteristics. An aluminum hot-dip galvanized steel sheet, a stainless steel sheet, etc. were processed and used.

Here, the high temperature characteristic is one of the characteristics when the processed product is used in a high temperature environment, such as sag resistance, high temperature strength and discoloration resistance, and the product characteristics may be deteriorated by local temperature rise when using a product such as an automobile exhaust system. Therefore, high temperature characteristics are required. The sag resistance is a phenomenon in which the steel sheet is repeatedly exposed to high temperature, causing a change in material and sagging. When such a phenomenon occurs, it is difficult to maintain the shape of the molded part, and when the thermal stress is concentrated to a specific place, Since the product shape is deformed or destroyed due to deterioration, it is necessary to satisfy the yield strength of 55 MPa or more at a high temperature of about 700 ° C. in order to secure the shape freezing property. Discoloration resistance, which is a surface property for securing, is required.

Conventionally, stainless steel sheet has been mainly used for heat-resistance, but stainless steel sheet is not only expensive to manufacture due to the addition of expensive alloy elements such as Cr and Ni, but also the grain of Cr is combined with C when heated at high temperatures. There is a problem in that corrosion resistance is inferior due to grain boundary corrosion in the Cr depleted zone formed by chromium carbide precipitation.

In addition, in order to secure oxidation resistance at high temperatures, an aluminum hot dip galvanized steel sheet may be used. However, when the aluminum hot dip galvanized steel sheet is heated to a high temperature of 400 ° C. or higher, an alloy layer of an interface is grown due to the interdiffusion reaction between Fe and Al. There is a problem in that the application can be applied because it loses the gloss of the surface in a short time and the color change is insufficient heat resistance.

In addition, the heat-resistant steel sheet is manufactured to accommodate products in a limited space in addition to the above-described high temperature characteristics, such as automobile exhaust system, home communication, oven and boiler, and formed into a complicated shape by various methods to expand or bend after pipework. Because the process is required, room temperature processability is required.

In order to solve this problem, Japanese Patent Laid-Open No. Hei 8-319548 intends to manufacture a hot-dip aluminum plated steel sheet having excellent high temperature strength by forming a coating layer on the surface of the steel sheet, but improving the plating conditions rather than improving the characteristics of the steel sheet. Since the present invention is not only difficult to adjust when the plating layer is changed, there is a problem that it is difficult to obtain target heat resistance.

In addition, Japanese Laid-Open Patent Publication No. 9-176816 attempts to improve heat resistance and workability by heat-treating a steel sheet after adjusting aluminum content of Al and solid solution N in steel, but the steel sheet is used at a temperature of 550 ° C. or higher. It is difficult to apply it to a member of, and it is not easy to adjust the amount of the steel component to be added.

In order to solve the above problems, the present inventors have repeatedly conducted research and experiments and propose the present invention based on the results, and the present invention has high temperature characteristics and room temperature processability, such as automobile exhaust system, home communication, oven and boiler. At the same time, the cold rolled steel sheet for processing and its manufacturing method which can be manufactured at low cost by optimizing steel components and processing conditions while reducing the addition of medium and low carbon and reducing the addition of expensive alloying elements for use in the required applications The purpose is to provide.

In the present invention, C: 0.01 to 0.10%, Ti: 0.07 to 0.15%, Sn: 0.05 to 0.25%, Mn: 0.10 to 0.35%, Al: 0.02 to 0.08%, P: 0.003 to 0.020%, and N: Provides a cold rolled steel sheet for processing having excellent heat resistance and discoloration resistance including 0.002 to 0.006%, S: 0.015% or less, balance Fe and other unavoidable impurities.

At this time, there is also a feature that the value of the atomic ratio Ti / C of Ti and C is 0.35 to 0.70.

In addition, the cold rolled steel sheet is also characterized in that the Ti-based carbide precipitates are formed.

In addition, the cold-rolled steel sheet is characterized by being composed of equiaxed ferrite and needle-like ferrite.

Furthermore, the volume fraction of the acicular ferrite structure is also characterized by 5 to 10%.

The Sn-based oxide layer is also formed on the surface of the cold-rolled steel sheet.

Here, the Sn-based oxide layer is also characterized by being a Sn ₂ O ₃ layer.

In addition, the present invention is in the weight% C: 0.01 ~ 0.10%, Ti: 0.07 ~ 0.15%, Sn: 0.05 ~ 0.25%, Mn: 0.10 ~ 0.35%, Al: 0.02 ~ 0.08%, P: 0.003 ~ 0.020%, Steel slab containing N: 0.002 ~ 0.006%, S: 0.015% or less, balance Fe and other unavoidable impurities is heated and hot rolled, cold rolled after winding, and then cold rolled steel sheet is annealed at a temperature above 750 ℃. Provided is a process for producing a cold rolled steel sheet for processing having excellent heat resistance and discoloration resistance, which is treated and cooled at a cooling rate of 30 ° C./sec or more with respect to the annealed steel sheet.

At this time, the steel slab is characterized in that the value of the atomic ratio Ti / C of the Ti and C is 0.35 ~ 0.70.

In addition, the hot rolling is characterized in that it comprises the step of finishing rolling at 880 ~ 950 ℃.

In addition, there is also a feature that further comprises the step of cooling the hot rolled hot rolled sheet in the finishing rolling step at a cooling rate of 20 ~ 80 ℃ / sec.

Furthermore, the said winding is also characterized by what is performed at 560-680 degreeC.

In addition, the annealing treatment is also characterized by being performed at 750 to 900 ° C.

As described above, according to the present invention, it is possible to manufacture at a lower cost than the conventional stainless steel sheet, and has various processing characteristics of elongation flangeability, bending property, and deep drawing property, so that it is excellent in room temperature processability, and age-resistant by solid element precipitation. Not only does the yield point draw phenomenon increase, so it is not only excellent in formability, but also excellent in high temperature strength, thus prolonging the life of the facility by securing the shape freezing property of the high temperature applied product, and manufacturing cold rolled steel sheet for high heat resistance processing having excellent discoloration resistance at high temperature. can do.

Hereinafter, the cold-rolled steel sheet of the present invention will be described in detail.

The inventors at 700 ° C., while satisfying all the processing characteristics, such as stretch-flangeability, bendability, deep drawing, anti-aging properties and corrosion resistance at low cost The present invention has been completed by repeating studies and experiments to secure yield strength of 55 MPa or more and discoloration resistance at high temperatures. As a result, the present invention contains the amount of low and medium carbon in the steel component, and control the amount of Ti and the atomic ratio of Ti and C to form fine Ti-based carbide precipitates, by optimizing the annealing and cooling conditions volume fraction of acicular ferrite structure By adding Sn to form Sn-based oxide layer on the surface of steel sheet, it is excellent in heat resistance, corrosion resistance and discoloration at high temperature, age resistance at room temperature, and workability, so it can be used for products such as automobile exhaust system, home communication, oven and boiler. It is characterized by the manufacture of suitable high temperature resistant cold rolled steel sheets.

First, the reasons for limiting components of the present invention will be described.

Carbon (C) is an element added to improve the strength of a steel sheet, and is mainly consumed in the present invention by reaction with Ti for Ti-based carbide formation. As the amount of C added increases, the tensile and yield strength increases, but when added excessively, the workability decreases, so the upper limit is preferably 0.1%. If less than 0.01%, however, sufficient Ti-based carbide precipitates may not be strengthened, and grain size may increase, causing a sharp change in material, so that the C content is limited to 0.01 to 0.1%.

Manganese (Mn) is a solid solution strengthening element, which improves the strength of steel and improves hot workability, but inhibits ductility and workability by MnS formation. Therefore, when Mn is added in excess, the ductility is lowered and the economical efficiency due to the addition of a large amount of alloying elements becomes a cause of generation of center segregation, so that the upper limit is preferably 0.35%. However, if less than 0.10%, the workability is improved, but it is difficult to secure the target high strength, Mn content is limited to 0.10 ~ 0.35%.

Aluminum (Al) is an element added for deoxidation of molten steel and is preferably contained in an amount of 0.02% or more because it is combined with solid solution elements in steel to improve aging characteristics. However, excessive addition of more than 0.08% increases the amount of inclusions in the steel, causing surface defects and lowering the workability, Al content is limited to 0.02 ~ 0.08%.

Phosphorus (P) is an important element that improves the strength and corrosion resistance of steel, and it is preferable to contain 0.003% or more in order to secure these properties. However, if the content exceeds 0.020%, it causes central segregation during casting and lowers workability. The content of is limited to 0.003 ~ 0.020%.

Nitrogen (N) is a solid element inside the steel and is effective for reinforcing the material. If it is contained less than 0.002%, sufficient rigidity cannot be obtained and the precipitate formation site is reduced. As a cause of aging and hardening occurs to deteriorate moldability, the content of N is limited to 0.002 ~ 0.006%.

Sulfur (S) combines with Mn in the steel to form non-metallic inclusions that serve as the starting point of corrosion and causes red shortness, so it is desirable to reduce the content as much as possible, so the content of S is limited to 0.015% or less. . However, in order to ensure the above effect, it is preferable to manage at 0.010% or less.

Titanium (Ti) is an effective element for increasing the strength of steel sheet and refining grains, and in the present invention, Ti-based carbide precipitates are combined with solid solution C in steel to improve aging and formability. It is preferably contained at least 0.07% because the strength is increased and the grain growth at a high temperature is suppressed to provide the effect of refining the ferrite particles, but when the content exceeds 0.15%, the material is cured and the operability of the continuous annealing treatment is decreased. Deteriorates the surface properties of the steel sheet, the content of Ti is limited to 0.07 ~ 0.15%.

Tin (Sn) is an element that exists in a solid state inside the steel to improve high temperature characteristics and corrosion resistance, and is heated and oxidized by heat treatment to form Sn-based oxides such as Sn ₂ O ₃ on the surface of the steel sheet, thereby forming an alloying layer on the surface of the steel sheet. It is preferable to add 0.05% or more in order to obtain such effects, but if the content exceeds 0.25%, it is a factor of increase in manufacturing cost rather than contributing to improvement of corrosion resistance or discoloration resistance. Therefore, the content of Sn is limited to 0.05 ~ 0.25%.

It is also important to manage Ti alone, but it is also important to maintain Ti / C, which is an atomic ratio of Ti and C, in a certain range to ensure room temperature aging resistance, processability and high temperature strength simultaneously.

That is, when the value of Ti / C, which is an atomic ratio of Ti and C, is 0.35 to 0.70, solid carbide element C is fixed in the steel by the formation of Ti-based carbide precipitates, thereby ensuring room temperature aging resistance and workability, and annealing and cooling conditions. By appropriately controlling the fine grains of Ti-based carbides, grain growth can be suppressed at a high temperature to control the ferrite microstructure, thereby obtaining excellent high temperature characteristics. However, when the value of Ti / C, which is an atomic ratio of Ti and C, is less than 0.35, there is a problem that the room temperature aging resistance and workability may be deteriorated due to excessive solid solution elements in the steel, and because the amount of Ti-based carbide precipitates is insignificant, high temperature is excellent. Securing strength can be difficult. On the other hand, if the value exceeds 0.70, the material may be cured, the temperature of the recrystallization may be increased rapidly, and the surface properties may be deteriorated, thereby degrading workability of the post-process. It is preferable to limit the value of Ti / C to 0.35-0.70.

The cold rolled steel sheet of the present invention comprises the above components and consists of the remainder Fe and other unavoidable impurities. And alloy elements may be further added as needed to improve the properties of the present cold-rolled steel sheet, alloy elements that are not identified in the embodiment of the present invention is not interpreted to be excluded from the scope of the present invention.

In addition, the cold-rolled steel sheet of the present invention is characterized by consisting of an equiaxed ferrite (polygonal ferrite) and acicular ferrite tissue, the needle-like ferrite tissue is a kind of bainite grown by nucleation in the mouth of austenite before transformation As the nucleation grows from the fine non-metallic inclusions dispersed in the steel, the ferrite laths are relatively superior in ductility or toughness due to the disordered structure in which the ferrite laths form a high angle boundary with each other.

The present invention secures the volume fraction of the needle-like ferrite structure by 5-10% by appropriately controlling the conditions of the annealing and cooling process to form a high-potential-density type microstructure, thereby suppressing abnormal growth of grains at high temperature, thereby increasing the high temperature strength. It is possible to further improve heat resistance. When the volume fraction of the acicular ferrite structure is less than 5%, it may be difficult to secure very good high temperature strength, so that it may be difficult to obtain target heat resistance, and when the volume fraction of the acicular ferrite structure exceeds 10%, the material is hardened. There is a problem that the workability may deteriorate, and it is preferable to limit the volume fraction of the needle-like ferrite to 5 to 10%.

Hereinafter, the manufacturing method of the high heat resistant cold rolled steel sheet for processing excellent in workability, heat resistance, and discoloration resistance of this invention is demonstrated in detail.

After reheating the steel slab having the above composition, it is hot rolled, cold rolled after winding, and cooled at a cooling rate of 30 ° C./sec or higher on an annealing steel sheet at a temperature of 750 ° C. or higher to provide excellent workability, heat resistance, and discoloration resistance. High heat resistant cold rolled steel sheet for processing can be produced.

After reheating the steel slab formed as the above-described component system at a normal temperature, the finish rolling temperature during hot rolling is preferably in the range of 880 to 950 ° C. If the finish rolling temperature is less than 880 ° C., hot rolling is performed at a relatively low temperature region. As this is terminated, the final formed grains may be mixed, resulting in deterioration of workability and rolling property, and when the finish rolling temperature exceeds 950 ° C., uniform hot rolling may not be performed throughout the thickness, resulting in insufficient grain refinement. In this case, the impact toughness may be lowered due to grain coarsening, so the finish rolling temperature is preferably limited to 880 to 950 ° C.

After the hot finish rolling, it is preferable to cool the hot rolled steel sheet in a run-out table at a cooling rate of 20 to 80 ° C./sec. If the cooling rate is less than 20 ° C./sec, it is necessary to promote grain growth. This is because coarse crystal grains are formed, which may be a cause of deterioration in strength and workability. When the cooling rate exceeds 80 ° C / sec, there is a possibility of acting as a cause of variation of materials due to the uneven cooling in the width direction.

After cooling in the runout table, the hot rolled steel sheet is preferably wound at a temperature of 560 ~ 680 ℃. At this time, when the coiling temperature is less than 560 ℃, the material of the hot rolled material is somewhat hardened and the load in the cold rolling process, which is the next process, becomes large, and thus it is difficult to secure the rolling property, and the non-uniformity of the widthwise temperature is increased, resulting in low temperature precipitates. Due to the difference in the production behavior of the material deviation may be caused, the workability may be reduced, there is a problem that the high temperature characteristics may also be deteriorated. In addition, when the coiling temperature exceeds 680 ° C, the structure of the final product may be coarse, and there is a problem that the workability and corrosion resistance may be lowered. Therefore, the coiling temperature is preferably limited to 560 to 680 ° C.

After the wound steel sheet is subjected to a pickling process and cold rolling to a target thickness, it is preferable to undergo a continuous annealing process at a temperature of 750 ° C. or higher for recrystallization and microstructure control. The annealing temperature of 750 ℃ or more corresponds to a temperature for sufficiently securing the transformation driving force of the needle-like ferrite structure. Here, when the annealing temperature is less than 750 ℃, it is difficult to obtain the volume fraction of the needle-like ferrite structure present in the microstructure of the target steel sheet, and thus there is a problem that it is difficult to secure very good room temperature and high temperature strength. However, since the surface defects of the steel sheet may increase during high temperature annealing, the annealing temperature is preferably managed at 900 ° C. or lower.

The annealed steel sheet can secure a volume fraction of the target acicular ferrite structure through a cooling process, for which the cooling rate is maintained at 30 ℃ / sec or more. If the cooling rate is less than 30 ° C / sec, it is difficult to obtain the volume fraction of the target needle-like ferrite due to slow cooling.

Hereinafter, the present invention will be described in more detail with reference to Examples.

[Example]

Invented steels 1 and 2 and Comparative steels 1 to 5 prepared by melting the composition shown in Table 1 below under the process conditions as shown in Table 2 to produce cold rolled steel invention materials 1 to 5 and comparative materials 1 to 10 After that, the volume fraction of the acicular ferrite structure and the characteristics at room temperature and high temperature were evaluated for each of the prepared cold rolled steel sheets.

Yield elongation phenomenon of the characteristics shown in Table 3 was measured when the yield point elongation was measured and occurred when the elongation occurred, and not occurred when the elongation did not occur, and the bending resistance test was the surface bending after the steel sheet processing. According to the degree of occurrence, the bending index representing this was divided into 5 stages, and 1 to 2 stages with relatively small bending were good, and 3 to 5 stages where the bending occurred to the extent that visual observation can be judged as bad. .

In addition, the sag resistance test was determined to be defective when the sagging of the steel sheet after measuring the sagging of the steel plate after heating the material of 250mm in length, 30mm in width for 100 hours at 700 ℃ using a heat treatment equipment, The high temperature yield strength test was judged to be bad if the yield strength was less than 55MPa at 700 ° C, and higher than that. The high temperature discoloration resistance test showed that the surface glossiness was lowered by more than 30% after maintaining the steel plate at 500 ° C for 48 hours. It was judged to be defective.

The machinability test was judged to be defective when a crack occurred during processing at room temperature.

At this time, in Table 1, the value of the atomic ratio Ti / C of Ti and C refers to the ratio of the value obtained by dividing the weight percent of each element component by its atomic weight.

Table 1 Components of Inventive and Comparative Steels

[Table 2] Condition of Manufacturing Process by Steel Plate

[Table 3] Evaluation of properties by steel plate

As shown in Table 3, Inventive Materials 1 to 5 in which the steel component and the process conditions satisfy the scope of the present invention had no yield point stretching phenomenon and good bending resistance, which was excellent in aging resistance, and Ti-based carbide precipitates. The yield strength at high temperatures and the sag resistance after heat treatment (sag resistance) were good due to the formation of and the optimization of the volume fraction of the acicular ferrite structure, and the Sn-based oxide layer was formed on the surface of the steel sheet, resulting in a 30% reduction in surface glossiness at high temperatures. Less than high temperature discoloration resistance was good, processing defects do not occur during processing at room temperature, the room temperature processability was also excellent.

On the other hand, although the steel components of Table 1 and the like are the invention steels satisfying the scope of the present invention, Comparative Materials 1 to 5, in which some of the process conditions of Table 2 deviate from the scope of the present invention, are mostly excellent in low volume fraction of acicular ferrite structure. It did not have high temperature characteristics, and workability and aging resistance were also poor in many cases.

In addition, although the process conditions of Table 2 satisfy the scope of the present invention, Comparative Materials 6 to 10 in which the steel components C, Ti, Sn or Ti and C in Table 1 are outside the scope of the present invention are acicular ferrite structures. In many cases, the volume fraction was low and the room temperature and high temperature characteristics were poor.

Among them, Comparative materials 7 and 8 had no yield point stretching phenomenon and good bending resistance, but poor sag resistance, high temperature yield strength and high temperature discoloration resistance corresponding to high temperature characteristics. This is because the surface characteristics are deteriorated and Sn-based oxide layers are not formed on the surface of the steel sheet due to the addition of Sn. In addition, the comparative materials 9 and 10 have a high amount of solid carbon in steel, which is not only poor in workability and aging resistance, but also have a low Ti / C value, so that the amount of Ti-based carbide precipitates is insignificant, and the volume fraction of the needle-like ferrite structure is low. This defect was difficult to satisfy the normal temperature workability and the high temperature characteristics at the same time.

Eventually, the compositional conditions of the steel and the conditions of the manufacturing process (particularly annealing and cooling conditions) can be optimized to form fine Ti-based carbide precipitates, the volume fraction of the acicular ferrite structure can be controlled, and Sn is added to the steel sheet surface. _By forming a Sn-based oxide layer such as ₂ O ₃ , it was possible to manufacture a cold rolled steel sheet for high heat treatment that satisfies workability, heat resistance, and discoloration resistance at low cost.

The above-described embodiments are illustrative examples of the present invention are not limited thereto. Anything having substantially the same constitution as the technical idea described in the claims of the present invention and achieving the same operational effect is included in the technical scope of the present invention.

Claims (13)

By weight% C: 0.01 ~ 0.10%, Ti: 0.07 ~ 0.15%, Sn: 0.05 ~ 0.25%, Mn: 0.10 ~ 0.35%, Al: 0.02 ~ 0.08%, P: 0.003 ~ 0.020%, N: 0.002 ~ 0.006 %, S: less than 0.015%, remainder Fe and other unavoidable impurities, the cold rolled steel sheet for processing, excellent in heat resistance and discoloration resistance, the Sn ₂ O ₃ layer is formed on the surface. The method of claim 1,
The cold rolled steel sheet having excellent heat resistance and discoloration resistance, wherein the atomic ratio Ti / C of Ti and C is 0.35 to 0.70. The method of claim 1,
The cold rolled steel sheet is a cold rolled steel sheet for processing excellent in heat resistance and discoloration, characterized in that the Ti-based carbide precipitates are formed. By weight% C: 0.01 ~ 0.10%, Ti: 0.07 ~ 0.15%, Sn: 0.05 ~ 0.25%, Mn: 0.10 ~ 0.35%, Al: 0.02 ~ 0.08%, P: 0.003 ~ 0.020%, N: 0.002 ~ 0.006 A cold rolled steel sheet having excellent heat resistance and discoloration resistance, comprising%, S: 0.015% or less, balance Fe and other unavoidable impurities, and consisting of an equiaxed ferrite and acicular ferrite structure. 5. The method of claim 4,
The volume fraction of the acicular ferrite structure is 5 ~ 10%, cold rolled steel sheet for processing excellent in heat resistance and discoloration resistance. The method according to claim 4 or 5,
A cold rolled steel sheet for processing having excellent heat resistance and discoloration resistance, wherein a Sn-based oxide layer is formed on a surface of the cold rolled steel sheet. The method according to claim 6,
The Sn-based oxide layer is a cold rolled steel sheet having excellent heat resistance and discoloration resistance, characterized in that the Sn ₂ O ₃ layer. By weight% C: 0.01 ~ 0.10%, Ti: 0.07 ~ 0.15%, Sn: 0.05 ~ 0.25%, Mn: 0.10 ~ 0.35%, Al: 0.02 ~ 0.08%, P: 0.003 ~ 0.020%, N: 0.002 ~ 0.006 Steel slab containing%, S: 0.015% or less, balance Fe and other unavoidable impurities is heated and hot rolled, cold rolled after winding, and then cold rolled steel sheet is annealed at a temperature above 750 ° C., annealing A method for producing a cold rolled steel sheet for processing having excellent heat resistance and discoloration resistance, wherein the sheet is cooled at a cooling rate of 30 ° C./sec or more, and a Sn ₂ O ₃ layer, which is a Sn-based oxide layer, is formed on the surface of the cooled steel sheet. 9. The method of claim 8,
The steel slab is a method of manufacturing a cold rolled steel sheet having excellent heat resistance and discoloration resistance, characterized in that the value of the Ti / C atomic ratio Ti / C of 0.35 ~ 0.70. 10. The method according to claim 8 or 9,
The hot rolling is a manufacturing method of the cold rolled steel sheet for processing excellent in heat resistance and discoloration, characterized in that it comprises the step of finishing rolling at 880 ~ 950 ℃. The method of claim 10,
The method of manufacturing a cold rolled steel sheet having excellent heat resistance and discoloration resistance further comprising the step of cooling the hot rolled hot rolled sheet in the finishing rolling step at a cooling rate of 20 to 80 ° C./sec. 10. The method according to claim 8 or 9,
Said winding is performed at 560-680 degreeC, The manufacturing method of the cold rolled steel sheet for processing excellent in heat resistance and discoloration resistance characterized by the above-mentioned. 10. The method according to claim 8 or 9,
The annealing treatment is carried out at 750 ~ 900 ℃ the manufacturing method of the cold rolled steel sheet for processing excellent in heat resistance and discoloration resistance.