KR20120127855A - Cold-rolled steel sheet having excellent formability, heat resistance, surface properties for working and manufacturing nethod thereof - Google Patents

Abstract

The present invention relates to a high heat-resistant cold-rolled steel sheet having excellent workability, heat resistance, and discoloration resistance, and a method for manufacturing the same, wherein the weight ratio is C: 0.002 to 0.005%, Ti: 0.03 to 0.08%, Sn: 0.05 to 0.25%, and Mn: Excellent workability, heat resistance and discoloration including 0.07 to 0.55%, Al: 0.01 to 0.10%, P: 0.003 to 0.020%, N: 0.002 to 0.006%, S: 0.015% or less, balance Fe and other unavoidable impurities High heat-resistant cold-rolled steel sheet and a method of manufacturing the same are the technical points.
According to the present invention, it can be manufactured at low cost compared to the existing stainless steel sheet, has various processing characteristics of elongation flangeability, bending property and deep drawing (excellent room temperature workability), and age-resistant by solid element precipitation As a result, the yield-point stretching phenomenon does not occur, so it is not only excellent in formability, but also excellent in high temperature strength, thereby prolonging equipment life by securing shape freezing properties of high-temperature applications, and manufacturing high-temperature cold rolled steel sheets having excellent discoloration resistance at high temperatures. can do.

Description

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

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

Cast iron is generally used for parts of products such as automobile exhaust systems, household flues, ovens and boilers, but aluminum is melted to secure such high temperature characteristics because it is continuously exposed to high temperatures of several hundred degrees (° C.) and requires high heat resistance. Plated steel sheet, stainless steel sheet, etc. were processed and used.

     Here, the high temperature property is one of the characteristics when the processed product is used in a high temperature environment, and includes sag resistance, high temperature strength, and discoloration resistance, and the product property may be degraded due to local temperature rise when using a product such as an automobile exhaust system. 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. 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. However, stainless steel sheet is not only expensive to manufacture due to the addition of expensive alloying elements such as Cr and Ni, but also has a grain boundary of Cr and C when heated at high temperature. By combining, grain boundary corrosion occurs in the Cr depleted zone, which is caused by the precipitation of chromium carbide (chromium carbide) at the grain boundary, resulting in poor corrosion resistance.

     In addition, in order to secure oxidation resistance at high temperature, an aluminum hot dip galvanized steel sheet may be used, but when the aluminum hot dip galvanized steel sheet is heated to a high temperature of 400 ° C. or higher, an alloy layer at an interface due to the interdiffusion reaction between Fe and Al is grown. 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, in addition to the high temperature characteristics described above, heat-resistant steel sheet is manufactured so that products such as automobile exhaust system, home communication, oven and boiler, etc. are accommodated in a limited space, and formed into a complicated shape by various methods to expand or bend after piping. In addition to the high temperature characteristics, a room temperature processability is also required because a process 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 be applied to a member of, and it is not easy to adjust the amount of the steel component 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, to provide a high-temperature cold-rolled steel sheet and a method of manufacturing the same which can be manufactured at low cost by optimizing steel components and process conditions while reducing the addition of expensive alloying elements for use in demanding applications. The purpose is.

In order to achieve the above object, the present invention provides a weight percentage of C: 0.002 to 0.005%, Ti: 0.03 to 0.08%, Sn: 0.05 to 0.25%, Mn: 0.07 to 0.55%, Al: 0.01 to 0.10%, and P: 0.003. It provides a high heat resistant cold rolled steel sheet having excellent processability, heat resistance, and discoloration resistance including ˜0.020%, N: 0.002˜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 2.5 to 4.0. In addition, the cold rolled steel sheet is characterized in that Ti-based carbide precipitates are formed.

     In addition, the cold rolled steel sheet is characterized in that it is made of an equiaxed ferrite and acicular ferrite structure. Here, the volume fraction of the acicular ferrite structure is also characterized by 5 to 15%.

     Furthermore, the Sn-type oxide layer is formed in the surface of the said cold rolled steel sheet, and it has the characteristics.

In addition, the Sn-based oxide layer is characterized in that it is a layer containing Sn ₂ O ₃ .

     In addition, the present invention is in the weight% C: 0.002 ~ 0.005%, Ti: 0.03 ~ 0.08%, Sn: 0.05 ~ 0.25%, Mn: 0.07 ~ 0.55%, Al: 0.01 ~ 0.10%, P: 0.003 ~ 0.020%, A steel slab containing N: 0.002 to 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 of 800 ° C. or higher. Provided is a method for producing a cold rolled steel sheet having excellent workability, heat resistance, and discoloration resistance, wherein the steel sheet is treated and cooled at a cooling rate of 30 ° C./sec or more.

     At this time, the steel slab is characterized in that the value of the atomic ratio Ti / C of the Ti and C is 2.5 to 4.0.

     In addition, the hot rolling is characterized in that it comprises the step of finishing rolling at 900 ~ 940 ℃.

     In addition, the hot rolling is characterized in that it further comprises the step of cooling the hot rolled hot rolled plate at a cooling rate of 20 ~ 80 ℃ / sec.

     The winding is also characterized by being performed at 560 to 680 ° C.

Furthermore, the annealing treatment is also characterized by being performed at 800 to 900 占 폚.

As described above, according to the present invention, it can be manufactured at a lower cost than the conventional stainless steel sheet, and satisfies various processing characteristics of extension flangeability, bending property, and deep drawing property, and thus has excellent room temperature workability, and solid solution element. Reduction of the aging resistance increases the aging resistance and does not cause the yield point stretching, not only excellent moldability, but also excellent high temperature strength ensures the shape freezing properties of high-temperature applications, prolongs the life of the equipment, excellent discoloration resistance at high temperatures High heat resistant cold rolled steel sheet can be produced.

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

The inventors of the present invention at 700 ° C satisfying various 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 a very low carbon content in the steel component, and control the amount of Ti and the atomic ratio of Ti and C to form a fine Ti-based carbide precipitate, by optimizing the annealing and cooling conditions volume of the needle-like ferrite structure It secures the fraction and forms Sn-based oxide layer on the surface of steel sheet by adding Sn, so it is excellent in heat resistance, corrosion resistance and discoloration at high temperature, and aging and workability at room temperature. It is characterized by the manufacture of suitable high heat resistant cold rolled steel sheets.

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

Carbon (C) is an element added for improving the strength of the steel sheet, and is mainly consumed by the reaction with Ti to form Ti-based carbide precipitates in the present invention. As the amount of C added increases, the tensile and yield strength increases, but when excessively added, the workability decreases, so the upper limit is preferably 0.005%. However, if less than 0.002%, sufficient Ti-based precipitates are not formed and the grain size increases, so that not only a sudden change of material occurs but also it is difficult to secure high-temperature characteristics, the content of C is limited to 0.002 to 0.005%.

     Manganese (Mn) is a solid solution strengthening element that increases the strength of steel and improves hot workability, but is an element that inhibits ductility and workability by MnS formation. Therefore, when Mn is added excessively, ductility falls and it becomes a factor of economic deterioration and center segregation by addition of a large amount of alloying elements, so an upper limit is 0.55%. However, if less than 0.07%, the workability is improved, but it is difficult to secure the target strength, the Mn content is limited to 0.07 ~ 0.55%.

     Aluminum (Al) is an element added for deoxidation of molten steel and is preferably contained in an amount of 0.01% or more because it is combined with solid solution elements in steel to improve aging characteristics. However, when excessively added in excess of 0.10%, the amount of inclusions in the steel increases to cause surface defects and workability is lowered, so the Al content is limited to 0.01 to 0.10%.

     Phosphorus (P) is an element that improves the strength and corrosion resistance of steel, and in order to secure these properties, it is preferable to contain 0.003% or more. However, if the content exceeds 0.020%, it causes central segregation during casting and lowers workability. The content is limited to 0.003 to 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 act as corrosion initiation points 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 said effect reliably, it is preferable to manage at 0.010% or less.

     Titanium (Ti) combines with solid solution in the steel to form Ti-based carbide precipitates to improve aging resistance and workability.Titanium carbide precipitates increase the strength of the steel sheet and suppress grain growth at high temperatures. It is preferable to contain 0.03% or more because it provides the effect of refining the particles, but if the content exceeds 0.08%, the content of Ti hardens, which leads to deterioration of the surface properties of the steel sheet and hardening of the material. Is limited to 0.03 to 0.08%.

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 a Sn-based oxide layer such as Sn ₂ O ₃ on the surface of the steel sheet to form an alloying layer on the surface of the steel sheet. It is preferable to add 0.05% or more in order to obtain such an effect, but it is preferable to add at least 0.05% in order to suppress formation and to improve corrosion resistance and discoloration resistance. Since it is a factor, the content of Sn is limited to 0.05 to 0.25%.

     In the case of Ti and C it is also important to manage alone, but in order to secure the high temperature and room temperature characteristics targeted by the present invention, it is necessary to take into account the effects of precipitate formation and solid solution elements in the steel. For this purpose, it is also important to keep the atomic ratio Ti / C of Ti and C in a certain range to ensure room temperature aging resistance, processability and high temperature strength at the same time.

     When the atomic ratio Ti / C of Ti and C is 2.5 to 4.0, solid solution elements in steel are fixed by forming Ti-based carbonized precipitates, thereby ensuring room temperature aging resistance and processability, and controlling annealing and cooling conditions appropriately. It is possible to secure excellent high temperature characteristics by forming a fine Ti-based precipitate to suppress grain growth at high temperatures to control the ferrite microstructure.

However, when the value of Ti / C is less than 2.5, there is a problem of deterioration of room temperature aging resistance and processability due to excessive solid solution elements in the steel, and it is difficult to secure excellent high temperature strength because the precipitation amount of Ti-based precipitates is insignificant. In addition, when the value exceeds 4.0, the material may be cured, the temperature of the recrystallization may be increased rapidly, and the surface properties may be degraded, thereby reducing the workability of the post-process. The value of is preferably limited to 2.5 to 4.0.

     The cold rolled steel sheet of the present invention comprises the above components and consists of the balance 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.

     On the other hand, 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 that is nucleated and grown in the mouth of austenite before transformation As it is nucleated and grown from fine non-metallic inclusions dispersed in steel, ferrite laths are relatively excellent in ductility and toughness due to the disordered structure in which ferrite laths form a high angle boundary with each other. .

The present invention secures the volume fraction of the needle-like ferrite structure by 5-15% by appropriately controlling the conditions of the annealing and cooling process to form a high-potential-density type microstructure, thereby inhibiting abnormal growth of grains at high temperature to secure high temperature strength. By doing so, heat resistance can be improved. When the volume fraction of the acicular ferrite structure is less than 5%, it is difficult to secure high-temperature strength, so that target heat resistance is difficult to obtain, and when the volume fraction of the acicular ferrite structure exceeds 15%, workability may be deteriorated by hardening of the material. There is a problem, and the volume fraction of the needle ferrite is limited to 5 to 15%.

     Hereinafter, the manufacturing method of the high heat resistant cold rolled steel sheet 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 800 ° C. or higher to provide excellent workability, heat resistance, and discoloration resistance. High heat resistant cold rolled steel sheet can be produced.

     After reheating the steel slab formed like the above-described component system at a normal temperature, the finish rolling temperature during hot rolling is 900 to 940 ° C. If the finish rolling temperature is less than 900 ° C, the hot rolling is completed in a relatively low temperature region. Workability and rolling property may be degraded due to hybridization of the finally formed crystal grains, and when the finish rolling temperature exceeds 940 ° C., uniform hot rolling may not be performed throughout the thickness, resulting in insufficient grain refinement and thus grains. Since impact toughness may fall due to coarsening, it is preferable to limit finish rolling temperature to 900-940 degreeC.

     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, when the cooling rate is less than 20 ° C./sec. This is because coarse grains are formed by acceleration, which can be a cause of strength and workability deterioration. When the cooling rate exceeds 80 ° C / sec, there is a possibility of acting as a cause of variation of material due to uneven cooling in the width direction. to be.

     After cooling in the runout table, the hot rolled steel sheet is preferably wound at a temperature of 560 ~ 680 ℃. 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 may be difficult to secure the rolling property. Due to the difference in behavior may cause a material deviation, 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 pickling treatment and cold rolling to a target thickness, it is preferable to undergo a continuous annealing process at a temperature of 800 ° C. or higher for recrystallization and microstructure control. The annealing temperature of 800 ° C. 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 800 ° C., it is difficult to obtain a volume fraction of the acicular ferrite structure present in the microstructure of the target steel sheet, which may cause difficulty in securing excellent high temperature characteristics. 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 less.

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. This is because when the cooling rate is less than 30 ° C./sec, it is difficult to obtain a volume fraction of the target acicular ferrite structure due to slow cooling.

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

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 expressed as occurrence when the elongation was generated by measuring the yield point elongation through the tensile test, non-occurrence when the elongation did not occur, the bending resistance test After the steel sheet was processed, it was divided according to the degree of surface bending, and the bending index representing this was divided into five stages, and 1 to 2 stages with relatively small bending were satisfactory. The step was determined to be bad.

In addition, the sag resistance test is bad when the sagging of the steel sheet after measuring the sagging of the steel sheet after heating the material of 250mm in length and 30mm in width for 100 hours at 700 ℃ using a heat treatment equipment, less than 5mm The high temperature yield strength test was good if the yield strength was 55 MPa or more at 700 ° C., and the bad was less than that. The high temperature discoloration resistance test was performed after maintaining the steel plate at the temperature of 500 ° C. for 48 hours to obtain surface gloss. Was lower than 30%, it was determined to be defective.

     In addition, the workability test was judged to be defective when a work crack occurred during normal temperature processing. 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 shows the components of the inventive steel and the comparative steel, and Table 2 shows the conditions of the steel sheet manufacturing process.

Table 3 shows the results of the evaluation of the characteristics of each steel sheet according to the manufacturing process in Table 2 above. 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 temperature 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 needle-like ferrite structure. There was no work cracking at the time, so the workability at room temperature 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 are out of the scope of the present invention, are mostly low in volume fraction of acicular ferrite structure. It did not have high temperature characteristics (sag resistance, high temperature yield strength, high temperature discoloration resistance), and also poor workability and aging resistance.

     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 the atomic ratio of Ti and C of Table 1, etc., 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 material 7 had no yield point stretching phenomenon and good bending resistance, so that aging resistance and workability were good, but sag resistance, high temperature yield strength and discoloration resistance corresponding to high temperature characteristics were poor. This is because the high value of deteriorates the surface characteristics and no Sn-based oxide layer is formed on the surface of the steel sheet due to the absence of Sn. In addition, the comparative materials 8 to 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, resulting in a small amount of Ti-based precipitates, and a low volume fraction of the needle-like ferrite structure. It was poor and it was difficult to satisfy | attain a normal temperature workability and a high temperature characteristic simultaneously.

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 high heat resistant cold rolled steel sheet satisfying workability, heat resistance and discoloration resistance at low cost.

     The present invention is not limited to the above-described embodiments. Any thing that has substantially the same structure and the same effect as the technical idea described in the claim of the present invention is included in the technical scope of this invention.

Claims (13)

By weight% C: 0.002 ~ 0.005%, Ti: 0.03 ~ 0.08%, Sn: 0.05 ~ 0.25%, Mn: 0.07 ~ 0.55%, Al: 0.01 ~ 0.10%, P: 0.003 ~ 0.020%, N: 0.002 ~ 0.006 High heat resistant cold rolled steel sheet with excellent workability, heat resistance and discoloration, including%, S: 0.015% or less, balance Fe and other unavoidable impurities. The method of claim 1,
A high heat resistant cold rolled steel sheet having excellent workability, heat resistance and discoloration resistance, wherein the atomic ratio Ti / C of Ti and C is 2.5 to 4.0. The method of claim 1,
The cold rolled steel sheet is a high heat resistant cold rolled steel sheet excellent in workability, heat resistance and discoloration characteristics, characterized in that the Ti-based carbide precipitates are formed. The method of claim 1,
The cold rolled steel sheet is a high heat-resistant cold-rolled steel sheet excellent in workability, heat resistance and discoloration, characterized in that consisting of an equiaxed ferrite and acicular ferrite structure. 5. The method of claim 4,
A high heat resistant cold rolled steel sheet having a processability, heat resistance and discoloration resistance, characterized in that the volume fraction of the acicular ferrite structure is 5 to 15%. The method according to any one of claims 1 to 5,
A high heat resistant cold rolled steel sheet having excellent workability, 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 high heat-resistant cold-rolled steel sheet excellent in workability, heat resistance and discoloration, characterized in that the layer containing Sn ₂ O ₃ . By weight% C: 0.002 ~ 0.005%, Ti: 0.03 ~ 0.08%, Sn: 0.05 ~ 0.25%, Mn: 0.07 ~ 0.55%, Al: 0.01 ~ 0.10%, 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 of 800 ° C. or higher, and annealed. A method for producing a high heat resistant cold rolled steel sheet having excellent workability, heat resistance and discoloration resistance, characterized by cooling at 30 ° C./sec or more with respect to the finished steel sheet. 9. The method of claim 8,
The steel slab is a method of manufacturing a high heat-resistant cold rolled steel sheet having excellent workability, heat resistance and discoloration, characterized in that the value of the Ti / C atomic ratio Ti / C of 2.5 ~ 4.0. 10. The method according to claim 8 or 9,
The hot rolling is a manufacturing method of high heat resistant cold rolled steel sheet having excellent workability, heat resistance and discoloration resistance, characterized in that it comprises the step of finishing rolling at 900 ~ 940 ℃. 10. The method according to claim 8 or 9,
The hot rolling is a method of manufacturing a high temperature resistant cold rolled steel sheet excellent in workability, heat resistance and discoloration, further comprising the step of cooling the hot rolled hot rolled sheet at a cooling rate of 20 ~ 80 ℃ / sec. 10. The method according to claim 8 or 9,
The winding is carried out at 560 ~ 680 ℃ manufacturing method of high heat resistant cold rolled steel sheet excellent in workability, heat resistance and discoloration resistance. 10. The method according to claim 8 or 9,
The annealing treatment is carried out at 800 ~ 900 ℃, characterized in that the workability, heat resistance and discoloration resistance excellent high temperature cold rolled steel sheet manufacturing method.