KR20120127857A - Cold-rolled steel sheet having excellent formability, high-heat resistance and surface properties for working and manufacturing nethod thereof - Google Patents

Abstract

PURPOSE: A cold-rolled steel sheet with excellent formability, heat resistance, and discoloring resistance and a manufacturing method thereof are provided to obtain room-temperature aging resistance and formability of a cold-rolled steel sheet. CONSTITUTION: A cold-rolled steel sheet comprises 0.002-0.005weight% of C, 0.03-0.10weight% of Zr, 0.02-0.20weight% of Co, 0.05-0.25weight% of Sn, 0.10-0.35weight% of Mn, 0.02-0.1weight% of Al, 0.003-0.020weight% of P, 0.002-0.006weight% of N, 0.015weight% or less of S, and the remaining amount of Fe and inevitable impurities, where the effective addition rate of C to Zr and Co, (Zr×Co)/C, is 1.5-3.0. The cold-rolled steel sheet comprises equiaxed ferrite and acicular ferrite structures.

Description

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

The present invention relates to a cold rolled steel sheet used in automobiles, home appliances, boilers, and the like, and to a method for manufacturing the same. It relates to a manufacturing method.

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% of C: 0.002 to 0.005%, Zr: 0.03 to 0.1%, Co: 0.02 to 0.20%, Sn: 0.05 to 0.25%, Mn: 0.10 to 0.35%, and Al: 0.02. It provides a high heat resistant cold rolled steel sheet having excellent workability, heat resistance, and discoloration resistance including ~ 0.1%, P: 0.003 ~ 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 effective addition ratio (Zr × Co) / C of C to Zr and Co is 1.5 to 3.0.

     In addition, the cold rolled steel sheet is characterized in that the (Zr, Co) C-based carbonized composite precipitate is 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%.

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

Furthermore, 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%, Zr: 0.03 ~ 0.10%, Co: 0.02 ~ 0.20%, Sn: 0.05 ~ 0.25%, Mn: 0.10 ~ 0.35%, Al: 0.02 ~ 0.10%, Steel slab containing P: 0.003 ~ 0.020%, N: 0.002 ~ 0.006%, S: 0.015% or less, remainder Fe and other unavoidable impurities is heated, hot rolled, cold rolled and then cold rolled steel sheet Annealing is carried out at a temperature of 800 ℃ or more, and provides a method for producing a high heat-resistant cold-rolled steel sheet excellent in workability, heat resistance and discoloration resistance characterized by cooling to an annealing steel sheet at a cooling rate of 30 ℃ / sec or more.

     In this case, the steel slab is also characterized in that the value of the effective addition ratio (Zr × Co) / C of C to Zr and Co is 1.5 to 3.0.

     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. As the precipitation resistance increases the aging resistance, there is no yield point stretching phenomenon, and it is not only excellent in moldability but also excellent in high temperature strength to secure shape freezing property of high temperature applied products, prolonging the life of the equipment and high discoloration resistance at high temperature. 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 have realized various processing characteristics such as stretch-flangeability, bendability and deep drawing, anti-aging properties, and corrosion resistance at low cost and 55 MPa at low cost. The present invention was completed by repeating the research and experiment to secure the above yield strength and discoloration resistance at high temperature. As a result, the present invention contains a very low carbon content in the steel components, and control the addition amount and the addition ratio of Zr, Co to form a fine (Zr, Co) C-based carbonized composite precipitate, and optimize the annealing and cooling conditions needle bed ferrite It secures the volume fraction of the tissue 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, age resistance at room temperature, and workability, so it is excellent in automobile exhaust system, home communication, oven and boiler, etc. It is characterized by the manufacture of a cold rolled steel sheet suitable as a product member.

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 Zr for forming Zr-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 strengthening effect of Zr-based carbide precipitates cannot be obtained, and the grain size is increased to cause a sudden change in material, so 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 preferably 0.35%. However, if less than 0.10% workability is improved, but the target strength is difficult to secure, the Mn content is limited to 0.10 to 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 0.10% increases the amount of inclusions in the steel, causing surface defects and lowering workability, Al content is limited to 0.02 ~ 0.10%.

     Phosphorus (P) is an 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 is limited to 0.003 to 0.020%.

     Nitrogen (N) exists in solid solution inside the steel and is effective for reinforcing the material. If it contains less than 0.002%, sufficient rigidity cannot be obtained, and the precipitate formation site is reduced. If the content exceeds 0.006%, Since it causes aging and hardening occurs and deteriorates moldability, N content is limited to 0.002% to 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.

     Zirconium (Zr) is an effective element for increasing the strength of steel sheet and refining grains, and in the present invention, it is combined with C dissolved in steel to form a (Zr, Co) C-based carbide composite precipitate to improve aging and formability. It is preferable to contain 0.03% or more because the strength is increased by the formation of the (Zr, Co) C-based carbonized composite precipitate and the grain growth at high temperature is suppressed to provide fine effect of the ferrite particles, but the content is 0.10% If exceeded, the material is hardened, and the workability of the continuous annealing treatment is lowered and the surface properties of the steel sheet are deteriorated, so the Zr content is limited to 0.03 to 0.10%.

     Cobalt (Co) is an element that promotes the formation of precipitates in the steel to increase strength and improve corrosion resistance. The cobalt (Co) is preferably contained in an amount of 0.02% or more in order to obtain such an effect. The Co content is limited to 0.02 to 0.20% because it acts as a factor in manufacturing cost by adding a large amount of expensive alloying elements rather than the effect of promoting precipitation.

     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 such as Sn 2 O 3 on the surface of the steel sheet to suppress the formation of an alloying layer on the surface of the steel sheet. In order to improve the corrosion resistance and discoloration resistance, it is preferable to add 0.05% or more in order to obtain such an effect, but if the content exceeds 0.25%, it is a factor of increase in manufacturing cost rather than a contribution to improving corrosion resistance or discoloration resistance. , Sn content is limited to 0.05 ~ 0.25%.

     In the case of Zr and Co, it is also important to manage alone, but it is also important to maintain the temperature addition ratio (Zr × Co) / C of C to C in a certain range to simultaneously secure room temperature aging resistance, processability, and high temperature strength. Do. That is, when the value of (Zr × Co) / C is 1.5 to 3.0, solid-solution element C is fixed in the steel by the formation of the (Zr, Co) C-based carbonitride composite precipitate, thereby ensuring room temperature aging resistance and processability, By appropriately controlling the annealing and cooling conditions, fine (Zr, Co) C-based composite precipitates are formed to suppress grain growth at high temperatures, thereby controlling the ferrite microstructure, thereby obtaining excellent high temperature characteristics. However, when the value of (Zr × Co) / C is less than 1.5, there is a problem of deterioration of room temperature aging resistance and processability due to excessive solid element in steel, and the amount of carbonitride complex precipitates such as (Zr, Co) C is insignificant. Therefore, excellent high temperature strength cannot be secured. In addition, when the value exceeds 3.0, the material hardens, the temperature of recrystallization is rapidly increased, the surface properties deteriorate and the workability of the post-process is lowered. Therefore, the value of (Zr × Co) / C Is limited to 1.5 to 3.0.

     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 to improve the properties of the present cold-rolled steel, if necessary, it is not interpreted to be excluded from the scope of the present invention by the addition of alloy elements not identified in the embodiment 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. .

Therefore, the present invention by controlling the conditions of the annealing and cooling process appropriately secures the volume fraction of the needle-like ferrite structure 5-15% to form a high-potential-density type microstructure to suppress abnormal growth of grains at high temperature to increase the high temperature strength By securing it, heat resistance can be improved. If the volume fraction of the acicular ferrite structure is less than 5%, it is difficult to secure the high temperature strength, so that target heat resistance is difficult to be obtained. If the volume fraction of the acicular ferrite structure is more than 15%, the workability is 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 composition described above, it is hot rolled, cold rolled after winding, and cooled to 30 ° C./sec or more for an annealing steel sheet at a temperature of 800 ° C. or higher to produce a cold rolled steel sheet having excellent workability and heat resistance. can do.

     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. When the final formed grains are mixed and workability and rolling property are lowered, and when the finish rolling temperature exceeds 940 ° C, uniform hot rolling is not performed throughout the thickness, resulting in insufficient grain refinement, which is caused by grain coarsening. Since impact toughness falls, it is preferable to limit finish rolling temperature to 900-940 degreeC.

     After the hot finish rolling, the hot rolled steel sheet is cooled at a run-out table at a cooling rate of 20 to 80 ° C./sec. If the cooling rate is less than 20 ° C./sec, the grain growth is promoted. This is because coarse crystal grains are formed, which is a factor of deterioration of strength and workability, and when the cooling rate exceeds 80 ° C / sec, it acts as a cause of variation of materials due to non-uniform width cooling.

     After cooling in the runout table, the hot rolled steel sheet is 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, so that the load in the cold rolling process, which is the next process, becomes large, making it difficult to secure rolling property, and the nonuniformity of the width direction increases, resulting in a difference in the production behavior of low-temperature precipitates. Due to this material variation is caused workability is lowered, there is a problem that the high temperature characteristics are deteriorated. When the coiling temperature exceeds 680 ° C, there is a problem that the structure of the final product is coarsened and the workability and corrosion resistance are 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, the steel sheet undergoes 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. If the annealing temperature is less than 800 ° C., there is a problem in that the volume fraction of the acicular ferrite structure present in the microstructure of the target steel sheet cannot be obtained, thereby making it difficult to secure 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 ° C / sec or more. This is because when the cooling rate is less than 30 ° C / sec, it is difficult to obtain the 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 with 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 Then, 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, and the results are shown in Table 3. Table 1 shows the components of the inventive steel and the comparative steel, and Table 2 the steel sheet. The manufacturing process is shown. At this time, in Table 1, the weight ratio of Zr and Co to C, and the value of (Zr × Co) / C, refer to the weight% ratio of each element component.

     Yield elongation phenomenon of the characteristics shown in Table 3 was indicated as occurring when the elongation was generated by measuring the yield point elongation through the tensile test, and not occurring when the elongation did not occur. 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. Was determined to be defective.

In addition, the sag resistance test is a case in which the sagging of the steel sheet is measured after heating the material having a length of 250 mm and a width of 30 mm at 700 ° C. for 100 hours using a heat treatment facility, and the sag is less than 5 mm. The high temperature yield strength test was judged to be poor when the yield strength was less than 55 MPa at 700 ° C, and good when it was higher. 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. Table 3 shows the characteristics evaluation for each steel sheet.

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 did not cause the yield point stretching phenomenon and had good bending resistance due to good aging resistance (Zr, Co The yield strength at high temperatures and the sag resistance after heat treatment (sag resistance) were good due to the generation of C-based carbonized composite precipitates and the optimization of the volume fraction of the acicular ferrite structure, and the decrease in surface glossiness at high temperatures was less than 30%. The discoloration was good, and at room temperature processing, no cracking occurred, so the workability at room temperature was excellent.

     On the other hand, although the steel component of Table 1 is an invention steel that satisfies 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 high in volume with low volume fraction of acicular ferrite structure. It did not have characteristics (sag resistance, high temperature strength, discoloration resistance), and workability and aging resistance (yielding point stretching phenomenon, bending resistance) were also poor.

     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 of Table 1 and the like fall outside the scope of the present invention, after evaluating the post-production characteristics, the volume fraction of the needle-like ferrite structure was It was either absent or low and often had poor room temperature and high temperature characteristics. Among them, Comparative Material 7 had no yield point stretching phenomenon and good bending resistance and workability, but poor sag resistance, high temperature strength, and discoloration resistance corresponding to high temperature characteristics. This is because the formation and promotion effects of Co) C-based composite precipitates were reduced. In addition, Comparative Materials 8 to 10 had a high amount of solid carbon in steel, so that the workability and aging resistance were poor, and Zr or Co was not added or the addition ratio was low, so that the amount of precipitates was insignificant and the volume fraction of acicular ferrite structure was low. The high temperature yield strength was poor and the discoloration resistance was also poor, which made it difficult to satisfy both the room temperature processability and the high temperature characteristics at the same time.

     As a result, the compositional conditions of the steel and the conditions of the manufacturing process (especially annealing and cooling conditions) can be optimized to form fine (Zr, Co) C-based carbonized composite precipitates and to control the volume fraction of the acicular ferrite structure. By forming a Sn-based oxide layer it is possible to produce a cold rolled steel sheet that satisfies workability, heat resistance and discoloration at the same time at low cost with excellent discoloration resistance.

     The above embodiment is only one example, and the present invention is not limited thereto. 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%, Zr: 0.03 ~ 0.10%, Co: 0.02 ~ 0.20%, Sn: 0.05 ~ 0.25%, Mn: 0.10 ~ 0.35%, Al: 0.02 ~ 0.1%, P: 0.003 ~ 0.020 High heat resistant cold rolled steel with excellent workability, heat resistance and discoloration, including%, N: 0.002 ~ 0.006%, S: 0.015% or less, balance Fe and other unavoidable impurities. The method of claim 1,
The high heat-resistant cold-rolled steel sheet excellent in workability, heat resistance and discoloration, characterized in that the effective addition ratio (Zr × Co) / C of C to Zr and Co is 1.5 to 3.0. 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, characterized in that (Zr, Co) C-based carbonized composite 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%, Zr: 0.03 ~ 0.10%, Co: 0.02 ~ 0.20%, Sn: 0.05 ~ 0.25%, Mn: 0.10 ~ 0.35%, Al: 0.02 ~ 0.1%, 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 the cold rolled steel sheet Process for annealing at high temperature, and a high temperature resistant cold rolled steel sheet excellent in workability, heat resistance and discoloration resistance characterized by cooling to an annealing-treated steel sheet at a cooling rate of 30 ℃ / sec or more. 9. The method of claim 8,
The steel slab is a method for producing a high heat resistant cold rolled steel sheet having excellent workability, heat resistance and discoloration, characterized in that the effective addition ratio (Zr × Co) / C of C to Zr and Co is 1.5 to 3.0. 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.