KR101351952B1 - High strength 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 high-strength cold-rolled steel sheet for processing and its manufacturing method excellent in heat resistance and discoloration resistance, by weight: C: 0.01 ~ 0.10%, Mn: 0.3 ~ 0.6%, P: 0.03 ~ 0.08%, Al: 0.02 ~ 0.08%, B: 0.001 to 0.003%, W: 0.05 to 0.30%, Sn: 0.05 to 0.25%, N: 0.002 to 0.010%, Ti: 0.07 to 0.15%, S: 0.015% or less, balance Fe and other unavoidable impurities The high-strength cold-rolled steel sheet for processing and its manufacturing method which are excellent in heat resistance and discoloration resistance including the above are the technical gist.
According to the present invention, it can be manufactured at a lower cost than the conventional stainless steel sheet, and has various processing characteristics of extension flange, bending, and deep drawing, so that it is excellent in room temperature workability, and the yield resistance is increased by increasing the aging resistance by precipitation of solid elements. Not only does not occur, it is excellent in formability, and excellent in high temperature strength, the life of the equipment is extended by securing the shape freezing property of the high-temperature application products, it is possible to manufacture a high-temperature cold-rolled steel sheet for processing of high strength excellent in discoloration resistance at high temperature. .

Description

High strength cold rolled steel sheet for processing and its manufacturing method excellent in heat resistance and discoloration resistance {HIGH STRENGTH COLD-ROLLED STEEL SHEET HAVING EXCELLENT FORMABILITY, HEAT RESISTANCE, SURFACE PROPERTIES FOR WORKING AND MANUFACTURING METHOD THEREOF}

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

Cast iron is generally used for products such as automobile exhaust system, household communication, oven, and boiler. However, since it is continuously exposed to a high temperature environment of several hundred degrees Celsius or more, high heat resistance characteristics are required. Therefore, Plated steel sheet, stainless steel sheet, and the like.

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, workability at room temperature is required, and the tensile strength of 350 MPa or more is required at room temperature in order to secure impact resistance characteristics of the use member.

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 addition, Japanese Laid-Open Patent Publication No. Hei 9-111396 intends to manufacture a high strength steel sheet having excellent impact resistance characteristics composed of two-phase structure of ferrite and martensite, but there is a problem in that moldability is not good due to insufficient stretching.

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, high strength cold rolled steel for processing and its manufacturing method which can be manufactured at low cost by optimizing steel components and process conditions while reducing the addition of expensive alloying elements, including medium and low carbon, for use in required applications The purpose is to provide.

In order to achieve the above-mentioned object, the present invention provides a weight% of C: 0.01 to 0.10%, Mn: 0.3 to 0.6%, P: 0.03 to 0.08%, Al: 0.02 to 0.08%, B: 0.001 to 0.003%, and W: 0.05 ~ 0.30%, Sn: 0.05 ~ 0.25%, N: 0.002 ~ 0.010%, Ti: 0.07 ~ 0.15%, S: 0.015% or less, high heat resistance and discoloration resistance including residual Fe and other unavoidable impurities Provide cold rolled steel sheet.

At this time, the characteristic of the atomic ratio Ti / C of the said Ti and C is 0.4-0.9.

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

In addition, the characteristic is that the value of the atomic ratio B / N of the B and N is 0.5 ~ 1.5.

Further, the cold rolled steel sheet is also characterized in that the B-based nitride precipitates are formed.

In addition, the cold rolled steel sheet is also characterized in that it is made of an equiaxed ferrite and acicular bainite structure.

Here, the volume fraction of the acicular bainite structure of the cold rolled steel sheet is also characterized by 10 to 20%.

In addition, the Sn-based oxide layer is formed on the surface of the cold-rolled steel sheet also has its characteristics.

At this time, the Sn-based oxide layer is also characterized in that the Sn ₂ O ₃ layer.

In addition, the present invention is in the weight% C: 0.01 ~ 0.10%, Mn: 0.3 ~ 0.6%, P: 0.03 ~ 0.08%, Al: 0.02 ~ 0.08%, B: 0.001 ~ 0.003%, W: 0.05 ~ 0.30%, Sn: 0.05 ~ 0.25%, N: 0.002 ~ 0.010%, Ti: 0.07 ~ 0.15%, S: 0.015% or less, hot rolled steel slab containing residual Fe and other unavoidable impurities, then hot rolled, cold rolled after winding Then, the cold-rolled steel sheet is subjected to annealing at a temperature of 800 ℃ or more, and to produce a high strength cold rolled steel sheet for processing excellent in heat resistance and discoloration resistance, characterized in that cooling to a cooling rate of 40 ℃ / sec or more with respect to the annealing steel sheet Provide a method.

At this time, the steel slab is characterized in that the value of the atomic ratio Ti / C of the Ti and C is 0.4 ~ 0.9.

In addition, the steel slab is characterized in that the value of the atomic ratio B / N of the B and N is 0.5 ~ 1.5.

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

Further, 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.

The winding is also performed at 560 to 680 캜.

In addition, the annealing treatment is also characterized by being performed at 800 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. High yield strength and high temperature resistant cold rolled steel sheet for processing Can be prepared.

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

The present inventors have satisfied various processing characteristics such as stretch-flangeability, bendability, deep drawing, etc., anti-aging properties, and corrosion resistance at low cost and 55 MPa at 700 ° C. The present invention was completed by repeating the research and experiment to secure the yield strength and the tensile strength of 350MPa or more at room temperature and discoloration resistance at high temperature at the same time. As a result, the present invention includes a low and low carbon content, increase the content of Mn, P in the steel components, and control the atomic ratio of Ti, C, B and N to form a fine Ti-based carbide and B-based nitride precipitates By optimizing the annealing and cooling conditions to secure the volume fraction of acicular bainite structure, it has excellent heat resistance, corrosion resistance and discoloration resistance at high temperature, aging resistance and processability at room temperature, It is characterized by producing a high strength, high temperature resistant cold rolled steel sheet suitable for use as a product member.

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 excessively, ductility falls and it becomes a factor of economical deterioration and center segregation by adding a large amount of alloying elements, and therefore an upper limit is preferably 0.6%. However, if less than 0.3% workability is improved, but the target high strength is difficult to secure, the Mn content is limited to 0.3 ~ 0.6%.

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 to improve the strength and corrosion resistance of the steel, it is preferable to contain 0.03% or more in order to secure these properties, but if the content exceeds 0.08%, the core segregation during casting and workability is reduced, P The content of is limited to 0.03 ~ 0.08%.

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 stiffness cannot be obtained, and precipitate formation sites are reduced. As the cause of aging causes hardening to deteriorate moldability, the content of N is limited to 0.002 to 0.010%.

Boron (B) is dissolved in the steel to increase the strength and toughness, and to improve the aging resistance and workability by forming boron-based nitride precipitates such as BN, effective in suppressing grain growth at high temperature. It is preferable to add more than 0.001%, but if the content exceeds 0.003%, material variation is caused, and retardation of recrystallization at a high temperature is a factor that degrades workability, so the content of B is limited to 0.001 to 0.003%.

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%.

Tungsten (W) is an effective element to enhance the precipitation precipitation and high temperature strength in steel. To achieve this effect, tungsten (W) needs to be added at least 0.05%. However, when the content of W exceeds 0.30%, it is more expensive than the contribution to the promotion of precipitation. Since it becomes a rising factor of the manufacturing cost according to the addition of alloying elements, the content of W is limited to 0.05 ~ 0.30%.

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%.

In the case of Ti and B alone, it is 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 consider the effects of precipitate formation and solid solution elements in the steel. To this end, it is important to maintain room temperature aging resistance, processability and high temperature strength simultaneously by maintaining the atomic ratio Ti / C of Ti and C and the atomic ratio B / N of B and N in a certain range.

When the Ti / C atomic ratio of Ti / C is 0.4 to 0.9, the solid carbide element C is fixed in the steel by the formation of Ti-based carbonized precipitates, thereby ensuring room temperature aging resistance and processability, and appropriately controlling the annealing and cooling conditions. By suppressing grain growth at high temperature through the formation of fine Ti-based carbide precipitates, it is possible to secure excellent high temperature characteristics by controlling the microstructure.

However, when the value of Ti / C is less than 0.4, there is a problem of deterioration of room temperature aging resistance and workability due to excessive solid solution elements in the steel, and because the amount of Ti-based carbide precipitates is insignificant, excellent high temperature strength cannot be secured. In addition, when the value exceeds 0.9, the material hardens, the temperature of the recrystallization is rapidly increased, the surface properties deteriorate and the workability of the post-process is lowered. Therefore, the Ti / C value is 0.4 to 0.9. It is limited to.

In order to optimize the aging resistance at room temperature, the workability, and the effect of inhibiting grain growth at high temperature, it is necessary to keep the values of the atomic ratio B / N of B and N at 0.5 to 1.5. When the B / N value is less than 0.5, there is a problem that the room temperature resistance is degraded due to excessive solid solution in steel, the grain suppression effect is insufficient at high temperature, and when the B / N value exceeds 1.5, the ductility is lowered and the workability is decreased. , The value of B / N is limited to 0.5 to 1.5.

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.

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 bainite structure, the acicular bainite is a plate-like ferrite structure having a carbide therein and has a high dislocation density. , Toughness is excellent.

The present invention, by appropriately controlling the conditions of the annealing and cooling process to secure a volume fraction of the needle-like bainite structure 10 to 20% to form a high-potential-density type microstructure to suppress abnormal growth of crystal grains at high temperature to room temperature and high temperature Strength can be improved. However, when the volume fraction of the acicular bainite structure is less than 10%, it is difficult to secure room temperature and high temperature strength, so that it is difficult to obtain excellent heat resistance. When the volume fraction of the acicular bainite structure is more than 20%, the material is hardened by curing. There is a problem that workability deteriorates, and the volume fraction of acicular bainite is limited to 10 to 20%.

Hereinafter, the manufacturing method of the high strength cold rolled steel sheet for processing excellent in 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 40 ° C./sec or more 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 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 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-shaped bainite structure. Here, if the annealing temperature is less than 800 ℃, it is difficult to obtain the volume fraction of the needle-like bainite structure present in the microstructure of the target steel sheet, and thus there is a problem that it may be difficult to ensure 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 bainite structure through a cooling process, for which the cooling rate is maintained at 40 ° C / sec or more. If the cooling rate is less than 40 ° C / sec, it is difficult to obtain the volume fraction of the target acicular bainite 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 to 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 bainite 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 described in Table 3 is expressed as occurrence when the elongation is generated by measuring the yield point elongation, and not occurred when the elongation is not generated, and the bending resistance test is performed after the steel sheet processing. The degree of bending was divided according to the degree of occurrence, and the bending index representing this was divided into five stages, and 1 to 2 stages with relatively small bending were good, and 3 to 5 stages where the bending occurred as bad as possible for visual observation. Determined.

In addition, the room temperature tensile strength test was determined to be good if the tensile strength of 350MPa or more at room temperature, less than that, the sag resistance test after heating the material of 250mm in length, 30mm in width using a heat treatment equipment for 100 hours at 700 ℃ Sagging of the steel plate was measured and it was judged to be bad when the deflection degree was 5 mm or more and less than 5 mm. The high temperature yield strength test was good when the yield strength was 55 MPa or more at 700 ° C., and less than that. In the high temperature discoloration test, the surface glossiness was lowered by more than 30% after maintaining the steel plate at a temperature of 500 ° C. for 48 hours.

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

In this case, in Table 1, the value of the atomic ratio Ti / C of Ti and C and the value of the atomic ratio B / N of B and N refer to the ratio of the value obtained by dividing the weight percent of each element 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 did not occur in the yield point stretching phenomenon, good bending resistance and excellent aging resistance, tensile strength is also room temperature The yield strength and sag resistance after heat treatment were satisfactory due to the formation of Ti-based carbide and B-nitride precipitates and optimization of the volume fraction of acicular bainite structure. The high temperature discoloration resistance was also good due to the formation of Sn-based oxide layer, and the processing cracks did not occur during normal temperature processing.

On the other hand, although the steel components of Table 1 and the like are 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 bainite structure. It did not have excellent high temperature properties (sag resistance, high temperature yield strength, high temperature discoloration resistance), and in many cases not only normal tensile strength but 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 of Table 1 and the like are outside the scope of the present invention were often poor in workability and aging resistance, Due to the low volume fraction, most of the high temperature properties were poor, and W was not added and Mn and P contents were low, so the room temperature tensile strength was often lowered. It was difficult to satisfy at the same time.

Among them, Comparative Material 7 had no yield point stretching phenomenon, good bending resistance, good aging resistance and workability, and good tensile strength of 350 MPa or more, but poor sag resistance, high temperature yield strength and high temperature discoloration resistance. This is due to the addition of Ti and non-addition of W, resulting in poor operability at the time of annealing, deterioration of the surface properties of the steel sheet, which do not secure the target high temperature properties, and poor Sn high temperature discoloration resistance. Because In addition, the comparative materials 8 and 9 were not only poor in workability and aging resistance, but also had a low Ti / C value, a low amount of Ti-based carbide precipitates, and a very low volume fraction of acicular bainite structure.

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 and B-based nitride precipitates, and the volume fraction of acicular bainite structure can be controlled. The high heat resistant cold rolled steel sheet for high-strength processing, which satisfies workability, heat resistance, and discoloration at a low cost by adding W, increasing the amount of Mn and P in a steel, and satisfying workability, heat resistance, and discoloration resistance at low cost.

The present invention is not limited to the above-described embodiments. 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 (16)

By weight% C: 0.01-0.10%, Mn: 0.3-0.6%, P: 0.03-0.08%, Al: 0.02-0.08%, B: 0.001-0.003%, W: 0.05-0.30%, Sn: 0.05-0.25 %, N: 0.002 ~ 0.010%, Ti: 0.07 ~ 0.15%, S: 0.015% or less, including residual Fe and other unavoidable impurities, and excellent heat resistance and discoloration resistance with Sn ₂ O ₃ layer formed on the surface Cold rolled steel sheet. The method of claim 1,
A high strength cold rolled steel sheet for processing having excellent heat resistance and discoloration resistance, wherein the atomic ratio Ti / C of Ti and C is 0.4 to 0.9. The method of claim 1,
The cold rolled steel sheet is a high strength cold rolled steel sheet for processing excellent in heat resistance and discoloration, characterized in that the Ti-based carbide precipitates are formed. The method of claim 1,
The high strength cold rolled steel sheet for processing excellent in heat resistance and discoloration, characterized in that the value of the atomic ratio B / N of the B and N is 0.5 ~ 1.5. The method of claim 1,
The cold rolled steel sheet is a high strength cold rolled steel sheet for processing excellent in heat resistance and discoloration, characterized in that the B-based nitride precipitates are formed. By weight% C: 0.01-0.10%, Mn: 0.3-0.6%, P: 0.03-0.08%, Al: 0.02-0.08%, B: 0.001-0.003%, W: 0.05-0.30%, Sn: 0.05-0.25 %, N: 0.002 ~ 0.010%, Ti: 0.07 ~ 0.15%, S: 0.015% or less, including residual Fe and other unavoidable impurities, heat resistant and discoloration characterized by consisting of equiaxed ferrite and acicular bainite structure High strength cold rolled steel sheet for processing. The method according to claim 6,
A high-strength cold rolled steel sheet having excellent heat resistance and discoloration resistance, wherein a volume fraction of the needle-shaped bainite structure of the cold rolled steel sheet is 10 to 20%. 8. The method according to claim 6 or 7,
A high strength 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. 9. The method of claim 8,
The Sn-based oxide layer is a high-strength 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%, Mn: 0.3-0.6%, P: 0.03-0.08%, Al: 0.02-0.08%, B: 0.001-0.003%, W: 0.05-0.30%, Sn: 0.05-0.25 Steel slab containing%, N: 0.002 ~ 0.010%, Ti: 0.07 ~ 0.15%, S: 0.015% or less, balance Fe and other unavoidable impurities is heated and hot rolled, cold rolled and then cold rolled The annealed steel sheet is annealed at a temperature of 800 ° C. or higher, and cooled to a cooling rate of 40 ° C./sec or more with respect to the annealed steel sheet, and a Sn ₂ O ₃ layer, which is a Sn-based oxide layer, is formed on the surface of the cooled steel sheet. Manufacturing method of high strength cold rolled steel sheet for processing excellent in heat resistance and discoloration resistance. The method of claim 10,
The steel slab is a method of manufacturing a high strength 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 0.4 ~ 0.9. The method of claim 10,
The steel slab is a method for producing a high strength cold rolled steel sheet for processing excellent in heat resistance and discoloration, characterized in that the value of the B / N atomic ratio B / N of 0.5 to 1.5. The method according to any one of claims 10 to 12,
The hot rolling is a manufacturing method of high strength 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 13,
The method of manufacturing a high strength 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. The method according to any one of claims 10 to 12,
Said winding is performed at 560-680 degreeC, The manufacturing method of the high strength cold rolled steel sheet for processing excellent in heat resistance and discoloration resistance characterized by the above-mentioned. The method according to any one of claims 10 to 12,
The annealing treatment is carried out at 800 ~ 900 ℃ the manufacturing method of high strength cold rolled steel sheet for processing excellent in heat resistance and discoloration resistance.