KR101353656B1 - Soft tempered black plate steel sheet having excellent antiaging property and weldability and manufacturing method thereof - Google Patents

Abstract

One aspect of the present invention is a soft stone disc excellent in aging resistance, in weight%, C: 0.0005 ~ 0.001%, Al: 0.03 ~ 0.08%, Mn: 0.5 ~ 0.6%, N: 0.002 ~ 0.006%, V: 0.005 ~ 0.015%, P: 0.01-0.03%, S: 0.001-0.02%, the remainder contains Fe and unavoidable impurities, and the structure is an equiaxed ferrite single phase with a grain size of 10-30 µm, and V (C, N) carbonaceous Contains cargo.
Another aspect of the present invention is a method for producing a soft stone disc excellent in age resistance, by weight, C: 0.0005 ~ 0.001%, Al: 0.03 ~ 0.08%, Mn: 0.5 ~ 0.60%, N: 0.002 ~ 0.006%, V: 0.005% to 0.015%, P: 0.01% to 0.03%, S: 0.001% to 0.02%, and the remainder is heated to 1100-1300 ° C. of the steel slab containing Fe and unavoidable impurities, and hot rolled the heated steel slab. To prepare a hot rolled steel sheet by finishing hot rolling at a temperature satisfying the following relational formula 1, winding the hot rolled steel sheet at a temperature satisfying the following relational formula 2, hot rolled steel sheet at a reduction ratio of 75 to 95% after the winding Cold rolling to produce a cold rolled steel sheet, the step of annealing the cold rolled steel sheet at a temperature of 600 ~ 750 ℃ and the step of temper rolling the annealing steel sheet.
Equation 1: Cooling Temperature (CT) +100 ≤ Hot Rolling Finish Temperature (FDT) (℃) ≤ Cond1 (℃) or 850 ℃ (Cond1 = 864.57-95.25 * C-43.5 * Mn + 26.39 * Si + 21.16 * C * Mn-23.1 * C * Si-128.65 * C ^(1/2) )
Relation 2: FDT (占 폚) -250 占 폚? CT (占 폚)? Cond1-50 (占 폚)

Description

SOFT TEMPERED BLACK PLATE STEEL SHEET HAVING EXCELLENT ANTIAGING PROPERTY AND WELDABILITY AND MANUFACTURING METHOD THEREOF}

The present invention relates to a stone master plate used as a raw material such as a steel sheet for cans and a manufacturing method thereof.

Seaweed discs used for food and beverage tubes are required to have durability and weldability. The endurance Hyosung means that the newly generated dislocations are fixed to the solid element in the steel during the processing of the can steel plate to form the peak stress during deformation and the dislocation of the dislocation and the solid element is released, It refers to resistance to repeated phenomena. In general, when aging occurs, the tendency of the stress-strain curve after the yield point in uniaxial tensile testing is significantly different from that in which no aging occurs. This phenomenon is called discontinuous yield behavior.

In general, in order to satisfy the above-mentioned aging characteristics, a method of removing hiring elements among the steels forming a fixation with a dislocation during processing is used. In particular, the most widely used method is an interstitial Free Steel). IF steel is a steel grade in which there is almost no employment element moving in the steel by addition of carbonitride element (Scavenger) such as Ti and Nb which can easily form carbonitride in the ultra-low carbon marble base plate. In the case of such steels, there is a continuous yielding behavior during uniaxial tensile test, and no aging occurs, so that the above-mentioned fluting defects during machining do not occur.

Such a technique, as in Patent Document 1, has been made to add titanium (Ti) to an extremely low carbon steel (3 ppm <C <100 ppm) steel to ensure the vitrification property. However, since the annealing temperature is high, a heat buckle There is a problem. In addition, in Patent Document 2, niobium (Nb) was added to ultra-low carbon-based steels and MnS, Nb (C, S) and other steels were developed to secure aging resistance. However, high annealing temperature caused various defects. There is a problem.

Japanese Patent Application Laid-Open No. 1993-287443 Japanese Laid-Open Patent Publication No. 1999-152543

The present invention is to provide a soft stone master plate excellent in aging resistance and weldability and a method of manufacturing the same.

One aspect of the present invention is a soft stone disc excellent in aging resistance, in weight%, C: 0.0005 ~ 0.001%, Al: 0.03 ~ 0.08%, Mn: 0.5 ~ 0.6%, N: 0.002 ~ 0.006%, V: 0.005 ~ 0.015%, P: 0.01-0.03%, S: 0.001-0.02%, the remainder contains Fe and unavoidable impurities, and the structure is an equiaxed ferrite single phase with a grain size of 10-30 µm, and V (C, N) carbonaceous Contains cargo.

Another aspect of the present invention is a method for producing a soft stone disc excellent in aging resistance and weldability in weight%, C: 0.0005 ~ 0.001%, Al: 0.03 ~ 0.08%, Mn: 0.5 ~ 0.60%, N: 0.002 ~ 0.006 %, V: 0.005% to 0.015%, P: 0.01% to 0.03%, S: 0.001% to 0.02%, the remainder being heated to 1100 to 1300 ° C of a steel slab containing Fe and unavoidable impurities, the heated steel slab Hot rolling and finishing hot rolling at a temperature satisfying relation 1 below to produce a hot rolled steel sheet, winding the hot rolled steel sheet at a temperature satisfying relation 2 below, at a reduction ratio of 75 to 95% after the winding. Cold rolling the hot rolled steel sheet to produce a cold rolled steel sheet, the step of annealing the cold rolled steel sheet at a temperature of 600 ~ 750 ℃ and the step of temper rolling the annealing steel sheet.

Equation 1: Cooling Temperature (CT) +100 ≤ Hot Rolling Finish Temperature (FDT) (℃) ≤ Cond1 (℃) or 850 ℃ (Cond1 = 864.57-95.25 * C-43.5 * Mn + 26.39 * Si + 21.16 * C * Mn-23.1 * C * Si-128.65 * C ^(1/2) )

Relation 2: FDT (占 폚) -250 占 폚? CT (占 폚)? Cond1-50 (占 폚)

In addition, the solution of the above-mentioned problems does not list all the features of the present invention. The various features of the present invention and the advantages and effects thereof will be more fully understood by reference to the following specific embodiments.

According to the present invention, the microstructure of the steel sheet is a ferrite single phase having a grain size of 10 to 30 µm, and has a hardness value of T3 level through the production of a steel sheet having V (C, N) carbonitride. In addition, due to active control of the employment element, the yield point stretching phenomenon does not occur, it is possible to provide a soft stone disc excellent in aging resistance improved workability and productivity.

1 is an optical micrograph of a raw stone disc according to the present invention.

The present inventors conducted a study to derive a soft stone disc excellent in aging resistance, and by optimizing the component system and manufacturing process of the steel while reducing the addition of expensive alloy elements, it has a carbonitride size and a ferrite single phase structure, It was confirmed that the steel sheet for cans excellent in aging resistance which does not generate | occur | produce a yield point led to this invention.

Hereinafter, the soft stone negative disc, which is one side of the present invention, will be described in detail.

One aspect of the present invention is a soft stone disc excellent in aging resistance, in weight%, C: 0.0005 ~ 0.001%, Al: 0.03 ~ 0.08%, Mn: 0.5 ~ 0.6%, N: 0.002 ~ 0.006%, V: 0.005 ~ 0.015%, P: 0.01-0.03%, S: 0.001-0.02%, the remainder contains Fe and unavoidable impurities, and the structure is an equiaxed ferrite single phase with a grain size of 10-30 µm, and V (C, N) carbonaceous Contains cargo.

Hereinafter, reasons for limiting each component or condition will be described.

Carbon (C): 0.0005 to 0.001 wt%

C is the most effective element to strengthen the steel, but it is an element that causes aging when it is present in the steel as an employment element. When the content of C is less than 0.0005% by weight, it is difficult to achieve the target strength intended in the present invention, and coarsening of grains during welding decreases weldability. On the other hand, when the content of C exceeds 0.002% by weight, the amount of solid solution in the steel is increased, which lowers the aging resistance. Therefore, the C is preferably included in 0.0005 ~ 0.002% by weight.

Aluminum (Al): 0.03-0.08 wt%

The Al is an element added for deoxidation of molten steel and has an effect of improving the aging property by being combined with a solid solution element in steel. In order to exhibit such an effect in the present invention, it is preferable to include 0.03% by weight or more. However, when the Al content exceeds 0.08% by weight, the amount of inclusions in the steel may be increased to cause surface defects and workability may be reduced. Therefore, the content of Al is preferably 0.03 to 0.08% by weight.

Manganese (Mn): 0.5-0.6 wt%

The Mn is an effective element for strengthening the steel and enhances the steel strength and hot workability. If the content of Mn is less than 0.5% by weight, it is difficult to achieve the target roughness intended in the present invention. On the other hand, if the Mn content exceeds 0.6% by weight, the center segregation may be developed during slab casting in the manufacturing process, thereby reducing the ductility. Therefore, the Mn is preferably included in 0.48 ~ 0.6% by weight.

Nitrogen (N): 0.002-0.006 wt%

N is an element effective for reinforcing a material while being present in a solid state in a steel. In order to exhibit such an effect in the present invention, it is preferable to include 0.002% by weight or more. However, when the content of N exceeds 0.006% by weight, the excessively high amount of solid solution causes aging and hardening may deteriorate moldability. Therefore, it is preferable that N is contained by 0.002 to 0.006 weight%.

Vanadium (V): 0.005 to 0.015 wt%

The V plays a role of suppressing the growth of the grain boundary at the time of welding and controlling the nitrogen and carbon which cause the aging in the steel to improve the anti-aging property. In order to exhibit such an effect in the present invention, the vanadium is preferably included in 0.005% by weight or more. However, when the content of vanadium exceeds 0.015% by weight, grain boundary embrittlement of vanadium occurs, which causes a problem of raising the recrystallization temperature of steel. Therefore, the V is preferably included in 0.005 ~ 0.015% by weight.

Phosphorus (P): 0.01-0.03 wt%

P is an element for improving the strength and corrosion resistance of steel. In order to exhibit such effects in the present invention, the content of phosphorus is preferably 0.01 wt% or more. However, when the content of P exceeds 0.03% by weight, the center segregation and workability may be reduced during casting. Therefore, it is preferable that P is contained in 0.01 to 0.03 weight%.

Sulfur (S): 0.001-0.02 wt%

S is an element that forms defects with manganese in steel to form a non-metallic inclusion serving as a corrosion start point and is a cause of red brittleness. When the content of S is less than 0.001% by weight, the content of MnS precipitates is small, which may greatly reduce the particle size growth inhibitory effect. On the other hand, when the content of S exceeds 0.02% by weight, there is a problem in securing a fine MnS because it is present in the solid solution S, not in the form of MnS, it is preferable to limit the upper limit to 0.02% by weight. Therefore, the S is preferably included in 0.001 ~ 0.02% by weight.

The remainder of the present invention is iron (Fe). However, impurities which are not intended from the raw material or the surrounding environment in the course of ordinary production can be inevitably incorporated, so that this can not be excluded. These impurities are not specifically mentioned in this specification, as they are known to any person skilled in the art of manufacturing.

According to one aspect of the present invention, the plasterboard comprises V (C, N) carbonitride. These V (C, N) precipitates are generally lower in restocking temperature than Ti and Nb, which are generally included as scavenger elements, and can effectively form carbonitrides such as C and N as solid solutions even at low contents. have. Therefore, in the present invention, the content of V is limited to 50 ppm or more to form carbonitrides for satisfying aging resistance. However, when the amount exceeds 0.02% by weight, since the effect of raising the recrystallization temperature, such as other Ti, Nb, etc. is caused, it is preferable to limit the content of V to 0.015% by weight or less.

Further, by satisfying the above-mentioned component system, it is possible to provide a stone disc having excellent anti-aging properties. Since the present invention corresponds to ultra low carbon steel having a C content of 3 ppm <C <100 ppm, the microstructure is composed of a ferrite single phase structure. More preferably an equiaxed phase ferrite single phase structure. The average grain size of the ferrite single phase structure is preferably controlled to 10 to 30 占 퐉. In addition, the more preferable microstructure of the present invention is characterized in that the equiaxed ferrite single phase structure has a grain size of 20% or more coarse than that of the equiaxed ferrite of a general IF cold rolled steel sheet having a degree of about 8 to 10.

It is preferable that the said stone plate has a roughness of T3 or more. If the quality is less than T3, the welded portion and the welded heat affected zone are not dense at the time of welding, resulting in processing defects such as fusing during processing.

Hereinafter, a method of manufacturing a soft stone disc excellent in aging resistance which is one aspect of the present invention will be described in detail.

Another aspect of the present invention is a method for producing a soft stone disc excellent in age resistance, by weight, C: 0.0005 ~ 0.001%, Al: 0.03 ~ 0.08%, Mn: 0.5 ~ 0.60%, N: 0.002 ~ 0.006%, V: 0.005% to 0.015%, P: 0.01% to 0.03%, S: 0.001% to 0.02%, and the remainder is heated to 1100-1300 ° C. of the steel slab containing Fe and unavoidable impurities, and hot rolled the heated steel slab. To prepare a hot rolled steel sheet by finishing hot rolling at a temperature satisfying the following relational formula 1, winding the hot rolled steel sheet at a temperature satisfying the following relational formula 2, hot rolled steel sheet at a reduction ratio of 75 to 95% after the winding Cold rolling to produce a cold rolled steel sheet, the step of annealing the cold rolled steel sheet at a temperature of 600 ~ 750 ℃ and the step of temper rolling the annealing steel sheet.

Equation 1: Cooling Temperature (CT) +100 ≤ Hot Rolling Finish Temperature (FDT) (℃) ≤ Cond1 (℃) or 850 ℃ (Cond1 = 864.57-95.25 * C-43.5 * Mn + 26.39 * Si + 21.16 * C * Mn-23.1 * C * Si-128.65 * C ^(1/2) )

Relation 2: FDT (占 폚) -250 占 폚? CT (占 폚)? Cond1-50 (占 폚)

Heating stage

It is preferable to heat the slab which satisfy | fills the component system mentioned above at 1100-1300 degreeC. If the heating temperature is less than 1100 ° C., the precipitates may not be sufficiently reused, and there may be a precipitate in solid solution. If the heating temperature is higher than 1300 ° C., coarse MnS precipitates may be formed to cause aging characteristics.

Hot rolling step

The heated slab is hot-rolled as described above. Hot rolling is preferably performed at a temperature at which the finish rolling temperature satisfies the following relational formula (1). When the finishing rolling temperature is higher than the temperature of Cond1, there is a high possibility that the hot rolling is terminated in the austenite zone or the ferrite + austenite zone to cause blistering during hot rolling, and there is a high possibility that the grain size defined in the present invention Therefore, it is preferable to perform finish rolling at a temperature of not more than cond1. In addition, the hot rolling finish temperature is preferably carried out at a cooling temperature (CT) + 100 ° C. or higher, which means that the recrystallization may be 100% complete if the minimum cooling rate in the cooling process after finishing rolling is assumed. To compensate for possible winding temperatures.

Equation 1: Cooling Temperature (CT) +100 ≤ Hot Rolling Finish Temperature (FDT) (℃) ≤ Cond1 (℃) or 850 ℃ (Cond1 = 864.57-95.25 * C-43.5 * Mn + 26.39 * Si + 21.16 * C * Mn-23.1 * C * Si-128.65 * C ^(1/2) )

Cooling stage

After the final rolling to the temperature is subjected to a cooling process, it is preferable to cool at a cooling rate of less than 30 ℃ in the cooling process. It is preferable that the upper limit of the average cooling rate be controlled at 30 ° C / sec or less because the following coiling temperature cannot be compensated when the cooling rate exceeds 30 ° C and the structure of the final hot rolled material does not change into a completely recrystallized structure.

Winding stage

Although it winds up after cold as mentioned above, it is preferable to wind up at the temperature which satisfy | fills following formula (2). If the winding temperature CT is less than FDT (° C.)-250 ° C., recrystallization is not completed in the winding section, resulting in a problem that the final hot rolled structure becomes stretched grains and thus stretched grains are obtained in the cold rolling process. On the other hand, when the coiling temperature exceeds cond1-50 ° C, since the uneven problem may occur due to abnormal grain growth of the grains of the final hot rolled material, it is preferable that the coiling temperature follows the following equation (2).

Relation 2: FDT (占 폚) -250 占 폚? CT (占 폚)? Cond1-50 (占 폚)

Cold rolling step

The cold rolling is preferably performed at a reduction rate of 75 to 95%. If the cold reduction rate is less than 70%, since the annealing recrystallization nucleation amount is small, the crystal grains grow too large during annealing, and the strength and formability decrease due to the coarsening of the annealing recrystallization grains. On the other hand, when the cold reduction ratio exceeds 95%, the rolling load is increased when the cold rolled sheet is rolled, which may cause problems such as breaking of the plate. Therefore, it is preferable to limit cold rolling to the cold reduction rate of 75 to 95%.

Annealing step

Continuous annealing temperature plays an important role in determining the material of the product. In this invention, it is preferable to carry out in the temperature range of 600-750 degreeC. If the continuous annealing temperature is less than 600 ℃ the recrystallization is not completed, the final microstructure exists in the form of elongation. On the other hand, if it exceeds 750 ℃ processing defects such as heat buckle and stamping defects occur in the annealing process. Therefore, it is preferable to perform the said annealing at the temperature of 600-750 degreeC.

Temper rolling step

It is preferable to subject the steel sheet subjected to the continuous annealing to temper rolling. By performing the above-described temper rolling, there is an effect that the generated electric potential fixes some carbons and improves the endurance. In the present invention, it is desirable that the reduction rate is 1% or more in order to exhibit such effects. However, when the reduction rate exceeds 2%, there is a problem that the elongation rate may decrease. Therefore, it is preferable that the temper rolling is performed at a reduction rate of 1 to 2%.

Hereinafter, the present invention will be described more specifically by way of examples.

It should be noted, however, that the following examples are intended to illustrate the invention in more detail and not to limit the scope of the invention. The scope of the present invention is determined by the matters set forth in the claims and the matters reasonably inferred therefrom.

(Example)

Inventive Steel 1 and Comparative Steels 1 to 3 prepared by dissolving the composition as shown in Table 1 were prepared under the process conditions as shown in Table 2 below to prepare the inventive original materials 1 and 2 and Comparative Materials 1 to 5.

Comparative steel 1 used as a comparative material of the following Table 1 is a Ti-added ultra-low carbon-based stone is also widely used, Comparative steel 2 is present in a much higher content of about 40ppm C than the component system of the invention steel 1. Comparative steel 3 has a similar component system as the invention steel, but is a comparative material characterized by a large amount of V 0.02% by weight.

Steel grade Ingredients (% by weight) C Mn P S Al N Ti V Inventive Steel 1 0.0012 0.50 0.018 0.007 0.041 0.0020 O 0.006 Comparative River 1 0.0020 0.3 0.007 0.011 0.038 0.0031 0.025 0 Comparative River 2 0.004 0.5 0.004 0.009 0.044 0.0029 0 0 Comparative Steel 3 0.0015 0.52 0.012 0.008 0.055 0.0015 O 0.02

Steel grade Steel plate Reheating temperature Finish rolling temperature Coiling temperature Annealing Temperature SPM Elongation Inventive Steel 1 Inventory 1 1150 DEG C 780 ° C 650 ° C 700 ℃ 1.2% Inventory 2 1150 DEG C 800 ° C 650 ° C 700 ℃ 1.8% Comparison 1 1250 ℃ 920 ℃ 680 ° C 700 ℃ 1.2% Comparative material 2 1250 ℃ 900 ℃ 700 ℃ 700 ℃ 1.8% Comparative River 1 Comparative material 3 1250 ℃ 920 ℃ 680 ° C 800 ° C 1.2% Comparative River 2 Comparison 4 1250 ℃ 920 ℃ 650 ° C 700 ℃ 1.2% Comparative Steel 3 Comparative material 5 1250 ℃ 780 ° C 680 ° C 700 ℃ 1.2%

The aging characteristics of each prepared raw stone material are evaluated and shown in Table 3 below.

Yield point elongation phenomenon of the characteristics shown in Table 3 is expressed as the occurrence when the elongation is generated by measuring the yield point elongation through the tensile test, and the non-occurrence when the elongation does not occur.

At this time, reflow and baking heat treatments were performed in a general heating furnace in order to simulate tin plating, which is a manufacturing process of a grain steel sheet, before measuring the yield point stretching phenomenon. At this time, the reflow process simulates the process of adding the master plate to the tin plating bath for tin plating, simulating the holding at 250 ° C. for 5 seconds, and using the continuous annealing heat treatment furnace for this purpose. The baking process is a process for tin plating to adhere closely to the stone master plate, and heat treatment was performed for 20 minutes in a heat treatment furnace heated to 200 ° C. for simulation thereof.

Then, the uniaxial room temperature tensile test was performed using the sample after each process, and the case where the yield point elongation occurred and the case where it did not occur are shown in Table 3 below.

On the other hand, the invention material 1 and the comparative material 7 simulated by the heat treatment as described above are shown in Figs. 1 (a) and (b), respectively. As shown in Figure 1 (a), the average grain size is about 16㎛ it can be seen that it has a microstructure of equiaxed crystals.

Steel plate Hardness (HR30T) Yield point stretching phenomenon ductility
(%) Dislocation density
(X10 ¹³ ea / m ² ) V-based carbonitride volume fraction
(ppm) Average grain size
(탆) Inventory 1 58 Not occurring 40 10 12 16 Inventory 2 60 Not occurring 40 15 10 18 Comparison 1 61 Occur 38 10 10 8 Comparative material 2 62 Occur 39 9 8 7.5 Comparative material 3 57 Not occurring 45 10 0 9 Comparison 4 50 Occur 35 12 0 9 Comparative material 5 72 Not occurring 23 65 22 5

As shown in Table 3, Inventive Materials 1 and 2, in which the steel component and the like satisfy the scope of the present invention, did not yield yield point phenomenon, and the hardness sufficiently satisfied 57 ± 3, which satisfies the T3 quality. On the other hand, even though the same or similar components were used, the yield point stretching occurred slightly in Comparative Materials 1 and 2, which had a high finishing temperature in the hot rolling section. Yield-point stretching did not occur in Comparative Material 3, which shows the characteristics of a general stone disc with Ti added to remove solid solution carbon.

However, even in the same case, in the case of Comparative Material 4 having a high C content, it was confirmed that the yield point stretching phenomenon occurred. In the case of Comparative Material 5 having a high content of V, the yield point stretching phenomenon did not occur, but due to the high content of V, it was confirmed that the recrystallized crystal grains were not completed in the continuous annealing process. It was also found that recrystallization was not completed, resulting in a high dislocation density in the grains, and the grains were not clear. Due to the incomplete organization of the recrystallization, the comparative material 5 had a low elongation of 23%, which could not be used as a working stone.

In addition, in the case of the steel handled in the present invention, because it is widely used for welding pipes, welding simulation was performed on the invention materials 1 and 2. In the welding simulation, after preparing a heat treatment furnace at 1100 ° C. in advance, thermocouples were attached to Inventive Materials 1 and 2, placed in a heat treatment furnace heated at 1100 ° C., and immediately cooled to observe the microstructure change. In the case of stone discs used for welding pipes, it is often observed that the fracture of the weld zone occurs due to coarsening of the microstructure of the weld zone or the heat-affected zone after welding. It was confirmed that the increase in grain size after the welding simulation test was relatively small compared to the comparative steel 4 not added.

Claims (4)

In weight%, C: 0.0005-0.001%, Al: 0.03-0.08%, Mn: 0.5-0.6%, N: 0.002-0.006%, V: 0.005-0.015%, P: 0.01-0.03%, S: 0.001- 0.02%, the remainder containing Fe and unavoidable impurities, the structure of which is an equiaxed ferrite single phase having a grain size of 10 to 30 µm, and a soft stone master plate having excellent aging resistance and weldability including V (C, N) carbonitride.
The method of claim 1,
The soft stone master plate is excellent in aging resistance and weldability, characterized in that having a roughness of T3 or more.
By weight%, C: 0.0005 to 0.001%, Al: 0.03 to 0.08%, Mn: 0.5 to 0.60%, N: 0.002 to 0.006%, V: 0.005 to 0.015%, P: 0.01 to 0.03%, S: 0.001 to Heating the steel slab containing 0.02%, the remainder Fe and inevitable impurities, to 1100-1300 ° C .;
Subjecting the heated steel slab to hot rolling and finishing hot rolling at a temperature satisfying the following relational expression 1 to produce a hot rolled steel sheet;
Winding the hot rolled steel sheet at a temperature that satisfies the following relation 2, manufacturing a cold rolled steel sheet by cold rolling the hot rolled steel sheet at a reduction ratio of 75 to 95% after the winding;
Annealing the cold-rolled steel sheet at a temperature of 600 to 750 ° C; And
A method of producing a soft stone master plate excellent in aging resistance and weldability comprising the step of temper rolling the annealed steel sheet.

Equation 1: Cooling Temperature (CT) +100 ≤ Hot Rolling Finish Temperature (FDT) (℃) ≤ Cond1 (℃) or 850 ℃ (Cond1 = 864.57-95.25 * C-43.5 * Mn + 26.39 * Si + 21.16 * C * Mn-23.1 * C * Si-128.65 * C ^(1/2) )

Relation 2: FDT (占 폚) -250 占 폚? CT (占 폚)? Cond1-50 (占 폚)
The method of claim 3, wherein
The temper rolling is carried out at a 1-2% reduction rate, the method of producing a soft stone master disc excellent in aging resistance and weldability.

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