KR100354917B1 - Production method of cold rolling roll - Google Patents

Abstract

Regarding a cold rolling roll and a method of manufacturing the

In the chemical composition of the material, the carbon content is 1.4 to 1.55 wt%, silicon 0.4 wt%, manganese 0.6 wt%, phosphorus 0.03 wt%, nickel 0.5 wt%, chromium 11.0 to 12.5 wt%, molybdenum 1.55 to 1.7 wt%, vanadium 0.7 to 0.7 Cold rolling rolls are manufactured from a tool steel for cold rolling containing 0.95 wt% and 0.3 to 0.5 wt% cobalt,

In the manufacturing method, the barrel portion to be rolled rolled during the rolling operation maintains the hardness of about HRC 63, and the neck portion holding the barrel portion covers the 20 mm thick high-temperature (1,200 ° C) ceramic asbestos while the hardness is HS 40-45. In the heat treatment, the spherical annealing operation was maintained at 700 ° C. for 8 hours to cool down to 400 ° C. after 15 ° C. furnace cooling per hour,

The rolls that have been turned are pre-loaded into a dedicated basket jig for 2 hours at 600 ° C and 2 hours at 800 ° C, and then maintained at 1030 ° C for 40 minutes / inch and then quenched in 70 ° C oil to produce mardenite starting sections. It was extracted by air cooling at 450 ° C.), and then tempered at a low temperature (100-130 ° C.) and then treated with a sub agent so as not to immobilize the retained austenite.

Description

Cold rolled roll and its manufacturing method {PRODUCTION METHOD OF COLD ROLLING ROLL}

TECHNICAL FIELD The present invention relates to a work roll for cold rolling and a method for manufacturing the same, and more particularly, to a method for manufacturing a work roll of a rolling mill suitable for cold rolling of metal and cold rolling.

When rolling in a roll for rolling metal, the surface of the roll is subjected to thermal shock due to a slip occurring between the rolled material and the roll or an accident in which the rolled material is wound on the roll.

If the thermal shock is too large, cracks are generated on the surface of the roll. Therefore, heat treatments such as quenching and tempering are performed to improve the thermal shock resistance of the roll. The heat treatment working temperature applied to the roll surface must be performed at a temperature higher than the working temperature of the roll so that the roll can effectively improve the thermal shock resistance.

Conventional work rolls are manufactured with a material composition ratio of 1.4 to 2.5% by weight of carbon, 0.4% by weight of silicon, 1% by weight of manganese, 3.0 to 6% by weight of chromium, and 0.2% by weight of molybdenum, and the rolled material is quenched and tempered. In order to obtain a hardness of HRC 63 or more in the treatment, the tempering temperature was set to 160 ° C or lower.

However, in order to improve the heat resistance and thermal shock resistance, the tempering temperature must be increased to 160 ° C. or higher. In this case, hardness exceeding HS 93 is difficult to be obtained, and thus wear resistance is deteriorated.

As a result, rolling is not satisfactory.

An object of the present invention is to provide a cold rolling roll having excellent heat shock resistance and wear resistance.

Conventionally, a method of coating low alloy steels on the outer surface of a roll core shaft has been applied, but this requires a long work process, a long time, and a concern that the outer layer material coated on the core shaft may be separated due to thermal shock and repeated fatigue loads. There is also a good result in reproducibility that can be used by regrinding.

1 is a hardness distribution graph according to the depth of the roll and the conventional roll according to the present invention

2 is a service life time graph according to the reproducibility of the roll and the conventional roll according to the present invention

Figure 3 is a graph showing a comparison of the wear resistance of the roll and the conventional roll according to the present invention

Figure 4 is a hardness representation of the barrel and neck portion of the work roll according to the present invention

5 is a cross-sectional view of the strip cold rolling portion using a work roll according to the present invention.

Figure 6 is a graph showing the remaining capacity and the tempering temperature of the roll and the conventional roll according to the present invention

The rolling roll according to the present invention is produced by the following method.

First, the chemical composition of the material is 1.4 to 1.55% by weight of carbon, 0.4% by weight of silicon, 0.6% by weight of manganese, 0.03% by weight or less, and is easy for heat treatment of large materials, and prevents brittleness and corrosion resistance at low temperatures. For the purpose of improvement, 0.5% by weight of nickel which was not used in the conventional rolling rolls was added, and chromium contained 11.0 to 12.5% by weight, molybdenum 1.55 to 1.7% by weight, vanadium 0.7 to 0.95% by weight, and cobalt 0.3 to 0.5% by weight. Used as a raw material for cold rolling rolls.

In addition, a method of manufacturing a rolling roll is called a barrel, in which a work roll for rolling a rolled material during a rolling operation is maintained. The barrel maintains the hardness of about HRC 63, and the neck for holding the barrel is 20 mm. By covering the high temperature (1,200 ℃) ceramic asbestos, the hardness is about HS 40-45, giving toughness to the thermal shock resistance to prevent breakage or cracks.

In the heat treatment, the spherical annealing operation is maintained at 700 ° C. for 8 hours and then cooled to 400 ° C. after 15 ° C. furnace cooling per hour.

The rolls that have been turned are prepared with a special basket jig and after preloading, they are preheated for 2 hours at 600 ° C and 2 hours at 800 ° C, and then maintained at 1030 ° C for 40 minutes / inch and then at 70 ° C oil. Quenched in air and withdrawn in a martensite start section (450 ° C) and air cooled.

Subsequently, after tempering at low temperature (100-130 ° C.) so that the residual austenite is not immobilized, a sub-zero treatment process is performed.

Sub-zero treatment is that the roll was able to maintain about -50 ℃ in the prior art, in the present invention can be deep-cooled to -100 ℃ to bring the effect of removing the amount of residual austenite within 4% It is possible to improve wear resistance, hardness, and thermal shock resistance.

Tempering is performed at high temperature (500-550 ° C.) to prolong life by preventing thermal shock and peeling or cracking. FIG. 1 shows hardness according to the depth of the roll of the present invention and the conventional roll. The distribution shows that the hardness of the barrel, which is the working part of the roll, should be about HRC 63, so that the roll has toughness due to thermal shock when rolling, so that it does not break or crack. The surface hardness of the roll is HRC 63. When the hardness of the roll 70 mm deep from the surface, the conventional roll has a HRC of about 45, whereas the roll of the present invention exhibits an HRC of about 55, indicating that the hardness of the roll of the present invention is significantly improved. 2 is a comparison of the service life time according to the reproducibility of the roll of the present invention and the conventional roll, while the roll of the present invention is used for about 6 months, while the conventional roll can be used for about 4 months It can be seen that when the roll is manufactured by the method of the present invention, the service life is extended. Fig. 3 compares the wear resistance of the roll according to the present invention and the conventional roll. The wear amount of the 400 mg or the roll of the present invention was 250 mg, and the roll of the present invention was shown to have improved the wear amount. FIG. 4 shows the hardness of the barrel and the neck of the work roll according to the present invention. 98 indicates that the hardness is optimal, and the neck portion indicates the optimum hardness when the HS 40 to 45. In the specification, the hardness of the barrel is described as optimum when the hardness of HRC 63. It is the same as the hardness of 98, and to express the hardness in the same manner as the hardness of the neck portion. Figure 5 is a rolling mill for rolling the cold rolling of the strap using the work roll according to the present invention. The cross-sectional view, which is described as the upper side, has an upper work roll, a first intermediate roll is positioned above the upper work roll, and a secondary intermediate roll is positioned above the primary intermediate roll. Secondary intermediate roll (Idle) is located between the secondary intermediate rolls, the secondary intermediate roll (Backdle) is located on the upper side (Back up roll) is located, one set of these are symmetrically located in the lower part of the rolling mill To form. When the rolling process is carried out, the steel sheet is put between the upper work roll and the lower work roll. FIG. 6 shows a correlation between the remaining capacity of the roll and the conventional roll and the tempering temperature according to the present invention, at a tempering temperature of 100 ° C. When the residual capacity is -110 kg / mm2 and the tempering temperature is increased and the residual capacity is examined at 500 ° C, the residual capacity of the roll of the present invention is about -90 kg / mm2, and the residual capacity of the conventional roll is about -30 kg / mm2. It can be seen that the remaining capacity of the roll of the present invention is significantly improved than that of the conventional roll.

The rolling roll manufactured by this invention is a working roll for metal rolling mills which has the outstanding thermal shock resistance and abrasion resistance.

Conventionally, the outer layer of the roll core shaft was coated with a different kind of outer layer material. However, in the present invention, Mo is increased based on the STD11 steel grade of the KS standard, and the Mo.V content is added to the STDll steel grade, and Co is added to the wear resistance and the wear resistance. Complementary and improved tempering, V is a hard material, with a focus on deep hardening and abrasion resistance. Co obtains high hardness by high temperature tempering. The state is implemented.

Claims (2)

Cold rolled tool steel material contains 1.4 to 1.55 wt% of carbon, 0.4 wt% of silicon, 0.6 wt% of manganese, 0.03 wt% of phosphorus, 0.5 wt% of nickel, 11.0 to 12.5 wt% of chromium, and 1.55 to 1.7 wt% of molybdenum. , 0.7 to 0.95% by weight of vanadium, 0.3 to 0.5% by weight of cobalt cold rolling roll. The barrel part to roll the rolled material to be rolled during the rolling operation maintains the hardness of about HRC 63, and the neck part holding the barrel part covers the 20 mm thick high temperature (1,200 ° C) ceramic asbestos, so that the hardness is about HS 40-45. In the heat treatment, the spherical annealing operation was maintained at 700 ° C. for 8 hours to cool down to 400 ° C. after 15 ° C. furnace cooling per hour, The rolls that have been turned are preheated in a dedicated basket jig for 2 hours at 600 ° C and 2 hours at 800 ° C, and then maintained at 1030 ° C for 40 minutes / inch and then quenched in 70 ° C oil to provide martensite starting sections. Cold-rolled at 450 ° C.), followed by air cooling, and then tempering at low temperature (100-130 ° C.) and sub-treatment to prevent residual austenite from immobilizing, and tempering at high temperature (500-550 ° C.). Roll manufacturing method.