KR20010094511A - Production method of cold rolling roll - Google Patents

Abstract

PURPOSE: A cold-rolling roll with superior thermal-impact resistance and corrosion resistance is provided to prevent spalling and crack. CONSTITUTION: In the manufacture method of cold-rolling roll comprising C 1.4-1.55wt.%, Si 0.4wt.%, Mn 0.6wt.%, P 0.03wt.%, Ni 0.5wt.%, Cr 11.0-12.5wt.%, Mo 1.55-1.7wt.%, V 0.7-0.95wt.%, Co 0.3-0.5wt.%, spheroidizing treatment of roll is carried out at 700deg.C for 8hrs, followed by furnace-cooling to the temperature 400deg.C at a cooling rate of 15deg.C/hr. The milled roll is charged in a basket for preheating at 600-800deg.C and then maintained at 1030deg.C for 40min/inch. Then, the roll is tempered in oil(70deg.C) until it is taken out in the martensite zone(450deg.C). The oil-tempered roll is re-tempered at low temperature(100-130deg.C), followed by carrying out sub-zero treatment.

Description

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a work roll for cold rolling and a method for producing the same, and more particularly, to a method for producing a work roll for a rolling mill suitable for cold rolling of a metal.

In rolls for metal rolling, the surface of the roll is subjected to thermal shock due to slip or rolling between the rolled material and the roll during rolling.

If this thermal shock is too large, a crack will arise on the surface of a roll. Therefore, in order to improve the thermal shock resistance of the roll, in order to effectively improve the quenching and tempering, that is, tempering at a temperature higher than the roll working temperature in the heat treatment applied to the roll surface.

Conventional working rolls include carbon 1.4 to 2.5% silicon 0.4% manganese 1% or less, chromium 3.0 to 6% molybdenum 0.2 or less to be quenched and tempered, and the tempering temperature is 160 ° C. or lower to obtain HRC 63 or higher in the treatment. It was set as.

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

As a result, rolling was not satisfactory.

Accordingly, it is an object of the present invention to provide a roll for cold rolling having excellent thermal shock resistance and wear resistance.

The purpose has been to coat a low alloy steel on the outer surface of the core shaft like a conventional roll, but this takes a long time to produce, and there is a risk of separation between the core shaft and the coated outer layer due to thermal shock and repeated fatigue loads. In addition, the work rolls invented by us are proven to be excellent in reproducibility that can be regrind.

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

Figure 4 is a view showing the hardness of the Barrell and Neck portion of the work roll according to the present invention

5 is a front view of a strip cold rolling mill using a working 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

7 is a schematic view of an apparatus for producing heat treatment by anoxic atmosphere

8 is a schematic diagram of deep cooling treatment of subzero M / C

The work roll can be produced by the following method.

First, the chemical composition of the material must be 1.4 to 1.55% by weight, 0.4% of silicon, 0.6% by weight of manganese, and 0.03% by weight of phosphorus to increase the hardenability by adding nickel which is not included in the conventional rolling rolls. For cold rolling by adding 0.5% by weight, 11.0 to 12.5% by weight of chromium, 1.55 to 1.7% by weight of molybdenum, 0.7% to 0.95% by weight of vanadium, and 0.3 to 0.5% by weight of cobalt for the purpose of preventing low temperature brittleness and improving corrosion resistance. The best material is used for tool steel.

In addition, the manufacturing method of the rolling roll is called a barrel portion (barrell) to roll the rolled roll during the rolling operation, the barrel portion to maintain the hardness of about HRC 63, the neck portion (neck) holding the barrel portion is 20mm high temperature By wrapping the dragon (1,200 ℃) ceramic asbestos to the hardness of about HS 40-45, and gave toughness to thermal shock resistance to prevent breakage or cracking.

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

Turned rolls are prepared in a dedicated basket jig and charged at 600 ℃ and 800 ℃, then preheated and maintained at 600 ℃ and 800 ℃, then maintained at 1030 ℃ for 40 minutes / inch, and then extracted with 70 ℃ oil and withdrawn from the MS section (450 ℃). do.

Subsequently, low-temperature tempering (100-130 ° C) is followed by a subzero treatment process so that the residual austenitic is not stabilized.

As a sub zero, conventional rolls were able to maintain about -50 ° C, and in the present invention, deep cooling can be carried out to -100 ° C, which can remove residual austenite within 4%, resulting in better wear resistance, hardness, and thermal shock resistance. One dimension can be improved.

Tampering was performed at a high temperature (500-550 ° C.) to prevent heat shock, splitting, cracks, and the like, thereby contributing to the life extension.

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

This work was a method of covering the outer surface of the core shaft with a different type of outer layer material like the conventional rolls. In the present invention, the STD11 steel grade of the KS standard is used as the base, and the Mo.V content is increased and Co added as compared to the STD11 steel grade. Mo improves the abrasion resistance and tempering resistance, V is a hard-hardened material with a focus on core hardening and abrasion resistance, and Co is a solid solution in BASE for rolling to obtain high hardness by high temperature tempering. It is optimally configured for tool steel.

Claims (2)

In the chemical composition of the material, carbon is 1.4 to 1.55% by weight, silicon 0.4% by weight, manganese 0.6% by weight, phosphorus is 0.03% by weight, nickel is 0.5% by weight, chromium 11.0 to 12.5% by weight, molybdenum 1.55 to 1.7% by weight, vanadium 0.7 A cold rolling roll comprising a tool steel for cold rolling containing% to 0.95% by weight and 0.3 to 0.5% by weight of cobalt. The barrel part to be rolled rolled during the rolling operation maintains the hardness of HRC 63, and the neck part holding the barrel part covers the 20mm high temperature (1,200 ℃) 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, and then cooled to 400 ° C. after 15 ° C. furnace cooling per hour. Turned rolls are prepared in a dedicated basket jig and charged at 600 ℃ and 800 ℃, then preheated and maintained at 600 ℃ and 800 ℃, then maintained at 1030 ℃ for 40 minutes / inch, and then extracted with 70 ℃ oil and withdrawn from the MS section (450 ℃). After the low-temperature tempering (100-130 ℃) and then treated with a sub agent so that the residual austenitic is not stabilized, the tempering is performed by 500-550 ℃ cold rolling roll manufacturing method characterized in that.