RU1770384C - Method for heat treatment of large sections, made of hypereutectoid steels - Google Patents

Abstract

Using the invention can be used in the production of long products from carbon steel. SUMMARY OF THE INVENTION: a tube made of evacuated bearing steel, after rolling, is accelerated by cooling to a metal surface temperature in the range (Tmin ustust - 50 ° C) ... MN, aged and accelerated heated to (АСт - 100 ° C) ... (ACt - 20 ° C), after exposure, cool to (Aci + 40 ° C). .Aci and incubated until the nonequilibrium excess phases are completely isolated from the solid solution, then cooled at a rate of 40., 250 ° C / hr to a temperature range (Cumin setting aust + 50 C) ... (Cumin setting aust 50 C), After exposure, 2 tablets are finally cooled.

Description

The invention relates to metallurgy, mainly to the production of coarse rolled products from hypereutectoid steels using heat from rolling heating

The closest technical solution is a method for heat treatment of rolled products from carbon and alloy steels, including heating, hot rolling, curing, holding, holding heating, holding cooling and final cooling. The disadvantages of this method include the low productivity and significant energy intensity of the process due to the insufficient use of the heat of rolling heating.

The purpose of the invention is to increase productivity and reduce energy consumption.

process while maintaining the required properties of the rental. This goal is achieved by the fact that in the known method, including heating, hot rolling, curing, curing, heating with curing, cooling with curing and final cooling, curing after rolling is carried out accelerated to a metal surface temperature in the range (Tmin - 50 ° C). Mn, heating is carried out accelerated to (Ast - 100 ° C) (Ast - 20 ° C) after cooling, it is cooled to (AC1 - C). Aci and kept until complete separation of nonequilibrium excess phases from the solid solution, then cooled at a rate of 40,. 250 ° C / h to the temperature range (caraway mouth aust 50 C) (caraway mouth aust

50 ° C).

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Curing after rolling is carried out accelerated to a metal surface temperature in the range (Tmin, set aust. - 50 ° C / ... Mn, so that a guaranteed temperature is achieved over the entire cross section of the rolled profile, ensuring a minimum conversion time.

Stirring above this temperature Cumin, set ast. - 50 ° C leads to the fact that due to the inhomogeneity of the temperature field over the cross section, when the steel profile is reinforced in the central part of the cross section, the first pearlite transformation does not occur completely. Stressing below Mn (the onset of martensitic transformation) leads to an increase in the duration upon subsequent heating for austenization and to the formation of cracks on the surface. Accelerated heating of the surface layers of rolled products to a surface temperature range from (Ast -100 ° C) to (Ast -20 ° C) is necessary to accelerate the achievement of the central part of the temperature profile above AC1 and accelerate the austenitic transformation over the entire cross section, which shortens the heat treatment cycle. Heating above (Ast - 20 ° C) leads to rapid grain growth and an unacceptable decrease in the carbide phase, which subsequently serves as centers of granular perlite formation. Heating to a temperature below (Ast - 100 ° C) slows down the temperature rise of the central part above Aci and prolongs the heat treatment cycle. The cooling of the metal surface after exposure to a temperature range from (AC1 + 40 ° C) to Aci is carried out to increase the number of crystallization centers in the surface layers of the rolling profile to form granular perlite. Cooling the rolled surface above temperature (Ac1 + 40 ° C) prevents the formation of plate perlite due to the insufficient number of crystallization centers, and below the point Ac1 also leads to the formation of plate perlite. At the same time, exposure is necessary to completely isolate nonequilibrium excess metal phases from the solid solution. Cooling of the heat profile of the rolled product at a speed of 40-250 ° C / h to the temperature range from Tmin.ust.Aust. + 50 ° C to Tmin.ust.aust. - 50 ° C is necessary to ensure that the austenite of the surface layers of the rolled profile is transformed into perlite with a hardness that meets the requirements of normative and technical documentation. Cooling at a rate of less than 40 ° C / h lengthens the heat treatment process, and more than 250 ° C / h leads to an unacceptable increase in the hardness of the metal. Cooling with

at a speed of 40-250 ° C / h higher (Cumin, set Aust. - 50 ° C); and then in air leads to an unacceptable increase in the hardness of the metal, and below (Tmin.ust.aust. - 50 ° C) - to elongation

heat treatment process.

An example of the method. Continuous cast billets with a cross section of ZOOx x 360 mm from steel ШХ15-В after heating to a temperature of 1180 ° C are rolled on a mill

0 700 for 13 passes into a tube stock with a diameter of 130 mm, cut into saws to measured lengths, then rapidly cooled in a rack refrigerator to a temperature of 600-560 ° C, and then planted in a seven-season methodical furnace with walking beams operating in a continuous mode: preforms are heated to a temperature of 800-880 ° C for 45-75 minutes, then cooled to a temperature of 780-740 ° C for 15-35 minutes,

0 stand for 15-25 minutes, then cooled at a speed of 40-250 ° C / h to a temperature of 580 680 ° C and put on the refrigerator, where it is cooled to the temperature of the workshop. In the table. 1 shows specific examples of testing5 of the proposed and known prototype methods.

In the table. 2 shows the test results of the proposed and known prototype methods.

0 The data given in tab. 1. allow us to conclude that the duration of the heat treatment of the proposed method is much shorter than the prototype.

The data table. 2 confirm that

5, the proposed heat treatment method allows to increase the hourly heat treatment productivity by 1.3-2.0 times and reduce the energy intensity (gas consumption) by 1.4-2.0 times.

0 Using the proposed method

heat treatment of coarse rolled products from

hypereutectoid steels allows to obtain

economic effect up to 10 rubles / ton of hire.

Claims (1)

The claims 5 A method of heat treatment of coarse rolled steel from hypereutectoid steels, including heating, hot rolling, curing, holding, heating with holding, cooling with holding and final cooling, characterized in that that, in order to increase productivity and reduce the energy intensity of the process while maintaining the required properties, reinforcement after rolling is accelerated to a metal surface temperature that is in the range (Tmin, set -50 ° C) ... MN, heating is carried out accelerated for (Ast-10 ° C) ... (AST -20 ° C). after exposure, cool to (AC1 + 40 ° C) AC1 and incubate until completely separated from the solid solution 517T03846 pa of nonequilibrium excess phases, then lost temperature (ТМin set Aust. cool at a speed of 40-250 ° С / h to in- (Тmin.ust. Aust. -50 С). Table 1 50 ° C). Surface temperature after rolling, 4C 650 Duration Pre600 580 560 Table