CN103572033B - Thermal treatment method of wide and thick plate supporting roll - Google Patents

Abstract

The invention discloses a thermal treatment method of a wide and thick plate supporting roll. The thermal treatment method is used for carrying out thermal treatment on the surface of a roll body with the length of 3500-4300mm of a supporting roll workpiece and comprises the following steps: step one. preheating; step two. carrying out differential temperature heating, to be specific, firstly carrying out air burning on a differential temperature furnace for more than or equal to 4 hours at the temperature of 800-850 DEG C, and then transferring the preheated workpiece to the differential temperature furnace; heating to 1000-1050 DEG C, carrying out heat preservation for 2-5 hours, then cooling to 900-950 DEG C, and carrying out heat preservation for 2-6 hours; step three. carrying out spray quenching; and step four. tempering. The thermal treatment method can be used for improving the wear resistance of the supporting roll and prolonging the service life of the supporting roll and ensuring that the surface of the roll body of the supporting roll has good hardness and abrasive resistance, and a core part of the roll body and a roll neck have good synthesized mechanical properties; the non-burning overall heating quenching process manner of a conventional large-sized wide and thick plate supporting roll car-bottom type furnace is changed, the tempering frequency is reduced, the production cycle is shortened, and the production cost is reduced.

Description

The heat treating method of Wide and Thick Slab support roll

Technical field

The present invention relates to a kind of heat treating method of forged steel, be specifically related to a kind of heat treating method of Wide and Thick Slab support roll.

Background technology

Wide and heavy plate mill is the four-high mill with support roll, and rolling loads passes to support roll by working roll, intermediate roll and finally to be born by support roll.The effect of support roll is exactly that support works roller makes its flexural deformation reducing working roll thus improves thickness of slab precision and strip shape quality.

Roll body length is the large-scale forged steel Wide and Thick Slab support roll of 3500 ~ 4300mm is the kind that in roll product, size is large, manufacture difficulty is high, there is the feature of high technology content, high added value, being widely used in the aspects such as ships, high pressure vessel, heavy caliber petroleum pipe, boiler, ocean exploitation and machinofacture, is the indispensable very important rolling shapes of modernization construction.Increasing sharply in recent years along with the four reversible wide and heavy plate mills of roller, the demand of high rigidity wide and heavy plate mill support roll constantly increases, simultaneously more and more higher to the requirement of the metallurgical quality of Wide and Thick Slab support roll, support roll material, depth of hardening zone, hardness of roll body homogeneity, super-huge support roll manufacturing technology.Wherein finished heat treatment is the critical process determining support roll operational layer tissue, Hardness Distribution, stress distribution and use properties, is also the core place that support roll manufactures.Tradition finished heat treatment mainly contains differential temperature thermal treatment, the quenching of car type furnace Differential Heating and the overall induction quenching of power frequency.

Large-scale forged steel Wide and Thick Slab support roll is because workpiece size is large, weight large, and body surface hardness, depth of hardening zone require higher, and limit by heating installation, and the general car type furnace Differential Heating that adopts quenches as final property heat treatment.Support roll is rapidly heated by common pallet car type gas furnace and fog quenching of coming out of the stove after suitable maintenance; owing to heating in support roll roll neck in the lump stove; need during fog quenching to increase the measure of protection roll neck; also double tempering is needed after overall tempering; to ensure the mechanical property requirements of roll neck; therefore existing heat treating method production cost is high, and production efficiency is low.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of heat treating method of Wide and Thick Slab support roll, and it can be enhanced productivity.

For solving the problems of the technologies described above, the technical solution of the heat treating method of Wide and Thick Slab support roll of the present invention is:

For being that the support roll workpiece body surface of 3500 ~ 4300mm is heat-treated to roll body length, comprise the steps:

The first step, preheating;

Workpiece is incubated 10 ~ 20 hours at the temperature of 300 ± 10 DEG C, then workpiece is preheated to 500 ~ 600 DEG C with the heat-up rate of≤30 DEG C/h, is incubated, soaking time >=35 hour;

Second step, differential heating;

First the workpiece after preheating, after >=4 hours, is proceeded to differential temperature stove by differential temperature stove empty burning at the temperature of 800 ~ 850 DEG C;

Again by workpiece with heat-up rate rapid temperature increases to 1000 ~ 1050 DEG C of 100 ~ 200 DEG C/h, be incubated, soaking time 2 ~ 5 hours;

Then workpiece is cooled to 900 ~ 950 DEG C with the cooling rate of 50 ~ 100 DEG C/h, is incubated, soaking time is 2 ~ 6 hours;

3rd step, fog quenching;

After differential heating terminates, workpiece is come out of the stove and goes to spray machine of quenching and carry out fog quenching;

The method of described fog quenching is as follows:

First stage, open the four row's nozzles spraying machine of quenching, hydraulic pressure and air pressure are all controlled at 0.20 ~ 0.35MPa, spray cooling is carried out 20 ~ 40 minutes to workpiece;

Subordinate phase, opens four row's nozzles, and make the hydraulic pressure being in clinodiagonal wherein two row's nozzles be 0, air pressure is 0.20 ~ 0.30MPa, and hydraulic pressure and the air pressure of other two row's nozzles all control at 0.20 ~ 0.30MPa, carry out spray cooling 20 ~ 40 minutes to workpiece;

Phase III, open and be in clinodiagonal two row's nozzles, its hydraulic pressure and air pressure are all controlled at 0.10 ~ 0.20MPa, spray cooling is carried out 20 ~ 40 minutes to workpiece;

Fourth stage, opens and is in clinodiagonal two row's nozzles, all control its hydraulic pressure and air pressure at 0.05 ~ 0.10MPa, carry out spray cooling 50 ~ 80 minutes to workpiece.

4th step, tempering;

After fog quenching terminates, workpiece is entered stove tempering, workpiece is incubated 10 ~ 20 hours at the temperature of 300 ± 10 DEG C;

Then be warming up to 550 ~ 600 DEG C with the heat-up rate of≤20 DEG C/h, be incubated, soaking time 80 ~ 120 hours, realizes tempering;

After tempering terminates, be cooled to 300 ± 10 DEG C with the cooling rate of≤20 DEG C/h, then with the cooling rate of≤10 DEG C/h be cooled to≤150 DEG C after, air cooling of coming out of the stove.

The technique effect that the present invention can reach is:

The present invention can reduce the overall operation of thoroughly not burning the protection of quenching roll neck and double tempering of car type furnace, reduces thermal treatment risk, saves production cost, effectively enhance productivity.

The present invention adopts differential temperature process of thermal treatment method, by adopting Horizontal different temperature stove, rapid heating is carried out to the support roll body of roll, then be placed in spray machine of quenching and carry out spray cooling, support roll body surface is made to obtain high hardness martensitic or the bainite structure of certain depth, and roll neck, core still keep the quenched and tempered state tissue with good mechanical properties, thus meet hardness of roll body, depth of hardening zone requires and body of roll core, the good comprehensive mechanical performance requirement of roll neck, improve support roll work-ing life.

The present invention can improve wear resistance and the work-ing life of support roll, makes support roll body surface have good hardness and wear resistance, and body of roll core and roll neck keep original good comprehensive mechanical performance; Change the technology mode that traditional large-scale Wide and Thick Slab support roll car type furnace does not burn integral heating quenching thoroughly simultaneously, decrease times of tempering, shorten the production cycle, reduce production cost.

The invention solves the manufacturing difficult point that roll body length is 3500 ~ 4300mm Wide and Thick Slab support roll, make the technical requirements such as hardness of roll body and depth of hardening zone all reach design requirements.

Accompanying drawing explanation

Below in conjunction with the drawings and specific embodiments, the present invention is further detailed explanation:

Fig. 1 is the schematic diagram of the heat treating method of Wide and Thick Slab support roll of the present invention.

Embodiment

As shown in Figure 1, the heat treating method of Wide and Thick Slab support roll of the present invention, for being that the support roll workpiece body surface of 3500 ~ 4300mm is heat-treated to roll body length, comprises the steps:

The first step, preheating;

Workpiece is incubated 10 ~ 20 hours at the temperature of 300 ± 10 DEG C, then workpiece is preheated to 500 ~ 600 DEG C with the heat-up rate of≤30 DEG C/h, is incubated, soaking time >=35 hour, make workpiece internal and external temperature even;

Support roll workpiece must carry out overall preheating before carrying out rapid heating, and the phenomenon of cracking to reduce external stress in the body of roll that follow-up rapid heating causes excessive, also can ensure the heat-up rate of differential heating simultaneously; Preheating temperature is advisable with 500 ~ 600 DEG C, should be able to ensure that body of roll internal-external temperature difference is consistent warm up time, make roll surface cross section enter plastic state completely, forging also can be made to have good differential heating effect;

Second step, differential heating;

Workpiece after preheating, after >=4 hours, is proceeded to differential temperature stove by differential temperature stove empty burning at the temperature of 800 ~ 850 DEG C;

First stage, by strong radiation and convection heat transfer type, make workpiece surface rapid temperature increases to 1000 ~ 1050 DEG C with the heat-up rate of 100 ~ 200 DEG C/h, be incubated, soaking time 2 ~ 5 hours;

Subordinate phase, workpiece is cooled to 900 ~ 950 DEG C with the cooling rate slow cooling of 50 ~ 100 DEG C/h, carry out being incubated that (soaking time is comprehensively determined by actual roll diameter, depth of hardening zone, be generally 2 ~ 6 hours, to avoid roll surface overheated), make material within the scope of body surface certain depth complete austenitizing;

The present invention, before workpiece proceeds to differential temperature stove, makes body of heater first 800 ~ 850 DEG C of empty burnings, can ensure that subsequent power heats up;

The present invention carries out rapid heating by high combustion rate burner jet flames to body surface, causes internal-external temperature difference, make workpiece surface obtain the austenitizing layer of certain depth, and workpiece core still maintains below transformation temperature.

3rd step, fog quenching;

After differential heating terminates, workpiece is come out of the stove and goes to spray machine of quenching and carry out fog quenching, and make spray quench four row's nozzles of machine relative to the center of turning circle circumference uniform distribution of workpiece;

As shown in table 1, the method for fog quenching is as follows:

First stage, open the four row's nozzles spraying machine of quenching, hydraulic pressure and air pressure are all controlled at 0.20 ~ 0.35MPa, spray cooling is carried out 20 ~ 40 minutes to workpiece;

Subordinate phase, open four row's nozzles, make the hydraulic pressure being in clinodiagonal wherein two row's nozzles be 0, air pressure is 0.20 ~ 0.30MPa, hydraulic pressure and the air pressure of other two rows' nozzle (being in another diagonally opposing corner) all control at 0.20 ~ 0.30MPa, carry out spray cooling 20 ~ 40 minutes to workpiece;

Phase III, open and be in clinodiagonal two row's nozzles (being in another clinodiagonal two row's nozzles to keep closing), its hydraulic pressure and air pressure are all controlled at 0.10 ~ 0.20MPa, spray cooling is carried out 20 ~ 40 minutes to workpiece;

Fourth stage, opens and is in clinodiagonal two row's nozzles (being in another clinodiagonal two row's nozzles to keep closing), all control its hydraulic pressure and air pressure at 0.05 ~ 0.10MPa, carry out spray cooling 50 ~ 80 minutes to workpiece;

Table 1

Fog quenching of the present invention is divided into four-stage, and the first stage adopts large hydraulic pressure, air pressure sprays by force, and jet is broken steam film and realized rapid cooling, makes body of roll temperature be down to rapidly less than 600 DEG C to suppress perlitic transformation; Subordinate phase suitably reduces hydraulic pressure, air pressure, and object makes workpiece surface temperature suitably return temperature, and the suitable tempering of martensitic stucture that effects on surface is formed, ftracture to prevent hard surfacing; Third and fourth stage weakens spray intensity gradually, and do not occur returning temperature for principle to maintain roll surface, make roll surface form stable heat exchange with inner, the maintenance body of roll returns temperature and is no more than 250 DEG C.

The gentle pressure energy of hydraulic pressure that the present invention sprays by adjustment machine nozzle of quenching enough obtains different cooling performances;

4th step, tempering;

After fog quenching terminates, workpiece is entered stove tempering, workpiece is incubated 10 ~ 20 hours at the temperature of 300 ± 10 DEG C, makes workpiece internal and external temperature be tending towards even;

Then be warming up to 550 ~ 600 DEG C with the heat-up rate of≤20 DEG C/h, be incubated, soaking time 80 ~ 120 hours, realizes tempering;

After tempering terminates, be cooled to 300 ± 10 DEG C with the cooling rate of≤20 DEG C/h, then with the cooling rate of≤10 DEG C/h be cooled to≤150 DEG C after, air cooling of coming out of the stove.

The hardness of roll body of the workpiece after thermal treatment of the present invention is HS50 ~ 65, roll neck hardness HS 30 ~ 50, depth of hardening zone >=100mm.

The present invention enters stove tempering immediately after fog quenching, can reduce residual-stress value, to obtain stable tempered martensite or tempering bainite tissue.

The present invention is by carrying out rapid heating and fog quenching cooling to the support roll body of roll, then the differential temperature thermal treatment of tempering is carried out, the higher hardness needed for body of roll working lining and depth of hardening zone can be obtained, and body of roll core, roll neck still keep compared with soft and good comprehensive mechanical performance, thus wear resistance and the work-ing life of support roll can be improved.

Claims (1)

1. a heat treating method for Wide and Thick Slab support roll, is characterized in that, for being that the support roll workpiece body surface of 3500 ~ 4300mm is heat-treated to roll body length, comprises the steps:

The first step, preheating;

Workpiece is incubated 10 ~ 20 hours at the temperature of 300 ± 10 DEG C, then workpiece is preheated to 500 ~ 600 DEG C with the heat-up rate of≤30 DEG C/h, is incubated, soaking time >=35 hour;

Second step, differential heating;

First the workpiece after preheating, after >=4 hours, is proceeded to differential temperature stove by differential temperature stove empty burning at the temperature of 800 ~ 850 DEG C;

Again by workpiece with heat-up rate rapid temperature increases to 1000 ~ 1050 DEG C of 100 ~ 200 DEG C/h, be incubated, soaking time 2 ~ 5 hours;

Then workpiece is cooled to 900 ~ 950 DEG C with the cooling rate of 50 ~ 100 DEG C/h, is incubated, soaking time is 2 ~ 6 hours;

3rd step, fog quenching;

After differential heating terminates, workpiece is come out of the stove and goes to spray machine of quenching and carry out fog quenching;

The method of described fog quenching is as follows:

First stage, open the four row's nozzles spraying machine of quenching, hydraulic pressure and air pressure are all controlled at 0.20 ~ 0.35MPa, spray cooling is carried out 20 ~ 40 minutes to workpiece;

Subordinate phase, opens four row's nozzles, and make the hydraulic pressure being in clinodiagonal wherein two row's nozzles be 0, air pressure is 0.20 ~ 0.30MPa, and hydraulic pressure and the air pressure of other two row's nozzles all control at 0.20 ~ 0.30MPa, carry out spray cooling 20 ~ 40 minutes to workpiece;

Phase III, open and be in clinodiagonal two row's nozzles, its hydraulic pressure and air pressure are all controlled at 0.10 ~ 0.20MPa, spray cooling is carried out 20 ~ 40 minutes to workpiece;

Fourth stage, opens and is in clinodiagonal two row's nozzles, all control its hydraulic pressure and air pressure at 0.05 ~ 0.10MPa, carry out spray cooling 50 ~ 80 minutes to workpiece;

4th step, tempering;

After fog quenching terminates, workpiece is entered stove tempering, workpiece is incubated 10 ~ 20 hours at the temperature of 300 ± 10 DEG C;

Then be warming up to 550 ~ 600 DEG C with the heat-up rate of≤20 DEG C/h, be incubated, soaking time 80 ~ 120 hours, realizes tempering;

After tempering terminates, be cooled to 300 ± 10 DEG C with the cooling rate of≤20 DEG C/h, then with the cooling rate of≤10 DEG C/h be cooled to≤150 DEG C after, air cooling of coming out of the stove.