CN103572033A - 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 load is passed to support roll and finally by support roll, born by working roll, intermediate roll.Thereby being exactly support works roller, the effect of support roll make its flexural deformation that reduces working roll improve thickness of slab precision and strip shape quality.

Roll body length is that 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, the feature with 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 along with the reversible wide and heavy plate mill of four rollers in recent years, 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 final thermal treatment is the critical process that determines support roll operational layer tissue, Hardness Distribution, stress distribution and use properties, is also the core place that support roll is manufactured.The final thermal treatment of tradition mainly contains differential temperature thermal treatment, car type furnace Differential Heating quenches and the whole induction quenching of power frequency.

Large-scale forged steel Wide and Thick Slab support roll is because workpiece size is large, weight is large, and body surface hardness, depth of hardening zone are had relatively high expectations, and limit by heating installation, generally adopts car type furnace Differential Heating to quench as final property heat treatment.Support roll by common pallet car type gas furnace, be rapidly heated and suitably keep after the fog quenching of coming out of the stove; owing to heating in support roll roll neck in the lump stove; during fog quenching, need to increase the measure of protection roll neck; after whole tempering, also need double tempering; to guarantee the mechanical property requirement 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 the support roll workpiece body surface that is 3500～4300mm to roll body length, heat-treat, comprise the steps:

The first step, preheating;

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

Second step, differential heating;

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

Again workpiece is warming up to rapidly to 1000～1050 ℃ with the heat-up rate of 100～200 ℃/h, is incubated soaking time 2～5 hours;

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

The 3rd step, fog quenching;

After differential heating finishes, workpiece is come out of the stove and go to the 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 that spray the machine of quenching, hydraulic pressure and air pressure are all controlled to 0.20～0.35MPa, workpiece is carried out to spray cooling 20～40 minutes;

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

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

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

The 4th step, tempering;

After fog quenching finishes, workpiece is entered to stove tempering, workpiece is incubated to 10～20 hours at the temperature of 300 ± 10 ℃;

Then the heat-up rate with≤20 ℃/h is warming up to 550～600 ℃, is incubated, and soaking time 80～120 hours, realizes tempering;

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

The technique effect that the present invention can reach is:

The present invention can reduce the operation that car type furnace integral body is not burnt the protection of quenching roll neck and double tempering thoroughly, reduces thermal treatment risk, saves production cost, effectively enhances productivity.

The present invention adopts differential temperature process of thermal treatment method, by adopting Horizontal different temperature stove to carry out rapid heating to the support roll body of roll, then be placed in the spray machine of quenching and carry out spray cooling, make support roll body surface obtain high hardness martensitic or the bainite structure of certain depth, and roll neck, core still keep having the quenched and tempered state tissue of good mechanical properties, thereby meet that hardness of roll body, depth of hardening zone require 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 the original good comprehensive mechanical performance of roll neck maintenance; Change traditional large-scale Wide and Thick Slab support roll car type furnace simultaneously and thoroughly do not burnt the technology mode of integral heating quenching, reduced times of tempering, shortened the production cycle, reduced production cost.

The invention solves roll body length is the manufacturing difficult point of 3500～4300mm Wide and Thick Slab support roll, makes the technical requirementss 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, heat-treats for the support roll workpiece body surface that is 3500～4300mm to roll body length, comprises the steps:

The first step, preheating;

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

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

Second step, differential heating;

By differential temperature stove empty burning after >=4 hours at the temperature of 800～850 ℃, the workpiece after preheating is proceeded to differential temperature stove;

First stage, by strong radiation and convection heat transfer type, makes workpiece surface be warming up to rapidly 1000～1050 ℃ with the heat-up rate of 100～200 ℃/h, is incubated soaking time 2～5 hours;

Subordinate phase, workpiece is cooled to 900～950 ℃ with the cooling rate slow cooling of 50～100 ℃/h, be 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 first 800～850 ℃ of empty burnings of body of heater, can guarantee 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 the austenitizing layer of workpiece surface acquisition certain depth, and workpiece core still maintains below transformation temperature.

The 3rd step, fog quenching;

After differential heating finishes, workpiece is come out of the stove and go to the spray machine of quenching and carry out fog quenching, and make spray quench four row's nozzles of machine with respect 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 that spray the machine of quenching, hydraulic pressure and air pressure are all controlled to 0.20～0.35MPa, workpiece is carried out to spray cooling 20～40 minutes;

Subordinate phase, open four row's nozzles, making in the clinodiagonal wherein hydraulic pressure of two row's nozzles is 0, and air pressure is 0.20～0.30MPa, hydraulic pressure and the air pressure of other two row's nozzles (in another diagonally opposing corner) are all controlled at 0.20～0.30MPa, and workpiece is carried out to spray cooling 20～40 minutes;

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

Fourth stage, opens in clinodiagonal two row's nozzles (keeping closing in another clinodiagonal two row's nozzles), and its hydraulic pressure and air pressure are all controlled to 0.05～0.10MPa, and workpiece is carried out to spray cooling 50～80 minutes;

Table 1

Fog quenching of the present invention is divided into four-stage, and the first stage adopts large hydraulic pressure, air pressure to spray by force, and it is cold soon that jet is broken steam film realization, makes body of roll temperature be down to rapidly 600 ℃ below to suppress perlitic transformation; Subordinate phase suitably reduces hydraulic pressure, air pressure, and object is to make workpiece surface temperature suitably return temperature, and the suitable tempering of martensitic stucture of effects on surface formation, to prevent hard surfacing cracking; Third and fourth stage is weakened spray intensity gradually, take to maintain roll surface and do not occur returning temperature as principle, makes roll surface form stable heat exchange with inner, maintains the body of roll and returns temperature and be no more than 250 ℃.

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

The 4th step, tempering;

After fog quenching finishes, workpiece is entered to stove tempering, workpiece is incubated to 10～20 hours at the temperature of 300 ± 10 ℃, make workpiece internal and external temperature be tending towards even;

Then the heat-up rate with≤20 ℃/h is warming up to 550～600 ℃, is incubated, and soaking time 80～120 hours, realizes tempering;

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

Hardness of roll body through 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 immediately stove tempering after fog quenching, can reduce residual-stress value, to obtain stable tempered martensite or tempering bainite tissue.

The present invention by the support roll body of roll is carried out to rapid heating and fog quenching cooling, then carry out the differential temperature thermal treatment of tempering, can obtain the required higher hardness of body of roll working lining and depth of hardening zone, 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 that can improve support roll.

Claims (2)

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

The first step, preheating;

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

Second step, differential heating;

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

Again workpiece is warming up to rapidly to 1000～1050 ℃ with the heat-up rate of 100～200 ℃/h, is incubated soaking time 2～5 hours;

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

The 3rd step, fog quenching;

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

The 4th step, tempering;

After fog quenching finishes, workpiece is entered to stove tempering, workpiece is incubated to 10～20 hours at the temperature of 300 ± 10 ℃;

Then the heat-up rate with≤20 ℃/h is warming up to 550～600 ℃, is incubated, and soaking time 80～120 hours, realizes tempering;

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

2. the heat treating method of Wide and Thick Slab support roll according to claim 1, is characterized in that, the method for described the 3rd step fog quenching is as follows:

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

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

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

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

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