CN103468889A - After-forged heat treatment technique of 9Cr2MoV chilled roll steel - Google Patents

Abstract

The invention relates to an after-forged heat treatment method of 9Cr2MoV chilled roll steel. The after-forged heat treatment method is characterized in that a chilled roll is made of 9Cr2MoV steel, the after-forged heat treatment method comprises the steps of normalizing and spheroidizing annealing, wherein the normalizing technique is performed at the temperature of 950 DEG C, higher temperature facilitates the dissolution of carbide and ensures the homogeneity of compositions. When normalization cooling is performed, the chilled roll is hoisted and cooled by atomizing water so as to prevent formation of continuous network carbide on grain boundary; in the spheroidizing annealing, fine carbide is easily molten from the middle through 820 DEG C insulation, so as to form a great amount of diffusely distributed carbide particles; carbide, as heterogeneous nucleus, is continuously separated out by austenite through retarded cooling, a carbon enrichment region of the austenite is formed into carbide crystal nucleus grown crystal grains, finally, the carbide crystal nucleus grown crystal grains are gathered and grown into particular cementite with certain size through 730 DEG C constant temperature, so that an excellent spheroidized structure can be obtained.

Description

The forging postheat treatment technique of 9Cr2MoV cold roller steel

Technical field

The present invention relates to a kind of forging postheat treatment technique of 9Cr2MoV cold roller steel.

Background technology

Roll is the main easily consumption spare part of milling train, and the quality of roll is the important factor that affects mill bar quality and the cost consumption of Steel Mill.Cr2 Series Steel roll is that Current Domestic milling train group is used maximum component, and the body of roll often operation such as annealed, rough turn, modified, half finish turning, hard surfacing processes.Cold-rolled products are with its good product performance, highly polished, the advantages such as surface quality is good make it have considerable effect in national economy, and for the quality of the main tool roll of direct processing metal with just be directly connected to production efficiency, quality product and the production cost of Rolling Production work-ing life.At present, domestic roll all exists a certain distance at aspects such as quality, description and production technique compared with developed countries, therefore, and for meeting the demand of each department of national economy to cold rolling steel, existing various cold rolls are carried out to the necessary technology transformation, have been imperative.

The manufacture of cold roll is the process of a very complex, and each process procedure plays a very important effect, heat treatment process especially wherein.Forge postheat treatment for roller stock, the keying action of normalizing and Spheroidizing Annealing is that carrying out sufficient tissue for afterwards modified and quenching technology prepares, improve antistripping and the break resistance of cold roll, can be for enhancing productivity, conforming product rate and make material after quenching technology in can bring into play its optimum performance and make outstanding contributions.

Existing domestic and international cold roll material adopts 9Cr2 system or 86CrMoV7 steel mostly, and the rigidity of these materials and toughness are all better, and have good wear resistance and break resistance, and work-ing life is longer.But, when the cold roll that adopts the large size forging stock to make, some will find cracking when rough turn, and, along with the forging stock size increases, cracking phenomena is more serious.This is the defect (banded segregation, carbide network etc.) of leaving over due in the forging of large size cold roll, adopts conventional thermal treatment process not eliminate fully, has caused the cracking of roll.According to producing reality, with the thermal treatment theory, combine, the final forging temperature of 9Cr2MoV steel will be controlled at 750～850 ℃, carry out immediately spray form water after forging and carry out coolingly, the body surface temperature is cooled to 350～400 ℃, prevent that the austenite carbide precipitate from forming continuous carbide network.Normalizing temperature is chosen in 950 ℃, and higher temperature is conducive to the dissolving of carbide, increases carbon and the rate of diffusion of alloying element in steel, guarantees the homogeneity of composition.When normalizing is cooling, cold roll should be hung to lower spray form water cooling, increase the rate of cooling of cold roll, suppress the Carbide Precipitation in austenite, prevent from forming continuous carbide network on crystal boundary, guarantee to form tiny lamellar pearlite or quasi-eutectoid perlite.In the Spheroidizing Annealing process, through 820 ℃ of insulations, the carbide in tiny lamellar pearlite is easy to, from centre fusing, be distributed in inhomogeneous austenite, has formed the carbide particle that a large amount of disperses distribute.Through slow cooling, austenite continues carbide precipitate, and these carbide particles are as non-spontaneous core, austenitic carbon enrichment district just becomes the carbide nucleus and grows up to crystal grain, finally by crossing 730 ℃ of isothermals, the nodular cementite that agglomeration is certain size, thus obtain good spherodized structure.Composition, microstructure and hardness that the forging postheat treatment technique that employing is optimized obtains are more even, have reduced distortion and the cracking of roll, make it have high machining ability and high lumber recovery.

Because of in the production actual procedure, consider roll geomery, stow the reasons such as various parameters of coefficient, process furnace, the soaking time of the stages of thermal treatment process need to further be determined reasonable and economic scheme according to production practice.

Summary of the invention

The forging postheat treatment technique that the object of the invention is to avoid the deficiencies in the prior art part and a kind of cold roll is provided, thus problems of the prior art effectively solved.

Purpose of the present invention can be by realizing by the following technical solutions: the forging postheat treatment technique of described a kind of cold roll, its characteristics are: described Cold Work Roll Material is the 9Cr2MoV steel, its heat treating method includes normalizing and carbide annealing process, and its heat treatment step is as follows:

(1) the normalizing stage: when cold rolling roll forging is water-cooled to 350 ℃～400 ℃ by spray form, it is heated in heat treatment furnace to M ₂₃c ₆the carbide of type chromium dissolves in 950 ℃ ± 10 ℃ of austenitic temperature, soaking time 4h～6h, and then spray form is water-cooled to 350 ℃～400 ℃.

(2) the nodularization tempering stage: the cold roll after the spray form water cooling is heated to 820 ℃ ± 10 ℃ in process furnace, cool to 730 ℃ ± 10 ℃ after soaking time 5h～8h with the furnace, cool to 400 ℃ after soaking time 7h～12h with the furnace again, then hang lower air cooling to room temperature.

The forging postheat treatment technique of described a kind of cold roll, its beneficial effect comprises that the globular carbide particle of a large amount of disperses distributions is arranged, and without carbide network, forms; Composition, microstructure and hardness that the normalizing that employing is optimized and carbide annealing process obtain are more even, have reduced distortion and the cracking of cold roll.In actual production, adopt the normalizing of optimization and the 9Cr2MoV steel cold roll after the carbide annealing process processing to there is high machining ability and high lumber recovery.

The accompanying drawing explanation

Fig. 1 is the cold rolling roll forging postheat treatment of 9Cr2MoV steel of the present invention artwork.

Fig. 2 is the metallograph of the 9Cr2MoV steel that obtains through common forging postheat treatment technique.

Fig. 3 is the stereoscan photograph of the 9Cr2MoV steel that obtains through common forging postheat treatment technique.

The metallograph of the 9Cr2MoV steel that Fig. 4 adopts technique of the present invention to obtain.

The stereoscan photograph of the 9Cr2MoV steel that Fig. 5 adopts technique of the present invention to obtain.

Embodiment

Embodiment 1, described a kind of cold rolling roll forging postheat treatment technique, and its characteristics are: the material of described cold roll is the 9Cr2MoV steel, and its heat treatment method after forging includes normalizing and carbide annealing process, and its heat treatment step is as follows:

(1) the normalizing stage: when cold rolling roll forging is cooled to 350 ℃ by spray water xi, it is heated in heat treatment furnace to 950 ℃, soaking time 5h, then hang lower spray form and be water-cooled to 400 ℃.

(2) the nodularization tempering stage: the cold roll after the spray form water cooling is heated to 820 ℃ in process furnace, cools to 730 ℃ after soaking time 7h with the furnace, then cool to 400 ℃ with the furnace after soaking time 10h, then hang lower air cooling to room temperature.

Embodiment 2, described a kind of cold rolling roll forging postheat treatment technique, and its characteristics are: the material of described cold roll is the 9Cr2MoV steel, and its heat treatment method after forging includes normalizing and carbide annealing process, and its heat treatment step is as follows:

(1) the normalizing stage: when cold rolling roll forging is water-cooled to 450 ℃ by spray form, it is heated in heat treatment furnace to 960 ℃, soaking time 4h, then hang lower spray form and be water-cooled to 400 ℃.

(2) the nodularization tempering stage: the cold roll after spray cooling is heated to 830 ℃ in process furnace, cools to 720 ℃ after soaking time 4h with the furnace, then cool to 400 ℃ with the furnace after soaking time 8h, then hang lower air cooling to room temperature.

The microstructure and hardness that the forging postheat treatment technique that employing is optimized obtains is more even, has reduced distortion and the cracking of cold roll, and high machining ability and high lumber recovery are arranged.

Claims (1)

1.9Cr2MoV the forging postheat treatment technique of cold roller steel is characterized in that: described Cold Work Roll Material is the 9Cr2MoV steel, and its heat treating method includes normalizing and carbide annealing process, and its heat treatment step is as follows:

(1) the normalizing stage: when cold rolling roll forging is water-cooled to 350 ℃～400 ℃ by spray form, it is heated in heat treatment furnace to M ₂₃c ₆the carbide of type chromium dissolves in 950 ℃ ± 10 ℃ of austenitic temperature, soaking time 4h～6h, and then spray form is water-cooled to 350 ℃～400 ℃.

(2) the nodularization tempering stage: the cold roll after the spray form water cooling is heated to 820 ℃ ± 10 ℃ in process furnace, cool to 730 ℃ ± 10 ℃ after soaking time 5h～8h with the furnace, cool to 400 ℃ after soaking time 7h～12h with the furnace again, then hang lower air cooling to room temperature.

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