CN108220561A

CN108220561A - A kind of method for refining 20CrMoA forging autstenitic grain sizes

Info

Publication number: CN108220561A
Application number: CN201710997615.XA
Authority: CN
Inventors: 顾晓明; 宋璐; 王昱程
Original assignee: Changzhou Tianshan Heavy Industry Machinery Co Ltd
Current assignee: Changzhou Tianshan Heavy Industry Machinery Co Ltd
Priority date: 2017-10-24
Filing date: 2017-10-24
Publication date: 2018-06-29

Abstract

The present invention relates to a kind of method for refining 20CrMoA forging autstenitic grain sizes, technique is as follows：(1) forging enters 980 ± 10 DEG C of high temperature furnace, extremely fast heats up, in 960 970 DEG C of short time sammings；(2) come out of the stove be air-cooled to 700 ± 10 DEG C be incorporated to stove isothermal keep 30 ± 10min；(3) furnace temperature is rapidly heated again to 960 970 DEG C, and short time samming；(4) forging, which is come out of the stove, is air-cooled to 650 680 DEG C and is incorporated to the holding of stove isothermal, obtains statenchyma P+F；(5) it comes out of the stove and is air-cooled to room temperature.Present invention process introduces quick dual forming core refinement concepts, can obtain uniform tiny statenchyma, crystal grain grow up sensibility and Structure Inheritance feature it is extremely weak, simulation carburizing and quenching crystal grain grow up detection when, superfine small autstenitic grain size can be obtained.

Description

A kind of method for refining 20CrMoA forging autstenitic grain sizes

Technical field

The invention belongs to technical field of metal material heat treatment, and in particular to a kind of refinement 20CrMoA forging austenite crystals The method of granularity.

Background technology

20CrMoA alloy steel hardenabilities are higher, and no temper brittleness, weldability is fairly good, form the tendency very little of cold cracking, can Machinability and cold strain plasticity are good.It is generally used under quenched or carburizing and quenching state, for manufacturing in non-aggressive medium And operating temperature less than 250 DEG C, the high-voltage tube that works in the medium containing mixture of nitrogen and hydrogen and various fasteners, higher ooze Carbon part, such as gear, axis.

20CrMoA is as a kind of common gear wheel carburization steel, and Mn contents are higher, so its crystal grain is grown up, sensibility is larger. The tendency of growing up of forging crystal grain in follow-up carburizing and quenching is assessed, is often heated to the forging aspect product after normalizing and tempering It quenches to detect grain size after 930 DEG C of heat preservation a few hours, to determine that can the forging meet the crystalline substance of final carburizing and quenching Granularity requirements.

The heat treatment after forging of usual forging increases temperature tempering using normalizing, and the normalizing temperature of 20CrMoA is 920-940 DEG C, Heat preservation rule keeps the temperature 2h for 100mm control interfaces austenitizing, and high tempering is using 650-680 DEG C of heat preservation a few hours.Using upper The forging of process route is stated, 930 DEG C of autstenitic grain size detections is carried out and finds mixed crystal problem often, big crystal grain and tiny crystalline substance is presented Grain mixing complexion.

Invention content

Invention broadly provides a kind of methods for refining 20CrMoA forging autstenitic grain sizes, and it is thin to introduce dual forming core Change concept, can obtain uniform tiny statenchyma, crystal grain grow up sensibility and Structure Inheritance feature it is extremely weak, simulation carburizing is quenched Burning hot processing crystal grain grow up detection when, superfine small autstenitic grain size can be obtained.Its technical solution is as follows：

A kind of method for refining 20CrMoA forging autstenitic grain sizes, includes the following steps：

(1) forging enters 980 ± 10 DEG C of high temperature furnace, extremely fast heats up, and improves nucleation rate, will obtain tiny starting Ovshinsky Body grain size, in 960-970 DEG C of short time samming, equal temperature time calculates according to forging section 100mm heat preservations 0.5h, is conducive to close The migration uniformity of golden ingredient, carbide etc. reduces isolated big crystal grain degree probability；

(2) come out of the stove be air-cooled to 700 ± 10 DEG C be incorporated to stove isothermal keep 30 ± 10min, by obtain F+P+A three-phase contexture and Partial austenitic is to F+P structural transformations；

(3) furnace temperature is rapidly heated again to 960-970 DEG C, the F+P for making 700 DEG C of isothermal stages again forming core is divided thin Change, tissue morphology is a large amount of tiny nucleation points of A+ at this time, then short time samming, and equal temperature time is according to forging section 100mm 0.5h is kept the temperature to calculate；

(4) forging come out of the stove be air-cooled to 650-680 DEG C be incorporated to stove isothermal holding, soaking time according to forging section 100mm protect Warm 1.2h is calculated, and obtains statenchyma P+F, and statenchyma preparation is carried out for final carburizing and quenching；

(5) it comes out of the stove and is air-cooled to room temperature, practical ferrite grain size can reach 8 grades.

Preferably, forging obtains tiny starting austenite grain size after extremely fast heating up in step (1), reaches 10 grades.

Preferably, furnace temperature fast heating ramp rate is 200-300 DEG C/h in step (3).

Preferably, grain size is 11 grades before forging samming in step (3), and grain size is 8 grades after samming.

Preferably, F contents are 70-80% in the statenchyma P+F obtained in step (4).

Preferably, the 20CrMoA forging after refinement is heated to 930 DEG C of heat preservations to quench within 5 hours to detect material Ovshinsky Body grain size, grain size are 9 grades, and crystal grain distribution is uniform and tiny.

Using the above scheme, the present invention has the following advantages：

(1) present invention process enters furnace technology using 980 DEG C of high temperature, abandons conventional large forgings low temperature into stove method, high temperature Internal fissure will not be generated for 20CrMoA materials into stove, the material alloy content is relatively low, and heat conduction is excellent with respect to high alloy material Good, the very big degree of superheat will not generate great temperature difference in center portion, advantageous to forming core instead, obtain tiny primary grain degree；

(2) dual forming core refinement concepts are introduced, need not be cooled to room temperature after first time forming core, be air-cooled to 700 DEG C or so, The isothermal structural transformation that demand can be completed in 30 minutes near Ar1 lines controls schizotype by the two secondary maximum degrees of superheat, obtains Obtain uniformly tiny statenchyma P+F；

(3) this technique is air-cooled to certain temperature isothermal after second of forming core samming, can both complete without being individually tempered Structural transformation, and can realize the demand for control of stress and hardness.Common technological requirement to be cooled to room temperature or slightly higher temperature, this To the significant wastage of time, as long as practice finds to complete corresponding structural transformation demand, cooling enters Ar3 lines and enters two Phase region, A changes to F, and when entering back into Ar1 lines, based on the transformation of F has become, F amounts are bigger, and the crystal boundary gross area is bigger, forming core carrier It is bigger, enough nucleation points will be provided for subsequent second nucleation, at this time can second nucleation processing, without being cooled to more low temperature Degree；

(4) since the very big degree of superheat heats during forming core, heat conduction is exceedingly fast, and corresponding structural transformation demand can be rapidly completed, Without long-time heat preservation, heat insulating coefficient is minimum, starting small grains degree will not fast growth, when soaking time, to reach crystal grain quick Cooling treatment has been carried out during the threshold point grown up, tiny primary grain degree will have been made to obtain heredity, short time heat insulating coefficient at this time Production cost can not only be greatly reduced, while keep the demand purpose of structural transformation；

(5) dual forming core adds Ar1 lines Isothermal Model by the uniform tiny statenchyma of acquisition, crystal grain grow up sensibility and Structure Inheritance feature is extremely weak, simulation carburizing and quenching crystal grain grow up detection when, superfine small austenite grain can be obtained Degree has done preparation for the crystal grain refinement after final carburizing and quenching and has estimated.

Description of the drawings

Fig. 1 is the forging original grain state diagram of 1 process of embodiment；

Fig. 2 be 1 process of embodiment forging through 930 DEG C quenching after crystalline form figure；

Fig. 3 be 1 process of comparative example forging through 930 DEG C quenching after crystalline form figure.

Specific embodiment

Experimental method in following embodiment is conventional method unless otherwise required, involved experiment reagent and material Material is conventional biochemical reagent and material unless otherwise required.

Embodiment 1

(1) forging enters 980 ± 10 DEG C of high temperature furnace, extremely fast heats up, and improves nucleation rate, carries out first time forming core refinement, Tiny starting austenite grain size is obtained, reaches 10 grades, in 960-970 DEG C of short time samming, equal temperature time is cut according to forging Face 100mm heat preservations 0.5h is calculated, and is conducive to the migration uniformity of alloying component, carbide etc., reduces isolated big crystal grain degree probability；

(2) come out of the stove be air-cooled to 700 ± 10 DEG C be incorporated to stove isothermal keep 30 ± 10min, Ar1 lines critical zone will obtain F+P+A Three-phase contexture and partial austenitic to F+P structural transformations；

(3) furnace temperature is rapidly heated again to 960-970 DEG C using heating rate as 200-300 DEG C/h, carries out second of shape Core refines, and short time samming, and equal temperature time is calculated according to forging section 100mm heat preservations 0.5h, and grain size is 11 grades before samming, Grain size is 8 grades after samming；

(4) forging come out of the stove be air-cooled to 650-680 DEG C be incorporated to stove isothermal holding, obtain statenchyma P+F, F content reach 70- 80%, soaking time is calculated according to forging section 100mm heat preservations 1.2h, and statenchyma standard is carried out for final carburizing and quenching Standby, practical ferrite grain size can reach 8 grades；

(5) it comes out of the stove and is air-cooled to room temperature.

Fig. 1 is the 20CrMoA forging crystalline form figures through refinement, and as shown in Figure 1, crystal grain distribution is uniform and tiny.

Comparative example 1

By the 920-940 DEG C of progress normalizing of 20CrMoA forging, the normalizing time calculates according to forging section 100mm heat preservations 2h, so After carry out it is air-cooled, it is air-cooled complete after 650-680 DEG C carry out high tempering, tempering time according to forging section 100mm keep the temperature 2- 3h calculate, be finally air-cooled to room temperature is sufficient.

Grain size detects

Example 1 through refinement 20CrMoA forging and by contrast 1 method of example heat treatment after forging, forging is distinguished It quenches to detect material autstenitic grain size, i.e. Grain growth trend after being heated to 930 DEG C of heat preservation a few hours, simulates final carburizing The grain size of quenching heat treatment.Fig. 2 be 20CrMoA forging high temperature quenched crystalline form figure of the embodiment 1 through refinement, Fig. 3 The quenched crystalline form figure of forging high temperature after being heat-treated for 1 method of example by contrast.By the comparison of Fig. 2 and Fig. 3 it is found that this hair Forging crystal grain distribution after bright process is uniform and tiny, and existing technique will appear big crystal grain and small grains aggregate sample Looks.

It will be apparent to those skilled in the art that technical solution that can be as described above and design, make other various Corresponding change and deformation, and all these changes and deformation should all belong to the protection domain of the claims in the present invention Within.

Claims

A kind of 1. method for refining 20CrMoA forging autstenitic grain sizes, it is characterised in that：Include the following steps：

(1) forging enters 980 ± 10 DEG C of high temperature furnace, extremely fast heats up, and improves nucleation rate, in 960-970 DEG C of short time samming, The warm time calculates according to forging section 100mm heat preservations 0.5h；

(2) come out of the stove be air-cooled to 700 ± 10 DEG C be incorporated to stove isothermal keep 30 ± 10min, three-phase contexture and the part of F+P+A will be obtained Austenite is to F+P structural transformations；

(3) furnace temperature is rapidly heated again to 960-970 DEG C, and short time samming, and equal temperature time is kept the temperature according to forging section 100mm 0.5h is calculated；

(4) forging come out of the stove be air-cooled to 650-680 DEG C be incorporated to stove isothermal holding, soaking time according to forging section 100mm keep the temperature 1.2h is calculated, and obtains statenchyma P+F；

(5) it comes out of the stove and is air-cooled to room temperature.
2. the method for refinement 20CrMoA forging autstenitic grain sizes according to claim 1, it is characterised in that：Step (1) Middle forging obtains tiny starting austenite grain size after extremely fast heating up, reach 10 grades.
3. the method for refinement 20CrMoA forging autstenitic grain sizes according to claim 1, it is characterised in that：Step (3) Middle furnace temperature fast heating ramp rate is 200-300 DEG C/h.
4. the method for refinement 20CrMoA forging autstenitic grain sizes according to claim 1, it is characterised in that：Step (3) Grain size is 11 grades before middle forging samming, and grain size is 8 grades after samming.
5. the method for refinement 20CrMoA forging autstenitic grain sizes according to claim 1, it is characterised in that：Step (4) F contents are 70-80% in the statenchyma P+F of middle acquisition.
6. the method for refinement 20CrMoA forging autstenitic grain sizes according to claim 1, it is characterised in that：It will be through thin 20CrMoA forging after change is heated to 930 DEG C of heat preservations and quenches within 5 hours to detect material autstenitic grain size, grain size 9 Grade.