CN115747426A - Method for improving mixed crystal structure of 17CrNiMo6 material - Google Patents
Method for improving mixed crystal structure of 17CrNiMo6 material Download PDFInfo
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- CN115747426A CN115747426A CN202211427569.7A CN202211427569A CN115747426A CN 115747426 A CN115747426 A CN 115747426A CN 202211427569 A CN202211427569 A CN 202211427569A CN 115747426 A CN115747426 A CN 115747426A
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Abstract
The invention relates to a method for improving a mixed crystal structure of a 17CrNiMo6 material, which comprises the following steps of: s1, placing the forge piece into a heating furnace, heating to 930-950 ℃, and then preserving heat for 4-5 hours; s2, normalizing and air-cooling the forge piece after heat preservation to 600-620 ℃, putting the forge piece into the heating furnace again, and carrying out isothermal tempering at 530-560 ℃ for heat preservation for 4-5 hours; s3, placing the tempered and heat-insulated forged piece into a heating furnace, and raising the temperature of the heating furnace to 850-860 ℃ for heat insulation for 2-3 hours; s4, normalizing, air-cooling the forge piece after heat preservation to 600-620 ℃, putting the forge piece into the heating furnace again, and carrying out isothermal heat preservation at 530-560 ℃ for 4-5 hours; and S5, air-cooling the forging to room temperature, machining, and then carburizing and quenching. The method for improving the mixed crystal structure of the 17CrNiMo6 material can effectively improve the mixed crystal condition of the 17CrNiMo6 material and ensure the stability of the 17CrNiMo6 material after being prepared into a product.
Description
Technical Field
The invention relates to the technical field of mixed crystal processing of forgings, in particular to a method for improving a mixed crystal structure of a 17CrNiMo6 material.
Background
The primary structure is an important factor for influencing the inheritance of the structure, if the primary structure of the steel is a non-equilibrium structure, such as martensite, tempered martensite, bainite, widmannstatten structure and the like. Tissue inheritance is facilitated by the apparent directionality of these tissues being retained. When the steel is heated by austenitizing, the inheritance of the same steel as that of martensite is stronger when the original structure of the steel is bainite. The primary tissue is widmannstatten tissue, and is easy to be inherited. When the primary structure is a mixed structure of ferrite and pearlite, the tissue inheritance phenomenon does not generally occur.
As a high-strength alloy steel, the 17CrNiMo6 has good mechanical properties and toughness, so that the alloy is widely applied to the industrial fields of industrial and mining, ships, aerospace and the like and is often used for preparing gear parts. However, under the common forging processing technology, the 17CrNiMo6 forge piece is directly cooled to room temperature by air after being heated and insulated, the structure mixed crystal is serious, the tissue structure which can generate tissue inheritance is easily formed, and the tissue structure can not be effectively eliminated after the conventional normalizing. And the product has larger modulus and more gear grinding allowance, needs deep carburization, causes mixed crystals in tissue inheritance after carburization and quenching, and is easy to crack during component testing.
Disclosure of Invention
Therefore, in order to solve the above problems, it is necessary to provide a method for improving the mixed crystal structure of a 17CrNiMo6 material, which can effectively improve the mixed crystal condition of the 17CrNiMo6 material and ensure the stability of the 17CrNiMo6 material after being made into a product.
The technical scheme is as follows:
on one hand, the method for improving the mixed crystal structure of the 17CrNiMo6 material comprises the following steps:
s1, placing the forge piece into a heating furnace, heating to 930-950 ℃, and then preserving heat for 4-5 hours;
s2, normalizing, air-cooling the forge piece after heat preservation to 600-620 ℃, putting the forge piece into the heating furnace again, and carrying out isothermal tempering and heat preservation at 530-560 ℃ for 4-5 hours;
s3, placing the tempered and heat-insulated forge piece into a heating furnace, and raising the temperature of the heating furnace to 850-860 ℃ for heat insulation for 2-3 hours;
s4, normalizing and air-cooling the forge piece after heat preservation to 600-620 ℃, putting the forge piece into the heating furnace again, and carrying out isothermal heat preservation at 530-560 ℃ for 4-5 hours;
and S5, air-cooling the forging to room temperature, machining, and then carburizing and quenching.
The technical solution is further explained below:
in one embodiment, the temperature of the forge piece in the step 1 after being heated in the heating furnace is 950 ℃.
In one embodiment, the forging normalizing in the step S2 is air-cooled to 600 ℃.
In one embodiment, the temperature of the forging placed into the heating furnace for heating in the step S3 is 860 ℃.
In one embodiment, the forging is normalized and air cooled to 600 ℃ in step S4.
In one embodiment, the temperature of the forging in the step S4 is 550 ℃ after the forging is put into the heating furnace again for isothermal heat preservation.
In one embodiment, the holding time in step S1 is 4 hours.
In one embodiment, the holding time in step S2 is 4 hours.
In one embodiment, the heat preservation time in step S3 is 2 hours.
In one embodiment, the heat preservation time in step S4 is 4 hours.
The invention has the beneficial effects that:
compared with the prior art, the method for improving the mixed crystal structure of the 17CrNiMo6 material comprises the steps of putting a forging into a heating furnace for heating, cooling to the pearlite transformation starting temperature between 600 ℃ and 620 ℃ according to the characteristic of isothermal normalizing at 930 ℃ to 950 ℃, putting the forging into the furnace again for isothermal treatment at 530 ℃ to 560 ℃, eliminating the Widmannstatten structure and avoiding upper bainite. And (4) tempering and heat preservation are carried out for 4-5 hours, the temperature is reheated to 850-860 ℃ after the pearlite transformation is finished, and the new austenite phase is re-nucleated and grows at the pearlite boundary. Due to the fact that reheating is fast in temperature rising and low in heat preservation temperature, the structure of the forged piece is just completely austenitized, but not enough to be homogenized, grain growth is limited, the forged piece is discharged from the furnace for air cooling after short-time heat preservation, and when the temperature is reduced to the pearlite transformation starting temperature of 600-620 ℃, the forged piece is continuously put into the furnace again to be subjected to isothermal treatment at the temperature of 530-560 ℃, widmannstatten structures are eliminated again, and upper bainite is avoided. And keeping the temperature isothermal for 4-5 hours, discharging the forged piece from the furnace and cooling to room temperature after the pearlite transformation is finished, so as to obtain a structure with mixed ferrite and pearlite and avoid the tissue inheritance phenomenon of the forged piece structure. After the forging is cooled to room temperature in the air, the subsequent machining, carburizing and quenching and other machining operations can be carried out, and the condition that the mixed crystals occur in the forging structure in the subsequent operations can be effectively avoided.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification.
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic step view of a method for improving mixed crystal structure of 17CrNiMo6 material according to the invention;
FIG. 2 is a metallographic view of an original structure of a 17CrNiMo6 forging;
FIG. 3 is a metallographic view of a 17CrNiMo6 forging processed by a prior art process;
FIG. 4 is a metallographic diagram of a 17CrNiMo6 forging produced by the method.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
As shown in fig. 1, in one embodiment, there is provided a method for improving mixed crystal structure of 17CrNiMo6 material, comprising the following steps:
s1, placing the forge piece into a heating furnace, heating to 930-950 ℃, and then preserving heat for 4-5 hours;
s2, normalizing, air-cooling the forge piece after heat preservation to 600-620 ℃, putting the forge piece into the heating furnace again, and carrying out isothermal tempering and heat preservation at 530-560 ℃ for 4-5 hours;
s3, placing the tempered and heat-insulated forge piece into a heating furnace, and raising the temperature of the heating furnace to 850-860 ℃ for heat insulation for 2-3 hours;
s4, normalizing and air-cooling the forge piece after heat preservation to 600-620 ℃, putting the forge piece into the heating furnace again, and carrying out isothermal heat preservation at 530-560 ℃ for 4-5 hours;
and S5, air-cooling the forging to room temperature, machining, and then carburizing and quenching.
In the embodiment, the forging is placed into a heating furnace for heating, and according to the characteristics of isothermal normalizing referenced when the temperature is normalized at 930-950 ℃, when the temperature is reduced to the pearlite transformation starting temperature between 600-620 ℃, the forging is placed into the furnace again for isothermal treatment at 530-560 ℃, so that Widmannstatten structures are eliminated and upper bainite is avoided. And (4) tempering and heat preservation are carried out for 4-5 hours, the temperature is reheated to 850-860 ℃ after the pearlite transformation is finished, and the new austenite phase is re-nucleated and grows at the pearlite boundary. Due to the fact that reheating is fast, the heat preservation temperature is low, the structure of the forged piece is just completely austenitized, but not enough to be homogenized, the crystal grain growth is limited, the forged piece is discharged from the furnace for air cooling after short-time heat preservation, when the temperature is reduced to the pearlite transformation starting temperature of 600-620 ℃, the forged piece is continuously fed into the furnace again to adopt isothermal treatment at the temperature of 530-560 ℃, the Widmannstatten structure is eliminated again, and meanwhile upper bainite is avoided. And keeping the temperature isothermal for 4-5 hours, discharging the forged piece from the furnace and cooling after the pearlite transformation is finished, so as to obtain a structure with mixed ferrite and pearlite and avoid the tissue inheritance phenomenon of the forged piece structure. After the forging is cooled to room temperature in the air, the subsequent machining, carburizing and quenching and other machining operations can be carried out, and the condition that the mixed crystals occur in the forging structure in the subsequent operations can be effectively avoided.
In one embodiment, the process parameters actually used in the present invention are as follows:
s1, placing a forging into a heating furnace, heating to 950 ℃, and then preserving heat for 4 hours;
s2, normalizing and air-cooling the forge piece after heat preservation to 600 ℃, facilitating the transformation of pearlite, and putting the forge piece into a heating furnace again to preserve heat for 4 hours by adopting isothermal tempering at 550 ℃;
s3, placing the tempered and heat-insulated forge piece into a heating furnace, and raising the temperature of the heating furnace to 860 ℃ for heat insulation for 2 hours;
s4, normalizing, air-cooling the forge piece after heat preservation to 600 ℃, facilitating the transformation of pearlite, and placing the forge piece into a heating furnace again to preserve heat at 550 ℃ for 4 hours in an isothermal way;
and S5, air-cooling the forging to room temperature, machining, and then carburizing and quenching.
Specifically, as shown in fig. 2 to 4, fig. 2 is a metallographic image of an original material, which has a mixed crystal structure, fig. 3 is a metallographic image of a material processed by a general normalizing process, which has not been eliminated yet, and fig. 4 is a metallographic image of a material processed by the above-mentioned process of the present invention, which has no mixed crystal structure. In the steel, 1-4 grade coarse grains and 5 grade or more fine grains exist in a metallographic field simultaneously, and the grain size difference in the field is 3 grade or more, so that the mixed crystal can be judged. As shown in fig. 4, the size of the relevant grains can be visually seen, and the difference between the maximum grain size and the minimum grain size is less than 3 grades, i.e. no mixed crystal exists.
The above examples only show some embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent should be subject to the appended claims.
Claims (10)
1. A17 CrNiMo6 material mixed crystal structure improving method is characterized by comprising the following steps:
s1, placing the forge piece into a heating furnace, heating to 930-950 ℃, and then preserving heat for 4-5 hours;
s2, normalizing, air-cooling the forge piece after heat preservation to 600-620 ℃, putting the forge piece into the heating furnace again, and carrying out isothermal tempering and heat preservation at 530-560 ℃ for 4-5 hours;
s3, placing the tempered and heat-insulated forge piece into a heating furnace, and raising the temperature of the heating furnace to 850-860 ℃ for heat insulation for 2-3 hours;
s4, normalizing, air-cooling the forge piece after heat preservation to 600-620 ℃, putting the forge piece into the heating furnace again, and carrying out isothermal heat preservation at 530-560 ℃ for 4-5 hours;
and S5, air-cooling the forging to room temperature, machining, and then carburizing and quenching.
2. The method for improving the mixed crystal structure of the 17CrNiMo6 material as claimed in claim 1, wherein the temperature of the forge piece in the step 1 after being heated in a heating furnace is 950 ℃.
3. The method for improving the mixed crystal structure of the 17CrNiMo6 material as claimed in claim 1, wherein the forging in the step S2 is normalized and air-cooled to 600 ℃.
4. The method for improving the mixed crystal structure of the 17CrNiMo6 material according to claim 1, wherein the temperature of the forge piece placed into a heating furnace for heating in the step S3 is 860 ℃.
5. The method for improving the mixed crystal structure of the 17CrNiMo6 material as claimed in claim 1, wherein the forging in the step S4 is normalized and air-cooled to 600 ℃.
6. The method for improving the mixed crystal structure of the 17CrNiMo6 material according to claim 1, wherein the temperature of isothermal heat preservation of the forging in the step S4 is 550 ℃ after the forging is placed into the heating furnace again.
7. The method for improving the mixed crystal structure of the 17CrNiMo6 material according to claim 1, wherein the heat preservation time in step S1 is 4 hours.
8. The method for improving the mixed crystal structure of the 17CrNiMo6 material according to claim 1, wherein the heat preservation time in step S2 is 4 hours.
9. The method for improving the mixed crystal structure of the 17CrNiMo6 material according to claim 1, wherein the heat preservation time in step S3 is 2 hours.
10. The method for improving the mixed crystal structure of the 17CrNiMo6 material as claimed in claim 1, wherein the heat preservation time in step S4 is 4 hours.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202211427569.7A CN115747426A (en) | 2022-11-15 | 2022-11-15 | Method for improving mixed crystal structure of 17CrNiMo6 material |
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| CN202211427569.7A CN115747426A (en) | 2022-11-15 | 2022-11-15 | Method for improving mixed crystal structure of 17CrNiMo6 material |
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| CN115747426A true CN115747426A (en) | 2023-03-07 |
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| CN202211427569.7A Pending CN115747426A (en) | 2022-11-15 | 2022-11-15 | Method for improving mixed crystal structure of 17CrNiMo6 material |
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