阅读说明：本技术 一种活塞的热处理工艺 (Heat treatment process of piston ) 是由 谢艳云 邱佳 刘少娟 于 2021-01-26 设计创作，主要内容包括：本发明提供一种活塞的热处理工艺,涉及活塞热处理技术领域,所述活塞的热处理工艺包括如下步骤：S1,渗碳,首先将工件置入具有活性渗碳介质当中,随后加热到850-950℃的单相奥氏体区,保温5-11小时后,使渗碳介质中分解出的活性碳原子渗入工件表层；S2,一次退火,随后将工件放入热处理炉中加热到共析温度进行退火,退火完成后进行保温操作,保温完成后,再进行降温操作,降温完成后出炉空冷；S3,二次退火,随后再将工件加热到共析温度进行第二次退火,随后保温2-4h,再降温至500-600℃,再加热至745℃,再降温至580℃,以上通过在工件表面生成表层高碳,从而加强工件的结构强度,同时生产过程中稳定性好,且能耗较低,利于实际的使用。(The invention provides a heat treatment process of a piston, which relates to the technical field of heat treatment of pistons, and comprises the following steps: s1, carburizing, namely firstly putting the workpiece into an active carburizing medium, then heating the workpiece to a single-phase austenite region with the temperature of 850-950 ℃, and after heat preservation is carried out for 5 to 11 hours, enabling active carbon atoms decomposed from the carburizing medium to permeate into the surface layer of the workpiece; s2, primary annealing, then putting the workpiece into a heat treatment furnace to be heated to a eutectoid temperature for annealing, carrying out heat preservation operation after annealing is finished, carrying out cooling operation after heat preservation is finished, and discharging from the furnace for air cooling after cooling is finished; s3, secondary annealing, heating the workpiece to eutectoid temperature for secondary annealing, preserving heat for 2-4h, cooling to 500-600 ℃, reheating to 745 ℃, and cooling to 580 ℃, wherein the surface layer high carbon is generated on the surface of the workpiece, so that the structural strength of the workpiece is enhanced, and meanwhile, the stability in the production process is good, the energy consumption is low, and the practical use is facilitated.)

1. The heat treatment process of the piston is characterized by comprising the following steps of:

s1, carburizing, namely firstly putting the workpiece into an active carburizing medium, then heating the workpiece to a single-phase austenite region with the temperature of 850-950 ℃, and after heat preservation is carried out for 5 to 11 hours, enabling active carbon atoms decomposed from the carburizing medium to permeate into the surface layer of the workpiece;

s2, primary annealing, then putting the workpiece into a heat treatment furnace to be heated to a eutectoid temperature for annealing, carrying out heat preservation operation after annealing is finished, carrying out cooling operation after heat preservation is finished, and discharging from the furnace for air cooling after cooling is finished;

s3, secondary annealing, heating the workpiece to a eutectoid temperature for secondary annealing, preserving heat for 2-4h, cooling to 500-600 ℃, reheating to 745 ℃, and cooling to 580 ℃;

s4, normalizing, heating the workpiece to 900-;

s5, isothermal quenching, namely heating the workpiece to 855-;

s6, tempering, namely tempering the workpiece, and cooling to room temperature to obtain the workpiece with the pearlite content of more than 60%;

and S7, freezing, cooling the workpiece to 50 ℃ below zero, keeping for 3-4 h, cooling the workpiece to room temperature in air, and taking out the workpiece.

2. A heat treatment process for a piston according to claim 1, wherein: in S1, after the activated carbon atoms penetrate into the surface layer of the workpiece, a surface layer high carbon may be generated on the surface of the workpiece.

3. A heat treatment process for a piston according to claim 1, wherein: in S2, the eutectoid temperature is 720-920 ℃, the heat preservation time is 2.1-2.5h, and the temperature reduction temperature is 420-660 ℃.

4. A heat treatment process for a piston according to claim 1, wherein: in S2, the tapping air cooling period is 1 h.

5. A heat treatment process for a piston according to claim 1, wherein: in S5, the molten salt is a mixture of KNO3, NaNO2 and NaNO3, and the mass ratio among KNO3, NaNO2 and NaNO3 is 53: 40: 7.

6. a heat treatment process for a piston according to claim 1, wherein: in S6, the tempering temperature is 510-590 ℃, and the holding time is 2-3 h.

7. A heat treatment process for a piston according to claim 1, wherein: in S6, after the workpiece is cooled to room temperature, the workpiece is left standing for 2 hours.

8. A heat treatment process for a piston according to claim 1, wherein: in S7, the air cooling time is 5h, and the workpiece is taken out vertically by the gripper.

Technical Field

The invention relates to the technical field of piston heat treatment, in particular to a heat treatment process of a piston.

Background

The heat treatment is a metal hot working process which is characterized in that a metal material is placed in a certain medium for heating, heat preservation and cooling, and the performance of the metal material is controlled by changing the metallographic structure on the surface or in the material. The heat treatment process comprises three processes of heating, heat preservation and cooling, and sometimes only comprises two processes of heating and cooling. These processes are connected with each other without interruption. Heating is one of the important steps of heat treatment. The heating methods for metal heat treatment are many, and charcoal and coal were used as heat sources for the first time, and liquid and gaseous fuels were used. The application of electricity makes the heating easy to control and has no environmental pollution. The heat source may be used for direct heating or may be used for indirect heating of the floating particles by means of molten salts or metals.

The existing piston heat treatment process has the problem that the hardness of a processed piston is low in the practical application process, the piston is easy to crack in the practical application process, the abrasion resistance of the piston is poor, and scratches are easy to leave on the surface of the piston in the long-term use process.

Disclosure of Invention

The invention aims to solve the defects in the prior art and provides a heat treatment process of a piston.

In order to achieve the purpose, the invention adopts the following technical scheme: a heat treatment process for a piston, the heat treatment process for a piston comprising the steps of:

s1, carburizing, namely firstly putting the workpiece into an active carburizing medium, then heating the workpiece to a single-phase austenite region with the temperature of 850-950 ℃, and after heat preservation is carried out for 5 to 11 hours, enabling active carbon atoms decomposed from the carburizing medium to permeate into the surface layer of the workpiece;

s2, primary annealing, then putting the workpiece into a heat treatment furnace to be heated to a eutectoid temperature for annealing, carrying out heat preservation operation after annealing is finished, carrying out cooling operation after heat preservation is finished, and discharging from the furnace for air cooling after cooling is finished;

s3, secondary annealing, heating the workpiece to a eutectoid temperature for secondary annealing, preserving heat for 2-4h, cooling to 500-600 ℃, reheating to 745 ℃, and cooling to 580 ℃;

s4, normalizing, heating the workpiece to 900-;

s5, isothermal quenching, namely heating the workpiece to 855-;

s6, tempering, namely tempering the workpiece, and cooling to room temperature to obtain the workpiece with the pearlite content of more than 60%;

and S7, freezing, cooling the workpiece to 50 ℃ below zero, keeping for 3-4 h, cooling the workpiece to room temperature in air, and taking out the workpiece.

Further, in S1, after the activated carbon atoms penetrate into the surface layer of the workpiece, a surface layer high carbon may be generated on the surface of the workpiece.

Further, in S2, the eutectoid temperature is 720-920 ℃, the heat preservation time is 2.1-2.5h, and the temperature reduction temperature is 420-660 ℃.

Further, in S2, the tapping air cooling period is 1 h.

Further, in S5, the molten salt is a mixture of KNO3, NaNO2 and NaNO3, and the mass ratio of KNO3, NaNO2 and NaNO3 is 53: 40: 7.

further, in S6, the tempering temperature is 510-590 ℃, and the holding time is 2-3 h.

Further, in S6, after the workpiece is cooled to room temperature, the workpiece is left standing for 2 hours.

Further, in S7, the air cooling time is 5h, and the workpiece is taken out by vertically clamping the workpiece by the clamping hand.

Compared with the prior art, the surface layer high carbon is generated on the surface of the workpiece, so that the structural strength of the workpiece is enhanced, the surface layer high carbon can effectively prevent the workpiece from being scratched, the service life of the workpiece is prolonged to a certain extent, and meanwhile, the surface layer high carbon film has the characteristic of high production efficiency in practical application, has good stability in the production process and low energy consumption, accords with the environmental protection concept, has less pollution, is beneficial to environmental protection, and simultaneously produces a product with stable quality, and is beneficial to practical use.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

In order to more clearly illustrate the embodiments or technical solutions of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts

Fig. 1 is a diagram illustrating a heat treatment process for a piston according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In a first embodiment, referring to fig. 1, the heat treatment process of the piston includes the following steps:

s1, carburizing, namely firstly putting the workpiece into an active carburizing medium, then heating the workpiece to a single-phase austenite region at 850 ℃, and after heat preservation is carried out for 5 hours, enabling active carbon atoms decomposed from the carburizing medium to permeate into the surface layer of the workpiece;

s2, primary annealing, then putting the workpiece into a heat treatment furnace to be heated to a eutectoid temperature for annealing, carrying out heat preservation operation after annealing is finished, carrying out cooling operation after heat preservation is finished, and discharging from the furnace for air cooling after cooling is finished;

s3, secondary annealing, heating the workpiece to a eutectoid temperature for secondary annealing, preserving heat for 2 hours, cooling to 500 ℃, reheating to 745 ℃, and cooling to 580 ℃;

s4, normalizing, heating the workpiece to 925 ℃, preserving heat for 2h, and then carrying out air cooling after batch charging;

s5, isothermal quenching, namely heating the workpiece to 855 ℃, and then putting the workpiece into 250 ℃ molten salt for heat preservation for 1.2 h;

s6, tempering, namely tempering the workpiece, and cooling to room temperature to obtain the workpiece with the pearlite content of more than 60%;

and S7, freezing, cooling the workpiece to 50 ℃ below zero, keeping the temperature for 3 hours, and taking the workpiece out after the workpiece is cooled to room temperature by air.

Preferably, in S1, after the activated carbon atoms penetrate into the surface layer of the workpiece, a surface layer high carbon may be generated on the surface of the workpiece.

Preferably, in S2, the eutectoid temperature is 720 ℃, the heat preservation time is 2.1h, and the temperature for temperature reduction is 420 ℃.

Preferably, in S2, the tapping air cooling period is 1 h.

Preferably, in S5, the molten salt is a mixture of KNO3, NaNO2 and NaNO3, and the mass ratio among KNO3, NaNO2 and NaNO3 is 53: 40: 7.

preferably, in S6, the tempering temperature is 510 ℃ and the holding time is 2 h.

Preferably, in S6, after the workpiece is cooled to room temperature, the workpiece is left standing for 2 hours.

Preferably, in S7, the air cooling time is 5h, and the workpiece is taken out vertically by a gripper.

In a second embodiment, referring to fig. 1, the heat treatment process of the piston includes the following steps:

s1, carburizing, namely putting the workpiece into an active carburizing medium, heating to a single-phase austenite region at 860 ℃, and keeping the temperature for 7 hours to ensure that active carbon atoms decomposed from the carburizing medium permeate into the surface layer of the workpiece;

s2, primary annealing, then putting the workpiece into a heat treatment furnace to be heated to a eutectoid temperature for annealing, carrying out heat preservation operation after annealing is finished, carrying out cooling operation after heat preservation is finished, and discharging from the furnace for air cooling after cooling is finished;

s3, secondary annealing, heating the workpiece to a eutectoid temperature for secondary annealing, preserving heat for 3 hours, cooling to 510 ℃, reheating to 745 ℃, and cooling to 580 ℃;

s4, normalizing, heating the workpiece to 905 ℃, preserving heat for 2.5 hours, and then carrying out air cooling after batch charging;

s5, isothermal quenching, heating the workpiece to 857 ℃, and then putting the workpiece into 305 ℃ molten salt for heat preservation for 1.4 h;

s6, tempering, namely tempering the workpiece, and cooling to room temperature to obtain the workpiece with the pearlite content of more than 60%;

and S7, freezing, cooling the workpiece to 50 ℃ below zero, keeping the temperature for 3.2 hours, and taking the workpiece out after the workpiece is cooled to room temperature by air.

Preferably, in S1, after the activated carbon atoms penetrate into the surface layer of the workpiece, a surface layer high carbon may be generated on the surface of the workpiece.

Preferably, in S2, the eutectoid temperature is 735 ℃, the heat preservation time is 2.2h, and the temperature for temperature reduction is 460 ℃.

Preferably, in S2, the tapping air cooling period is 1 h.

Preferably, in S5, the molten salt is a mixture of KNO3, NaNO2 and NaNO3, and the mass ratio among KNO3, NaNO2 and NaNO3 is 53: 40: 7.

preferably, in S6, the tempering temperature is 520 ℃, and the holding time is 2.2 h.

Preferably, in S6, after the workpiece is cooled to room temperature, the workpiece is left standing for 2 hours.

Preferably, in S7, the air cooling time is 5h, and the workpiece is taken out vertically by a gripper.

In a third embodiment, referring to fig. 1, the heat treatment process of the piston includes the following steps:

s1, carburizing, namely putting the workpiece into an active carburizing medium, heating to a single-phase austenite region at 870 ℃, and after heat preservation for 7 hours, enabling active carbon atoms decomposed from the carburizing medium to permeate into the surface layer of the workpiece;

s2, primary annealing, then putting the workpiece into a heat treatment furnace to be heated to a eutectoid temperature for annealing, carrying out heat preservation operation after annealing is finished, carrying out cooling operation after heat preservation is finished, and discharging from the furnace for air cooling after cooling is finished;

s3, secondary annealing, heating the workpiece to a eutectoid temperature for secondary annealing, preserving heat for 2.8 hours, cooling to 509 ℃, reheating to 745 ℃, and cooling to 580 ℃;

s4, normalizing, heating the workpiece to 933 ℃, preserving heat for 2.8h, and then performing air cooling after batch furnace charging;

s5, isothermal quenching, namely heating the workpiece to 858 ℃, and then putting the workpiece into 260 ℃ molten salt for heat preservation for 2 hours;

s6, tempering, namely tempering the workpiece, and cooling to room temperature to obtain the workpiece with the pearlite content of more than 60%;

and S7, freezing, cooling the workpiece to 50 ℃ below zero, keeping for 4 hours, and taking out the workpiece after the workpiece is cooled to room temperature by air.

Preferably, in S1, after the activated carbon atoms penetrate into the surface layer of the workpiece, a surface layer high carbon may be generated on the surface of the workpiece.

Preferably, in S2, the eutectoid temperature is 790 ℃, the heat preservation time is 2.3 hours, and the temperature for temperature reduction is 550 ℃.

Preferably, in S2, the tapping air cooling period is 1 h.

Preferably, in S5, the molten salt is a mixture of KNO3, NaNO2 and NaNO3, and the mass ratio among KNO3, NaNO2 and NaNO3 is 53: 40: 7.

preferably, in S6, the tempering temperature is 540 ℃ and the holding time is 3 h.

Preferably, in S6, after the workpiece is cooled to room temperature, the workpiece is left standing for 2 hours.

Preferably, in S7, the air cooling time is 5h, and the workpiece is taken out vertically by a gripper.

In a fourth embodiment, referring to fig. 1, the heat treatment process of the piston includes the following steps:

s1, carburizing, namely firstly putting the workpiece into an active carburizing medium, then heating the workpiece to a single-phase austenite region at 950 ℃, and after heat preservation is carried out for 11 hours, enabling active carbon atoms decomposed from the carburizing medium to permeate into the surface layer of the workpiece;

s2, primary annealing, then putting the workpiece into a heat treatment furnace to be heated to a eutectoid temperature for annealing, carrying out heat preservation operation after annealing is finished, carrying out cooling operation after heat preservation is finished, and discharging from the furnace for air cooling after cooling is finished;

s3, secondary annealing, heating the workpiece to a eutectoid temperature for secondary annealing, preserving heat for 4 hours, cooling to 600 ℃, reheating to 745 ℃, and cooling to 580 ℃;

s4, normalizing, heating the workpiece to 940 ℃, preserving heat for 3 hours, and then carrying out air cooling after batch charging;

s5, isothermal quenching, namely heating the workpiece to 865 ℃, and then putting the workpiece into 310 ℃ molten salt for heat preservation for 2.5 hours;

s6, tempering, namely tempering the workpiece, and cooling to room temperature to obtain the workpiece with the pearlite content of more than 60%;

and S7, freezing, cooling the workpiece to 50 ℃ below zero, keeping for 4 hours, and taking out the workpiece after the workpiece is cooled to room temperature by air.

Preferably, in S1, after the activated carbon atoms penetrate into the surface layer of the workpiece, a surface layer high carbon may be generated on the surface of the workpiece.

Preferably, in S2, the eutectoid temperature is 920 ℃, the heat preservation time is 2.5 hours, and the temperature for temperature reduction is 660 ℃.

Preferably, in S2, the tapping air cooling period is 1 h.

Preferably, in S5, the molten salt is a mixture of KNO3, NaNO2 and NaNO3, and the mass ratio among KNO3, NaNO2 and NaNO3 is 53: 40: 7.

preferably, in S6, the tempering temperature is 590 ℃, and the holding time is 3 h.

Preferably, in S6, after the workpiece is cooled to room temperature, the workpiece is left standing for 2 hours.

Preferably, in S7, the air cooling time is 5h, and the workpiece is taken out vertically by a gripper.

The workpieces prepared in the first to fourth examples were subjected to the following performance tests:

and (3) testing hardness performance: the hardness test is carried out on an HRS-150 Rockwell hardness tester, and the test loading force is 150k_gThe test force retention time was 8 seconds.

And (3) testing tensile property: processing the material into a tensile sample according to GBT228.1-2010 metal material tensile test, wherein the tensile speed in the test is 2mm/min, the extensometer is Y25/5-N type, and the precision grade is 0.5.

And (3) impact performance test: the samples were prepared by wire cutting into standard impact specimens, and the dimensional deviation of the specimens should be strictly controlled in terms of shape, size and surface roughness according to GB/T229-1994.

The results are shown in Table 1.

Table 1 performance test data

Test specimen	HRC	Tensile strength (MPa)	Yield strength (MPa)	Impact work (J)
					Example one	48.8	989	596	156
Example two	47.6	976	582	146
					EXAMPLE III	45.8	968	559	145
Example four	46.1	912	586	155

As can be seen from the data in table 1, the first to fourth examples all have good performance, and the first example is the most preferable example, which has the highest hardness of 48.8HRC and the highest strength.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.