阅读说明：本技术 一种汽车发动机活塞环的热处理方法 (Heat treatment method for piston ring of automobile engine ) 是由 胡大维 张雪梅 胡敬华 于 2021-07-28 设计创作，主要内容包括：本发明公开了一种汽车发动机活塞环的热处理方法,其包含加热阶段、淬火阶段及回火阶段三阶段的处理,通过对加热阶段、淬火阶段及回火阶段温度的控制,有效解决了同批次硬度落差大,金相组织容易出现过量铁素体的技术问题,经本发明热处理后的活塞环硬度为31-35HRC,同一批活塞环硬度落差≤4HRC,同一活塞环的硬度差≤4HRC,金相组织为回火索氏体,铁素体小于5％,碳化物小于5％。(The invention discloses a heat treatment method of an automobile engine piston ring, which comprises three stages of treatment of a heating stage, a quenching stage and a tempering stage, and effectively solves the technical problems that the hardness drop of the same batch is large and excessive ferrite is easily generated in a metallographic structure by controlling the temperature of the heating stage, the quenching stage and the tempering stage, the hardness of the piston ring after heat treatment is 31-35HRC, the hardness drop of the piston ring of the same batch is less than or equal to 4HRC, the hardness difference of the same piston ring is less than or equal to 4HRC, the metallographic structure is a tempered sorbite, the ferrite is less than 5 percent, and the carbide is less than 5 percent.)

1. A heat treatment method for a piston ring of an automobile engine is characterized by comprising the following steps:

s1, heating stage: the piston ring made of RIK20 is sent into a heating furnace and enters an I area and a V area in sequence, and the heating temperature of each area is controlled as follows: area I880 + -5 deg.C, area II-IV 905 + -5 deg.C, and area V880 + -5 deg.C;

s2, quenching: the piston ring heated in the step S1 enters an oil groove for quenching, the oil temperature of quenching oil is 60-80 ℃, and thermal cycle quenching oil is stirred;

s3, tempering: after quenching in step S2, the piston ring enters a tempering furnace, and the tempering temperature is 545 ℃.

2. The heat treatment method for a piston ring of an automobile engine according to claim 1, characterized in that: in step S1, the heating time for the piston ring to be fed into the heating furnace is 71 min.

3. The heat treatment method for a piston ring of an automobile engine according to claim 1, characterized in that: in step S1, the heating furnace is a protective atmosphere mesh belt furnace.

4. The heat treatment method for a piston ring of an automobile engine according to claim 1, characterized in that: in step S2, the quenching oil is ultra-speed bright quenching oil.

5. The heat treatment method for a piston ring of an automobile engine according to claim 1, characterized in that: in step S2, the oil temperature of the quenching oil is 70 ℃.

6. The heat treatment method for a piston ring of an automobile engine according to claim 1, characterized in that: in step S2, the stirring speed for stirring the quenching oil is 44 HZ.

7. The heat treatment method for a piston ring of an automobile engine according to claim 1, characterized in that: in step S2, the quenching time was 7 min.

8. The heat treatment method for a piston ring of an automobile engine according to claim 1, characterized in that: in step S3, the tempering time is 120 min.

9. The heat treatment method for a piston ring of an automobile engine according to claim 1, characterized in that: after the treatment of the heating stage, the quenching stage and the tempering stage, the metallographic structure of the piston ring is a tempered sorbite, wherein the ferrite content is less than 5 percent, and the carbide content is less than 5 percent.

10. A piston ring for an automobile engine treated by the heat treatment method according to any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of heat treatment, and particularly relates to a heat treatment method for a piston ring of an automobile engine.

Background

The piston ring is an important part of an automobile engine, occupies a basic position in the whole automobile manufacturing process, and is an important link of subsequent service of automobile products. Its main function is air-tight action, and controls the oil quantity of cylinder wall, and transfers the heat quantity received by piston to the cylinder wall, and its functional quality can directly affect engine power, oil consumption and cylinder body life. With the development of the engine towards high speed and strengthening direction, the working conditions of the piston ring are more and more rigorous, and higher requirements on the performance are also put forward. As a piston ring material, it must have wear resistance, oil storage properties, thermal stability and fatigue resistance. The nodular cast iron is the first choice material for piston rings of automobile engines at home and abroad at present. The key to guarantee the internal quality of the piston ring is to select high-quality nodular cast iron and adopt an advanced heat treatment process.

The nodular cast iron standard of japan RIK EN piston ring company (RIK EN) represents the highest level of piston rings. The RIK EN nodular cast iron piston ring is made of RIK20 with chemical components of C3.5-4.2%, Si 2.2-3.4%, Mn 0.2-0.8%, P not more than 0.2% and S not more than 0.05%. The RIK20 piston ring is heat treated, the technical requirements are that the hardness after quenching is more than 50HRC, the hardness after tempering is 30-37HRC, the hardness fall (in the same batch) is less than or equal to 4HRC, and the metallographic structure is a tempered sorbite.

The technical problem encountered in the actual production process of heat treatment of the material RIK20 piston ring at present is that the hardness drop of the same batch is large, and the metallographic structure is easy to generate excessive ferrite (more than 5%).

Disclosure of Invention

The invention aims to provide a heat treatment method of a piston ring of an automobile engine, which can solve the technical problems in the background technology.

Therefore, the invention adopts the following technical proposal,

a heat treatment method for a piston ring of an automobile engine comprises the following steps:

s1, heating stage: the piston ring made of RIK20 is sent into a heating furnace, and enters an I area and a V area in sequence, and the heating temperature of each area is controlled as follows: area I880 + -5 deg.C, area II-IV 905 + -5 deg.C, and area V880 + -5 deg.C;

s2, quenching: the piston ring heated in the step S1 enters an oil groove for quenching, the oil temperature of quenching oil is 60-80 ℃, and thermal cycle quenching oil is stirred;

s3, tempering: after quenching in step S2, the piston ring enters a tempering furnace, and the tempering temperature is 545 ℃.

Further, in step S1, the heating time for the piston ring to be sent into the heating furnace is 71 min.

Further, in step S1, the heating furnace is a protective atmosphere mesh belt furnace.

Further, in step S2, the quenching oil is ultra-speed bright quenching oil.

Further, in step S2, the oil temperature of the quenching oil is 70 ℃.

Further, in step S2, the stirring speed for stirring the quenching oil is 44 HZ.

Further, in step S2, the quenching time was 7 min.

Further, in step S3, the tempering time is 120 min.

Further, after the treatment of the heating stage, the quenching stage and the tempering stage, the metallographic structure of the piston ring is a tempered sorbite, wherein the ferrite content is less than 5 percent, and the carbide content is less than 5 percent.

The invention also provides a piston ring of the automobile engine, which is obtained by the heat treatment method.

Compared with the background technology, the technical scheme at least has the following advantages:

1. the heating furnace quenching and tempering composite heat treatment process provided by the invention can effectively solve the technical problems that the hardness drop of the same batch is large and excessive ferrite is easy to appear in a metallographic structure by controlling the temperature of the heating stage, the quenching stage and the tempering stage, the hardness of the piston ring after heat treatment is 31-35HRC, the hardness drop of the piston ring of the same batch is less than or equal to 4HRC, the hardness difference of the same piston ring is less than or equal to 4HRC, the metallographic structure is a tempered sorbite, the ferrite is less than 5%, and the carbide is less than 5%;

2. the heating temperature of the piston ring in each area of the heating furnace in the heating stage of the invention is controlled to be 880 +/-5 ℃ in the area I, 905 +/-5 ℃ in the area II-IV and 880 +/-5 ℃ in the area V; not only reduces the production cost and shortens the heat preservation time, but also ensures the complete austenitization of the nodular cast iron matrix structure;

3. the invention ensures the quenching uniformity by controlling the temperature of quenching oil to be 60-80 ℃, the quenching cooling speed/quenching time and high-speed stirring, and avoids the problem of large hardness difference of the same batch in the actual production of heat treatment by the synergistic effect of the temperature control in the heating stage and the temperature control in the tempering stage.

Drawings

Fig. 1 is a metallographic structure diagram (400X) of a piston ring provided by the invention after quenching and tempering.

Detailed Description

The technical problems that the hardness fall of the same batch is large and the excessive ferrite (more than 5%) easily appears in the metallographic structure in the actual heat treatment production process of the material RIK20 piston ring exist in the prior art.

Therefore, the invention provides a novel heat treatment method for a piston ring of an automobile engine, which aims to solve the technical problem.

In order that the objects, features and advantages of the invention will be more clearly understood, a detailed description of the embodiments of the invention which follows is taken in conjunction with the accompanying drawings, in which many specific details are set forth in order to provide a thorough understanding of the invention, but the invention may be practiced in many ways other than as described. Therefore, the present invention is not limited to the specific embodiments disclosed below.

The invention provides a heat treatment method of an automobile engine piston ring, which can meet the technical requirements of heat treatment of RIK20 nodular cast iron piston rings, effectively solve the technical problems of hardness drop and metallographic structure and obtain high-quality technical products.

The heat treatment method comprises the following steps:

s1, heating stage

Sending the nodular cast iron piston ring made of RIK20 into a heating furnace of a mesh belt furnace production line, sequentially entering a zone I and a zone V, and controlling the heating temperature of each zone as follows: the heating time for feeding the piston ring into the heating furnace is 71min specifically, wherein the temperature of a region I is 880 +/-5 ℃, the temperature of a region II-IV is 905 +/-5 ℃, the temperature of a region V is 880 +/-5 ℃.

The heating of the nodular cast iron piston ring is to obtain austenite, and the heating is carried out to 30-50 ℃ above the critical transformation temperature AC 1. The heating temperature selected in the heating stage depends on the chemical components and the original structure of the nodular cast iron, and the AC1 point is different due to different silicon contents, so that the silicon content of the nodular cast iron piston ring of RIK20 is 2.2-3.4%, and the heating temperature can be selected from 850-.

The invention adopts a protective atmosphere mesh belt furnace production line (manufacturer: Gusu technology Limited company in Suzhou industrial park, model CST-860), piston rings sequentially enter an I area-V area of a mesh belt furnace, and the piston rings are still in a normal temperature state when entering the I area, and are heated at 880 ℃; then heating at 905 ℃ in a region II-IV, heating at 880 ℃ in a region V, and taking 880 ℃ as a quenching temperature, wherein the heating and quenching temperature is selected to prevent excessive ferrite from appearing in a metallographic structure.

When the heat treatment process is designed, the complete austenitization of the matrix structure of the nodular cast iron is ensured, and the production cost and the heat preservation time are reduced from the economic point of view. Therefore, a higher heating quenching temperature and a shorter heat preservation time are selected through a plurality of tests.

S2, quenching stage

The piston ring heated in the step S1 enters an oil bath for quenching, and the quenching oil is ultra-fast bright quenching oil (manufactured by bright quenching oil factory, model US), the quenching oil temperature is 60-80 ℃, the thermal cycle quenching oil is stirred, and the stirring speed is 44 HZ.

The quenching temperature is 880 ℃, because the hardenability of the nodular cast iron is low, quenching oil with a proper cooling speed is selected to completely quench the workpiece, the metallographic structure of the workpiece is guaranteed, the hardness is uniform, the deformation is small, the oil temperature for quenching is 60-80 ℃, the temperature is preferably 70 ℃, the high-speed stirring is carried out, and the quenching time is 7 min.

S3 tempering stage

And (4) after the piston ring is quenched in the step S2, putting the piston ring into a tempering furnace, controlling the tempering temperature to be 545 ℃ and the tempering time to be 120 min. The tempering temperature is selected by a plurality of tests according to the hardness requirement of 30-37HRC after tempering.

After the heat treatment process is adopted to carry out heat treatment on the nodular cast iron piston ring of the automobile engine, the hardness is 31-35HRC, the hardness drop of the same batch is less than or equal to 4HRC, the hardness difference of the same piston ring is less than or equal to 4HRC, the metallographic structure is a tempered sorbite (as can be known from figure 1, the metallographic structure treated by the heat treatment process is completely a sorbite), the ferrite is less than 5%, and the carbide is less than 5%.

The invention solves the problems that the hardness difference of the nodular cast iron piston ring in the same batch is large and the metallographic structure has excessive ferrite in the heat treatment actual production in the background technology: the problem of large hardness difference of the same batch is prevented, and firstly, the nodular cast iron is completely austenitized by ensuring the heating uniformity under the premise of preferably selecting the heating quenching temperature and the heat preservation time; secondly, the quenching uniformity is ensured, and the quenching oil temperature, the quenching cooling speed and high-speed stirring are controlled; thirdly, the heating quenching temperature is controlled to be +/-5 ℃, namely 905 +/-5 ℃ and 880 +/-5 ℃, and the three are matched and cooperated to solve the problem; the problem of excessive ferrite in the metallographic structure is prevented, on one hand, the heating quenching temperature is increased, and on the other hand, the quenching uniformity measure is adopted.

The nodular cast iron piston ring is subjected to quenching and tempering treatment, so that good comprehensive mechanical properties of high toughness and high strength can be obtained.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.