Super-huge ferrule carbon potential fine control process

Abstract

The invention relates to a super-huge ring carbon potential fine control process. A bearing ring is subjected to heat treatment; the heat treatment process comprises the steps of austenitizing treatment heating, salt bath quenching, lower bainite isothermal tempering, air cooling, cleaning and drying. In the austenitizing treatment heating process, the temperature ranges from 860 DEG C to 880 DEG C, the carbon potential ranges from 0.70% to 0.90%, and the time ranges from 3 h to 5 h; in the salt bath quenching process, the temperature ranges from 210 DEG C to 230 DEG C, and the time ranges from 15 min to 45 min; in the bainite isothermal tempering process, the temperature ranges from 210 DEG C to 235 DEG C, and the time ranges from 8 h to 10 h; in the air cooling process, the surface temperature of 235 DEG C in isothermal tempering is reduced to the room temperature smaller than or equal to 30 DEG C, and the time is 20-60 min; the carbon potential of the ferrule is finely controlled in the heating process, and the workpiece is heated sufficiently and uniformly by adopting a mode that the workpiece reciprocates in two heating areas of the heating furnace in the heating process, so that the deformation caused by thermal expansion of a metal material can be reduced, and the service life of the workpiece is prolonged. The problems of decarburization and uneven surface hardness and core hardness caused by uneven carbon potential of the cylindrical roller bearing are well solved.

Description

Technical Field

[0001] The invention relates to heat treatment of a bearing ring, in particular to a fine control process of carbon potential of an extra-large ring, and belongs to the technical field of bearing heat treatment. Background Art

[0002] Traditional large cylindrical roller bearings often lead to local decarburization due to uneven carbon potential distribution, uneven surface hardness and core hardness of the bearing, which affects the wear resistance and service life of the bearing. Based on this problem, it is necessary to develop a treatment process that can prevent decarburization and make the surface hardness and core hardness uniform to meet the requirements of this bearing. Summary of the invention

[0003] In view of the defects of the above-mentioned prior art, the purpose of the present invention is to provide a process for finely controlling the carbon potential of extra-large rings. This process can constrain the axial displacement of the shaft or the housing in two directions within the axial clearance area and can accept a smaller bidirectional axial load. It is mainly used in internal combustion engines, gas turbines, reduction gearboxes, rolling mills, etc.

[0004] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is: a super-large ring carbon potential fine control process, the bearing ring is made of GCR18Mo raw material, and the bearing ring is heat treated; the heat treatment process includes: austenitizing treatment heating, salt bath quenching, lower bainite isothermal tempering, air cooling, cleaning, and drying; the austenitizing treatment heating process, the temperature is 860℃-880℃, the carbon potential is 0.70%-0.90%, and the time is 3h-5h; the salt bath quenching process, the temperature is 210℃-230℃, the time is 15min-45min; the lower bainite isothermal tempering process, the temperature is 210℃-235℃, the time is 8h-10h; the air cooling process, the surface temperature is reduced from 235℃ in isothermal tempering to room temperature≤30℃, the time is 20min-60min; the cleaning process, the room temperature temperature, the time is 10min-40min; the drying process, the room temperature temperature, the time is 10min-30min; The extra-large bearings handled by this solution use cylindrical roller bearings, which are applicable to diameters of 1250-1800mm and heights of 250-450mm; Furthermore, the bearing ring is made of 1GCR18Mo raw material, which has higher hardenability than traditional bearing steel (GCR15, etc.).

[0005] Furthermore, a box-type roller production line is used for heating during the austenitizing treatment. The box-type furnace requires carbon setting three times a day to ensure that the carbon potential in the furnace is within the allowable range. At the same time, each atmosphere must meet the process so that decarburization, surface and core troostite can meet customer requirements. This process realizes the fine control of the ring carbon potential of this solution; Furthermore, the specific method for achieving the above-mentioned refined control of carbon potential is as follows: before the ferrule product enters the furnace, the process nitrogen flow rate is increased to 12±0.2L / h, and a small amount of propane is supplied to form a protective atmosphere to prevent decarburization on the product surface. After stabilization for 30 minutes, the process nitrogen supply is reduced to 5-8L / h, and propane is supplied normally to form a protective atmosphere, and the carbon potential is further controlled to fluctuate within the range of ±0.03%; Furthermore, the allowable deviation range of carbon potential is: ±0.03%.

[0006] In this scheme, the bearing material is GCR18Mo steel. In order to ensure uniform lower bainite structure transformation, it is necessary to ensure a small heat treatment deformation, and the main change in diameter during the heat treatment process is the diameter change in the diameter direction.

[0007] Furthermore, the heating furnace during the austenitizing treatment is divided into two heating zones, and the temperatures of the two heating zones are consistent, so that the product can be heated as evenly as possible; the workpiece moves back and forth between the two heating zones at a constant speed during heating, so that it can be heated sufficiently evenly during heating, reducing deformation caused by thermal expansion of the metal material; Furthermore, the workpiece is moved back and forth between the two heating zones by means of a roller and a motor drive, and the reciprocating motor is controlled by a program-controlled motor; Specifically, the workpiece is transferred by rollers in two heating zones to swing back and forth in a small range; the two heating zones are heated to the set temperatures respectively, thus meeting the standard of fully uniform heating.

[0008] Furthermore, the salt bath quenching process includes two stages of fast stirring and slow stirring, the fast stirring is 17 minutes / 1300 revolutions, and the slow stirring is 10 minutes / 350 revolutions.

[0009] The beneficial effects of the process using this solution are: By finely controlling the carbon potential of the ring during the heating process, the decarburization, surface and core troostite can meet customer needs; the material selected is GCR18Mo raw material, which has high hardenability compared with traditional bearing steel (GCR15, etc.); at the same time, during the heating process, the workpiece is moved back and forth in the two heating zones of the heating furnace to ensure that the workpiece is heated sufficiently and evenly, which can reduce the deformation caused by the thermal expansion of the metal material, and effectively solve the problem of decarburization, surface hardness and core hardness caused by uneven carbon potential of cylindrical roller bearings. This process is used to improve the wear resistance and service life of the bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a flow chart of the process curve for finely controlling the carbon potential of an extra-large ferrule of the present invention.

[0011] Figure 2This is a product picture of a cylindrical roller bearing. DETAILED DESCRIPTION

[0012] In order to make the structure and function of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0013] See also Figure 1 , this solution is specifically described with specific process parameters of an embodiment of the present invention; Extra large ring carbon potential refined control process, bearing ring with GCR18Mo raw material, heat treatment for bearing ring; the heat treatment process includes: austenitizing treatment heating, salt bath quenching, lower bainite isothermal tempering, air cooling, cleaning, drying; the austenitizing treatment heating process, temperature 875 ℃, carbon potential 0.85%, time 3h; start nitrogen: 10-15m³ / h, 30 minutes later nitrogen: 5-8m³ / h, methanol: 2.0-2.5L / h, propane: 0-1.2 L / h; the salt bath quenching process, temperature 225 ℃, time, the first stage stirring and the second stage stirring for a total of 27 minutes; the lower bainite isothermal tempering, temperature 235 ℃, time 10h; the air cooling process, temperature, from the isothermal tempering 235 ℃ surface temperature to room temperature ≤ 30 ℃, time 60min; the cleaning process, room temperature temperature, time 35min; the drying process, room temperature temperature, time 20min; The salt bath quenching process includes a first stirring stage and a second stirring stage; the first stage fast stirring is 17 minutes / 1300 revolutions, the second stage slow stirring is 10 minutes / 350 revolutions, and the water content is 1.7-2.0HRC; Based on the above technical solution, since the carbon potential distribution of the bearing ring is uneven during the heat treatment process, local decarburization often occurs, and the surface hardness and core hardness of the bearing are uneven; therefore, in order to solve this problem, the present invention has made corresponding improvements during the heat treatment process.

[0014] 1. Fine control of carbon potential The box-type roller production line is used for heating. The box-type furnace requires carbon setting three times a day to ensure that the carbon potential in the furnace is within the allowable range. At the same time, each atmosphere must comply with the process so that the decarburization, surface and core troostite can meet customer requirements; The carbon potential requirement in this embodiment is: 0.85%, and the deviation range is: ±0.03%.

[0015] 2. Reduce deformation In order to ensure uniform lower bainite microstructure transformation for GCR18Mo steel, it is necessary to ensure small heat treatment deformation, which is mainly the diameter change in the diameter direction during the heat treatment process. The workpiece is moved back and forth in the two heating zones of the heating furnace by rollers and a motor, and the reciprocating movement is controlled by a program-controlled motor. This method allows the heating to be sufficiently uniform. In this embodiment, the two heating zones are heated to a set temperature of 875°C respectively, and the actual temperature reached is 875°C, which meets the standard of sufficient uniformity.

[0016] The physical test results of the product are as follows: Decarburization depth: 0.01mm Lower bainite structure: ≤1 level Troostite in functional area (3-4 mm): None, Troostite in non-functional area (heart): Level 1 Surface hardness: 60.4HRC 60.7HRC 60.2HRC Core hardness: 59.0HRC 59.3HRC 59.2HRC Retained austenite: ≤3% Grain size: 11 levels It should be noted that the parts not described in detail in the present invention are prior art.

[0017] The above examples are only the best embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and many variations are possible. All variations that can be directly derived or associated with the contents disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. The carbon potential fine control process of the extra-large bearing ring is characterized in that the bearing ring is made of GCR18Mo raw material and the bearing ring is heat treated; the heat treatment process includes: Austenitizing treatment heating, salt bath quenching, lower bainite isothermal tempering, air cooling, cleaning and drying; The austenitizing treatment heating process has a temperature of 860°C-880°C, a carbon potential of 0.70%-0.90%, and a time of 3h-5h; the salt bath quenching process has a temperature of 210°C-230°C and a time of 15min-45min; the lower bainite isothermal tempering process has a temperature of 210°C-235°C and a time of 8h-10h; the air cooling process has a surface temperature of 235°C in isothermal tempering reduced to room temperature ≤30°C, and a time of 20min-60min; the cleaning process has a room temperature and a time of 10min-40min; the drying process has a room temperature and a time of 10min-30min.

2. The carbon potential fine control process for extra-large bearing rings according to claim 1 is characterized in that the bearing rings are made of 1GCR18Mo as raw material.

3. The process for finely controlling the carbon potential of extra-large ferrules according to claim 1 is characterized in that a box-type furnace is used for heating during the austenitizing treatment heating process, and the box-type furnace requires carbon setting once a day to ensure that the carbon potential in the furnace is within the allowable range, thereby achieving fine control of the carbon potential.

4. The process for finely controlling carbon potential of extra-large ferrules according to claim 3 is characterized in that: the specific method for achieving finely controlling carbon potential is: before the ferrule product enters the furnace, the process nitrogen flow rate is increased to 12±0.2L / h, and a small amount of propane is supplied to form a protective atmosphere; after stabilization for 30 minutes, the process nitrogen supply is reduced to 5-8L / h, and propane is supplied normally to form a protective atmosphere, and the carbon potential is further controlled to fluctuate within the range of ±0.03%.

5. The carbon potential fine control process of the extra-large ferrule according to claim 1 is characterized in that: the heating furnace during the austenitizing treatment heating process is divided into two heating zones, and the temperatures of the two heating zones are consistent; the workpiece moves back and forth between the two heating zones at a constant speed during heating.

6. The carbon potential fine control process for extra-large ferrules according to claim 5 is characterized in that the workpiece moves back and forth between the two heating zones by means of rollers and motor transmission, and the reciprocating control is performed by a program-controlled motor.

7. The process for finely controlling carbon potential of extra-large ferrules according to claim 1 is characterized in that the salt bath quenching process includes two stages of fast stirring and slow stirring, the fast stirring is 17 minutes / 1300 revolutions, and the slow stirring is 10 minutes / 350 revolutions.

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