Heat treatment method for large size bearing rings

Abstract

The present invention provides a large-size bearing ring heat treatment method, including quenching and tempering, wherein the quenching includes heating the bearing ring to 840-860°C at a heating rate of 8-12°C / min and keeping the temperature for 3-4 hours; firstly, the bearing ring is extruded and shaped for oil cooling, and the bearing ring is cooled to 110-130°C at a cooling rate of 3-5°C / S, and kept warm for 30-40 minutes for pre-tempering, and then the bearing ring is immediately cryogenically treated for 1-1.5 hours by liquid nitrogen, and the tempering includes placing the bearing ring in a heating furnace and heating it to 160-200°C at a heating rate of 5-8°C / min, and keeping the temperature for 8 hours to complete the tempering. The present invention reduces the deformation probability of the bearing ring in the quenching step, and the process scheme obtains a bearing ring with a hardness of 58-62HRC and a deformation of less than 1mm, while ensuring the comprehensive performance of the bearing ring such as strength and hardness, while reducing the deformation probability of the bearing ring.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical processing heat treatment, and in particular to a heat treatment method for a large-size bearing ring. Background Art

[0002] Bearing rings are mainly high-carbon chromium steel, with a carbon content of about 1%, chromium of about 1.5%, and a small amount of manganese and silicon. Chromium can improve heat treatment performance, hardenability, uniformity of organization, tempering stability, and can also improve the rust resistance and grinding performance of steel. Through quenching and tempering heat treatment, the hardness of bearing steel and other good comprehensive properties are improved. At present, it is widely used in military, industrial, agricultural, transportation and other fields.

[0003] At present, the bearing ring is heated to a certain temperature, kept warm for a certain period of time, and then subjected to conventional heat treatment by oil cooling, and then heated again to complete the tempering treatment.

[0004] However, after the large-sized bearing ring is heated and then cooled conventionally with a cooling medium, the deformation of the bearing ring is large and irregular, with a deformation of about 10 mm. Therefore, a margin of more than 10 mm should be left before the bearing ring is heat treated. If irregular deformation occurs, the large-sized bearing ring may be scrapped, and even if it is not scrapped, the margin needs to be removed by machining after heat treatment, which prolongs the machining time and increases the cost. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the existing technology and propose a solution to the problem of large deformation of large-size bearing rings during heat treatment and quenching. A method combining changing the cooling mode and the cooling rate is proposed to reduce the probability of deformation caused by quenching, shorten the processing cycle for subsequent mechanical processing, and reduce production costs.

[0006] To achieve the above object, the present invention adopts the following specific technical solutions:

[0007] A method for heat treatment of large-size bearing rings, i.e., bearing rings with a size greater than The process includes quenching and tempering. The quenching step includes heating the bearing ring to 840-860°C at a heating rate of 8-12°C / min and keeping the temperature for 3-4 hours.

[0008] Preferably, the quenching step comprises heating the bearing ring to 840-860° C. at a heating rate of 8-12° C. / min and keeping the temperature for 3-4 hours;

[0009] The bearing ring is extruded and shaped. The extrusion shaping includes placing the bearing ring flat in a temperature-controlled oil tank immediately after heating. A tooling platform is placed at the bottom of the oil tank. The tooling platform extrude the bearing ring in the axial direction and adopts an oil pump circulation cooling method to cool the bearing ring to 110-130°C at a cooling rate of 3-5°C / S;

[0010] Take out the bearing ring and place it in a heating furnace for 30 to 40 minutes for pre-tempering, then use liquid nitrogen for deep freezing treatment, keep it for 1 to 1.5 hours, and temper it immediately after deep freezing treatment;

[0011] Tempering step: Place the bearing ring in a heating furnace and heat it to 160-200°C at a heating rate of 5-8°C / min, and keep it warm for 8 hours to complete the tempering heat treatment.

[0012] Preferably, the bearing ring is cooled to 110-130° C. at a cooling rate of 4° C. / S.

[0013] Preferably, the bearing ring is cooled to 120° C. at a cooling rate of 3-5° C. / s. The bearing ring is taken out and placed in a heating furnace for 30-40 minutes for pre-tempering.

[0014] Preferably, the bearing ring is cooled to 120° C. at a cooling rate of 4° C. / S, and the bearing ring is taken out and placed in a heating furnace for 30 to 40 minutes for pre-tempering.

[0015] Preferably, in the tempering step, the bearing ring is placed in a heating furnace and heated to 160-200° C. at a heating rate of 6° C. / min, and kept warm for 8 hours to complete the tempering heat treatment.

[0016] Preferably, in the tempering step, the bearing ring is placed in a heating furnace and heated to 180° C. at a heating rate of 6° C. / min, and kept at this temperature for 8 hours to complete the tempering heat treatment.

[0017] Preferably, the cryogenic treatment is performed using liquid nitrogen vapor.

[0018] Preferably, in the quenching step, the bearing ring is heated to 840-860° C. at a heating rate of 10° C. / min and kept at that temperature for 3-4 hours.

[0019] Preferably, in the quenching step, the bearing ring is heated to 850° C. at a heating rate of 8-12° C. / min and kept at that temperature for 3.5 hours.

[0020] Preferably, after the tempering step, a detection and machining step is also included;

[0021] The testing steps include testing whether the hardness of the bearing ring meets the technical requirements and testing whether the deformation is within the range of the deformation margin reserved before machining;

[0022] The machining step includes re-finishing the bearing ring to ensure that the process dimensions of the bearing ring meet the technical requirements of the drawing.

[0023] The present invention can achieve the following technical effects:

[0024] By changing the cooling method and cooling rate, the deformation of the bearing ring is less than 1mm, and the hardness of the bearing ring is 58-62HRC. While ensuring the comprehensive performance of the bearing ring such as strength and hardness, the probability of deformation of the bearing ring is reduced, the time for subsequent bearing ring machining is reduced, and the cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic flow chart of a large-size bearing ring heat treatment method provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0028] Figure 1 A schematic flow chart of a large-size bearing ring heat treatment method provided according to an embodiment of the present invention is shown.

[0029] like Figure 1 As shown, the heat treatment method for a large-size bearing ring provided in an embodiment of the present invention includes the steps of quenching, tempering, testing, and machining.

[0030] Quenching steps:

[0031] Heat the bearing ring to 840°C to 860°C at a heating rate of 8 to 12°C / min and keep it warm for 3 to 4 hours;

[0032] The bearing ring is extruded and shaped. The extrusion shaping includes placing the bearing ring flat in a temperature-controlled oil tank immediately after heating. A tooling platform is placed at the bottom of the oil tank. The tooling platform extrude the bearing ring in the axial direction and adopts an oil pump circulation cooling method to cool the bearing ring to 110-130°C at a cooling rate of 3°C / S-5°C / S.

[0033] In order to reduce the residual austenite in the quenched structure, increase dimensional stability and hardness, the bearing is cryogenically treated. Liquid nitrogen or liquid nitrogen vapor is used for cryogenic treatment of the bearing ring, and the holding time is 1 to 1.5 hours. In order to avoid cracking caused by cryogenic treatment immediately after quenching, pre-tempering is carried out at 110 to 130 ° C for 30 to 40 minutes, and then cryogenic treatment is carried out. Tempering is carried out immediately after cryogenic treatment.

[0034] Tempering steps:

[0035] The bearing ring is placed in a heating furnace and heated to 160°C to 200°C at a heating rate of 5°C / min to 8°C / min, and kept at this temperature for 8 hours to complete the tempering heat treatment.

[0036] Testing steps:

[0037] Check whether the hardness of the bearing ring meets the technical requirements and whether the deformation is within the range of the deformation allowance reserved before machining.

[0038] Machining steps:

[0039] The bearing ring is further refined to ensure that the process dimensions of the bearing ring meet the technical requirements of the drawing.

[0040] Embodiment 1:

[0041] Quenching steps:

[0042] The bearing ring was heated to 850°C at a heating rate of 10°C / min and kept at this temperature for 4 hours;

[0043] The bearing ring is extruded and shaped, and oil-cooled, and cooled to 130°C at a cooling rate of 3°C / S; the bearing ring is taken out and placed in a heating furnace for 30 to 40 minutes for pre-tempering, and then immediately subjected to deep freezing treatment for 1 hour.

[0044] Tempering steps:

[0045] The bearing ring is placed in a heating furnace and heated to 180°C at a heating rate of 5°C / min, and kept at this temperature for 8 hours to complete the tempering heat treatment.

[0046] Testing steps:

[0047] The test results show that the bearing ring hardness is 59.5HRC and the deformation is 0.6mm.

[0048] Embodiment 2:

[0049] Quenching steps:

[0050] The bearing ring was heated to 850°C at a heating rate of 10°C / min and kept at this temperature for 4 hours;

[0051] The bearing ring is extruded and shaped, and oil-cooled, and cooled to 130°C at a cooling rate of 4°C / S; the bearing ring is taken out and placed in a heating furnace for 30 to 40 minutes for pre-tempering, and then immediately subjected to deep freezing treatment for 1 hour.

[0052] Tempering steps:

[0053] The bearing ring is placed in a heating furnace and heated to 180°C at a heating rate of 5°C / min, and kept at this temperature for 8 hours to complete the tempering heat treatment.

[0054] Testing steps:

[0055] The test results show that the bearing ring hardness is 59.3HRC and the deformation is 0.8mm.

[0056] Embodiment 3:

[0057] Quenching steps:

[0058] The bearing ring was heated to 850°C at a heating rate of 10°C / min and kept at this temperature for 4 hours;

[0059] The bearing ring is extruded and shaped, and oil-cooled, and cooled to 130°C at a cooling rate of 5°C / S; the bearing ring is taken out and placed in a heating furnace for 30 to 40 minutes for pre-tempering, and then immediately subjected to deep freezing treatment for 1 hour.

[0060] Tempering steps:

[0061] The bearing ring is placed in a heating furnace and heated to 180°C at a heating rate of 5°C / min, and kept at this temperature for 8 hours to complete the tempering heat treatment.

[0062] Testing steps:

[0063] The test results show that the bearing ring hardness is 60.2HRC and the deformation is 0.9mm.

[0064] Embodiment 4:

[0065] Quenching steps:

[0066] The bearing ring was heated to 850°C at a heating rate of 10°C / min and kept at this temperature for 4 hours;

[0067] The bearing ring is extruded and shaped, and oil-cooled, and cooled to 120°C at a cooling rate of 3°C / S; the bearing ring is taken out and placed in a heating furnace for 30 to 40 minutes for pre-tempering, and then immediately subjected to deep freezing treatment for 1 hour.

[0068] Tempering steps:

[0069] The bearing ring is placed in a heating furnace and heated to 160°C at a heating rate of 3°C / min, and kept at this temperature for 8 hours to complete the tempering heat treatment.

[0070] Testing steps:

[0071] The test results show that the bearing ring hardness is 61.3HRC and the deformation is 0.7mm.

[0072] Embodiment 5:

[0073] Quenching steps:

[0074] The bearing ring was heated to 850°C at a heating rate of 10°C / min and kept at this temperature for 4 hours;

[0075] The bearing ring is extruded and shaped, and oil-cooled, and cooled to 120°C at a cooling rate of 4°C / S; the bearing ring is taken out and placed in a heating furnace for 30 to 40 minutes for pre-tempering, and then immediately subjected to deep freezing treatment for 1 hour.

[0076] Tempering steps:

[0077] The bearing ring is placed in a heating furnace and heated to 160°C at a heating rate of 5°C / min, and kept at this temperature for 8 hours to complete the tempering heat treatment.

[0078] Testing steps:

[0079] The test results show that the bearing ring hardness is 61.3HRC and the deformation is 0.8mm.

[0080] Embodiment 6:

[0081] Quenching steps:

[0082] The bearing ring was heated to 850°C at a heating rate of 10°C / min and kept at this temperature for 4 hours;

[0083] The bearing ring is extruded and shaped, and oil-cooled, and cooled to 120°C at a cooling rate of 5°C / S; the bearing ring is taken out and placed in a heating furnace for 30 to 40 minutes for pre-tempering, and then immediately subjected to deep freezing treatment for 1 hour.

[0084] Tempering steps:

[0085] The bearing ring is placed in a heating furnace and heated to 160°C at a heating rate of 5°C / min, and kept at this temperature for 8 hours to complete the tempering heat treatment.

[0086] Testing steps:

[0087] The test results show that the bearing ring hardness is 61.5HRC and the deformation is 0.9mm.

[0088] Embodiment 7:

[0089] Quenching steps:

[0090] The bearing ring was heated to 850°C at a heating rate of 10°C / min and kept at this temperature for 4 hours;

[0091] The bearing ring is extruded and shaped, and oil-cooled, and the bearing ring is cooled to 110°C at a cooling rate of 3°C / S; the bearing ring is taken out and placed in a heating furnace for 30 to 40 minutes for pre-tempering, and then immediately subjected to deep freezing treatment for 1 hour.

[0092] Tempering steps:

[0093] The bearing ring is placed in a heating furnace and heated to 200°C at a heating rate of 5°C / min, and kept at this temperature for 8 hours to complete the tempering heat treatment.

[0094] Testing steps:

[0095] The test results show that the bearing ring hardness is 58.6HRC and the deformation is 0.6mm.

[0096] Embodiment 8:

[0097] Quenching steps:

[0098] The bearing ring was heated to 850°C at a heating rate of 10°C / min and kept at this temperature for 4 hours;

[0099] The bearing ring is extruded and shaped, and oil-cooled, and the bearing ring is cooled to 110°C at a cooling rate of 4°C / S; the bearing ring is taken out and placed in a heating furnace for 30 to 40 minutes for pre-tempering, and then immediately subjected to deep freezing treatment for 1 hour.

[0100] Tempering steps:

[0101] The bearing ring is placed in a heating furnace and heated to 200°C at a heating rate of 5°C / min, and kept at this temperature for 8 hours to complete the tempering heat treatment.

[0102] Testing steps:

[0103] The test results show that the bearing ring hardness is 58.8HRC and the deformation is 0.8mm.

[0104] Embodiment 9:

[0105] Quenching steps:

[0106] The bearing ring was heated to 850°C at a heating rate of 10°C / min and kept at this temperature for 4 hours;

[0107] The bearing ring is extruded and shaped, and oil-cooled, and the bearing ring is cooled to 110°C at a cooling rate of 5°C / S; the bearing ring is taken out and placed in a heating furnace for 30 to 40 minutes for pre-tempering, and then immediately subjected to deep freezing treatment for 1 hour.

[0108] Tempering steps:

[0109] The bearing ring is placed in a heating furnace and heated to 200°C at a heating rate of 5°C / min, and kept at this temperature for 8 hours to complete the tempering heat treatment.

[0110] Testing steps:

[0111] The test results show that the bearing ring hardness is 59.0HRC and the deformation is 0.9mm.

[0112]

[0113]

[0114] It can be seen that when the cooling rate is in the range of 3 to 5°C / S, the hardness and deformation of the steel are the best. When it is less than 3°C / S or greater than 5°C / S, the hardness will be too low or the deformation will be large. Based on the above experimental results, the beneficial effect of controlling the cooling rate at 3 to 5°C / S is the best.

[0115] According to the thickness of the workpiece, the insulation time is calculated according to the following formula:

[0116] (T=B+A×D)

[0117] The meaning of the parameters in the formula:

[0118] T—quenching and holding time, min;

[0119] B—heating and insulation constant, min;

[0120] A—heating and thermal insulation coefficient, min / mm;

[0121] D—effective thickness of the part, mm;

[0122] The heating and insulation constant B (min) value range is 10 to 30;

[0123] The heating and thermal insulation coefficient A (min / mm) has a numerical range of 1 to 1.5.

[0124] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

Claims

1. A bearing ring heat treatment method, characterized in that: The bearing ring has a size greater than φ1200 mm and includes: Quenching steps: The bearing ring was heated to 850°C at a heating rate of 10°C / min and kept at this temperature for 4 hours; The bearing ring is subjected to extrusion shaping, wherein the extrusion shaping includes placing the bearing ring flat in a temperature-controllable oil tank immediately after being heated, a tooling platform is placed at the bottom of the oil tank, the tooling platform extrude the bearing ring in the axial direction, and the bearing ring is cooled to 120° C. at a cooling rate of 3° C. / S by using an oil pump circulation cooling method; Take out the bearing ring and place it in a heating furnace for 30-40 minutes for pre-tempering, then use liquid nitrogen for deep freezing treatment, keep it for 1 hour, and temper it immediately after deep freezing treatment; Tempering step: placing the bearing ring in a heating furnace and heating it to 160° C. at a heating rate of 3° C. / min, and keeping the temperature for 8 hours to complete the tempering heat treatment.

2. The bearing ring heat treatment method according to claim 1, characterized in that: The cryogenic treatment is performed using liquid nitrogen vapor.

3. The bearing ring heat treatment method according to claim 1, characterized in that: After the tempering step, there are also inspection and machining steps; The detection step includes detecting whether the hardness of the bearing ring meets the technical requirements and detecting whether the deformation is within the range of the deformation margin reserved before machining; The mechanical processing step includes re-finishing the bearing ring to ensure that the process dimensions of the bearing ring meet the technical requirements of the drawing.

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