CN110042217B - Nano bainite bearing heat treatment method and bearing manufactured by same - Google Patents

Abstract

The invention discloses a nano-bainite bearing heat treatment method. The method comprises: austenitizing the bearing parts to be treated; cooling the surface of the bearing parts to be treated in a water bath to a first temperature; isothermally treating the to-be-treated bearing parts at a second temperature Bearing parts, so that the material of the bearing part to be processed undergoes bainite transformation; wherein, the first temperature is lower than the martensite transformation temperature of the bearing part material to be processed, and the second temperature is higher than the martensite start of the bearing part material to be processed. transition temperature. The present invention also discloses a bearing produced by the aforementioned method. The water bath is used to cool the bearing parts to be treated, and the salt bath method is avoided, thereby reducing the cost and avoiding the pollution to the environment.

Description

Heat treatment method for nano-bainite bearing and bearing made therefrom

technical field

The invention relates to the field of bearing manufacturing, in particular to a heat treatment method for a nano-bainite bearing and a bearing prepared therefrom.

Background technique

Nano bainite bearing is a kind of bainite bearing with high fatigue life, excellent wear resistance, and high impact toughness. Therefore, nano bainite bearing is suitable for shock load conditions. The patented technology of nano-bainite bearing steel disclosed in recent years, whether it is conventional bainite treatment or low-temperature nano-bainite treatment, requires salt bath method for isothermal treatment.

However, the salt bath method requires specialized salt bath equipment for handling. Among them, the quenching intensity is improved by adding a certain amount of crystal water to the molten salt, and the rapid cooling of the bearing is realized. However, this kind of salt bath equipment is expensive and also causes certain pollution to the environment.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a nano-bainite bearing heat treatment method and the prepared bearing, which avoids the salt bath method, uses water bath cooling to reduce costs, and at the same time avoids environmental pollution.

The technical scheme of the present invention is as follows: the present invention discloses a method for heat treatment of a nano-bainite bearing, comprising:

Step 1. Austenitizing the bearing parts to be treated: heating the bearing parts to be treated to 810°C-870°C, and keeping the temperature for 0.5h-1h;

Step 2, water bath to cool the surface temperature of the bearing part to be treated: when the temperature difference between the surface temperature of the bearing part to be treated and the temperature of the core of the bearing part to be treated is greater than or equal to 200°C, stop the water bath and let stand The bearing parts to be treated can reduce the temperature difference between the surface temperature of the bearing parts to be treated and the core of the bearing parts to be treated; When the temperature difference is less than or equal to 50°C, continue the water bath until the surface of the bearing part to be treated reaches the first temperature;

Step 3, isothermally treating the bearing parts to be treated at a second temperature, so that the bearing parts to be treated undergo bainite transformation; the martensite of the first temperature lower than the bearing parts to be treated begins to transform a temperature, the second temperature being higher than the martensitic onset temperature of the bearing part material to be treated; and

Step 4: Tempering the bearing part to be processed at 170°C-200°C, so as to remove the tissue stress of the material of the bearing part to be processed.

Preferably, in step 2, the water bath cooling includes multiple times of water bath cooling of the bearing parts to be processed.

Preferably, the first temperature is 130°C-160°C, and the second temperature is 180°C-210°C.

Preferably, the water bath is performed with flowing water at 40°C-70°C.

Preferably, in step 3, a low temperature inert atmosphere furnace is used to perform isothermal treatment on the bearing parts to be treated.

Preferably, in step 3, the content of bainite generated in the structure of the bearing part material to be processed is 50%-70% of the material structure of the bearing part to be processed.

Preferably, in step 3, the isothermal time is 3h-8h.

On the other hand, the present invention also provides a nano-bainite bearing obtained by the above method.

Compared with the prior art, the present invention has the following advantages:

The water bath is used to cool the bearing parts to be treated, and the salt bath method is avoided, thereby reducing the cost and avoiding the pollution to the environment.

Further, during the cooling process by using a water bath, the bearing parts to be treated are first cooled to a first temperature lower than the starting temperature of martensite transformation, so that a certain amount of martensite is generated in the material structure of the bearing parts to be treated, thereby promoting the formation of shells. The intenite transformation effectively shortens the heat treatment cycle.

Description of drawings

Fig. 1 is the flow chart of the heat treatment method of the nano-bainite bearing of the present invention.

Detailed ways

Due to the high cost of salt bath equipment, it will also cause certain pollution to the environment. Based on this, the present invention provides a nano-bainite bearing heat treatment method, comprising the following steps:

Step 1. Austenitizing the bearing parts to be treated: heating the bearing parts to be treated to 810°C-870°C, and keeping the temperature for 0.5h-1h;

Step 2, water bath to cool the surface temperature of the bearing parts to be treated: when the temperature difference between the surface temperature of the bearing parts to be treated and the core of the bearing parts to be treated is greater than or equal to 200°C, stop the water bath and let the bearing parts to be treated stand still to reduce the temperature to be treated The temperature difference between the surface temperature of the bearing part and the core of the bearing part to be treated; and when the temperature difference between the surface temperature of the bearing part to be treated and the core of the bearing part to be treated is less than or equal to 50°C, continue the water bath until the surface of the bearing part to be treated reaches the first temperature;

Step 3, isothermally treating the bearing parts to be treated at the second temperature, so that the bearing parts to be treated undergo bainite transformation; the first temperature is lower than the starting temperature of martensite transformation of the bearing parts to be treated, and the second temperature is higher than that of the bearing parts to be treated. The martensitic onset temperature of the processed bearing component material; and

In step 4, the bearing parts to be treated are tempered at 170° C. to 200° C., so as to remove the tissue stress of the material of the bearing parts to be treated.

It can be seen that in the embodiment of the present invention, the water bath is used to cool the bearing parts to be treated, which avoids the high cost of salt bath equipment when the salt bath method is used, thereby reducing the cost and avoiding pollution to the environment.

Further, during the cooling process by using a water bath, the bearing steel to be treated is first cooled to a first temperature lower than the starting temperature of martensite transformation, so that a certain amount of martensite is formed in the material structure of the bearing parts to be treated, thereby promoting the formation of shells. The intenite transformation effectively shortens the heat treatment cycle.

In order to make the above objects, features and advantages of the present invention more clearly understood, specific embodiments of the present invention will be described in detail below.

Referring to FIG. 1, an embodiment of the present invention first provides a heat treatment method for a nano-bainite bearing, including:

Step S01: austenitizing the bearing parts to be treated;

The bearing parts to be processed may be finished bearing parts or semi-finished bearing parts. In this embodiment, the bearing parts are the bearing parts obtained by processing and forming the steel ingot after spheroidizing annealing treatment. The bearing parts may include the bearing inner ring, the bearing outer ring and rolling elements, and the rolling elements and the raceway of the bearing inner ring. Matches the raceway of the outer ring of the bearing.

Specifically, in this step, the bearing parts to be treated are heated to 810° C. to 870° C. and kept for 0.5 h to 1 h to perform austenitization treatment.

Step S02: cooling the surface of the bearing part to be treated with a water bath to a first temperature;

Wherein, the first temperature is lower than the starting temperature of martensite transformation of the bearing part material to be processed. Specifically, the first temperature may be 130°C to 160°C, and in this embodiment, the first temperature may be 145°C.

The surface of the bearing parts to be treated is cooled to the first temperature lower than the starting temperature of martensite transformation, so that a certain amount of martensite is formed in the structure of the bearing parts to be treated, thereby promoting the bainite transformation and effectively shortening the heat treatment cycle .

In this step, the water bath cooling treatment may specifically include cooling the bearing part to be treated in a water bath for several times until the surface of the bearing part to be treated reaches the first temperature. This is because the cooling rate of the water bath in this step is high, and there will be a certain temperature difference between the surface and the core of the bearing parts to be treated. If the temperature difference is too large, the bearing parts may crack. The use of multiple water bath cooling methods can ensure that the temperature difference between the surface temperature of the bearing parts to be treated and the core part is kept within a certain range, so as to avoid cracking of the bearing parts.

Specifically, in the process of multiple water baths, when the temperature difference between the surface of the bearing part to be treated and the temperature of the core of the bearing part to be treated is greater than or equal to 200°C, the water bath is stopped, and the bearing steel to be treated is left to stand to reduce the surface of the bearing part to be treated. When the temperature difference between the surface temperature of the bearing part to be processed and the core part of the bearing part to be processed is less than or equal to 50°C, continue the water bath until the surface of the bearing part to be processed reaches the first temperature.

In this embodiment, the surface of the bearing part to be treated obtained by cooling in a water bath for many times can be 130°C to 160°C, and the core temperature is 200°C to 250°C.

Moreover, in this embodiment, it is preferable to use flowing water at 40°C to 70°C for the water bath, so as to avoid surface defects of the bearing parts to be treated caused by the supercooled water temperature.

Step S03: isothermally treating the bearing parts to be treated at the second temperature, so that the bearing parts to be treated undergo bainite transformation.

Wherein, the second temperature is greater than the martensite transformation temperature of the bearing part material to be processed. Specifically, the second temperature may be 180°C to 210°C, and in this embodiment, the second temperature may be 195°C.

In this embodiment, the isothermal time for isothermally treating the bearing parts to be treated is 3 h to 8 h, and may be 5 h in this embodiment. From another perspective, in this step, the content of bainite generated in the material structure of the bearing part to be processed should be 50% to 70% of the material structure of the bearing part to be processed. That is, the isothermal treatment in this step is performed until the bainite content of the material structure of the bearing part to be treated reaches 50% to 70%, and then the corresponding isothermal time is determined according to the actual transformation amount.

This step can be performed in a low temperature inert atmosphere furnace. The inert atmosphere refers to an inert gas environment, and a specific inert gas may be helium, neon, argon, nitrogen, and the like.

Moreover, in this embodiment, after step S03, it also includes or may further include:

Step S04: Temper the bearing parts to be treated at 170°C to 200°C.

Through the tempering treatment, the stress of the material structure of the bearing parts to be treated can be effectively eliminated, and the material structure of the bearing parts can be further stabilized and the performance can be improved.

For the convenience of description, the present invention further provides two specific examples.

Example 1: A high-carbon chromium nano-bainite bearing steel is used, and the mass percentages of the main chemical components are: C: 0.92, Si: 1.51, Mn: 0.45, Cr: 1.42, Mo: 0.20. After spheroidizing annealing, the bearing steel is processed into bearing parts, and the wall thickness of the bearing ring is 40mm. Then heat the bearing parts to 830°C for 40 minutes, put them in warm water at 70°C for 10s, take them out, let them stand for 65s and then cool them in water for 6s, the surface temperature reaches 135°C, put the bearing ring into the inert 200°C Isothermal treatment was carried out in an atmosphere furnace. After holding for 3.5 hours, the content of bainite reached 50%. It was taken out and cooled. Finally, it was held in a furnace at 175 °C for 1 hour for tempering treatment. After this method, the surface hardness of the bearing ring is 62.5HRC, the core hardness is 58.6HRC, and the unnotched impact toughness is 68J/cm ² .

Example 2: A carburized nano-bainite bearing is used, and the mass percentages of the main chemical components are: C: 0.23, Si: 1.46, Mn: 0.62, Cr: 1.56, Ni: 0.59, Mo: 0.25. The bearing steel is processed into bearing parts, and the wall thickness of the bearing ring is 85mm. Then, carburizing treatment was carried out, and the C content on the surface after carburizing reached 0.95 wt.%. The carburized bearing parts are spheroidized and tempered at high temperature. Then, heat the bearing parts to 865°C for 60 minutes, put them in warm water at 50°C for 25s, take them out, let them stand for 100s and then cool them in water for 10s, the surface temperature reaches 155°C, put the bearing ring into the inert 185°C Isothermal treatment was carried out in an atmosphere furnace. After holding for 7.5 hours, the amount of bainite formed reached 65%. It was taken out and cooled. Finally, it was held in a furnace at 180 °C for 1 hour for tempering treatment. After this method, the surface hardness of the bearing ring is 61.5HRC, the core hardness is 41.6HRC, and the core U-notch impact toughness is 112J/cm ² .

In this embodiment, the water bath is used to cool the bearing parts to be treated, so that the salt bath method is avoided, thereby reducing the cost and avoiding the pollution to the environment.

Further, in the cooling process using a water bath, the bearing parts to be treated are first cooled to a first temperature lower than the starting temperature of martensite transformation, so that a certain amount of martensite is generated in the material structure of the bearing parts to be treated, thereby promoting Bainite. The bulk phase transformation effectively shortens the heat treatment cycle.

In another embodiment of the present invention, a nano-bainite bearing is also provided, and the parts of the nano-bainite bearing are obtained by the method described in the above embodiment. The bearing parts may be formed by the forming methods described in the foregoing embodiments. For the specific description of the bearing parts in this embodiment, reference may be made to the corresponding descriptions in the foregoing embodiments, which will not be repeated here.

It should be noted that, in the present invention, in specific numerical ranges, endpoint values are also included within the scope of the present invention. Although the present invention is disclosed above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be based on the scope defined by the claims.

Claims (5)

1. a nano-bainite bearing heat treatment method, is characterized in that, comprises the following steps: Step 1. Austenitizing the bearing parts to be treated: heating the bearing parts to be treated to 810°C-870°C, and keeping the temperature for 0.5h-1h; Step 2, the surface temperature of the bearing part to be treated is cooled in a water bath: the bearing part to be treated is cooled in a water bath for several times, when the temperature difference between the surface temperature of the bearing part to be treated and the core of the bearing part to be treated is greater than or equal to When the temperature is 200°C, the water bath is stopped, and the bearing parts to be treated are allowed to stand to reduce the temperature difference between the surface temperature of the bearing parts to be treated and the core of the bearing parts to be treated; and when the surface of the bearing parts to be treated is When the temperature difference between the temperature and the core of the bearing part to be treated is less than or equal to 50°C, continue the water bath until the surface of the bearing part to be treated reaches the first temperature of 130°C-160°C; wherein, 40°C-70°C is used The running water is used for the water bath; the method of multiple water bath cooling can ensure that the temperature difference between the surface temperature of the bearing parts to be treated and the temperature of the core is kept within a certain range, so as to avoid cracking of the bearing parts; Step 3, isothermally treating the bearing parts to be treated at a second temperature of 180°C-210°C, so that the bearing parts to be treated undergo bainite transformation; the first temperature is lower than the temperature of the bearing parts to be treated. a martensite onset temperature, the second temperature being higher than the martensite onset temperature of the bearing part material to be treated; and Step 4: Tempering the bearing part to be processed at 170°C-200°C, so as to remove the tissue stress of the material of the bearing part to be processed. 2 . The method for heat treatment of a nano-bainite bearing according to claim 1 , wherein, in step 3, a low temperature inert atmosphere furnace is used to perform isothermal treatment on the bearing parts to be treated. 3 . 3. The method for heat treatment of nano-bainite bearings according to claim 1, characterized in that, in step 3, the content of bainite generated in the structure of the material of the bearing part to be treated is the 50%-70% of the material organization. 4 . The method for heat treatment of nano-bainite bearings according to claim 1 , wherein, in step 3, the isothermal time is 3h-8h. 5 . 5 . A nano-bainite bearing, characterized in that, a bearing obtained by the heat-treatment method for a nano-bainite bearing according to any one of claims 1-4.

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