Heat treatment box-type furnace and bearing ring heat treatment process

Abstract

The invention relates to the technical field of bearing ring heat treatment processes, in particular to a heat treatment box-type furnace and a bearing ring heat treatment process, the heat treatment box-type furnace comprises a furnace shell, a first grating, a second grating, a third grating, a fourth grating and an observation hole, a furnace door is arranged on one side of the furnace shell, and an access door is arranged on the other side of the furnace shell; the first grating and the second grating are arranged on the furnace walls on the two sides respectively, the first grating and the second grating are arranged along the axial symmetry center line of the furnace shell, and the first grating and the second grating are a set of first correlation gratings. Through the design of the heat preservation observation hole of the box-type furnace production line, the product quality is optimized, and the heat preservation time can be precisely controlled without opening a door.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment technology for bearing rings, in particular to a heat treatment box furnace and a heat treatment technology for bearing rings. Background Art

[0002] Heat treatment observation and insulation are important characteristics in the heat treatment process. The difference between the box-type furnace and the through-type roller furnace main furnace is that the box-type furnace has only one zone. For example, for large spherical bearing rings, GCr15SiMn is selected as the material with a diameter of 1200-1500mm. It is generally processed in a box-type furnace combined with a salt bath quenching line. Because the box-type furnace heating and insulation observation holes were placed on the back wall in the past, it is difficult to confirm the heating furnace insulation time, and the total heating time cannot be determined. Finally, it was found through dissection and analysis that the surface tissue was overheated. When observing the insulation of the bearing ring through the insulation hole of the box-type furnace, it was found that the color state of the insulation for 2 hours and 6 hours was the same, so it was impossible to accurately determine the insulation of the product, and thus it was impossible to meet the technical requirements.

[0003] The traditional box-type furnace production line cannot determine the holding time, and thus cannot accurately determine the holding time of the process, which ultimately leads to insufficient or excessive holding time of the ring during the heating process, resulting in underheating or overheating of the structure, which further leads to coarse internal grain size and reduces the fatigue life of the bearing ring. Summary of the invention

[0004] In view of the defects of the prior art, the present invention provides a heat treatment box furnace and a bearing ring heat treatment process, which optimizes the quality of the product by designing an insulation observation hole for the box furnace production line and can accurately control the insulation time without opening the door.

[0005] In order to achieve the above-mentioned purpose, the technical solution provided by the present invention is a heat treatment box furnace, comprising a furnace shell, a first grating, a second grating, a third grating, a fourth grating and an observation hole, a furnace door is arranged on one side of the furnace shell, and an inspection door is arranged on the other side; the first grating and the second grating are respectively arranged on the furnace walls on both sides, the first grating and the second grating are arranged along the axial symmetry center line of the furnace shell, and the first grating and the second grating are a group of opposing gratings one; the third grating and the fourth grating are respectively arranged on the furnace walls on both sides, the third grating and the fourth grating are arranged along the axial symmetry center line of the furnace shell, and the third grating and the fourth grating are a group of opposing gratings two; the material tray moves back and forth in the furnace shell, and the range of the back and forth movement of the material tray is the range in which the detection range of the opposing grating one and the detection range of the opposing grating two overlap; the observation hole is obliquely arranged on the furnace wall on one side, and the overlapping range and the furnace wall on the other side are observed through the observation hole.

[0006] Furthermore, the detection range of the first opposing grating is smaller than the distance between the first opposing grating and the second opposing grating.

[0007] Furthermore, the detection range of the second opposing grating is smaller than the distance between the first opposing grating and the second opposing grating.

[0008] Furthermore, the observation hole includes a protective tube, a protective cover, a hole sleeve and a glass mirror, one end of the protective cover is arranged with the protective tube, the other end of the protective cover is operably associated with the hole sleeve, and the glass mirror is arranged at one end of the hole sleeve away from the protective cover.

[0009] Furthermore, the inner wall of the protective tube is provided with thermal insulation cotton, the outer side of the protective cover is provided with an exhaust pipe, the pipe mouth of the exhaust pipe is provided with a pipe cap, and the hole sleeve is provided with an insulating steel plate. The insulating steel plate controls the switch through a connecting rod, one end of the connecting rod is inserted into the hole sleeve and connected to the insulating steel plate, and the other end of the connecting rod extends out of the hole sleeve.

[0010] Furthermore, a sealing ring is provided at one end of the hole sleeve close to the glass mirror.

[0011] Furthermore, the inclination angle between the observation hole and the furnace wall is 72°, the field of view angle of the observation hole is 45°, and the diameter of the observation hole is 65 mm.

[0012] Furthermore, a thermocouple and a waste combustion pipeline system are arranged on the furnace shell, the thermocouple is arranged on one side of the inspection door, and the waste combustion pipeline system is arranged on the other side of the inspection door.

[0013] Furthermore, the furnace wall inside the furnace shell is provided with insulation bricks and insulation cotton, the insulation cotton is arranged outside the insulation bricks, and the furnace shell is arranged outside the insulation cotton.

[0014] The bearing ring heat treatment process using the heat treatment box furnace includes the following steps: S100, pre-cleaning, including cleaning and drying, the bearing ring is first cleaned and then dried; The cleaning temperature is 30-40℃ and the cleaning time is 20-30min; The drying temperature is 110°C and the time is 20-30 minutes; S200, heating and heat preservation, heating the bearing ring first and then heat preservation; Heat the bearing ring to 820-860℃ for 2h, then start heat preservation. Observe the contrast between the color of the workpiece at high temperature and the color of the furnace wall through the observation hole. When the color of the workpiece at high temperature is consistent with the color of the furnace wall, it is confirmed that the heat preservation time of the workpiece has ended. S300, quenching, cooling the bearing ring to 175°C; S400, post-cleaning, including air cooling, cleaning and drying, air cooling 20min-60min, cleaning 10min-40min, drying 10min-30min; S500, deep cooling, cooling the bearing ring to 0-7℃ and keeping it warm, the processing time is 50min; S600, temper the bearing ring at high temperature to 180-200℃ and keep it warm. The processing time is 8h.

[0015] The beneficial effects of the present invention are as follows: the present invention provides precise control over the process parameters of the heating and holding time for the curing heat treatment and the organizational level and grain size of the product after the heat treatment. The present invention designs the insulation observation hole of the box-type furnace production line and optimizes the precise control over the insulation time of the product in the furnace without opening the furnace door. The insulation time of the martensitic product processed by the box-type furnace production line is further quantitatively managed through statistical analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of an embodiment of the present invention; Figure 2 It is a structural schematic diagram of the observation hole of the present invention; Figure 3 is a process flow chart of the heat treatment process of the bearing ring of the present invention; In the figure: 100, furnace shell, 110, furnace door, 120, inspection door, 130, furnace wall, 131, first grating, 132, second grating, 133, third grating, 134, fourth grating, 300, observation hole, 310, protective tube, 320, protective cover, 321, exhaust pipe, 330, hole sleeve, 331, heat insulation steel plate, 332, connecting rod, 333, sealing ring, 340, glass mirror, 400, Thermocouple installation 400, 500. Waste gas combustion pipeline system, 600, insulation bricks, 700, thermal insulation cotton, A. Detection range of the first beam grating, B. Detection range of the second beam grating, C. Overlapping range, D. Field of view range. DETAILED DESCRIPTION

[0017] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0018] like Figure 1 , Figure 2 As shown, a heat treatment box furnace in an embodiment of the present invention comprises a furnace shell 100, a first grating 131, a second grating 132, a third grating 133, a fourth grating 134 and an observation hole 300. A furnace door 110 is arranged on one side of the furnace shell 100, and an inspection door 120 is arranged on the other side; the first grating 131 and the second grating 132 are respectively arranged on the furnace walls 130 on both sides, and the first grating 131 and the second grating 132 are arranged along the axisymmetric center line of the furnace shell 100. The first grating 131 and the second grating 132 form a group of opposing gratings 1 (photoelectric switches); the third grating 133 and the fourth grating 134 are arranged on the furnace shell 100. The gratings 134 are respectively arranged on the furnace walls 130 on both sides, the third grating 133 and the fourth grating 134 are arranged along the axially symmetrical center line of the furnace shell 100, and the third grating 133 and the fourth grating 134 form a group of opposite-beam gratings 2 (photoelectric switches); the material tray is driven back and forth in the furnace shell 100 through rollers and a transmission system, and the range of the back-and-forth transmission of the material tray is the range C where the detection range A of the opposite-beam grating 1 and the detection range B of the opposite-beam grating 2 overlap; the observation hole 300 is obliquely arranged on the furnace wall 130 on one side, and the overlapping range C and the furnace wall 130 on the other side are observed through the observation hole 300.

[0019] It should be noted that the inspection door 120 is closed and sealed during normal production. When the equipment is inspected, it is opened for inspection, and the material tray moves back and forth in the furnace shell 100 through rollers and a transmission system.

[0020] In one embodiment, the detection range A of the first opposing grating is smaller than the distance between the first opposing grating and the second opposing grating.

[0021] In one embodiment, the detection range B of the second opposing grating is smaller than the distance between the first opposing grating and the second opposing grating.

[0022] In one embodiment, the observation hole 300 includes a protective tube 310, a protective cover 320, a hole sleeve 330 and a glass mirror 340. One end of the protective cover 320 is arranged with the protective tube 310, and the other end of the protective cover 320 is operably associated with the hole sleeve 330. The glass mirror 340 is arranged at one end of the hole sleeve 330 away from the protective cover 320. The glass mirror 340 is made of high-temperature resistant glass and is used for the observation hole 300 of a heat treatment heating furnace with a temperature of 300°C-1200°C.

[0023] In one embodiment, the inner wall of the protective tube 310 is provided with insulation cotton 700, and the insulation cotton 700 is used to prevent the heat loss in the furnace. An exhaust pipe 321 is provided on the outer side of the protective cover 320, and a pipe cap is provided at the pipe mouth of the exhaust pipe 321. Under normal conditions, the exhaust pipe 321 is not opened for use, but can be opened during maintenance. An insulating steel plate 331 is provided in the hole sleeve 330 to prevent the heat loss in the furnace. The insulating steel plate 331 controls the switch through a connecting rod 332. One end of the connecting rod 332 is inserted into the hole sleeve 330 and connected to the insulating steel plate 331, and the other end of the connecting rod 332 extends out of the hole sleeve 330. When it is necessary to observe the heat preservation of the product, the connecting rod 332 is lifted and the insulating steel plate 331 is opened; when it is not necessary to observe the heat preservation of the product, the connecting rod 332 is lowered and the insulating steel plate 331 is closed.

[0024] Furthermore, a sealing ring 333 is provided at one end of the hole sleeve 330 close to the glass mirror 340, which is a high temperature resistant sealing ring 333 and is used for sealing the observation hole 300 of the heat treatment heating furnace at a temperature of 300°C-1200°C.

[0025] Furthermore, the inclination angle between the observation hole 300 and the furnace wall 130 is 72°, the viewing angle of the observation hole 300 is 45°, and the diameter of the observation hole 300 is 65 mm.

[0026] It should be noted that the furnace wall 130 of the heat treatment box furnace has a height of 2960 mm, and the observation hole 300 is located at 1 / 2 of the furnace wall 130 .

[0027] In one embodiment, a thermocouple installation location 400 and a waste combustion pipeline system are provided on the furnace shell 100. The thermocouple installation location 400 is provided on one side of the inspection door 120, and the waste combustion pipeline system is provided on the other side of the inspection door 120. The waste combustion pipeline system is used to volatilize the waste replaced in the heating furnace by burning through an open flame, and the thermocouple installation location 400 is used to detect the temperature in the heating furnace.

[0028] In one embodiment, the furnace wall inside the furnace shell 100 is provided with insulation bricks 600 and insulation cotton 700, the insulation cotton 700 is provided outside the insulation bricks 600, and the furnace shell 100 is provided outside the insulation cotton 700.

[0029] See attached Figure 1When loading, the ring or workpiece is placed on the tray, the tray is 1800mm long *1800mm wide and 10mm high. The grating is used to detect the tray and determine its position. The tray is driven from left to right by the roller. When it just enters the heating furnace, it is detected by grating 3 and grating 4 and then stops in the detection range B of the opposite grating 2. After a delay of 2 seconds, the roller rotates in the opposite direction, stops after being detected by grating 1 and grating 2, and rotates in the opposite direction after a delay of 2 seconds. This is repeated until the material is discharged after the heating time is completed. The repeated transmission is to protect the roller from bending easily under high temperature. Therefore, the workpiece moves between the detection range A of the opposite grating 1 and the detection range B of the opposite grating 2 in the furnace. During the processing, the field of view D of the observation hole 300 includes the detection range A of the opposite grating 1 and the detection range B of the opposite grating 2. The furnace wall (equipment furnace wall 130) can be seen at the same time during the movement of the tray. When heating and heat preservation, observe whether the color of the workpiece is consistent with that of the furnace wall under high temperature, so as to confirm the heat preservation time of the workpiece and avoid overheating of the bearing ring due to too long heat preservation time.

[0030] It should be noted that the traditional heat treatment box furnace for large spherical bearing ring heat treatment process flow is loading - pre-cleaning - heating and insulation - quenching - post-cleaning - deep cooling - tempering - unloading, austenitizing treatment during heating and insulation: 860℃-880℃, carbon potential 0.70%-0.90%, total austenitizing heating time: 6 hours, including salt bath quenching: 170℃-180℃ 15min-45min, cold treatment: 0-7℃, tempering: 180℃-200℃, 8h-10h, post-cleaning includes air cooling, cleaning and drying, including air cooling 20min-60min, cleaning 10min-40min, drying 10min-30min, in order to observe the state of the bearing ring during insulation, it can only be observed by opening the furnace door 110 or through the maintenance port behind the furnace door 110.

[0031] After processing, the above-mentioned physical rings were dissected and tested and it was found that the surface structure was overheated. When observing the insulation through the maintenance port of the box furnace during the process, it was found that the color state of the insulation after 2 hours and 6 hours of heating was the same. Therefore, it was impossible to accurately determine the insulation of the product through the maintenance port. Furthermore, observation by opening the furnace door 110 would affect the heating of the bearing ring.

[0032] like Figure 3 As shown, the bearing ring heat treatment process using the heat treatment box furnace in the above embodiment includes the following steps: S100, pre-cleaning, including cleaning and drying, the bearing ring is first cleaned and then dried; The cleaning temperature is 40°C and the time is 20-30 minutes. The specific cleaning method is spraying, and the cleaning liquid is a metal detergent.

[0033] The drying temperature is 110℃ and the time is 20-30min; the drying is carried out by electric heating. S200, heating and heat preservation, heating the bearing ring first and then heat preservation; Heat the bearing ring to 860℃, heating time is 2h, holding time is 1h, process nitrogen 10-15L / h, propane: 0.4-0.8m3 / h in the heating furnace heating stage, process nitrogen 5-10L / h, propane: 0.8-1.2m3 / h to reach the set temperature in the holding stage; It should be noted that during the loading, heating and insulation of the bearing ring, the insulation time of the box-type furnace heating furnace is the martensite insulation time = product effective wall thickness * 0.7-1.2.

[0034] S300, quenching, cool the bearing ring to 175℃ and keep it warm. The first quenching time is 20 minutes, the stirring speed is 1600 rpm, and the second quenching time is 10 minutes, the stirring speed is 400 rpm; quenching is carried out using quenching nitrate, and the composition of the quenching nitrate is: (50% KNO3 + 50% NaNO2) ± 5%.

[0035] S400, post-cleaning, including air cooling, cleaning and drying, air cooling for 40 minutes, cleaning for 25 minutes, and drying for 20 minutes; after quenching, the product surface temperature is 175 degrees Celsius and needs to be moved to the air cooling tank to cool the product surface by fan cooling. When the temperature drops to 40-50 degrees Celsius, it enters the post-cleaning to foam and clean the salt on the product surface, and finally blow dry, using a strong fan to blow away the water stains on the surface.

[0036] S500, deep cooling, cools the bearing ring to 7°C and keeps it warm, the processing time is 50 minutes; deep cooling uses liquid nitrogen to cool down.

[0037] S600, temper the bearing ring at high temperature to 200℃ and keep it warm for 8 hours; tempering is carried out in a salt bath, the salt bath medium has the same composition as the quenching nitrate in the quenching tank, and the tempering time is generally 8-10 hours.

[0038] It should be noted that the present invention observed the product insulation analysis through the insulation hole on the rear wall of the box-type furnace in the early stage and found that the product insulation time could not be determined here, resulting in the ring heating time being too long and the tissue being overheated, which could not meet the technical requirements. Therefore, the box-type furnace insulation observation hole 300 is set on the side furnace wall 130, and the observation hole 300 is designed at an angle with the furnace wall 130 to maximize the observation field of view in the furnace (see Figure 2 ), and then the bearing ring is heat treated using the above process route, with a heating time of 2 hours and a holding time of 1 hour. After the product is out of the furnace, the organization test finds that the martensitic organization is at level 3, which meets the industry standard JB / T1255-2014 version 1-4 levels.

[0039] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0040] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0041] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] In the present invention, unless otherwise clearly specified and limited, the first feature "above" or "below" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature may be that the first feature is directly above or obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature "below", "below" and "below" the second feature may be that the first feature is directly below or obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature. It should be noted that when an element is referred to as "fixed to" or "set on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

Claims

1. A heat treatment box furnace, comprising a furnace shell, a furnace door on one side and an inspection door on the other side, characterized in that: It also includes a first grating and a second grating, wherein the first grating and the second grating are respectively arranged on the furnace walls on both sides, the first grating and the second grating are arranged along the axisymmetric center line of the furnace shell, and the first grating and the second grating form a set of opposing gratings; A third grating and a fourth grating, wherein the third grating and the fourth grating are respectively arranged on the furnace walls on both sides, the third grating and the fourth grating are arranged along the axially symmetrical center line of the furnace shell, and the third grating and the fourth grating form a set of opposing gratings 2; The material tray moves back and forth in the furnace shell, and the range of the material tray's back and forth movement is the range where the detection range of the first opposing grating and the detection range of the second opposing grating overlap; An observation hole is obliquely arranged on the furnace wall on one side, through which the overlapping range and the furnace wall on the other side can be observed.

2. The heat treatment box furnace according to claim 1, characterized in that: The detection range of the first opposing grating is smaller than the distance between the first opposing grating and the second opposing grating.

3. The heat treatment box furnace according to claim 1, characterized in that: The detection range of the second opposing grating is smaller than the distance between the first opposing grating and the second opposing grating.

4. The heat treatment box furnace according to claim 1, characterized in that: The observation hole comprises a protective tube, a protective cover, a hole sleeve and a glass mirror. One end of the protective cover is arranged with the protective tube, the other end of the protective cover is operably associated with the hole sleeve, and the glass mirror is arranged at one end of the hole sleeve away from the protective cover.

5. The heat treatment box furnace according to claim 4, characterized in that: The inner wall of the protective tube is provided with thermal insulation cotton, the outer side of the protective cover is provided with an exhaust pipe, the pipe mouth of the exhaust pipe is provided with a pipe cap, and the hole sleeve is provided with an insulating steel plate. The insulating steel plate controls the switch through a connecting rod, one end of the connecting rod is inserted into the hole sleeve and connected to the insulating steel plate, and the other end of the connecting rod extends out of the hole sleeve.

6. The heat treatment box furnace according to claim 4, characterized in that: A sealing ring is arranged at one end of the hole sleeve close to the glass mirror.

7. The heat treatment box furnace according to claim 1, characterized in that: The inclination angle between the observation hole and the furnace wall is 72°, the viewing angle of the observation hole is 45°, and the diameter of the observation hole is 65 mm.

8. The heat treatment box furnace according to claim 1, characterized in that: A thermocouple installation location and a waste combustion pipeline system are arranged on the furnace shell. The thermocouple installation location is arranged on one side of the inspection door, and the waste combustion pipeline system is arranged on the other side of the inspection door.

9. The heat treatment box furnace according to claim 1, characterized in that: The furnace wall inside the furnace shell is provided with insulation bricks and insulation cotton, the insulation cotton is arranged outside the insulation bricks, and the furnace shell is arranged outside the insulation cotton.

10. A bearing ring heat treatment process using a heat treatment box furnace as claimed in any one of claims 1 to 9, characterized in that: Steps include S100, pre-cleaning, including cleaning and drying, the bearing ring is first cleaned and then dried; The cleaning temperature is 30-40℃ and the cleaning time is 20-30min; The drying temperature is 110°C and the time is 20-30 minutes; S200, heating and heat preservation, heating the bearing ring first and then heat preservation; Heat the bearing ring to 820-860℃ for 2h, then start heat preservation. Observe the contrast between the color of the bearing ring at high temperature and the color of the furnace wall through the observation hole. When the color of the bearing ring at high temperature is consistent with the color of the furnace wall, it is confirmed that the heat preservation time of the workpiece is terminated. S300, quenching, cooling the bearing ring to 175℃ and keeping it warm for a certain period of time; S400, post-cleaning, including air cooling, cleaning and drying, cooling the bearing ring to 40-50℃, air cooling for 20min-60min, cleaning for 10min-40min, and drying for 10min-30min; S500, deep cooling, cooling the bearing ring to 0-7℃ and keeping it warm, the processing time is 50min; S600, temper the bearing ring at high temperature to 180-200℃ and keep it warm. The processing time is 8h.

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