Nitrogen carburizing heat treatment process

Abstract

The invention provides a carburizing and nitriding heat treatment process. The carburizing and nitriding heat treatment process comprises the following steps: S1, establishing optimal nitriding heat treatment parameters of a rolling bearing; s2, the ammonia gas flow in the carburizing nitrogen heat treatment process is planned, the optimal ammonia gas flow is obtained, and reference parameters are obtained; s3, the rolling bearing is subjected to heat treatment through the optimal ammonia gas flow, and a primary recycled product is obtained; s4, acquiring actual parameters of the primary recycled product; s5, comparing the reference parameters with the actual parameters, and if the primary return residual ausfield iron content (RA%) and the primary return carburizing and nitriding layer depth of the channel diameter surface of the primary return product are within the ranges of the first standard value and the second standard value respectively and the primary return life parameter is not smaller than the second reference life parameter, judging that the primary return product is the primary return product. If the primary return life parameter is at least within the range of the second reference life parameter and the first reference life parameter, the primary return product is qualified; and S6, importing field production parameters. The rolling bearing is high in foreign matter resistance, and the service life is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment, and in particular to a carbonitriding heat treatment process. Background Art

[0002] At present, SUJ2 bearing steel has good comprehensive performance and is usually used to produce rolling bearings. Lubricant is usually added between the outer ring and the inner ring of the rolling bearing to increase the life of the rolling bearing. However, during the operation of the rolling bearing, foreign matter, especially hard foreign matter, is inevitably mixed into the lubricant. Hard foreign matter can easily cause the inner ring, outer ring, and ball to malfunction, damage, and fall off, which greatly reduces their life. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a carbonitriding heat treatment process in order to overcome the defect of the prior art rolling bearing having a low life span against foreign matter.

[0004] The present invention solves the above technical problems through the following technical solutions:

[0005] The present invention provides a carbonitriding heat treatment process, which is applied to a rolling bearing. The rolling bearing is made of SUJ2 bearing steel. The carbonitriding heat treatment process comprises the following steps:

[0006] S1. Establishing optimal nitriding heat treatment parameters for the rolling bearing, wherein the optimal nitriding heat treatment parameters include an optimal ammonia flow rate;

[0007] S2, planning the ammonia flow rate in the carbonitriding heat treatment process, and obtaining the optimal ammonia flow rate; obtaining reference parameters, wherein the reference parameters include a first reference life parameter obtained by performing a foreign body intrusion life test on a hand part, a residual austenitic iron content (RA%) on the groove diameter surface of the rolling bearing, a carbonitriding layer depth, and a first standard value, a second standard value, and a second reference life parameter corresponding to the life parameters, wherein the first reference life parameter is not less than the second reference life parameter;

[0008] S3, using the optimal ammonia flow rate to heat treat the rolling bearing and obtain a primary product;

[0009] S4, obtaining actual parameters of the first return product, wherein the actual parameters include the first return life parameter obtained by performing the foreign matter intrusion life test on the first return product, the first return residual austenite content (RA%) of the groove diameter surface of the first return product, and the depth of the first return carbonitriding layer;

[0010] S5, comparing the reference parameters with the actual parameters of the first return product, if the first return residual austenite iron content (RA%) and the first return carbonitriding layer depth of the groove diameter surface of the first return product are respectively within the range of the first standard value and the second standard value, and the first return life parameter is not less than the second reference life parameter, and the first return life parameter is at least between the second reference life parameter and the first reference life parameter, then the first return product is qualified;

[0011] S6. Importing on-site production parameters, using the optimal ammonia flow rate to process the SUJ2 bearing steel to produce the rolling bearing.

[0012] Preferably, S3 also includes the following steps:

[0013] S21, in the heating stage before quenching in the carbonitriding heat treatment process, use the optimal ammonia flow rate to heat treat the rolling bearing and obtain the initial product.

[0014] Preferably, after the rolling bearing is heat treated using the optimal ammonia flow rate in the heating stage before quenching in the carbonitriding heat treatment process, the groove surface of the rolling bearing is ground and polished to obtain the initial product.

[0015] Preferably, the first standard value is 20-35%, and the second standard value is 0.3-0.5 mm.

[0016] Preferably, the groove diameter surface of the counterpart is the contact surface between the rolling element of the counterpart and the inner ring and the outer ring, and the groove diameter surface of the initial return product is the contact surface between the rolling element of the initial return product and the inner ring and the outer ring.

[0017] Preferably, the optimal nitriding heat treatment parameters further include quenching temperature, carbon dioxide concentration and oil temperature, and S2 includes the following steps:

[0018] S21. Keep the quenching temperature, the carbon dioxide concentration and the oil temperature consistent, and select a plurality of different ammonia flow rates to heat treat the inner rings and outer rings of several rolling bearings, and respectively detect the residual austenite content (RA%) of the inner ring and the residual austenite content (RA%) of the outer ring on the groove diameter surfaces corresponding to the inner rings and outer rings of several rolling bearings.

[0019] Preferably, the step S21 includes the following steps:

[0020] S211, selecting several positions on the inner rings and outer rings of several rolling bearings, and detecting several inner ring residual austenitic iron contents (RA%) and outer ring residual austenitic iron contents (RA%) of the groove diameter surfaces corresponding to the inner rings and outer rings at the several positions for several times, respectively obtaining the average values ​​of the inner ring residual austenitic iron contents (RA%) and the outer ring residual austenitic iron contents (RA%) at the several positions and comparing them with the first standard value;

[0021] S212, selecting the ammonia flow rate corresponding to the average value of the residual austenitic iron content (RA%) of the inner ring and the residual austenitic iron content (RA%) of the outer ring that does not exceed the first standard value as the optimal ammonia flow rate.

[0022] Preferably, the optimal ammonia flow rate is 10m 3 / hr.

[0023] Preferably, the life parameter is the ratio of the test life L10 to the theoretical life L10.

[0024] Preferably, the foreign matter intrusion life test on the counterpart or the first-return product is a contaminated lubricant life test performed by adding contaminated lubricant to the counterpart or the first-return product.

[0025] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0026] The positive progressive effect of the present invention is that in the present invention, by increasing the ammonia flow rate during the heating stage between heat treatment and quenching, the residual austenitic iron content (RA%) and the depth of the carbonitriding layer on the groove surface of the rolling bearing can be greatly increased, thereby enhancing the ability of the rolling bearing to resist hard foreign matter, thereby increasing the life of the rolling bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The figure is a flow chart of the carbonitriding heat treatment process of the present invention.

[0028] Figure 2 This is a relationship diagram between RA% and depth distance of the present invention.

[0029] Figure 3 FIG. 4 is another relationship diagram between RA% and depth distance of the present invention.

[0030] Figure 4 This is a relationship diagram of RA%, depth distance, and ammonia flow rate of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be described more clearly and completely below by way of embodiments in conjunction with the accompanying drawings, but the present invention is not limited to the scope of the embodiments.

[0032] The present invention discloses a carbonitriding heat treatment process, named 6Sigma project, which is applied to rolling bearings, such as Figure 1-Figure 4 As shown, the material of the rolling bearing is SUJ2 bearing steel, and the carbonitriding heat treatment process includes the following steps:

[0033] S1. Establishing optimal nitriding heat treatment parameters for the rolling bearing, wherein the optimal nitriding heat treatment parameters include an optimal ammonia flow rate;

[0034] S2, planning the ammonia flow rate in the carbonitriding heat treatment process, and obtaining the optimal ammonia flow rate; obtaining reference parameters, wherein the reference parameters include a first reference life parameter obtained by performing a foreign body intrusion life test on a hand part, a residual austenitic iron content (RA%) on the groove diameter surface of the rolling bearing, a carbonitriding layer depth, and a first standard value, a second standard value, and a second reference life parameter corresponding to the life parameters, wherein the first reference life parameter is not less than the second reference life parameter;

[0035] S3, using the optimal ammonia flow rate to heat treat the rolling bearing and obtain a primary product;

[0036] S4, obtaining actual parameters of the first return product, wherein the actual parameters include the first return life parameter obtained by performing the foreign matter intrusion life test on the first return product, the first return residual austenite content (RA%) of the groove diameter surface of the first return product, and the depth of the first return carbonitriding layer;

[0037] Specifically, for 6 first-time products, numbered BA-19011A to BA-19016A, the life hours of the outer ring peeling (initial life parameter) and RA% were measured at 0.00mm on the outer ring groove diameter surface, and multiple sets of data with RA% and life hours of outer ring peeling (hrs) corresponding to each other were obtained: 16, 69; 14.7, 67; 16.1, 94; 17.2, 80; 28.4, 115; 15.3, 44. By analyzing this set of data, it was found that RA% was positively correlated with the initial life parameter, and the correlation R-sq was measured to be 61.94%.

[0038] S5, comparing the reference parameters with the actual parameters of the first return product, if the first return residual austenite iron content (RA%) and the first return carbonitriding layer depth of the groove diameter surface of the first return product are respectively within the range of the first standard value and the second standard value, and the first return life parameter is not less than the second reference life parameter, and the first return life parameter is at least between the second reference life parameter and the first reference life parameter, then the first return product is qualified;

[0039] Specifically, the theoretical life L10 of the 6205 rolling bearing is 133.71 hrs, and the life parameter, namely, the life test ratio = test life L10 / theoretical life L10. Through the same foreign body intrusion life test, 6 types of bearings were tested and the following data were obtained:

[0040] The test life L10 of the general product (SUJ2) of 6205 without carbonitriding is 26.35hrs, and the life test ratio is 0.2;

[0041] The test life L10 of 2A-6205 (2A treatment) is 56.18 hrs, and the life test ratio is 0.42;

[0042] The test life L10 of 2A1-6205 (2A1 treatment) is 71.11 hrs, and the life test ratio is 0.53 (second reference life parameter);

[0043] The test life L10 of 2A1-6205 (6Sigma) is 112.04 hrs, and the life test ratio is 0.84;

[0044] The test life L10 of TPI CSB205 is 116.19 hrs, and the life test ratio is 0.87 (first reference life parameter);

[0045] The test life L10 of NTN TMB205 is 125.64 hrs, and the life test ratio is 0.94.

[0046] The first reference life parameter is greater than the second reference life parameter.

[0047] From this, it can be seen that in the 4B type life test of the present invention, which is also the foreign body intrusion life test, the 2A-6205 rolling bearing with carbonitriding (2A treatment) will have a better life performance than the general 6205 rolling bearing without carbonitriding (SUJ2). And the 2A1-6205 rolling bearing treated with 2A1 with increased carbonitriding time can further increase the life. The 2A1-6205 (6Sigma) rolling bearing of the present invention, which increases the ammonia flow rate (m3 / hr) from 5 to 10 based on the 2A1 treatment, the residual austenitic iron content (RA%) of the inner ring and the residual austenitic iron content (RA%) of the outer ring on the groove surface of the inner ring and the outer ring are both increased from less than 20% to 20-35%, and the 4B type life ratio is increased from 0.53 to 0.84.

[0048] Increasing the ammonia flow rate during the heating phase can increase the residual austenite content RA% on the groove surface (RA%↑), thereby improving the life performance of the 4B type foreign body intrusion.

[0049] S6. Importing on-site production parameters, using the optimal ammonia flow rate to process the SUJ2 bearing steel to produce the rolling bearing.

[0050] In this embodiment, S3 further includes the following steps:

[0051] S21, in the heating stage before quenching in the carbonitriding heat treatment process, use the optimal ammonia flow rate to heat treat the rolling bearing and obtain the initial product.

[0052] In this embodiment, after the rolling bearing is heat treated using the optimal ammonia flow rate in the heating stage before quenching in the carbonitriding heat treatment process, the groove surface of the rolling bearing is ground and polished to obtain the initial product.

[0053] The production process of rolling bearings includes feeding, heating, quenching, cleaning, tempering, rust prevention, counting and packaging. 3 / hr increased to 10m 3 / hr, increased by 1 times.

[0054] Specifically, the depth distances of the outer ring and the inner ring refer to the distances from the outer surface of the carbonitriding layer to the inside. 3 / hr、10m 3 / hr, quenching temperature is 850℃, carbon dioxide (CO2%) is 0.4, oil temperature is 120℃. Taking the first return product No. BA-19011A as an example, the ammonia flow rate is 5m 3 / hr、10m 3 / hr were named 2A1-6205 (2A1 treatment) and 2A1-6205 (6Sigma), and the depth distance (mm) and RA% data of multiple groups of outer rings were obtained. Figure 2 The above is 2A1-6205 (2A1 treatment) at 5m 3 The relationship between the depth distance and the residual austenitic iron content (RA%) of the inner ring and the residual austenitic iron content (RA%) of the outer ring under the treatment condition of / hr, such as Figure 3 The figure shows 2A1-6205 (6Sigma) at 10m 3 The relationship between the depth distance and the residual austenitic iron content (RA%) of the inner ring and the residual austenitic iron content (RA%) of the outer ring under the treatment condition of / hr. Figure 4 The figure shows the relationship between RA%, depth distance and ammonia flow rate, wherein A and B both represent ammonia flow rates, and ammonia flow rate A>ammonia flow rate B.

[0055] It can be seen that the RA% on the surface of the groove surface should be between 20% and 35%. Since the RA% will decrease with the increase of the depth (mm) of the carbonitriding layer, considering that the groove surface will be ground and polished (grinding replacement amount) from the hot finished product to the finished product, the deepest depth (mm) of the groove surface of the hot finished product with RA%>20% should be selected, or the depth (mm) of RA%=20% should be more than 0.20 (the maximum grinding replacement amount does not exceed this value) to ensure that the RA% on the groove surface after grinding and polishing can still be between 20% and 35%. The purpose of increasing the ammonia flow rate is to increase the depth of the nitriding layer, that is, the depth of the carbonitriding layer, which is the key to increasing the service life.

[0056] In this embodiment, the first standard value is 20-35%, and the second standard value is 0.3-0.5 mm.

[0057] In this embodiment, the groove diameter surface of the counterpart is the contact surface between the rolling element of the counterpart and the inner and outer rings, and the groove diameter surface of the initial return product is the contact surface between the rolling element of the initial return product and the inner and outer rings.

[0058] In this embodiment, the optimal nitriding heat treatment parameters also include quenching temperature, carbon dioxide concentration and oil temperature, and S2 includes the following steps:

[0059] S21. Keep the quenching temperature, the carbon dioxide concentration and the oil temperature consistent, and select a plurality of different ammonia flow rates to heat treat the inner rings and outer rings of several rolling bearings, and respectively detect the residual austenite content (RA%) of the inner ring and the residual austenite content (RA%) of the outer ring on the groove diameter surfaces corresponding to the inner rings and outer rings of several rolling bearings.

[0060] In this embodiment, the following steps are included in S21:

[0061] S211, selecting several positions on the inner rings and outer rings of several rolling bearings, and detecting several inner ring residual austenitic iron contents (RA%) and outer ring residual austenitic iron contents (RA%) of the groove diameter surfaces corresponding to the inner rings and outer rings at the several positions for several times, respectively obtaining the average values ​​of the inner ring residual austenitic iron contents (RA%) and the outer ring residual austenitic iron contents (RA%) at the several positions and comparing them with the first standard value;

[0062] S212, selecting the ammonia flow rate corresponding to the average value of the residual austenitic iron content (RA%) of the inner ring and the residual austenitic iron content (RA%) of the outer ring that does not exceed the first standard value as the optimal ammonia flow rate.

[0063] Specifically, multiple positions were selected at the surface of the outer ring and inner ring of the first run product at a depth of 0.00 mm, and multiple RA% values ​​were measured at each position, and the average value was taken. The first run product 2A1-6205 (6Sigma) of BA-19011A was tested for RA% on the surface of the groove surface of the inner ring and the surface of the groove surface of the outer ring, and multiple sets of data at multiple positions were obtained:

[0064] Inner ring position 1: 27.2, 28.6, 27.5, 22.1, 24.5, the average is 26.0, and the standard deviation is 2.64;

[0065] Inner ring position 2: 28.3, 27.4, 27.2, 21.9, 20.5, the average is 25.1, and the standard deviation is 3.58;

[0066] Inner ring position three: 23.2, 20.6, 23.1, 22.3, 21.9, the average is 22.2, and the standard deviation is 1.06;

[0067] Outer ring position 1: 34.5, 32, 32.3, 33.4, 34.2, the average is 33.3, and the standard deviation is 1.11;

[0068] Outer ring position 2: 30.9, 30.9, 33.9, 30.1, 32.3, the average is 31.6, and the standard deviation is 1.50;

[0069] Outer ring position three: 29.8, 33.1, 32, 33.8, 31.3, the average is 32, and the standard deviation is 1.56.

[0070] It can be seen that the ammonia flow rate is 10m 3 / hr, RA% is between 20 and 35%, which meets the requirements. The optimal ammonia flow rate is 10m3 / hr.

[0071] In this embodiment, the optimal ammonia flow rate is 10m 3 / hr.

[0072] Specifically, under the same conditions of other optimal nitriding heat treatment parameters, when the ammonia flow rate was adjusted from 5m3 / hr to 10m3 / hr, the ratio of the experimental life L10 to the theoretical life L10 increased from 0.53 to 0.84, an increase of 58.5%.

[0073] In this embodiment, the life parameter is the ratio of the test life L10 to the theoretical life L10.

[0074] In this embodiment, the foreign matter intrusion life test on the counterpart or the first-return product is a contaminated lubricant life test performed by adding contaminated lubricant to the counterpart or the first-return product.

[0075] Specifically, for 2A1-6205 (6Sigma) rolling bearing, the test conditions are: speed 4000rpm, radial load 450×2kgw, lubricating oil Turbine56, oil temperature 60-80℃ (equilibrium temperature after natural heating), foreign matter type is alumina, particle size 100#, HV2400, mixed amount is 0.001g. Multiple sets of data on running time (hrs) and failure mode are obtained: 253, inner ring peeling; 253, suspended; 118, outer ring peeling, 118, suspended; 111, outer ring peeling; 111, suspended; 157, inner ring peeling; 157, suspended. Take the basic rated dynamic load of 2A1-6205 (6Sigma) as 1430. The slope e of 2A1-6205 (6Sigma) rolling bearing is 3.36, the intercept b is -8.23, the depth of the carbonitriding layer of the outer ring and the inner ring is 0.49mm and 0.38mm respectively, the residual austenitic iron content (RA%) of the outer ring and the residual austenitic iron content (RA%) of the inner ring are 32.00% and 24.40% respectively, and the test life L10 is calculated to be 112.04, the test life L50 is 196.24, the rated life is 133.71, and the rated life ratio of the test life L10 is 0.84, that is, the life parameter is 112.04 / 133.71=0.84. The formula for L10 is:

[0076]

[0077] Among them: n is the spindle speed, C is the basic dynamic rated load, and P is the test load, which is the radial load here.

[0078] Although the specific embodiments of the present invention are described above, it should be understood by those skilled in the art that this is only for illustration and the protection scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A carbonitriding heat treatment process, applied to rolling bearings, characterized in that: The rolling bearing is made of SUJ2 bearing steel, and the carbonitriding heat treatment process includes the following steps: S1. Establishing optimal nitriding heat treatment parameters for the rolling bearing, wherein the optimal nitriding heat treatment parameters include an optimal ammonia flow rate; S2, planning the ammonia flow rate in the carbonitriding heat treatment process to obtain the optimal ammonia flow rate; Obtaining reference parameters, the reference parameters including a first reference life parameter obtained by performing a foreign body intrusion life test on a hand part, a residual austenitic iron content (RA%) of a groove diameter surface of the rolling bearing, a carbonitriding layer depth, and a first standard value, a second standard value, and a second reference life parameter corresponding to the life parameters, wherein the first reference life parameter is not less than the second reference life parameter; S3, using the optimal ammonia flow rate to heat treat the rolling bearing and obtain a primary product; S4, obtaining actual parameters of the first return product, wherein the actual parameters include the first return life parameter obtained by performing the foreign matter intrusion life test on the first return product, the first return residual austenite content (RA%) of the groove surface of the first return product, and the depth of the first return carbonitriding layer; S5, comparing the reference parameters with the actual parameters of the first return product, if the first return residual austenite iron content (RA%) and the first return carbonitriding layer depth of the groove diameter surface of the first return product are respectively within the range of the first standard value and the second standard value, and the first return life parameter is not less than the second reference life parameter, and the first return life parameter is at least between the second reference life parameter and the first reference life parameter, then the first return product is qualified; S6. Importing on-site production parameters, using the optimal ammonia flow rate to process the SUJ2 bearing steel to produce the rolling bearing.

2. The carbonitriding heat treatment process according to claim 1, characterized in that: The S3 also includes the following steps: S21, in the heating stage before quenching in the carbonitriding heat treatment process, use the optimal ammonia flow rate to heat treat the rolling bearing and obtain the initial product.

3. The carbonitriding heat treatment process according to claim 2, characterized in that: After the rolling bearing is heat treated using the optimal ammonia flow rate during the heating stage before quenching in the carbonitriding heat treatment process, the groove surface of the rolling bearing is ground and polished to obtain the initial product.

4. The carbonitriding heat treatment process according to claim 1, characterized in that: The first standard value is 20-35%, and the second standard value is 0.3-0.5 mm.

5. The carbonitriding heat treatment process according to claim 1, characterized in that: The groove diameter surface of the counterpart is the contact surface between the rolling element of the counterpart and the inner ring and the outer ring, and the groove diameter surface of the initial return product is the contact surface between the rolling element of the initial return product and the inner ring and the outer ring.

6. The carbonitriding heat treatment process according to claim 5, characterized in that: The optimal nitriding heat treatment parameters also include quenching temperature, carbon dioxide concentration and oil temperature, and S2 includes the following steps: S21. Keep the quenching temperature, the carbon dioxide concentration and the oil temperature consistent, and select a plurality of different ammonia flow rates to heat treat the inner rings and outer rings of several rolling bearings, and respectively detect the residual austenite content (RA%) of the inner ring and the residual austenite content (RA%) of the outer ring on the groove diameter surfaces corresponding to the inner rings and outer rings of several rolling bearings.

7. The carbonitriding heat treatment process according to claim 6, characterized in that: The S21 includes the following steps: S211, selecting several positions on the inner rings and outer rings of several rolling bearings, and detecting several inner ring residual austenitic iron contents (RA%) and outer ring residual austenitic iron contents (RA%) of the groove diameter surfaces corresponding to the inner rings and outer rings at the several positions for several times, respectively obtaining the average values ​​of the inner ring residual austenitic iron contents (RA%) and the outer ring residual austenitic iron contents (RA%) at the several positions and comparing them with the first standard value; S212, selecting the ammonia flow rate corresponding to the average value of the residual austenitic iron content (RA%) of the inner ring and the residual austenitic iron content (RA%) of the outer ring that does not exceed the first standard value as the optimal ammonia flow rate.

8. The carbonitriding heat treatment process according to claim 7, characterized in that: The optimal ammonia flow rate is 10m 3 / hr.

9. The carbonitriding heat treatment process according to claim 1, characterized in that: The life parameter is the ratio of the test life L10 to the theoretical life L10.

10. The carbonitriding heat treatment process according to claim 1, characterized in that: The foreign matter intrusion life test on the counterpart or the first-return product is a contaminated lubricant life test performed by adding contaminated lubricant to the counterpart or the first-return product.

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