High-carbon chromium roller workpiece and multi-stage heat treatment preparation process thereof

Abstract

The invention relates to the technical field of heat treatment of high-carbon-chromium materials, in particular to a high-carbon-chromium roller workpiece and a multi-stage heat treatment preparation process thereof. The workpiece is prepared by the process. The process comprises the following steps: loading a plurality of high-carbon chromium roller workpieces into a heating furnace in a staggered arrangement manner; carrying out first heat treatment on the high-carbon chromium roller workpiece; carrying out second heat treatment on the high-carbon chromium roller workpiece; performing third heat treatment on the high-carbon chromium roller workpiece; carrying out salt bath quenching treatment on the high-carbon chromium roller workpiece; the high-carbon-chromium roller workpiece is subjected to water quenching treatment; and performing post-treatment on the high-carbon chromium roller workpiece to obtain a target high-carbon chromium roller workpiece. According to the method, the core hardness of the high-carbon-chromium roller workpiece can be improved, and the hardness gradient attenuation degree and the retained austenite content can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment of high-carbon chromium materials, and in particular to a high-carbon chromium roller workpiece and a multi-stage heat treatment preparation process thereof. Background Art

[0002] The main bearing of the shield machine is a key core component of the tunnel boring machine. It is a large-scale bearing with low speed and heavy load, and can simultaneously withstand large axial loads, radial loads, overturning moments and other comprehensive loads. Since the main bearing of the shield machine is mainly used in harsh working conditions such as high impact, high load and large offset load, high requirements are placed on the bearing capacity of the main bearing roller and the dimensional stability during service. Therefore, the industry requires that the main bearing roller should have the characteristics of high surface hardness, high core hardness, gentle hardness gradient decay and low residual austenite content. However, the following shortcomings are prone to occur when the traditional martensitic quenching heat treatment process is used: for example, when the traditional martensitic quenching heat treatment process is used for the main bearing roller with a size of φ70* (80-120) mm, it is easy to have problems such as low core hardness (less than 50HRC), significant hardness gradient decay (gradient difference greater than 15HRC) and residual austenite content greater than 15%.

[0003] In summary, it is necessary to develop a high carbon chromium roller workpiece and its multi-stage heat treatment preparation process to solve the problems of low core hardness, significant hardness gradient attenuation and high retained austenite content in the traditional martensitic quenching heat treatment process. Summary of the invention

[0004] The object of the present invention is to provide a high carbon chromium roller workpiece and a multi-stage heat treatment preparation process thereof. The specific technical scheme is as follows: In a first aspect, the present invention provides a multi-stage heat treatment preparation process for a high carbon chromium roller workpiece, comprising: Step S1, loading a plurality of high carbon chromium roller workpieces into a heating furnace in a staggered arrangement; Step S2, performing a first heat treatment on the high carbon chromium roller workpiece; the first heat treatment comprises controlling the heating furnace to heat to a temperature of A at a first heating speed. c1 , the holding time is t1; among them, A c1 It is the temperature at which the structure of the high carbon chromium roller workpiece begins to transform into austenite; Step S3, performing a second heat treatment on the high carbon chromium roller workpiece; the second heat treatment comprises controlling the heating furnace to heat to a temperature of A at a second heating rate. c1 +30~A c1 +50℃, holding time is t2; Step S4, performing a third heat treatment on the high carbon chromium roller workpiece; the third heat treatment comprises controlling the heating furnace to heat to a temperature of A at a third heating rate.c1 +60~A c1 +80℃, holding time is t3; Step S5, performing salt bath quenching treatment on the high carbon chromium roller workpiece; wherein the salt bath quenching temperature is M s -20~M s -10℃, salt bath quenching time is t4; M s It is the temperature at which the high carbon chromium roller workpiece begins to produce martensite structure; Step S6, performing water quenching treatment on the high carbon chromium roller workpiece; the water quenching temperature is 0-5°C, and the water quenching time is t5; Step S7, post-processing the high carbon chromium roller workpiece to obtain a target high carbon chromium roller workpiece.

[0005] Optionally, the first heating rate used in step S2 is 90-110° C. / h, and the insulation time t1 used is 25-35 min.

[0006] Optionally, the second heating rate used in step S3 is 55-65° C. / h, and the insulation time t2 used is 8-12 min.

[0007] Optionally, the third heating rate used in step S4 is 77-83° C. / h, and the insulation time t3 used is 8-12 min.

[0008] Optionally, the salt bath quenching time t4 used in step S5 is 30~60min; the transfer time of transferring the high carbon chromium roller workpiece from the heating furnace to the salt bath is less than 20s; the salt bath quenching treatment also includes a first stirring treatment; wherein the stirring speed is 1000~1500r / min.

[0009] Optionally, the water content of the salt bath used in step S5 is W1=k·D+z·H; wherein W1 is the water content of the salt bath, D is the diameter of the high carbon chromium roller workpiece, H is the height of the high carbon chromium roller workpiece, k is 0.005~0.02, and z is 0.002~0.02.

[0010] Optionally, the water quenching time t5 used in step S6 is 15~25min; the transfer time of transferring the high carbon chromium roller workpiece from the salt bath to the water is less than 20s; the water quenching treatment also includes a second stirring treatment; wherein the stirring speed is 1000~1500r / min.

[0011] Optionally, in step S7, the post-processing includes sequentially performing a cleaning process and a tempering process on the high carbon chromium roller workpiece; The tempering temperature used in the tempering treatment is 160-200°C, and the tempering time is 12-14h.

[0012] In a second aspect, the present invention provides a high carbon chromium roller workpiece, which is prepared by the multi-stage heat treatment preparation process of the high carbon chromium roller workpiece.

[0013] Optionally, the high carbon chromium roller workpiece includes a GCr15SiMn high carbon chromium roller workpiece.

[0014] The application of the technical solution of the present invention has at least the following beneficial effects: The present invention provides a high-carbon chromium roller workpiece and a multi-stage heat treatment preparation process thereof. The step S1 is used to load a plurality of high-carbon chromium roller workpieces into a heating furnace in a staggered arrangement, so as to facilitate subsequent uniform heating of each high-carbon chromium roller workpiece; the step S2 is used for a first heat treatment, the step S3 is used for a second heat treatment, and the step S4 is used for a third heat treatment to achieve multi-stage heating treatment of the high-carbon chromium roller workpiece, and by strictly controlling the heating speed, heating temperature, and holding time, the carbides and alloy elements in the high-carbon chromium roller workpiece material can be significantly dissolved into the matrix, which is beneficial to improving the core hardness of the high-carbon chromium roller workpiece during the salt bath quenching treatment in the step S5 and the water quenching treatment in the step S6, and reducing the degree of hardness gradient attenuation. and residual austenite content; specifically, the use of salt bath quenching treatment is beneficial to the cooling rate of the high carbon chromium roller workpiece surface exceeding the critical speed of martensitic transformation, and at the same time will not quench the surface of the high carbon chromium roller workpiece; the use of water quenching treatment is to increase the cooling rate of the core of the high carbon chromium roller workpiece, reduce the production of troostite in its core, and improve the hardness of the core of the workpiece; while improving the hardness of the core of the workpiece, the gradient attenuation degree of the hardness of the core of the workpiece and the surface hardness of the workpiece can be reduced; the use of multi-stage heating treatment can significantly dissolve the carbides and alloy elements in the high carbon chromium roller workpiece material into the matrix, improve the hardenability of the high carbon chromium roller workpiece material, improve the hardness of the core of the workpiece, and help reduce the residual austenite content.

[0015] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is a schematic structural diagram of a plurality of high-carbon chromium roller workpieces arranged in a staggered manner in Example 1 of the present invention; Figure 2 Schematic diagram of a multi-stage heat treatment process for preparing a carbon-chromium roller workpiece in Example 1 of the present invention; Figure 3is a metallographic diagram of the core structure of the high carbon chromium roller workpiece prepared in Example 1 of the present invention; Figure 4 is a metallographic diagram of the core structure of the high carbon chromium roller workpiece prepared in Comparative Example 1 of the present invention; Among them, 1. High carbon chromium roller workpiece. DETAILED DESCRIPTION

[0017] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention. Embodiment 1:

[0018] A multi-stage heat treatment preparation process for a high carbon chromium roller workpiece, comprising: Step S1, multiple high carbon chromium roller workpieces 1 (the high carbon chromium material is selected from GCr15SiMn high carbon chromium material that complies with the national standard GB / T18254-2016 high carbon chromium bearing steel, and the size of the high carbon chromium roller workpiece 1 can be selected in the range of φ70*(70-120) mm. In this embodiment 1, the size of the high carbon chromium roller workpiece 1 is φ70*120 mm) are arranged in a staggered manner (i.e., in a spaced manner, see Figure 1 ) is loaded into the heating furnace; Step S2, see Figure 2 , performing a first heat treatment on the high carbon chromium roller workpiece 1; the first heat treatment comprises controlling the heating furnace to heat to a temperature of A at a first heating rate of 100°C / h c1 , the holding time is t1=30min; among them, A c1 A is the temperature at which the structure of the high carbon chromium roller workpiece 1 begins to transform into austenite. c1 The value range is 750±10℃. In this embodiment 1, A c1 The specific value is 750℃; Step S3, performing a second heat treatment on the high carbon chromium roller workpiece 1; the second heat treatment comprises controlling the heating furnace to heat to a temperature of A at a second heating rate of 60°C / h. c1 +40℃, holding time is t2=10min; Step S4, performing a third heat treatment on the high carbon chromium roller workpiece 1; the third heat treatment comprises controlling the heating furnace to heat to a temperature of A at a third heating rate of 80°C / h. c1 +70℃, holding time is t3=10min; Step S5, performing salt bath quenching treatment on the high carbon chromium roller workpiece 1; wherein the salt bath quenching temperature is M s-15℃, salt bath quenching time is t4; M s M is the temperature at which the high carbon chromium roller workpiece 1 begins to generate martensite structure. s The value range is 170±5°C. In this embodiment 1, M s The specific value is 172℃; M s =441.04-360.4X γc +11.79ln(d γ ), where d γ is the austenite grain size, and its value range is 12.6±5μm. In this embodiment 1, d γ The specific value is 13μm; X γc is the molar fraction of carbon atoms in austenite, and its value range is 0.8-0.85. In this embodiment 1, X γc The specific value is 0.83; Step S6, performing water quenching treatment on the high carbon chromium roller workpiece 1; the water quenching temperature is 0° C., and the water quenching time is t5; Step S7, post-processing the high carbon chromium roller workpiece 1 to obtain a target high carbon chromium roller workpiece 1.

[0019] The salt bath quenching time t4 used in step S5 is 10 minutes; the transfer time of transferring the high carbon chromium roller workpiece 1 from the heating furnace to the salt bath is less than 20 seconds; the salt bath quenching treatment also includes a first stirring treatment; wherein the stirring speed is 1250 r / min.

[0020] The water content of the salt bath used in step S5 is W1=k·D+z·H, wherein W1 is the water content of the salt bath, D is the diameter of the high carbon chromium roller workpiece 1, H is the height of the high carbon chromium roller workpiece 1, k is 0.012, and z is 0.01. Limiting the water content of the salt bath can ensure that the cooling rate of the surface of the high carbon chromium roller workpiece 1 exceeds the critical speed of martensitic transformation, and at the same time, the surface of the high carbon chromium roller workpiece 1 will not be quenched.

[0021] The water quenching time t5 used in step S6 is 20 minutes; the transfer time of transferring the high carbon chromium roller workpiece 1 from the salt bath to the water is less than 20 seconds; the water quenching treatment also includes a second stirring treatment; wherein the stirring speed is 1250 r / min.

[0022] In step S7, the post-processing includes sequentially performing cleaning and tempering on the high carbon chromium roller workpiece 1; The tempering temperature used in the tempering treatment is 180° C. and the tempering time is 14 h. Embodiment 2:

[0023] The same as in Example 1, the tempering time is 12 h.

[0024] Comparative Example 1: The high carbon chromium roller workpiece 1 is prepared by a conventional martensitic quenching heat treatment process. Specifically, the high carbon chromium roller workpiece 1 of the same material and size as in Example 1 is loaded into a heating furnace in a staggered arrangement; the heating furnace is controlled to heat at a heating rate of 100°C / h to a temperature of A. c1 +70℃, the holding time is 60min; the high carbon chromium roller workpiece 1 is subjected to salt bath quenching treatment, and the salt bath quenching treatment adopted is different from that in Example 1 in that the quenching time is 45min; the high carbon chromium roller workpiece 1 is subjected to air cooling treatment, and after cooling to room temperature, the cleaning treatment is carried out in the same manner as in Example 1; the high carbon chromium roller workpiece 1 is subjected to deep cryogenic treatment with liquid nitrogen, the treatment temperature is -80℃, and the treatment time is 2h; after the temperature of the high carbon chromium roller workpiece 1 returns to room temperature, it is tempered at 180℃ for 12h.

[0025] Comparative Example 2: Different from Comparative Example 1, the cryogenic treatment was eliminated.

[0026] Comparative Example 3: The difference from Example 2 is that the water quenching treatment is replaced by air cooling treatment, that is, the high carbon chromium roller workpiece 1 is subjected to air cooling treatment, and then the post-treatment as in Example 2 is performed after cooling to room temperature.

[0027] The high carbon chromium roller workpieces 1 prepared in Examples 1-2 and Comparative Examples 1-3 and samples of the high carbon chromium roller workpieces 1 provided by a domestic bearing factory were subjected to performance tests, respectively. The performance test results are shown in Table 1.

[0028] Table 1 Performance test results

[0029] From the data in Table 1, it can be seen that compared with comparative examples 2-3 and the high carbon chromium roller workpiece samples provided by a domestic bearing factory, the present invention uses a combination of multi-stage heating treatment, two-stage quenching treatment and appropriate tempering time in Examples 1-2, so that the prepared high carbon chromium roller workpiece 1 can significantly improve the core hardness while ensuring that the surface hardness remains basically unchanged, and significantly reduce the degree of hardness gradient attenuation and the content of retained austenite. Compared with comparative example 1, the present invention uses a combination of multi-stage heating treatment, two-stage quenching treatment and appropriate tempering time in Example 1, so that the prepared high carbon chromium roller workpiece 1 can significantly improve the core hardness while ensuring that the surface hardness remains basically unchanged, and significantly reduce the degree of hardness gradient attenuation.

[0030] Depend on Figure 3-Figure 4It can be seen that compared with Comparative Example 1, the high carbon chromium roller workpiece prepared in Example 1 has fine structure, good uniformity, and significantly reduced troostite content, which is beneficial to improving the core hardness of the workpiece and reducing the gradient attenuation of the core hardness of the workpiece and the surface hardness of the workpiece.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-stage heat treatment preparation process for a high carbon chromium roller workpiece, characterized in that: include: Step S1, loading a plurality of high carbon chromium roller workpieces into a heating furnace in a staggered arrangement; Step S2, performing a first heat treatment on the high carbon chromium roller workpiece; the first heat treatment comprises controlling the heating furnace to heat to a temperature of A at a first heating speed. c1 , the insulation time is t1; Among them, A c1 It is the temperature at which the structure of the high carbon chromium roller workpiece begins to transform into austenite; Step S3, performing a second heat treatment on the high carbon chromium roller workpiece; the second heat treatment comprises controlling the heating furnace to heat to a temperature of A at a second heating rate. c1 +30~A c1 +50℃, holding time is t2; Step S4, performing a third heat treatment on the high carbon chromium roller workpiece; the third heat treatment comprises controlling the heating furnace to heat to a temperature of A at a third heating rate. c1 +60~A c1 +80℃, holding time is t3; Step S5, performing salt bath quenching treatment on the high carbon chromium roller workpiece; wherein the salt bath quenching temperature is M s -20~M s -10℃, salt bath quenching time is t4; M s It is the temperature at which the high carbon chromium roller workpiece begins to produce martensite structure; Step S6, performing water quenching treatment on the high carbon chromium roller workpiece; the water quenching temperature is 0-5°C, and the water quenching time is t5; Step S7: post-processing the high carbon chromium roller workpiece to obtain a target high carbon chromium roller workpiece.

2. The multi-stage heat treatment preparation process for high carbon chromium roller workpiece according to claim 1 is characterized in that: In step S2, the first heating rate used is 90-110°C / h, and the insulation time t1 used is 25-35min.

3. The multi-stage heat treatment preparation process for high carbon chromium roller workpiece according to claim 1, characterized in that: The second heating rate used in step S3 is 55-65° C. / h, and the insulation time t2 used is 8-12 min.

4. The multi-stage heat treatment preparation process for high carbon chromium roller workpiece according to claim 1, characterized in that: The third heating rate used in step S4 is 77-83° C. / h, and the insulation time t3 used is 8-12 min.

5. The multi-stage heat treatment preparation process for high carbon chromium roller workpiece according to claim 1, characterized in that: The salt bath quenching time t4 used in step S5 is 30-60 minutes; the transfer time of transferring the high carbon chromium roller workpiece from the heating furnace to the salt bath is less than 20 seconds; the salt bath quenching treatment also includes a first stirring treatment; wherein the stirring speed is 1000-1500 r / min.

6. The multi-stage heat treatment preparation process for high carbon chromium roller workpiece according to claim 1, characterized in that: The water content of the salt bath used in step S5 is W1=k·D+z·H; wherein W1 is the water content of the salt bath, D is the diameter of the high carbon chromium roller workpiece, H is the height of the high carbon chromium roller workpiece, k is 0.005~0.02, and z is 0.002~0.

02.

7. The multi-stage heat treatment preparation process for high carbon chromium roller workpiece according to claim 1, characterized in that: The water quenching time t5 used in step S6 is 15-25 minutes; the transfer time of transferring the high carbon chromium roller workpiece from the salt bath to the water is less than 20 seconds; the water quenching treatment also includes a second stirring treatment; wherein the stirring speed is 1000-1500 r / min.

8. The multi-stage heat treatment preparation process for high carbon chromium roller workpiece according to claim 1, characterized in that: In step S7, the post-processing includes sequentially performing a cleaning process and a tempering process on the high carbon chromium roller workpiece; The tempering temperature used in the tempering treatment is 160-200°C, and the tempering time is 12-14h.

9. A high carbon chromium roller workpiece, characterized in that: The high carbon chromium roller workpiece is prepared by the multi-stage heat treatment preparation process as described in any one of claims 1 to 8.

10. The high carbon chromium roller workpiece according to claim 9, characterized in that: The high carbon chromium roller workpiece includes a GCr15SiMn high carbon chromium roller workpiece.

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