2.25 Cr1Mo0.25 V steel thick-wall forge piece as well as post-forging heat treatment method and application thereof
By employing a three-stage heat treatment method after forging, the problems of long heat treatment cycles and high hardness of thick-walled forgings for coal liquefaction reactors have been solved, resulting in shorter preparation cycles, improved processing performance, and reduced energy consumption and costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-15
- Publication Date
- 2026-03-10
AI Technical Summary
In the existing technology, the post-forging heat treatment cycle of thick-walled forgings for coal liquefaction reactors is long, energy consumption is high, and the high hardness makes processing difficult, affecting product quality.
A three-stage heat treatment method for post-forging heat treatment is adopted, in which the holding temperature is gradually increased and the time of each stage is controlled, including holding at 250-350℃, 650-750℃ and 900-960℃. Combined with slow and fast heating rates, the temperature is reduced to 600-700℃ and then furnace cooled to 450℃ before being taken out of the furnace.
It shortens the post-forging heat treatment time by more than 40%, reduces the surface hardness of forgings to below 150HB, improves machinability, and saves energy and costs.
Smart Images
Figure CN121629121A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of heat treatment, in particular to a 2.25Cr1Mo0.25V steel thick-wall forge piece and a post-forging heat treatment method and application thereof. BACKGROUND
[0002] The coal liquefaction reactor is a core device of petroleum chemical industry. With the development of the petrochemical industry, the demand for several hundred to several thousand tons of coal liquefaction reactors will increase substantially. The coal liquefaction reactor has high design temperature, large wall thickness of the forge piece and strict performance requirements, which brings new challenges to the manufacture of the forge piece.
[0003] At present, the post-forging heat treatment of the thick-wall forge piece of the coal liquefaction reactor is mainly prepared by using the traditional normalizing + tempering heat treatment method. However, due to the large thick-wall size of the coal liquefaction reactor, especially the thickness of more than 300mm, in order to ensure the full heat penetration of the overall thickness, a long heating time is required, which leads to a long manufacturing cycle and high energy consumption. In addition, the coal liquefaction reactor needs to be processed after heat treatment, but the hardness of the obtained coal liquefaction reactor is high after the traditional heat treatment, which accelerates the tool wear and damages the surface quality of the coal liquefaction reactor during processing. SUMMARY
[0004] In view of the above analysis, the present application aims to provide a 2.25Cr1Mo0.25V steel thick-wall forge piece and a post-forging heat treatment method and application thereof, which shorten the preparation period and reduce the hardness.
[0005] In one aspect, the present application provides a post-forging heat treatment method for a 2.25Cr1Mo0.25V steel thick-wall forge piece, comprising the following steps:
[0006] S1: first, the forge piece is subjected to first stage heat preservation, and the heat preservation temperature is 250-350℃;
[0007] S2: then, the temperature is raised to the second stage heat preservation, and the heat preservation temperature is 650-750℃;
[0008] S3: finally, the temperature is raised to the third stage heat preservation, and the heat preservation temperature is 900-960℃;
[0009] S4: after the third stage heat preservation, the temperature is lowered, first to 600-700℃, then furnace cooling to below 450℃, and the forge piece is taken out of the furnace to obtain a 2.25Cr1Mo0.25V steel thick-wall forge piece.
[0010] Further, the temperature rising time from the first stage heat preservation to the second stage is controlled to be 6-8h.
[0011] Further, the temperature rising time from the second stage heat preservation to the third stage is controlled to be 4-6h.
[0012] Further, after the third stage of holding, cooling is performed, and the cooling time is controlled to be 25-30h.
[0013] Further, according to the mass percentage, the C of the 2.25Cr1Mo0.25V steel thick-wall forge piece is 0.14%-0.16%, Si≤0.1%, Mn: 0.3%-0.6%, P≤0.005%, S≤0.002%, Cr: 1.90%-2.60%, Mo: 0.9%-1.1%, Ni≤0.2%, Cu≤0.2%, Nb≤0.05%, V≤0.35%, Ti≤0.03%, Al≤0.04%, B≤0.0020%, Sb≤0.004%, Sn≤0.01%, As≤0.01%, O≤0.003%, N≤0.007%, H≤0.0001%, and the rest is Fe and inevitable impurities.
[0014] Further, the total heat treatment time is 70-88h, which is shortened by more than 40%.
[0015] Further, the surface hardness of the 2.25Cr1Mo0.25V steel thick-wall forge piece is below 150HB.
[0016] Further, the microstructure of the 2.25Cr1Mo0.25V steel thick-wall forge piece is ferrite and pearlite; and the grain size is 5.
[0017] On the other hand, the application provides a 2.25Cr1Mo0.25V steel thick-wall forge piece prepared by the post-forging heat treatment method.
[0018] Compared with the prior art, the application can achieve at least one of the following beneficial effects:
[0019] 1. The application provides a post-forging heat treatment method, which mainly adopts three stages of holding, and controls the gradually increasing holding temperature and the time of each heating stage.
[0020] 2. The post-forging heat treatment method of the application reduces the surface hardness of the heat-treated forge piece to below 150HB, which is beneficial to subsequent machining and ensures the quality of the product.
[0021] The technical solutions in the present application can be combined with each other to realize more preferred combination solutions. Other features and advantages of the present application will be described in the subsequent description, and some advantages will become apparent from the description, or will be understood by those skilled in the art through implementation of the present application. The objects and other advantages of the present application can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF DRAWINGS
[0022] The accompanying drawings are included to provide a further understanding of the present application, and are incorporated in and constitute a part of this specification, illustrate embodiments of the present application, and together with the description serve to explain the principles of the present application, and should not be considered limiting of the present application in scope, as numerous embodiments of the present application can be made and are encompassed by the present application.
[0023] Figure 1 Microstructure diagram of the forged piece obtained after heat treatment of the example 1;
[0024] Figure 2 Microstructure diagram of the forged piece obtained after heat treatment of the example 2;
[0025] Figure 3 Microstructure diagram of the forged piece obtained after heat treatment of the comparative example 1. DETAILED DESCRIPTION
[0026] Preferred embodiments of the present application will be described in detail below with reference to the drawings, wherein the drawings constitute a part of this specification and are used to explain the principles of the embodiments of the present application together with the description, and should not be considered limiting the scope of the present application, as numerous embodiments of the present application can be made and are encompassed by the present application.
[0027] The coal liquefaction reactor is a core device of the petrochemical industry, and with the development of the petrochemical industry, the demand for several hundred to several thousand tons of coal liquefaction reactors will increase substantially. The coal liquefaction reactor has high design temperature, large wall thickness of the forged piece, and strict performance index requirements, which brings new challenges to the manufacture of the forged piece.
[0028] At present, the forged piece of the coal liquefaction reactor is mainly prepared by using the traditional heat treatment method, and the traditional heat treatment method is normalizing + tempering. However, due to the large size of the thick wall of the coal liquefaction reactor, especially the coal liquefaction reactor with a thickness of 300 mm or more, in order to ensure that the overall thickness is fully heat penetrated, a long heating time is required, which leads to a long manufacturing cycle and high energy consumption. In addition, the coal liquefaction reactor needs to be processed after heat treatment, but the hardness of the obtained coal liquefaction reactor is high after the traditional heat treatment method, which accelerates the tool wear and damages the surface quality of the coal liquefaction reactor during the processing.
[0029] Therefore, the present application provides a heat treatment method for a 2.25Cr1Mo0.25V steel thick-walled forged piece after forging, which comprises the following steps:
[0030] S1: first, the forged piece is subjected to first stage heat preservation, and the heat preservation temperature is 250-350 DEG C;
[0031] S2: then the temperature is raised to the second stage of holding, the holding temperature is 650-750 DEG C;
[0032] S3: finally, the temperature is raised to the third stage of holding, the holding temperature is 900-960 DEG C;
[0033] S4: after the third stage of holding, the temperature is lowered, first to 600-700 DEG C, then the furnace is cooled to below 450 DEG C, the forged piece is taken out of the furnace, and a 2.25Cr1Mo0.25V steel thick-wall forged piece is obtained.
[0034] Compared with the prior art, the present application provides a post-forging heat treatment method, which mainly adopts three stages of holding, and controls the holding temperature to gradually increase and the time of each heating stage, the total time of the post-forging heat treatment method is 70-88h, compared with the traditional normalizing + tempering heat treatment process, the total time is shortened by more than 40%, the preparation period is shortened, energy is saved and manufacturing cost is saved.
[0035] Specifically, the temperature of the first stage of holding is 250-350 DEG C, and the holding time is 1-2h.
[0036] It should be noted that the purpose of holding at this temperature is to heat the forged piece after cooling after forging, improve its plasticity, and prevent cold cracking due to uneven internal temperature when heating at low temperature. Therefore, the first stage of holding temperature can be 250 DEG C, 260 DEG C, 270 DEG C, 280 DEG C, 290 DEG C, 300 DEG C, 310 DEG C, 320 DEG C, 330 DEG C, 340 DEG C or 350 DEG C.
[0037] Specifically, the temperature of the second stage of holding is 650-750 DEG C, and the holding time is 7-9h.
[0038] It should be noted that the purpose of holding at this temperature is to reduce the internal temperature difference and transformation difference of the forged piece when heating transformation occurs, reduce the stress and deformation in the workpiece, and prepare for rapid heating in the high temperature stage. Therefore, the second stage of holding temperature can be 650 DEG C, 660 DEG C, 670 DEG C, 680 DEG C, 690 DEG C, 700 DEG C, 710 DEG C, 720 DEG C, 730 DEG C, 740 DEG C or 750 DEG C.
[0039] Specifically, the temperature of the third stage of holding is 900-960 DEG C, and the holding time is (1.5-2)h / 100mm.
[0040] It should be noted that the temperature is kept for a certain time, the austenitizing is carried out during heating, the new structure is nucleated and grown, the transformation is completed, the recrystallization is carried out, the grain refinement is carried out; it is beneficial to the hot penetration of the forging, so that the forging is completely austenitized; it is beneficial to the diffusion of alloying elements and the uniform structure. The holding time is (1.5-2)h / 100mm according to the effective thickness of the forging, and the waiting time is about 1 / 3 of the holding time. The forging structure is completely austenitized, and the forging is hot penetrated.
[0041] Specifically, the heating time from the first stage to the second stage is controlled to be 6-8h.
[0042] It should be noted that the first stage is heated to the second stage, and a slow heating rate is adopted during heating, that is, the heating time from the first stage to the second stage is controlled to be 6-8h. In this stage, the forging is in a low temperature section, is cold and hard, and has poor plasticity. If the heating rate is large, the temperature difference between the inside and outside of the forging is large, and if the instantaneous thermal stress generated by the temperature difference exceeds the plasticity of the material, cracking will occur.
[0043] Specifically, the heating time from the second stage to the third stage is controlled to be 4-6h.
[0044] It should be noted that the second stage is heated to the third stage, and a relatively fast heating rate is adopted during heating, that is, the heating time from the second stage to the third stage is controlled to be 4-6h. In this stage, the forging temperature is high, the material plasticity has been improved, the heating speed of the large workpiece is increased, and the overheat degree of the forging during heating transformation is increased to refine the grains.
[0045] Specifically, after the third stage of holding is completed, the temperature is decreased, first decreased to 600-700℃, the cooling time is controlled to be 25-30h, then the furnace is cooled to below 450℃, and the forging is taken out of the furnace, and the furnace cooling time is 25-30h.
[0046] It should be noted that the third stage of holding is formally entered into the cooling stage, and is first cooled to 600-700℃. In this temperature, the transformation from austenite to ferrite+pearlite is completed, the phase change recrystallization is carried out, and the structure is refined. Slow cooling is required in this stage, that is, the cooling time is controlled to be 25-30h. The forging is slowly reduced to the critical transformation point, the near-equilibrium structure is obtained, the coarse structure caused by uneven deformation during forging and the banded structure caused by too low forging temperature are eliminated, the forging stress is eliminated, the material hardness is reduced, and the cutting processing is facilitated. In this stage, the austenite is completely decomposed and transformed, the structure is recrystallized, and the grains are refined.
[0047] Specifically, according to the mass percentage, the C of the 2.25Cr1Mo0.25V steel thick-wall forge piece is 0.14% to 0.16%, Si is less than or equal to 0.1%, Mn is 0.3% to 0.6%, P is less than or equal to 0.005%, S is less than or equal to 0.002%, Cr is 1.90% to 2.60%, Mo is 0.9% to 1.1%, Ni is less than or equal to 0.2%, Cu is less than or equal to 0.2%, Nb is less than or equal to 0.05%, V is less than or equal to 0.35%, Ti is less than or equal to 0.03%, Al is less than or equal to 0.04%, B is less than or equal to 0.0020%, Sb is less than or equal to 0.004%, Sn is less than or equal to 0.01%, As is less than or equal to 0.01%, O is less than or equal to 0.003%, N is less than or equal to 0.007%, H is less than or equal to 0.0001%, and the rest is Fe and inevitable impurities.
[0048] The application provides a 2.25Cr1Mo0.25V steel thick-wall forge piece, which is prepared by the post-forging heat treatment method and has a surface hardness of less than or equal to 150 HB, a ferrite and pearlite structure and a grain size of 5.
[0049] The 2.25Cr1Mo0.25V steel thick-wall forge piece obtained by the application can be used to prepare a coal liquefaction reactor, and the coal liquefaction reactor comprises a cylinder segment.
[0050] In order to more clearly describe the application, the following examples and comparative examples are further illustrated.
[0051] Example 1
[0052] The forge piece is obtained by smelting and forging, and has the following chemical components according to the mass percentage: C is 0.14% to 0.16%, Si is less than or equal to 0.1%, Mn is 0.3% to 0.6%, P is less than or equal to 0.005%, S is less than or equal to 0.002%, Cr is 1.90% to 2.60%, Mo is 0.9% to 1.1%, Ni is less than or equal to 0.2%, Cu is less than or equal to 0.2%, Nb is less than or equal to 0.05%, V is less than or equal to 0.35%, Ti is less than or equal to 0.03%, Al is less than or equal to 0.04%, B is less than or equal to 0.0020%, Sb is less than or equal to 0.004%, Sn is less than or equal to 0.01%, As is less than or equal to 0.01%, O is less than or equal to 0.003%, N is less than or equal to 0.007%, H is less than or equal to 0.0001%, and the rest is Fe and inevitable impurities.
[0053] The forge piece is heat treated, and the steps are as follows:
[0054] S1: first, the forge piece is subjected to first-stage heat preservation, the heat preservation temperature is 250 DEG C, and the heat preservation time is 1.5 h;
[0055] S2: then, the temperature is raised to the second-stage heat preservation, the heat preservation temperature is 650 DEG C, the heat preservation time is 7 h, and the temperature rising time is 6 h;
[0056] S3: finally, the temperature is raised to the third stage of holding, the holding temperature is 930℃, the holding time is 15h, and the temperature rising time is 4h;
[0057] S4: after the third stage of holding, the temperature is lowered, the temperature is lowered to 600℃ first, the temperature lowering time is 29h; then the furnace is cooled to 420℃, the forging is discharged, the furnace cooling time is 12h; and a 2.25Cr1Mo0.25V steel thick-wall forging is obtained.
[0058] The total time of this embodiment is 74.5h, the structure is ferrite and pearlite, the surface hardness of the forging is 128HB, and the grain size is 5 levels.
[0059] Example 2
[0060] Example 2 is basically the same as the preparation process of Example 1, except that the forging heat treatment in Example 2 includes the following steps:
[0061] S1: first, the forging is subjected to the first stage of holding, the holding temperature is 300℃, and the holding time is 2h;
[0062] S2: then, the temperature is raised to the second stage of holding, the holding temperature is 700℃, the holding time is 9h, and the temperature rising time is 8h;
[0063] S3: finally, the temperature is raised to the third stage of holding, the holding temperature is 945℃, the holding time is 16h, and the temperature rising time is 5h;
[0064] S4: after the third stage of holding, the temperature is lowered, the temperature is lowered to 620℃ first, the temperature lowering time is 30h; then the furnace is cooled to 400℃, the forging is discharged, the furnace cooling time is 15h; and a 2.25Cr1Mo0.25V steel thick-wall forging is obtained.
[0065] The total time of this embodiment is 85h, the structure is ferrite and pearlite, the surface hardness of the forging is 126HB, and the grain size is 5 levels.
[0066] Example 3
[0067] Example 3 is basically the same as the preparation process of Example 1, except that the forging heat treatment in Example 3 includes the following steps:
[0068] S1: first, the forging is subjected to the first stage of holding, the holding temperature is 350℃, and the holding time is 2h;
[0069] S2: then, the temperature is raised to the second stage of holding, the holding temperature is 750℃, the holding time is 9h, and the temperature rising time is 8h;
[0070] S3: finally, the temperature is raised to the third stage of holding, the holding temperature is 960℃, the holding time is 16h, and the temperature rising time is 5h;
[0071] S4: After the third stage holding is finished, cooling is performed, first to 640℃, the cooling time is 30h; then furnace cooling to 350℃, the forging is discharged, the furnace cooling time is 15h; the 2.25Cr1Mo0.25V steel thick wall forging is obtained.
[0072] The total time of this embodiment is 85h, the organization is ferrite and pearlite, the surface hardness of the forging is 124HB, and the grain size is 5 levels.
[0073] Comparative Example 1
[0074] Comparative Example 1 and Example 1 are basically the same in the preparation process, except that the traditional heat treatment process, normalizing + tempering, is used in Comparative Example 1.
[0075] In the normalizing stage:
[0076] Step 1, waiting and holding at 360℃ for 4h;
[0077] Step 2, heating to 710℃; for 6h.
[0078] Step 3, holding at 710℃; for 8h.
[0079] Step 4, heating the forging to 960℃; for 4h; the organization is austenitized, and the grains are refined.
[0080] Step 5, holding at 950℃ for 16h.
[0081] Step 6, air cooling to 320℃ for about 10h.
[0082] In the tempering stage:
[0083] Step 8, tempering waiting, 300℃, for 3h.
[0084] Step 9, heating to 690℃, for 8h.
[0085] Step 10, holding at 690℃ for 25h;
[0086] Step 11, slowly cooling to 400℃, for 20h;
[0087] Step 12, stopping the fire, closing the furnace door, furnace cooling to 250℃, discharging, for 25h.
[0088] The total time of this comparative example is 131h, the organization is bainite, and the surface hardness of the forging is 325HB.
[0089] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.
Claims
1. A method of post-wrought heat treatment of a 2.25Cr1Mo0.25V steel thick-walled forging, characterized in that, The method comprises the following steps: S1: first stage heat preservation is carried out on the forging, and the heat preservation temperature is 250-350℃; S2: then the temperature is raised to the second stage heat preservation, and the heat preservation temperature is 650-750℃; S3: finally the temperature is raised to the third stage heat preservation, and the heat preservation temperature is 900-960℃; S4: after the third stage heat preservation, the temperature is lowered, the temperature is first lowered to 600-700℃, then the furnace is cooled to below 450℃, the forging is discharged from the furnace, and a 2.25Cr1Mo0.25V steel thick-wall forging is obtained.
2. The method of claim 1, wherein the 2.25Cr1Mo0.25V steel thick-walled forging is heated to a temperature of 1,100°C to 1,200°C after the forging. The temperature rising time from the first stage heat preservation to the second stage is controlled to be 6-8h. 3. The method of claim 1, wherein the 2.25Cr1Mo0.25V steel thick-walled forging is heated to a temperature of 1,100°C to 1,200°C after the forging. The temperature rising time from the second stage heat preservation to the third stage is controlled to be 4-6h. 4. The method of claim 1, wherein the 2.25Cr1Mo0.25V steel thick wall forging is characterized by, After the third stage heat preservation, the temperature is lowered, and the temperature lowering time is controlled to be 25-30h.
5. The method of claim 1, wherein the 2.25Cr1Mo0.25V steel thick wall forging is characterized by, According to the mass percentage, the C of the 2.25Cr1Mo0.25V steel thick-wall forging is 0.14%-0.16%, the Si is ≤0.1%, the Mn is 0.3%-0.6%, the P is ≤0.005%, the S is ≤0.002%, the Cr is 1.90%-2.60%, the Mo is 0.9%-1.1%, the Ni is ≤0.2%, the Cu is ≤0.2%, the Nb is ≤0.05%, the V is ≤0.35%, the Ti is ≤0.03%, the Al is ≤0.04%, the B is ≤0.0020%, the Sb is ≤0.004%, the Sn is ≤0.01%, the As is ≤0.01%, the O is ≤0.003%, the N is ≤0.007%, the H is ≤0.0001%, and the rest is Fe and inevitable impurities.
6. The method of claim 1, wherein the 2.25Cr1Mo0.25V steel thick wall forging is characterized by, The total heat treatment time is 70-88h, which is shortened by more than 40%.
7. The method of claim 1, wherein the 2.25Cr1Mo0.25V steel thick wall forging is characterized by, The surface hardness of the 2.25Cr1Mo0.25V steel thick-wall forging is below 150HB.
8. The method of claim 1, wherein the 2.25Cr1Mo0.25V steel thick wall forging is characterized by, The structure of the 2.25Cr1Mo0.25V steel thick-wall forging is ferrite and pearlite structure, and the grain size is 5 levels.
9. A 2.25Cr1Mo0.25V steel thick wall forging, characterized in that, The 2.25Cr1Mo0.25V steel thick-wall forging is prepared by the post-forging heat treatment method in any one of claims 1-8.
10. The 2.25Cr1Mo0.25V steel thick-wall forging obtained by the post-forging heat treatment method in any one of claims 1-8 is used for preparing a coal liquefaction reactor, and the coal liquefaction reactor comprises a cylinder segment.