A forming method to achieve low-magnification microstructure effect of martensitic forgings by controlling parameters

Abstract

The present invention belongs to the field of forging hot working and relates to a method for forming martensitic forgings by controlling parameters to achieve the desired macrostructure level of the forging; setting different pretreatment parameters and forging parameters for the desired macrostructure level of the forging; and performing normalizing, forging, heat treatment, and machining using these pretreatment parameters and forging parameters.

Description

Technical Field

[0001] The invention belongs to the field of forging hot processing and relates to a forming method for completing the macrostructure effect of a martensitic forging by controlling parameters. Background Art

[0002] 1Cr10Co6MoVNbN steel is a martensitic creep-resistant, heat-strength stainless steel reinforced with multiple elements, including Co, Mo, V, and Nb. This steel contains solid-solution strengthening elements such as Mo, C, Co, and N, precipitation strengthening elements such as Nb and V, and the trace element B, which strengthens and purifies grain boundaries. The addition of 6% Co to a 12% Cr martensitic steel mitigates the downward trend in the steel's Ac1 and Ms points caused by the addition of Ni. Compared to ordinary Cr12 steel, this steel exhibits higher heat strength, thermal stability, low notch sensitivity, and excellent creep resistance. It is widely used in cutting-edge aviation and aerospace applications, including key engine components.

[0003] Due to the different requirements for the internal structure of 1Cr10Co6MoVNbN alloy forgings, the control requirements for the production parameters of the forgings are different. If the production method is not properly controlled, the internal structure of the forging will change, affecting the final macrostructure of the forging, making the product unable to meet the final requirements, resulting in product scrapping and a large waste of resources. Therefore, choosing reasonable forging parameters is particularly important for improving the internal structure of 1Cr10Co6MoVNbN forgings. The following is a conventional forging method for 1Cr10Co6MoVNbN forgings.

[0004] Conventional forging method:

[0005] Cutting - heating - billet making - forming - heat treatment - physical and chemical testing - machining - corrosion - final inspection - warehousing; the common forging method is free forging billet, and the firing times are carried out on demand. However, there are no strict requirements for the billet forging time and the final forming equipment expansion parameters. The terminal temperature is difficult to control, resulting in low magnification of physical and chemical testing of forgings, which exceeds the standard and affects the qualified delivery of forgings;

[0006] Conventional processing methods lack strict requirements for hammer forging time and final forming equipment expansion parameters, making final temperature control difficult and preventing forgings from meeting the requirements for magnetic particle testing. Therefore, properly controlling the required billet forging time and final forming equipment expansion parameters to increase the final forging temperature is crucial for influencing the material's microstructure and performance. In particular, conventional forging methods increase the number of open-die forgings, resulting in partial burnout, prolonged forging times, and difficulty maintaining a final forging temperature. This affects the physical and chemical microstructure of the forging's macrostructure, which meets the requirements for the inner wall microstructure, leading to a large number of unqualified forgings being scrapped. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for re-forging 1Cr10Co6MoVNbN bars after normalizing treatment, thereby improving the original structure of the raw material and controlling the forging time of the blank and the hole expansion parameters of the final forming equipment. The forging method is used to meet the internal structure requirements of the forging design requirements and obtain qualified and stable low-magnification indicators.

[0008] To solve this technical problem, the technical solution of the present invention is:

[0009] A forming method for achieving low-magnification microstructure effects of martensitic forgings by controlling parameters, comprising:

[0010] Determine the level of macrostructure requirements for forgings;

[0011] Set different pretreatment parameters and forging parameters for the required level of macrostructure of forgings;

[0012] Using the above pretreatment parameters and forging parameters, normalizing treatment, forging, heat treatment and machining are carried out.

[0013] The pretreatment parameter is the normalizing temperature, and the forging parameters include: holding time, billet making time, expansion time, hole expansion time, ring speed increasing rate, and main variable ring speed increasing value.

[0014] When the macrostructure requirement of forgings is level 4, the normalizing temperature is 1040℃-1045℃, and the holding time is 8.5 hours-9 hours; when the macrostructure requirement of forgings is level 5, the normalizing temperature is 1045℃-1050℃, and the holding time is 9 hours-9.5 hours; when the macrostructure requirement of forgings is level 6, the normalizing temperature is 1050℃-1055℃, and the holding time is 9.5 hours-10 hours.

[0015] When the macrostructure requirement of forgings is level 4, the forging time of a single piece of ring, upsetting and punching is 175s-180s; the forging time of a single piece of Ma-kuang is 75s-80s; when the macrostructure requirement of forgings is level 5, the forging time of a single piece of ring, upsetting and punching is 180s-185s; the forging time of a single piece of Ma-kuang is 80s-85s; when the macrostructure requirement of forgings is level 6, the forging time of a single piece of ring, upsetting and punching is 185s-190s; the forging time of a single piece of Ma-kuang is 85s-90s.

[0016] When the macrostructure requirement of forgings is level four, the ring growth rate is 2-3 mm / s; the main deformation ring growth rate cannot be lower than 4-4.5 mm / s; when the macrostructure requirement of forgings is level five, the ring growth rate is 3-4 mm / s; the main deformation ring growth rate cannot be lower than 4.5-5 mm / s; when the macrostructure requirement of forgings is level six, the ring growth rate is 4-5 mm / s; the main deformation ring growth rate cannot be lower than 5-5.5 mm / s.

[0017] Heat treatment, including: normalizing ≤800℃ into the furnace, heating with the furnace to 1070±10℃ and holding for 180min±15min; dispersed air cooling; annealing ≤700℃ into the furnace, heating with the furnace to 740±10℃ and soaking for 180min±15min; holding for 120+12min; dispersed air cooling.

[0018] Machining, including: full polishing of forgings.

[0019] A computer-readable storage medium stores a computer program, which implements the above method when executed by a processor.

[0020] The present invention has the following beneficial effects: 1Cr10Co6MoVNbN steel is a martensitic creep-resistant, heat-resistant stainless steel reinforced with multiple elements, including Co, Mo, V, and Nb. A method for forming martensitic forgings with low-magnification microstructures is achieved by controlling parameters. This forging method achieves a rational forging scheme with a reasonable internal microstructure that meets the design requirements of the forging, resulting in qualified and stable low-magnification indicators. This improves the forging qualification rate, reduces scrap losses, and enhances economic efficiency. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0022] This solution achieves the required macrostructure of Cr10Co6MoVNbN forgings by improving the original internal structure of the raw material through heat treatment and controlling the forging production parameters. According to the required level of the macrostructure of the forging, the original structure of the raw material is normalized, and after temperature treatment is performed according to the table below, appropriate corresponding forging parameters are selected to complete the forging. The method described in the present invention uses a method of improving the original internal structure of the raw material through heat treatment and controlling the forging production parameters to pre-treat the internal structure of the raw material, i.e., normalizing treatment, with a treatment temperature of 1045°C to 1050°C; cooling after 8-10 hours in a heat preservation tank, and then controlling the forging parameters: that is, after hammer forging and hole expansion forming, heat treatment and physical and chemical testing after surface processing are performed, and finally macroscopic inspection is performed. The inspection results are shown in Table 1.

[0023] Table 1

[0024]

[0025] The method comprises the following steps:

[0026] Step 1: Normalize the bar stock required for the raw material, that is, select the appropriate heat treatment system according to the macrostructure requirements of the forging and perform preliminary heat treatment. The heat treatment system is as follows:

[0027] When the macrostructure requirement of forgings is level 4, the normalizing temperature is 1040℃-1045℃, and the holding time is 8.5 hours-9 hours; when the macrostructure requirement of forgings is level 5, the normalizing temperature is 1045℃-1050℃, and the holding time is 9 hours-9.5 hours; when the macrostructure requirement of forgings is level 6, the normalizing temperature is 1050℃-1055℃, and the holding time is 9.5 hours-10 hours;

[0028] Step 2: Select the forging parameters required for billet forging, that is, select appropriate billet forging parameters according to the macrostructure requirements of the forging. The billet forging parameters are as follows:

[0029] When the macrostructure requirement of forgings is level 4, the forging time of a single piece of ring, upsetting and punching is 175s-180s; the forging time of a single piece of Ma-kuang is 75s-80s; when the macrostructure requirement of forgings is level 5, the forging time of a single piece of ring, upsetting and punching is 180s-185s; the forging time of a single piece of Ma-kuang is 80s-85s; when the macrostructure requirement of forgings is level 6, the forging time of a single piece of ring, upsetting and punching is 185s-190s; the forging time of a single piece of Ma-kuang is 85s-90s;

[0030] Step 3: Select the forging parameters required for hole expansion and forming forging, that is, select appropriate hole expansion forging parameters according to the macrostructure requirements of the forging. The hole expansion forging parameters are as follows:

[0031] When the macrostructure requirement of forgings is level 4, the ring growth rate is 2-3 mm / s; the main deformation ring growth rate cannot be lower than 4-4.5 mm / s; when the macrostructure requirement of forgings is level 5, the ring growth rate is 3-4 mm / s; the main deformation ring growth rate cannot be lower than 4.5-5 mm / s; when the macrostructure requirement of forgings is level 6, the ring growth rate is 4-5 mm / s; the main deformation ring growth rate cannot be lower than 5-5.5 mm / s;

[0032] Step 4. Final heat treatment: according to heat treatment: normalizing ≤800℃ into the furnace, heating with the furnace to 1070±10℃ and holding for 180min±15min; disperse air cooling; annealing ≤700℃ into the furnace, heating with the furnace to 740±10℃ and soaking for 180min±15min; holding for 120+12min; disperse air cooling;

[0033] Step 5: Machining: Perform all the polishing treatment on the forgings. Follow the rough machining drawing of the forgings.

[0034] Step 8: 100% mechanical property inspection and low-magnification inspection of forgings.

[0035] Example 1:

[0036] (1) Design process flow: forging bar → sawing to the length required by the process → processing to the forging blank required by the process → heat treatment → forging → hole expansion → heat treatment → physical and chemical treatment.

[0037] (2) The blank with the following process requirements (Φ200×460);

[0038] (3) Processing the raw material blanks;

[0039] (4) The processed workpiece is normalized at a temperature of 1049°C for 9.5 hours;

[0040] (5) After the bar material is upset to Φ310×190, it is rounded and then punched in the center. The punching core material size is ≤Φ110×60; after punching, the hole is expanded and the end face is flattened to Φ380×Φ220×171; the forging time of a single piece of ring upset punching is 180s-185s; the forging time of a single piece of expansion is 80s-85s;

[0041] (6) Expand the Φ380×Φ220×171 piece to the Φ492×Φ385×169 forging size; the ring growth rate is 3-4 mm / s; the main deformation ring growth rate cannot be lower than 4.5-5 mm / s;

[0042] (7) Stress relief annealing.

[0043] Before forging, a natural gas furnace or electric furnace should be prepared for annealing. The formed parts should be immediately subjected to stress relief annealing. The system is to directly transfer them into a natural gas furnace at 600℃ and keep them for 6 hours (air cooling after forging is not allowed). Then cool them to 500℃ and keep them for 1 hour. After taking them out of the furnace, cover them with high-temperature cotton in a windproof place and cool them (no exposure is allowed). After air cooling to room temperature, remove the high-temperature cotton.

[0044] The furnace door must not be opened after the forgings are placed in the furnace for stress relief annealing (the furnace door must be ensured to be at the bottom, and the dial line can be allowed to rise ≤50°C). It is required that the conventional heat treatment process must be carried out 24 hours after the stress relief annealing is completed;

[0045] (8) After heat treatment, the forgings are subjected to physical and chemical tests to meet the requirements shown in the figure.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should all be covered by the scope of protection of the present invention.

Claims

1. A forming method for achieving low-magnification structure effect of martensitic forgings by controlling parameters, characterized in that: include: Determine the required level of macrostructure of forgings; the material of forgings is 1Cr10Co6MoVNbN steel; Set different pretreatment parameters and forging parameters for the required level of macrostructure of forgings; Using the above pretreatment parameters and forging parameters, normalizing, forging, heat treatment and machining are performed; Among them, when the macrostructure requirement of forgings is level 4, the forging time of a single piece of ring upsetting and punching is 175s-180s; the forging time of a single piece of Ma-kuang is 75s-80s; when the macrostructure requirement of forgings is level 5, the forging time of a single piece of ring upsetting and punching is 180s-185s; the forging time of a single piece of Ma-kuang is 80s-85s; when the macrostructure requirement of forgings is level 6, the forging time of a single piece of ring upsetting and punching is 185s-190s; the forging time of a single piece of Ma-kuang is 85s-90s; When the macrostructure requirement of forgings is level four, the ring growth rate is 2-3 mm / s; the main deformation ring growth rate cannot be lower than 4-4.5 mm / s; when the macrostructure requirement of forgings is level five, the ring growth rate is 3-4 mm / s; the main deformation ring growth rate cannot be lower than 4.5-5 mm / s; when the macrostructure requirement of forgings is level six, the ring growth rate is 4-5 mm / s; the main deformation ring growth rate cannot be lower than 5-5.5 mm / s.

2. The molding method according to claim 1, characterized in that The pretreatment parameters are normalizing temperature and holding time, and the forging parameters include: upsetting and punching single piece forging time, machette expansion time, hole expansion time, ring speed increasing rate, and main transformer ring speed increasing value.

3. The method according to claim 2, characterized in that When the macrostructure requirement of forgings is level 4, the normalizing temperature is 1040℃-1045℃, and the holding time is 8.5 hours-9 hours; when the macrostructure requirement of forgings is level 5, the normalizing temperature is 1045℃-1050℃, and the holding time is 9 hours-9.5 hours; when the macrostructure requirement of forgings is level 6, the normalizing temperature is 1050℃-1055℃, and the holding time is 9.5 hours-10 hours.

4. The method according to claim 1, wherein Heat treatment, including: normalizing ≤800℃ into the furnace, heating with the furnace to 1070±10℃ and holding for 180min±15min; dispersed air cooling; annealing ≤700℃ into the furnace, heating with the furnace to 740±10℃ and soaking for 180min±15min; holding for 120+12min; dispersed air cooling.

5. The method according to claim 1, wherein Machining, including: full polishing of forgings.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

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