Warm and hot forming method of high-silicon austenitic stainless steel pipeline equipment

Abstract

The invention belongs to the technical field of material hot working, and relates to a warm forming method for high-silicon austenitic stainless steel pipeline equipment, which comprises the following steps of: heating a high-silicon austenitic stainless steel ingot to a first set temperature at a first set rate, and preserving heat for a first set time to obtain a first high-silicon austenitic stainless steel ingot; the first set temperature ranges from 1150 DEG C to 1170 DEG C; the first set time is 10-12 hours; and the first high-silicon austenitic stainless steel ingot is heated to the initial forging temperature at the first set speed and then subjected to heat preservation for second set time. According to the method, the stainless steel of the model is subjected to homogenizing heat treatment and warm forming under the conditions of proper temperature and strain rate, and then the forged stainless steel is subjected to solution treatment by utilizing waste heat after forging, so that the performance of the stainless steel of the model is improved, energy is saved, and the problems of cracks, fracture defects and the like generated in the forging process are avoided; and the internal structure uniformity is high, and the problem of warm forming machining of the high-silicon stainless steel is solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of material hot working, and particularly relates to a warm forming method for high-silicon austenitic stainless steel pipeline equipment. BACKGROUND

[0002] High-silicon austenitic stainless steel is a kind of metal material with good high-temperature corrosion resistance. The silicon content of this type of stainless steel is relatively high, being 4.8% to 6.0%. Silicon as an alloying element can improve the stress corrosion cracking resistance of stainless steel to chlorides, the corrosion resistance to strong oxidizing media (such as nitric acid and sulfuric acid), and the high-temperature oxidation resistance. However, the addition of silicon aggravates the element segregation and the precipitation of intermetallic ferrite phase, resulting in the deterioration of the hot working performance of the alloy, and the alloy is prone to cracking. Through the hot compression simulation experiment of high-silicon austenitic stainless steel, the warm forming process of the pipeline equipment of the material is studied, so as to break through the technical barriers in the field of petrochemical industry, and the high-silicon austenitic stainless steel is widely used in the production and transportation process of high-temperature concentrated sulfuric acid, such as drying tower, transportation pipeline, acid tank, etc. Silicon as an alloying element can improve the stress corrosion cracking resistance of stainless steel to chlorides, the corrosion resistance to strong oxidizing media (such as nitric acid and sulfuric acid), and the high-temperature oxidation resistance. The higher the content of silicon in austenitic stainless steel, the better the corrosion resistance, and the more severe the service conditions. However, the addition of silicon aggravates the element segregation and the precipitation of intermetallic ferrite phase, resulting in the deterioration of the hot working performance of the alloy, and the alloy is prone to cracking.

[0003] In the forging process, the hot working process parameters determine the quality of the product. If the hot working process parameters are not reasonably designed, cracks and cracks may occur in the alloy during forging, resulting in a serious reduction in the yield of finished products. Therefore, in order to optimize the subsequent processing performance of the alloy, it is urgent to develop a forging process method suitable for high-silicon austenitic stainless steel, so as to solve the problems of cracks and cracks in the alloy during hot working process and low yield of finished products. The cracking position after forging is shown in FIG. Figure 1 SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a warm forming method for high-silicon austenitic stainless steel pipeline equipment, which includes the homogenization heat treatment temperature before forging, the forging process parameters, and the heat treatment parameters after forging. The method solves the problems of cracks and cracks in high-silicon austenitic stainless steel during forging, improves the hot working plasticity of stainless steel, obtains high-silicon austenitic stainless steel with good hot plasticity, meets the subsequent reprocessing requirements, and has important significance for the self-production of high-end pressure vessels and strong acid pipeline equipment in the field of petrochemical industry.

[0005] To achieve the above object, the present application discloses the following technical scheme: ​The application discloses a warm forming method for a high-silicon austenitic stainless steel pipeline, which comprises the following steps: uniformly heating a high-silicon austenitic stainless steel ingot to a first set temperature at a first set rate, and then maintaining the temperature for a first set time; performing a homogenizing heat treatment on the high-silicon austenitic stainless steel ingot; cooling the high-silicon austenitic stainless steel ingot to room temperature after the maintaining; and obtaining a first high-silicon austenitic stainless steel ingot; the first set temperature is 1150-1170 DEG C; the first set time is 10-12 h; uniformly heating the first high-silicon austenitic stainless steel ingot to a start forging temperature at a first set rate, and then maintaining the temperature for a second set time; obtaining a second high-silicon austenitic stainless steel ingot; the start forging temperature is 1100-1120 DEG C; the second set time is 10-15 min; repeatedly forging the second high-silicon austenitic stainless steel ingot based on set forging parameters and a final forging temperature; obtaining an initial part; the set forging parameters comprise a forging rate and a deformation amount; the forging rate is 1-10 s-1; the final forging temperature is 950-1050 DEG C; uniformly heating / cooling the initial part to a second set temperature at a second set rate, and then maintaining the temperature for a third set time; obtaining a heat-treated part; the second set temperature is 1000-1050 DEG C; cooling the heat-treated part to room temperature; and obtaining a part forged by warm forging.

[0006] Further, the first set rate is 8-10 DEG C / s.

[0007] Further, the deformation amount is 30-60%.

[0008] Further, the second set rate is 5-8 DEG C / s.

[0009] Further, the third set time is 30 min-60 min.

[0010] Further, the content of silicon in the high-silicon austenitic stainless steel ingot is 4.8-6%.

[0011] Further, the high-silicon austenitic stainless steel ingot comprises the following components and contents: C: ≤0.07%, Si: 4.8-6%, Mn: ≤2%, P: ≤0.045%, S: ≤0.03%, Cr: 16.5-19.5%, Ni: 19-22%, Cu: 19-22% and Mo: 0.3-1.5%.

[0012] Further, the second high-silicon austenitic stainless steel ingot is repeatedly forged based on the set forging parameters and the final forging temperature to obtain the initial part, and the method specifically comprises the following steps: forging the second high-silicon austenitic stainless steel ingot based on the set forging parameters; monitoring the temperature of the second high-silicon austenitic stainless steel ingot during the forging; if the temperature is lower than the final forging temperature, re-heating the second high-silicon austenitic stainless steel ingot to the start forging temperature, and then forging the second high-silicon austenitic stainless steel ingot; repeating the process until the part is obtained.

[0013] Compared with the prior art, the present application has the following beneficial effects: The forging method of high-Si content austenitic stainless steel of the present application can forge high-silicon austenitic stainless steel with Si content of 4.8-6%, without cracking defects in the forging process, and the forged structure is relatively compact and uniform. The method has wide applicability, simple operation, low requirement for equipment, easy large-scale industrial production, high yield, and solves the cracking problem in the forging process. The heat treatment after forging utilizes the residual heat after forging for heat treatment, saving energy. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The microstructure of the stainless steel ingot of this type after homogenization heat treatment in Example 1; Figure 2 The microstructure of the stainless steel ingot of this type after forging in Example 1; Figure 3 The microstructure of the stainless steel after forging and heat treatment in Example 1; Figure 4 The flange plate forged using the process in Example 3; Figure 5 The cracking position of the stainless steel ingot after forging. DETAILED DESCRIPTION

[0015] Exemplary embodiments, features and aspects of the present application will be described in detail below with reference to the accompanying drawings. The same reference numbers in the drawings represent functionally identical or similar elements. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0016] The present application provides a warm forming method for high-silicon austenitic stainless steel pipe equipment, such as Figures 1-5The method comprises the following steps: uniformly heating a high-silicon austenitic stainless steel ingot to a first set temperature at a first set rate, holding for a first set time, and then cooling to room temperature to obtain a first high-silicon austenitic stainless steel ingot; the first set temperature is 1150-1170 DEG C; the first set time is 10-12 hours; uniformly heating the first high-silicon austenitic stainless steel ingot to a forging starting temperature at the first set rate, holding for a second set time, and then obtaining a second high-silicon austenitic stainless steel ingot; the forging starting temperature is 1100-1120 DEG C; the second set time is 10-15 minutes; repeatedly forging the second high-silicon austenitic stainless steel ingot based on set forging parameters and a final forging temperature, and the repeatedly forging is forging according to specified parameters to obtain an initial part; the set forging parameters include a forging rate and a deformation amount; the forging rate is 1-10 s-1; the final forging temperature is 950-1050 DEG C; heating or cooling the initial part to a second set temperature at a second set rate, holding for a third set time, and then obtaining a heat-treated part; the second set temperature is 1000-1050 DEG C; cooling the heat-treated part to room temperature to obtain a part forged at a warm temperature.

[0017] The first set rate is 8-10 DEG C / s.

[0018] The deformation amount is 30-60%.

[0019] The second set rate is 5-8 DEG C / s.

[0020] The third set time is 30-60 minutes.

[0021] The content of silicon in the high-silicon austenitic stainless steel ingot is 4.8-6%.

[0022] The high-silicon austenitic stainless steel ingot comprises the following components and contents: C: ≤0.07%, Si: 4.8-6%, Mn: ≤2%, P: ≤0.045%, S: ≤0.03%, Cr: 16.5-19.5%, Ni: 19-22%, Cu: 19-22%, and Mo: 0.3-1.5%.

[0023] The repeatedly forging the second high-silicon austenitic stainless steel ingot based on the set forging parameters and the final forging temperature to obtain the initial part, specifically: Forging the second high-silicon austenitic stainless steel ingot based on the set forging parameters, and monitoring the temperature of the second high-silicon austenitic stainless steel ingot during the forging process; if the temperature is lower than the final forging temperature, the second high-silicon austenitic stainless steel ingot is reheated to the forging starting temperature and then forged, and the process is repeated until the part is obtained.

[0024] In the forging process, the temperature, strain rate, deformation amount and other data of the ingot are collected and input into the machine learning model to predict whether the ingot is likely to crack. If the model predicts a high risk of cracking, the forging parameters are adjusted to reduce the risk of cracking.

[0025] The machine learning model used is an LSTM model, and the input data is the heat treatment temperature, strain rate, temperature and other parameters in the early stage of warm forging. The output result is the prediction of cracking.

[0026] Example 1 The present application provides a forging method suitable for high-silicon austenitic stainless steel with Si content of 4.8-6.0wt.%. The specific forging process is as follows: 1) Select the chemical composition (wt.%) of high-Si content austenitic stainless steel alloy: C: ≤0.07%, Si: 4.8-6%, Mn: ≤2%, P: ≤0.045%, S: ≤0.03%, Cr: 16.5-19.5%, Ni: 19-22%, Cu: 19-22%, Mo: 0.3-1.5%.

[0027] 2) High-temperature demolding: After the smelting of this type of stainless steel is completed, high-temperature demolding is carried out at 600-800℃, and then homogenization heat treatment is carried out in a heat treatment furnace.

[0028] 3) In step 2), the ingot homogenization heat treatment: the ingot after high-temperature demolding is immediately placed in a heat treatment furnace with a temperature of 800-850℃ for 5min, and then homogenization heat treatment is carried out at a rate of 10℃ / s to 1150℃, and the holding time is 10min. The microstructure after homogenization heat treatment is as shown in Figure 1 .

[0029] 4) Initial forging temperature preparation: the ingot after homogenization heat treatment is first cooled to the initial forging temperature for 10min. The ingot after homogenization heat treatment in step 2) is reheated to the initial forging temperature at a rate of 5℃ / s during forging.

[0030] 5) Isothermal forging: the initial forging temperature is 1100℃, and the temperature of the billet after being taken out of the furnace will decrease too quickly, which will cause the precipitation of brittle phase and surface cracking. Therefore, the final forging temperature should not be lower than 950℃, and the forging rate is 1-10s -1 , air hammer is used for rapid forging, and the deformation amount is 50%. When the temperature is lower than 950℃, it needs to be reheated to 1100℃ and held for 10min before forging. The microstructure after forging is as shown in Figure 2 .

[0031] 6) Forging after cooling and heat treatment: after the forging of the billet, the water cooling method is used for rapid cooling to prevent the rapid growth and large amount of precipitation of the precipitated phase. The forged ingot is kept in the heat treatment furnace used in step 2) for heat treatment, and the temperature in the furnace is reduced to 1050℃ at a rate of 5℃ / s for 1h to save energy. The microstructure of the heat treatment after forging is shown in Figure 3 .

[0032] The forged ingot does not have cracking phenomenon, and the internal part is also free of cracks. Through metallographic analysis, it is known that the forging structure is uniformly distributed.

[0033] Example 2 1) The chemical composition of the ingot is as follows (wt, %): C: ≤0.07%, Si: 4.8-6%, Mn: ≤2%, P: ≤0.045%, S: ≤0.03%, Cr: 16.5-19.5%, Ni: 19-22%, Cu: 19-22%, Mo: 0.3-1.5%. After the end of smelting, the ingot is demolded at 800℃ and immediately put into a heat treatment furnace at 800-850℃ for homogenization heat treatment.

[0034] 2) Ingot homogenization heat treatment: the high-temperature heat treatment furnace is heated to 1150℃ at a rate of 10℃ / s for homogenization heat treatment, and the holding time is 10min.

[0035] 3) Ingot initial forging temperature preparation: the ingot after homogenization heat treatment is reduced to the initial forging temperature at a rate of 5℃ / s, and the initial forging temperature is 1100℃.

[0036] 4) Constant temperature multi-pass forging: after the billet is discharged from the furnace, the air hammer is used for rapid forging, and the billet is upset along the axial direction with a deformation of 20%, and then further upset with a deformation of 40% and 60%. In the forging process, the temperature gun is used for temperature monitoring, and the temperature is lower than 1100℃. The billet is immediately returned to the furnace for reheating.

[0037] 5) Forging after cooling and heat treatment: after the forging of the billet, the water cooling method is used for rapid cooling to prevent the rapid growth and large amount of precipitation of the precipitated phase. The forged ingot is kept in the heat treatment furnace used in step 2) for heat treatment, and the temperature in the furnace is reduced to 1050℃ at a rate of 5℃ / s for 1h.

[0038] The forged ingot does not have cracking phenomenon, and the internal part is also free of cracks. Through metallographic analysis, it is known that the forging structure is uniformly distributed.

[0039] Example 3 The present application can be applied to the forging of flanges in industrial production. The specific steps are as follows: 1) The stainless steel of this type is used to remove the mold at 800℃ after smelting, and then immediately put into a heat treatment furnace at 800-850℃ for homogenization heat treatment.

[0040] 2) Homogenization heat treatment: the temperature in the furnace is raised to 1150℃ at a rate of 10℃ / s, and the temperature is kept for 10 minutes.

[0041] 3) Isothermal forging: forging is carried out at 1000℃, and if the temperature of the billet decreases too fast after being taken out of the furnace, brittle phase will be precipitated, causing surface cracking, so the final forging temperature should be no less than 950℃, and the forging rate is 1-10s -1 , air hammer is used for rapid forging, and the deformation is 50%. When the temperature is lower than 950℃, the billet needs to be reheated to 1100℃ and kept for 10 minutes before forging.

[0042] 4) Cooling and heat treatment after forging: water cooling is used to prevent the rapid growth and large precipitation of precipitated phase. The forged ingot is kept in the heat treatment furnace used in step 2) for heat treatment to save energy, and the temperature in the furnace is reduced to 1050℃ at a rate of 5℃ / s for 1 hour.

[0043] The above-mentioned process is used to cast the stainless steel ingot in the appropriate mold, and after cleaning and polishing, the flange plate used in industrial production is obtained as shown in Figure 4 , without surface cracks and internal cracking.

[0044] As shown in Figure 5 , if the homogenization heat treatment is not carried out or the heat treatment temperature is not appropriate, and the forging temperature is too high or too low, cracking will occur.

[0045] The above-mentioned examples only describe the preferred embodiments of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for hot forging of parts based on high-silicon austenitic stainless steel, characterized in that, It includes the following steps: S1. Heat the high-silicon austenitic stainless steel ingot to 1150-1170℃ at a first set rate and hold for 10-12 hours to homogenize the high-silicon austenitic stainless steel ingot. After holding, cool to room temperature to obtain the first high-silicon austenitic stainless steel ingot. S2. Heat the first high-silicon austenitic stainless steel ingot to the initial forging temperature of 1100-1120℃ at the first set rate and hold for 10-15 minutes to obtain the second high-silicon austenitic stainless steel ingot. S3. Based on the set forging parameters, the second high-silicon austenitic stainless steel ingot is repeatedly forged at a final forging temperature of 950-1050℃ to obtain the initial parts; the set forging parameters include forging rate and deformation amount; the forging rate is 1-10s. -1 ; S4. Heat / cool the initial component to 1000-1050℃ at the second set rate and hold it at that temperature for the third set time to obtain the heat-treated component. S5. Cool the heat-treated parts to room temperature to obtain the parts after warm forging.

2. The method for hot forging of parts based on high-silicon austenitic stainless steel according to claim 1, characterized in that, In step S1, the first set rate is 8-10℃ / s.

3. The method for hot forging of parts based on high-silicon austenitic stainless steel according to claim 1, characterized in that, The deformation amount in step S3 is 30-60%.

4. The method for hot forging of parts based on high-silicon austenitic stainless steel according to claim 1, characterized in that, In step S4, the second set rate is 5-8℃ / s.

5. The method for hot forging of parts based on high-silicon austenitic stainless steel according to claim 1, characterized in that, In step S4, the third time setting is 30min-60min.

6. The method for hot forging of parts based on high-silicon austenitic stainless steel according to claim 1, characterized in that, In step S1, the silicon content in the high-silicon austenitic stainless steel ingot is 4.8-6%.

7. The method for hot forging of parts based on high-silicon austenitic stainless steel according to claim 1, characterized in that, The composition and content of the high-silicon austenitic stainless steel ingot in step S1 are as follows: C: ≤0.07%, Si: 4.8-6%, Mn: ≤2%, P: ≤0.045%, S: ≤0.03%, Cr: 16.5-19.5%, Ni: 19-22%, Cu: 19-22% and Mo: 0.3-1.5%.

8. The method for hot forging of parts based on high-silicon austenitic stainless steel according to claim 1, characterized in that, Step S3 is as follows: The second high-silicon austenitic stainless steel ingot is forged based on the set forging parameters. During the forging process, the temperature of the second high-silicon austenitic stainless steel ingot is monitored. If the temperature is lower than the final forging temperature, the second high-silicon austenitic stainless steel ingot is reheated to the initial forging temperature and forged again. This process is repeated until the parts are obtained.

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