Forging process of super duplex stainless steel S32760 large-wall-thickness bar

Abstract

The invention relates to the technical field of duplex stainless steel bar forging, in particular to a forging process of a super duplex stainless steel S32760 large-wall-thickness bar, which comprises the following steps: S1, collecting data and constructing a forging simulation model: collecting previous forging data, and constructing the forging simulation model through a finite element technology; s2, proper materials are selected to be made into steel billets, specifically, the materials are selected according to the machining requirement of a to-be-forged bar, and the materials are melted; through anvil block preheating and temperature control in each step in the forging process, the internal and external temperature difference of the forge piece is delayed, the cracking tendency of the forge piece is reduced, and no obvious forging crack is generated on the surface; the final forging temperature is guaranteed to be larger than or equal to 950 DEG C, the forging ratio is increased, grains are refined, and UT detection is free of defects; in addition, the transfer speed during quenching is controlled, and no sigma brittle phase is generated in the structure. The S32760 round bar with the diameter of 260 circles produced by the process has no cracking phenomenon, the T / 4 and T / 2 transverse and longitudinal low-temperature impact of the forged piece subjected to heat treatment exceeds 100J, and the transverse spot corrosion performance is qualified.

Description

Technical Field

[0001] The invention relates to the technical field of duplex stainless steel bar forging, and in particular to a forging process of a super duplex stainless steel S32760 heavy-walled bar. Background Art

[0002] Duplex stainless steel is a special type of stainless steel, consisting of ferrite and austenite. Its performance combines the different advantages of the two phases. Therefore, while maintaining high strength, duplex stainless steel also has better resistance to chloride ions and intergranular corrosion than austenitic stainless steel and better low-temperature impact toughness than ferritic stainless steel. It has been widely used in petrochemical, marine, nuclear power, food and other fields.

[0003] For example, a special forging method suitable for super duplex stainless steel bars with the authorization announcement number CN105689613B and the authorization announcement date 20171107. The present invention makes full use of the respective advantages and disadvantages of the radial forging machine and the fast forging machine, and combines the characteristics of super duplex stainless steel to create a new special forging method for super duplex stainless steel bars. The method uses steel ingots as raw materials, and includes the following steps in sequence: radial forging and fast forging combined blanking, radial forging, air cooling and solution treatment. The super duplex stainless steel bars forged by this process have a high finished product yield rate (the forging yield rate is increased by more than 5% compared with the original method), high production efficiency, and low energy consumption. The invention can forge square or polygonal steel ingots with a cross-section of (200-700) × (200-700) mm into bars of Φ60-400 mm.

[0004] S32760 super duplex stainless steel is a type of duplex stainless steel with PREN≥40, which contains a large amount of Cr, Mo, N elements and a small amount of W and Cu elements, further improving the corrosion resistance of the material and making it suitable for harsh service environments such as deep sea. However, it also increases the formation temperature of brittle precipitation phases such as σ, which is prone to forging cracking, or low low-temperature impact toughness of the material. At the same time, large forgings are prone to large temperature differences between the surface and the core of the forging, and uneven deformation, which reduces the performance of the material. In view of this, it is urgent to design a forging process for super duplex stainless steel S32760 thick wall bars to solve the above problems. Summary of the invention

[0005] The object of the present invention is to provide a forging process for super duplex stainless steel S32760 thick wall bars to solve the above-mentioned deficiencies in the prior art.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A forging process for a super duplex stainless steel S32760 thick wall bar comprises the following steps:

[0008] S1. Collect data and build a forging simulation model: collect previous forging data and build a forging simulation model through finite element technology;

[0009] S2. Select appropriate materials and make steel billets: Select materials according to the processing requirements of the bars to be forged, and melt the materials. During the melting process, the materials will be oxidized and form electroslag, which will be cooled and solidified to obtain a rod-shaped steel billet;

[0010] S3. Run the simulation model to open the steel billet: according to the processing requirements of the bar to be forged, input parameters to the simulation model, and then run the simulation model to obtain simulation data. After the simulation is completed, preheat the steel billet;

[0011] S4. Forging the steel billet according to the model operation results: performing optimal analysis on the simulation data to obtain the optimal result of the model operation, placing the preheated steel billet into the forging heating device, and subsequently starting the forging heating device for forging processing;

[0012] S5. After forging, water cooling is performed and non-destructive testing is performed: After forging is completed, the bar is obtained and then non-destructive testing is performed on the bar;

[0013] S6. Heat-treat the workpiece by oil quenching and water cooling: After the inspection, the rod is sent to the heat treatment equipment for heat treatment, and then cooled by oil quenching and water quenching to obtain the treated rod.

[0014] Furthermore, the previous forging data in step S1 is the forging data of bars previously produced by the workshop, and the finite element technology in step S1 adopts POLIGONSOFT simulation software.

[0015] Furthermore, the materials selected in step S2 and their percentages are as follows: C: ≤0.03%, Mn: ≤1.00%, P: ≤0.03%, S: ≤0.01%, Si: ≤1.00%, Cr: 24.00-26.00%, Ni: 6.0-8.0%, Mo: 3.0-4.0%, Cu: 0.5-1.0%, W: 0.5-1.0%, N: 0.20-0.30%, and the remaining elements are Fe and other residual elements.

[0016] Furthermore, the simulation model in step S3 is run 3-5 times, and the preheating temperature of the steel billet in step S3 is 900-1100°C.

[0017] Furthermore, during the forging process of step S4, the charging temperature is ≤300°C, the heating rate is ≤100°C / h, the forging temperature is 1220°C, the initial forging temperature is ≥1120°C, and the final forging temperature is ≥950°C. During the forging process of step S4, the forging is performed according to the optimal result of the simulation model.

[0018] Furthermore, the forging process of step S4 is divided into three steps, and the details are as follows:

[0019] (1) First fire: roughing, forging ratio>1.5, remelting and heat preservation for not less than 1.5h;

[0020] (2) Second fire: drawing, forging ratio>1.5, remelting and heat preservation for not less than 1.5h;

[0021] (3) Third fire: stretch and round, forging ratio > 1.5, air cooling.

[0022] Furthermore, during the forging process of step S4, the anvil and other tooling need to be preheated, and during the forging process of step S4, the forging ratio of each fire is ≥1.5.

[0023] Furthermore, the nondestructive testing in step S5 includes three testing methods: ultrasonic testing, optical testing, and eddy current testing.

[0024] Furthermore, the heat treatment in step S6 is quenching treatment, and the quenching times are three times, the first quenching uses water cooling, the second quenching uses oil quenching, the third quenching uses water cooling, and the time for the furnace to be transferred to the quenching tank does not exceed 60s.

[0025] Furthermore, in the heat treatment process of step S6, the quenching heating rate is ≤200°C / h, the temperature is raised to 1100-1140°C, and the holding time is ≥5h.

[0026] In the above technical solution, the present invention provides a forging process for a super duplex stainless steel S32760 thick wall bar, and the beneficial effects are:

[0027] (1) The present invention delays the temperature difference between the inside and outside of the forging by preheating the anvil and controlling the temperature at each step of the forging process, reduces the cracking tendency of the forging, and produces no obvious forging cracks on the surface; ensures that the final forging temperature is ≥950℃, increases the forging ratio, refines the grains, and has no defects in UT detection; in addition, the transfer speed during quenching is controlled, and no σ brittle phase is produced in the organization. The S32760 round bars with a diameter of 260 produced by this process have no cracking phenomenon. After heat treatment, the transverse and longitudinal low-temperature impacts of the forgings at T / 4 and T / 2 are both over 100J, and the transverse pitting corrosion performance is qualified.

[0028] (2) The forging process designed in the present invention adds a simulation link, and the steel billet can be forged through the optimal simulation result, which reduces the probability of errors in the forging process and can ensure the quality of the bar after forming.

[0029] (3) The forging process designed in the present invention can improve the strength and other mechanical properties of the bar through three quenching processes, and the simultaneous oil quenching and water quenching processes can significantly improve the toughness, stiffness and other properties of the bar. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0031] Figure 1 The present invention provides a schematic diagram of a method flow for a forging process embodiment of a super duplex stainless steel S32760 thick wall bar.

[0032] Figure 2 A schematic diagram of a forging process is provided for a forging process embodiment of a super duplex stainless steel S32760 thick wall bar of the present invention.

[0033] Figure 3 A schematic diagram of a round bar heat treatment process is provided for a forging process embodiment of a super duplex stainless steel S32760 thick wall bar of the present invention.

[0034] Figure 4 A diagram of the metallographic structure at T / 4 of a super duplex stainless steel S32760 thick-walled bar after heat treatment is provided in an embodiment of the forging process of the present invention.

[0035] Figure 5 Figure B is a metallographic structure diagram at T / 4 of a super duplex stainless steel S32760 thick-walled bar after heat treatment, provided in an embodiment of the forging process of the present invention. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] like Figure 1-5 As shown, a forging process of a super duplex stainless steel S32760 thick wall bar provided by an embodiment of the present invention comprises the following steps:

[0038] S1. Collect data and build a forging simulation model: collect previous forging data, which is the forging data of bars produced in the workshop in the past, and build a forging simulation model through finite element technology. The finite element technology uses POLIGONSOFT simulation software;

[0039] S2. Select appropriate materials to make steel billets: select materials according to the processing requirements of the bars to be forged, and the material selection and their percentages are as follows: C: ≤0.03%, Mn: ≤1.00%, P: ≤0.03%, S: ≤0.01%, Si: ≤1.00%, Cr: 24.00-26.00%, Ni: 6.0-8.0%, Mo: 3.0-4.0%, Cu: 0.5-1.0%, W: 0.5-1.0%, N: 0.20-0.30%, and the remaining elements are Fe and other residual elements, and the materials are melted. During the melting process, the materials will be oxidized and form electroslag, and the electroslag is cooled and solidified to obtain a rod-shaped steel billet;

[0040] S3. Run the simulation model to open the billet: according to the processing requirements of the bar to be forged, input parameters to the simulation model, and then run the simulation model to obtain simulation data. The simulation model is run 3-5 times. After the simulation is completed, the billet is preheated at a preheating temperature of 900-1100°C.

[0041] S4. Forging of steel billets according to the results of model operation: optimal analysis of simulation data is performed to obtain the optimal results of model operation, and the preheated steel billets are placed in the forging heating equipment, and then the forging heating equipment is turned on for forging. During the forging process, the furnace temperature is ≤300℃, the heating rate is ≤100℃ / h, the forging temperature is 1220℃, the initial forging temperature is ≥1120℃, and the final forging temperature is ≥950℃. During the forging process, the anvil and other tooling need to be preheated. During the forging process, the forging ratio of each fire is ≥1.5. During the forging process, forging is performed according to the optimal results of the simulation model, and the forging process is divided into three steps, as follows:

[0042] (1) First fire: roughing, forging ratio>1.5, remelting and heat preservation for not less than 1.5h;

[0043] (2) Second fire: drawing, forging ratio>1.5, remelting and heat preservation for not less than 1.5h;

[0044] (3) Third fire: elongation and rounding, forging ratio>1.5, air cooling;

[0045] S5. After forging, water cooling is performed and non-destructive testing is performed: After forging, the bars are obtained and then non-destructive testing is performed on the bars. The non-destructive testing includes three testing methods: ultrasonic testing, optical testing, and eddy current testing;

[0046] S6. Heat treatment of the workpiece, oil quenching and water cooling treatment: After the inspection, the rod is sent to the heat treatment equipment for heat treatment, and then cooled by oil quenching and water quenching to obtain the treated rod. The heat treatment is solid solution treatment and quenching treatment, and the quenching times are three times. The first quenching is water cooling, the second quenching is oil quenching, and the third quenching is water cooling. The time from the furnace to the quenching tank does not exceed 60s. When solid solution, the temperature is raised to 1100-1140℃ at a rate of ≥150℃ / h for solid solution treatment. When quenching, the quenching heating rate is ≤200℃ / h, the temperature is raised to 1100-1140℃, and the insulation time is ≥5h.

[0047] Embodiment 1

[0048] A forging process for a super duplex stainless steel S32760 thick wall bar comprises the following steps:

[0049] S1. Collect data and build a forging simulation model: collect previous forging data, which is the forging data of bars produced in the workshop in the past, and build a forging simulation model through finite element technology. The finite element technology uses POLIGONSOFT simulation software;

[0050] S2. Select appropriate materials to make steel billets: Select materials according to the processing requirements of the bars to be forged. The materials and their percentages are as follows: C: 0.018%, Si: 0.44%, Mn: 0.66%, P: 0.023%, S: 0.001%, Cr: 25.07%, Ni: 7.14%, Mo: 3.28%, Cu: 0.63%, W: 0.64%, N: 0.26%, and the remaining elements are Fe and other residual elements. The materials are melted. During the melting process, the materials will be oxidized and form electroslag. The electroslag is cooled and solidified to obtain a 350 round bar-shaped steel billet;

[0051] S3. Run the simulation model to open the billet: according to the processing requirements of the bar to be forged, input parameters to the simulation model, and then run the simulation model to obtain simulation data. The simulation model runs 3-5 times. After the simulation is completed, the 420kg billet is preheated at a preheating temperature of 900-1100°C.

[0052] S4. Forging of steel billets according to the model operation results: optimal analysis of the simulation data is performed to obtain the optimal results of the model operation, the preheated steel billets are placed in the forging heating equipment, and the forging heating equipment is subsequently turned on forging treatment. During the forging process, the furnace temperature is ≤300°C, the heating rate is ≤100°C / h, the forging temperature is 1220°C, the initial forging temperature is 1120°C, and the final forging temperature is 950°C. During the forging process, the anvil and other tooling need to be preheated. During the forging process, the forging ratio of each fire is within the range of 1.2-1.3. During the forging process, forging is performed according to the optimal results of the simulation model, and the forging process is divided into three steps, as follows:

[0053] (1) First fire: roughening to 425 high, controlling the forging ratio to 1.2-1.3, and the return to the furnace for a holding time of not less than 1.5h;

[0054] (2) Second fire: longitudinally draw to 350 square meters, control the forging ratio to 1.2-1.3, and return to the furnace for a holding time of no less than 1.5 hours;

[0055] (3) Third fire: longitudinally draw to 300 square meters, control the forging ratio to 1.2-1.3, and return to the furnace for a holding time of no less than 1.5 hours;

[0056] (4) Fourth fire: longitudinally draw to 260 square, control the forging ratio to 1.2-1.3, and return to the furnace for a holding time of not less than 1.5 hours;

[0057] (5) Fourth fire: longitudinally elongated and rounded to 260 degrees, controlling the forging ratio to 1.2-1.3, air cooling;

[0058] S5. After forging, water cooling is performed and non-destructive testing is performed: After forging, the bars are obtained and then non-destructive testing is performed on the bars. The non-destructive testing includes three testing methods: ultrasonic testing, optical testing, and eddy current testing;

[0059] S6. Heat treatment of the workpiece, oil quenching and water cooling treatment: After the inspection, the rod is sent to the heat treatment equipment for heat treatment, and then cooled by oil quenching and water quenching to obtain the treated rod. The heat treatment is solid solution treatment and quenching treatment, and the quenching times are three times. The first quenching is water cooling, the second quenching is oil quenching, and the third quenching is water cooling. The time from the furnace to the quenching tank does not exceed 60s. During solid solution treatment, the temperature is raised to 1100-1140℃ at a rate of ≥150℃ / h for solid solution treatment, and the temperature is kept for 5h and then water cooled; during subsequent quenching, the quenching heating rate is 150℃ / h≤quenching heating rate≤200℃ / h, the temperature is raised to 1100-1140℃, and the temperature is kept for ≥5h.

[0060] Embodiment 2

[0061] A forging process for a super duplex stainless steel S32760 thick wall bar comprises the following steps:

[0062] S1. Collect data and build a forging simulation model: collect previous forging data, which is the forging data of bars produced in the workshop in the past, and build a forging simulation model through finite element technology. The finite element technology uses POLIGONSOFT simulation software;

[0063] S2. Select appropriate materials to make steel billets: Select materials according to the processing requirements of the bars to be forged. The materials and their percentages are as follows: C: 0.018%, Si: 0.44%, Mn: 0.66%, P: 0.023%, S: 0.001%, Cr: 25.07%, Ni: 7.14%, Mo: 3.28%, Cu: 0.63%, W: 0.64%, N: 0.26%, and the remaining elements are Fe and other residual elements. The remaining elements are Fe and other residual elements, and the materials are melted. During the melting process, the materials will be oxidized and form electroslag. The electroslag is cooled and solidified to obtain a 350 round bar-shaped steel billet;

[0064] S3. Run the simulation model to open the billet: according to the processing requirements of the bar to be forged, input parameters to the simulation model, and then run the simulation model to obtain simulation data. The simulation model runs 3-5 times. After the simulation is completed, the 420kg billet is preheated at a preheating temperature of 900-1100°C.

[0065] S4. Forging of steel billets according to the results of model operation: optimal analysis of simulation data is performed to obtain the optimal results of model operation, and the preheated steel billets are placed in the forging heating equipment, and then the forging heating equipment is turned on for forging. During the forging process, the furnace temperature is ≤300℃, the heating rate is ≤100℃ / h, the forging temperature is 1220℃, the initial forging temperature is 1120℃, and the final forging temperature is 960℃. During the forging process, the anvil and other tooling need to be preheated. During the forging process, the forging ratio of each fire is within the range of 1.2-1.3. During the forging process, forging is performed according to the optimal results of the simulation model, and the forging process is divided into three steps, as follows:

[0066] (1) First fire: roughing, forging ratio>1.5, remelting and heat preservation for not less than 1.5h;

[0067] (2) Second fire: drawing, forging ratio>1.6, remelting and heat preservation for not less than 1.5h;

[0068] (3) Third fire: elongation and rounding, forging ratio>1.6, air cooling;

[0069] S5. After forging, water cooling is performed and non-destructive testing is performed: After forging, the bars are obtained and then non-destructive testing is performed on the bars. The non-destructive testing includes three testing methods: ultrasonic testing, optical testing, and eddy current testing;

[0070] S6. Heat treatment of the workpiece, oil quenching and water cooling treatment: After the inspection, the rod is sent to the heat treatment equipment for heat treatment, and then cooled by oil quenching and water quenching to obtain the treated rod. The heat treatment is solid solution treatment and quenching treatment, and the quenching times are three times. The first quenching is water cooling, the second quenching is oil quenching, and the third quenching is water cooling. The time from the furnace to the quenching tank does not exceed 60s. During solid solution treatment, the temperature is raised to 1100-1140℃ at a rate of ≥150℃ / h for solid solution treatment, and the temperature is kept for 5h and then water cooled; during subsequent quenching, the quenching heating rate is 150℃ / h≤quenching heating rate≤200℃ / h, the temperature is raised to 1100-1140℃, and the temperature is kept for ≥5h.

[0071] The performance of the round bars made in Example 1 and Example 2 was tested, and the following table was obtained:

[0072]

[0073] It can be seen from the table that the lateral impact of the bar made in Example 1 is not high, and the FeCl3 pitting corrosion test is unqualified. In the forging process of Example 2, increasing the deformation can refine the grains in the core of the forging. At the same time, the larger deformation promotes the transformation of ferrite to austenite, increases the content of austenite, and improves the low-temperature impact toughness of the forging. The electroslag ingot containing a small amount of inclusions reduces the organizational defects to a certain extent and reduces the nucleation points of pitting corrosion. The larger deformation refines the austenite grains and increases the ∑3 grain boundaries in the austenite, so the product has good pitting corrosion resistance.

[0074] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A forging process for super duplex stainless steel S32760 thick wall bar, characterized in that: The following steps are involved: S1. Collect data and build a forging simulation model: collect previous forging data and build a forging simulation model through finite element technology; S2. Select appropriate materials and make steel billets: Select materials according to the processing requirements of the bars to be forged, and melt the materials. During the melting process, the materials will be oxidized and form electroslag, which will be cooled and solidified to obtain a rod-shaped steel billet; S3. Run the simulation model to open the steel billet: according to the processing requirements of the bar to be forged, input parameters to the simulation model, and then run the simulation model to obtain simulation data. After the simulation is completed, preheat the steel billet; S4. Forging the steel billet according to the model operation results: performing optimal analysis on the simulation data to obtain the optimal result of the model operation, placing the preheated steel billet into the forging heating device, and subsequently starting the forging heating device for forging processing; S5. After forging, water cooling is performed and non-destructive testing is performed: After forging is completed, the bar is obtained and then non-destructive testing is performed on the bar; S6. Heat-treat the workpiece by oil quenching and water cooling: After the inspection, the rod is sent to the heat treatment equipment for heat treatment, and then cooled by oil quenching and water quenching to obtain the treated rod.

2. The forging process of super duplex stainless steel S32760 thick wall bar according to claim 1, characterized in that: The previous forging data in step S1 are forging data of bars produced in the workshop in the past, and the finite element technology in step S1 adopts POLIGONSOFT simulation software.

3. The forging process of super duplex stainless steel S32760 thick wall bar according to claim 1, characterized in that: The materials selected in step S2 and their percentages are as follows: C: ≤0.03%, Mn: ≤1.00%, P: ≤0.03%, S: ≤0.01%, Si: ≤1.00%, Cr: 24.00-26.00%, Ni: 6.0-8.0%, Mo: 3.0-4.0%, Cu: 0.5-1.0%, W: 0.5-1.0%, N: 0.20-0.30%, and the remaining elements are Fe and other residual elements.

4. The forging process of super duplex stainless steel S32760 thick wall bar according to claim 1, characterized in that: The simulation model in step S3 is run 3-5 times, and the preheating temperature of the steel billet in step S3 is 900-1100°C.

5. The forging process of super duplex stainless steel S32760 thick wall bar according to claim 1, characterized in that: During the forging process of step S4, the furnace charging temperature is ≤300°C, the heating rate is ≤100°C / h, the forging temperature is 1220°C, the initial forging temperature is ≥1120°C, and the final forging temperature is ≥950°C. During the forging process of step S4, the forging is performed according to the optimal result of the simulation model.

6. The forging process of super duplex stainless steel S32760 thick wall bar according to claim 1, characterized in that: The forging process of step S4 is divided into three steps, and the details are as follows: (1) First fire: roughing, forging ratio>1.5, remelting and heat preservation for not less than 1.5h; (2) Second fire: drawing, forging ratio>1.5, remelting and heat preservation for not less than 1.5h; (3) Third fire: stretch and round, forging ratio > 1.5, air cooling.

7. The forging process of super duplex stainless steel S32760 thick wall bar according to claim 1, characterized in that: During the forging process of step S4, the anvil and other tools need to be preheated, and the forging ratio of each fire during the forging process of step S4 is ≥1.

5.

8. The forging process of super duplex stainless steel S32760 thick wall bar according to claim 1, characterized in that: The nondestructive testing in step S5 includes three testing methods: ultrasonic testing, optical testing, and eddy current testing.

9. The forging process of super duplex stainless steel S32760 thick wall bar according to claim 1, characterized in that: The heat treatment in step S6 is solution treatment and quenching treatment, and the quenching times are three times. The first quenching is water cooling, the second quenching is oil quenching, and the third quenching is water cooling. The time for the furnace to be transferred to the quenching tank does not exceed 60s. During the solution treatment, the temperature is raised to 1100-1140°C at a rate of ≥150°C / h for solution treatment.

10. The forging process of super duplex stainless steel S32760 thick wall bar according to claim 1, characterized in that: In the step S6 heat treatment process, the quenching heating rate is ≤200°C / h, the temperature is raised to 1100-1140°C, and the holding time is ≥5h.

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