A short-process rolling forming method for large-scale structural steel stainless steel ring forgings

Abstract

The present invention belongs to the technical field of hot processing of metal materials, and discloses a short-process rolling forming method for large-scale structural steel stainless steel ring forgings. The method comprises the following steps: step one: select qualified re-inspected bar materials for blanking; step two: grind the edges and corners of the bar materials into rounded corners; and preheat the tooling for production; step three: heat the ground bar materials to 1100°C to 1180°C and keep them warm; step four: punch the heated bar materials in step three on a fast forging machine; then move them to a pre-rolling ring rolling machine for pre-rolling, and then move them to a final rolling ring rolling machine for final rolling; step five: heat treat the forgings after final rolling. The present invention forms the forgings by upsetting, punching-pre-expansion-final expansion in one fire step. This method can greatly improve the production efficiency of structural steel and stainless steel ring forgings of forging enterprises, and the total forging ratio is 7 to 10, which can effectively improve the organizational state of the ring forgings and improve the comprehensive mechanical properties of structural steel and stainless steel ring forgings.

Description

Technical Field

[0001] The invention belongs to the technical field of hot processing of metal materials, and in particular relates to a short-process rolling forming method for a large-scale structural steel stainless steel ring forging. Background Art

[0002] Structural steel and stainless steel ring forgings are a common forging product, mainly used in engine casings, bearing seats, petrochemical flanges, pressure vessel cylinders and other fields. The traditional production process is usually: cutting → upsetting, punching → pre-expansion → final expansion → heat treatment → physical and chemical → machining. The forging process: upsetting, punching → pre-expansion → final expansion generally requires one to several fires to complete, especially for large structural steel and stainless steel ring forgings with a weight of ≥50Kg and an outer diameter of ≥500mm. Each link requires more fires. Multiple heating of ring forgings virtually prolongs the production cycle and causes great energy waste and material loss. The burnout rate of each fire in a gas furnace is 1.5-2.5%, and the burnout rate of each fire in a resistance furnace is 1-1.5%. A short-process casting and rolling composite forming method for metal rings disclosed in Chinese patent publication number CN101817134A and a die forging and rolling composite forming method for large rings with different cross-sections disclosed in Chinese patent publication number CN102689163A have shortened the production process to a certain extent, achieved the beneficial effects of saving energy and improving efficiency, but the above two methods are highly dependent on centrifugal casting or extrusion casting equipment, are not suitable for forging enterprises, and the total forging ratio of the ring blank from casting to forging is 2 to 3 smaller, and the comprehensive performance cannot meet the increasingly stringent market requirements. Summary of the invention

[0003] The purpose of the present invention is to provide a short-process rolling forming method for large-scale structural steel stainless steel ring forgings. According to the characteristics of structural steel and stainless steel having a wide forging temperature range, a fast forging machine and a ring rolling machine are used for combined forging to achieve the completion of upsetting, punching, pre-expansion and final expansion in one pass.

[0004] A short-process rolling forming method for a large-scale structural steel stainless steel ring forging comprises the following steps:

[0005] Step 1: Select the qualified bar material for cutting;

[0006] Step 2: Grind the edges and corners of the bar into rounded corners; and preheat the production tooling;

[0007] Step 3: Heat the polished bar to 1100℃~1180℃ and keep it warm;

[0008] Step 4: Punch the heated bar material in step 3 on a fast forging machine; then move it to a pre-rolling ring rolling machine for pre-rolling, and then move it to a final rolling ring rolling machine for final rolling;

[0009] Step 5: Heat treatment of the forging after final rolling.

[0010] Furthermore, in step one, the aspect ratio of the rod is not greater than 2.5.

[0011] Furthermore, in the step 2, the fillet diameter is 3 mm to 5 mm, and the preheating temperature of the production tooling is 150° C. to 350° C.

[0012] Furthermore, in the step three, for the rods with an alloy element content not exceeding 5% and a diameter not exceeding 200 mm or a carbon content not exceeding 0.65% and a diameter not exceeding 200 mm, they are heated to 1100°C to 1180°C in a furnace at a temperature not exceeding 800°C, and the insulation coefficient is 0.3min / mm to 0.8min / mm.

[0013] Furthermore, in step 3, for bars with a diameter greater than 200 mm or a bar alloying element content greater than 5% or a bar carbon content greater than 0.65%,

[0014] Put the bar into the furnace at a temperature not exceeding 800℃, raise the temperature to 800±50℃ for preheating, with a thermal insulation coefficient of 0.3min / mm~0.8min / mm, and then heat the bar to 1100℃~1180℃ for thermal insulation, with a thermal insulation time coefficient of 0.3min / mm~0.8min / mm.

[0015] Furthermore, in the step 4, the punching time t1 of the upset cake is 150s to 210s; the rolling time t2 of the pre-rolling ring rolling machine is 90s to 150s; and the rolling time t3 of the final rolling ring rolling machine is 150s to 210s.

[0016] Furthermore, in the step 4, the transfer time of the forging between the fast forging machine and the pre-rolling ring rolling machine is t4; the transfer time of the forging between the pre-rolling ring rolling machine and the final rolling ring rolling machine is t5;

[0017] Both t4 and t5 do not exceed 60s.

[0018] Further, in the step 4, the total forging time T=t1+t2+t3+t4+t5;

[0019] 8min≤T≤12min.

[0020] Furthermore, the total forging ratio of the forging is between 7 and 10.

[0021] The beneficial effect of the present invention is that on the basis of the traditional ring forging method, the combination of fast forging machine and ring rolling machine can realize the forming of upsetting, punching, pre-expansion and final expansion at the final forging temperature. This method can greatly improve the production efficiency of structural steel and stainless steel ring forgings of forging enterprises and effectively reduce the energy consumption of enterprises. The total forging ratio is 7 to 10, which can effectively improve the organizational state of the ring forgings and improve the comprehensive mechanical properties of structural steel and stainless steel ring forgings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the microstructure of large structural steel stainless steel ring forgings after forming. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] A short-process rolling forming method for large-scale structural steel stainless steel ring forgings, based on the characteristics of structural steel and stainless steel with a wide forging temperature range of 850-1180℃, adopts a combination of fast forging machine and ring rolling machine forging to complete the upsetting, punching-pre-expansion-final expansion process in one pass. The steps are:

[0025] (1) Cutting: Select appropriate specifications from the qualified bars after re-inspection, and the height-to-diameter ratio of the bars should be ≤2.5;

[0026] (2) Preparation before forging: Grind the bar material in step (1) to R3-5, and preheat the hammer anvil, ring rolling machine mandrel, rolling wheel and other tools for production to 150-350°C;

[0027] (3) Heating: Place the bar material in step (2) at ≤800°C into the furnace, heat it to 800±50°C for preheating, and keep it warm for 0.3-0.8min / mm. Then heat it up with the furnace to the heating temperature of 1100-1180°C and keep it warm for 0.3-0.8min / mm. Heat it once. For structural steel and stainless steel with simpler alloy composition and smaller specifications and a diameter of ≤200mm, it is allowed to be loaded into the furnace at a temperature not higher than the heating temperature, and then heat it up with the furnace to the heating temperature of 1100-1180°C and keep it warm for 0.3-0.8min / mm.

[0028] (4) Forging: The bar material heated in step (3) is taken out of the furnace for forging. First, it is upset and punched on a fast forging machine, and the forging time is 150s to 210s; it is transferred to a pre-rolling ring rolling machine for pre-rolling, and rolled to an appropriate inner diameter size, which is 30mm larger than the size of the mandrel for final rolling. The transfer time does not exceed 1min, and the rolling time is 90s to 150s; then it is transferred to a final rolling ring rolling machine for final rolling, and rolled to the size of the forging drawing. The transfer time does not exceed 1min, and the rolling time is 150s to 210s. The total time of the entire forging process is 8 to 12 minutes, which is subject to the final forging temperature control. If the inner hole size of the ring blank after upsetting and punching is appropriate, the inner diameter size is 30mm larger than the size of the mandrel for final rolling, and the core roller for final rolling can ensure the final wall thickness of the ring forging, it is allowed to be directly transferred to the final rolling ring rolling machine for final rolling and rolled to the size of the forging drawing;

[0029] (5) Heat treatment: The ring forgings in step (4) are heat treated using a special structural steel or stainless steel heat treatment system;

[0030] (6) Physical and chemical properties: The ring forgings in step (5) are subjected to physical and chemical testing. The microstructure and mechanical properties of the final forgings meet the standard requirements and meet the use requirements of subsequent forgings.

[0031] Embodiment 1

[0032] Taking the production of rectangular section forgings of a certain type of engine casing as an example, the material is: 0Cr17Ni4Cu4Nb precipitation hardening stainless steel, the forging size is: φ1980±5×φ1900±5×180±5, the forging weight is: 342Kg, and the specific implementation process is as follows.

[0033] (1) Cutting: among the qualified 0Cr17Ni4Cu4Nb bars, according to the above scheme, the bar height-to-diameter ratio is ≤2.5, the cutting specification is determined to be Φ300×660, the cutting weight is 363Kg, and the cutting is carried out;

[0034] (2) Preparation before forging: Grind the 0Cr17Ni4Cu4Nb bar material in step (1) to R3-5, and preheat the hammer anvil, ring rolling machine mandrel, rolling wheel and other tools for production to 200°C;

[0035] (3) Heating: Place the 0Cr17Ni4Cu4Nb rod material ≤ 800°C in step (2) into a furnace, heat it to 800°C for preheating and insulation for 150 min, then heat it to a heating temperature of 1140°C and insulation for 120 min, for primary heating;

[0036] (4) Forging: The 0Cr17Ni4Cu4Nb bar material heated in step (3) is taken out of the furnace for forging. First, it is upset and punched on a fast forging machine to ~φ522×φ200±5×240±5, and the forging time is 128s; it is transferred to a pre-rolling ring rolling machine for pre-rolling, and rolled to ~φ596×φ350±5×240±5, the transfer time is 75s, and the rolling time is 46s; then it is transferred to a final rolling ring rolling machine for final rolling, and rolled to ~φ1980±5×φ1900±5×180±5, the transfer time is 65s, and the rolling time is 226s. The total time of the whole forging process is 9min, and the final forging temperature is ≥910℃;

[0037] (5) Heat treatment: The 0Cr17Ni4Cu4Nb ring forging in step (4) is heat treated by a special solid solution treatment system of 1040±10°C / 2h / air cooling and aging of 550±10°C / 4h / air heat treatment;

[0038] (6) Physical and chemical testing: The 0Cr17Ni4Cu4Nb ring forging in step (5) is subjected to physical and chemical testing, such as Figure 1 As shown in the figure, the microstructure and mechanical properties of the final forgings all meet the standard requirements and meet the use requirements of subsequent forgings.

[0039] The total forging ratio of a certain type of engine casing forging rolled by this scheme is 7.6, and its organizational and performance indicators meet the requirements of relevant standards.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A short-process rolling forming method for large structural steel or stainless steel ring forgings, Features: The method comprises the following steps: Step 1: Select the qualified re-inspected bar materials for cutting, and the height-to-diameter ratio of the bar materials shall not be greater than 2.5; Step 2: Grind the edges and corners of the bar into rounded corners; and preheat the production tooling; Step 3: Heat the polished bar to 1100℃~1180℃ and keep it warm; for bars with alloy element content not exceeding 5% and diameter not exceeding 200mm or carbon content not exceeding 0.65% and diameter not exceeding 200mm, put them into the furnace and heat them to 1100℃~1180℃ for insulation when the temperature does not exceed 800℃, and the insulation coefficient is 0.3min / mm~0.8min / mm; for bars with a diameter greater than 200mm, put them into the furnace at a temperature not exceeding 800℃, heat them to 800±50℃ for preheating, and the insulation coefficient is 0.3min / mm~0.8min / mm, and then heat them to 1100℃~1180℃ for insulation, and the insulation time coefficient is 0.3min / mm~0.8min / mm; Step 4: Punch the heated bar material in step 3 on the fast forging machine, the punching time t1: 150s-210s; then move it to the pre-rolling ring rolling machine for pre-rolling, the rolling time t2: 90s-150s; then move it to the final rolling ring rolling machine for final rolling, the rolling time t3: 150s-210s; the transfer time of the forging between the fast forging machine and the pre-rolling ring rolling machine is t4; the transfer time of the forging between the pre-rolling ring rolling machine and the final rolling ring rolling machine is t5; t4 and t5 are not more than 60s; the total forging time T = t1 + t2 + t3 + t4 + t5; 8min≤T≤12min; Step 5: Heat treatment of the forging after final rolling.

2. A short-process rolling forming method for large structural steel or stainless steel ring forgings according to claim 1, Features: In the step 2, the fillet diameter is 3 mm to 5 mm, and the preheating temperature of the production tooling is 150° C. to 350° C.

3. A short-process rolling forming method for large structural steel or stainless steel ring forgings according to claim 2, Features: The total forging ratio of forgings is between 7 and 10.

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