Production method of flange forge piece with forced low-temperature impact toughness requirement

Abstract

The invention discloses a production method of a flange forge piece with the requirement for forced low-temperature impact toughness. The production method sequentially comprises the steps of upsetting and drawing, punching, ring rolling, normalizing and hardening and tempering. The forging is made of 09Mn2Si low-carbon alloy steel, and the 09Mn2Si low-carbon alloy steel is prepared from, by mass, smaller than or equal to 0.12% of C, 0.5%-0.8% of Si, 1.3%-1.7% of Mn, smaller than or equal to 0.15% of Ni, smaller than or equal to 0.02% of P, smaller than or equal to 0.02% of S, smaller than or equal to 0.3% of Cr, smaller than or equal to 0.12% of V, smaller than or equal to 0.008% of N, smaller than or equal to 0.3% of Cu, smaller than or equal to 0.08% of As and the balance Fe and inevitable impurities. According to the production method, a steel blank is forged and then rolled into a plurality of connected flange forgings, the connected flange forgings are cut and separated after air cooling, and a plurality of independent flange forgings are obtained; the impact performance of the independent flange forgings at the temperature of minus 60 DEG C ranges from 150 J to 171J. In addition, the mechanical performance difference between the independent flange forgings is small, and particularly, the impact performance difference at the temperature of minus 60 DEG C is within 20%.

Description

Technical Field

[0001] The invention relates to the technical field of forging production, and in particular to a production method of flange forgings with mandatory low-temperature impact toughness requirements. Background Art

[0002] 09Mn2Si is a low-carbon alloy steel grade in the Russian standard GOST. 09Mn2Si material has excellent high strength, toughness, welding performance, etc. At present, some domestic manufacturers have undertaken the processing of 09Mn2Si material for Russian customers.

[0003] 09Mn2Si material is generally used in Russia to make steel plates and bars. When preparing paired flange forgings, its mechanical properties are difficult to meet Russian service conditions, especially the -60℃ impact performance difference between the two flanges in the paired flange is large. The specific mechanical property requirements that meet Russian service conditions are as follows: 20℃ tensile strength (Rm) ≥470Mpa, 20℃ yield strength (Rp0.2) ≥245MPa, 20℃ elongation (δ) ≥19%, 20℃ section shrinkage (Z) ≥42%, 20℃ impact performance (KV) ≥39J, -60℃ impact performance (KV) ≥24.5J, among which the -60℃ impact performance difference between the two flanges of the paired flange forgings should be within 20%. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects in the prior art and provide a production method for flange forgings with mandatory low-temperature impact toughness requirements. On the basis of 09Mn2Si low-carbon alloy steel, the mass percentages of P, S and Ni are controlled, and reasonable process optimization measures for forging and post-forging heat treatment and performance heat treatment are formulated to produce multiple flange forgings at one time.

[0005] In order to achieve the above technical effects, the technical solution of the present invention is: a method for producing flange forgings with mandatory low-temperature impact toughness requirements, comprising sequential upsetting, punching, ring rolling, normalizing and quenching and tempering steps; the forgings are made of 09Mn2Si low-carbon alloy steel, and the element composition of the 09Mn2Si low-carbon alloy steel is as follows by mass percentage: C: ≤0.12%, Si: 0.5%~0.8%, Mn: 1.3% ~1.7%, Ni: ≤0.15%, P: ≤0.02%, S: ≤0.02%, Cr: ≤0.3%, V: ≤0.12%, N: ≤0.008%, Cu: ≤0.3%, As: ≤0.08%, the balance is Fe and unavoidable impurities. Further, the mass percentage of Ni is ≤0.07%, the mass percentage of S is ≤0.006%, and the mass percentage of P is ≤0.006%. Specifically, in the production process of steel billets for forgings, Ni, P and S are not added, and the contents of Ni, P and S in other steel billet alloy raw materials are controlled.

[0006] The preferred technical solution is that the upsetting and punching steps are the first fire, the ring rolling step is divided into pre-forming ring rolling and ring rolling forming, the pre-forming ring rolling is the second fire, and the ring rolling forming is the third fire; the initial forging temperature of the first, second and third fires is not greater than 1220°C, and the final forging temperature of the first, second and third fires is not less than 850°C. Further, the initial forging temperature of the first, second and third fires is 1220°C~1300°C.

[0007] A preferred technical solution is that the upsetting step includes three upsettings and two drawing steps performed alternately in sequence, and the total product of the upsetting forging ratios of the three upsettings and the drawing forging ratios of the two drawing steps is not less than 7.

[0008] The preferred technical solution is that in the three upsetting steps and two stretching steps: The first upsetting forging ratio is 1.74~1.8; The first drawing forging ratio is 1.32~1.4; The second upsetting forging ratio is 1.7~1.76; The second drawing forging ratio is 1.41~1.49; The third upsetting forging ratio is 1.85~1.92.

[0009] The preferred technical solution is that the ring rolling step includes pre-forming ring rolling, and the ratio of the product of the wall thickness and the length of the forging before and after the pre-forming ring rolling is the pre-forming ring rolling forging ratio, and the pre-forming ring rolling forging ratio is 1.08~1.12.

[0010] A preferred technical solution is that the forging is a combined forged flange forging, and the ring rolling step rolls the combined forged flange forging into a plurality of connected flange forgings.

[0011] The preferred technical solution is that the normalizing process is: After the forgings are hot-charged into the furnace, the temperature is raised to 890~910℃ at a heating rate of no more than 100℃ / h, and the forgings are kept warm for 3.6~4.1h / 100mm according to the effective thickness of the forgings. After the insulation is completed, the forgings are cooled by air. Furthermore, the heating rate of the forgings after hot charging into the furnace is 90~100℃ / h.

[0012] The preferred technical solution is that the quenching and tempering step is divided into quenching and high temperature tempering in sequence, and the quenching process is: The forging is heated to 670-690°C and kept warm for 1.2-1.5h / 100mm according to the effective thickness of the forging. After the insulation, the temperature is raised to 910-930°C and kept warm for 3.3-3.8h / 100mm according to the effective thickness of the forging, and then cooled by water quenching.

[0013] The preferred technical solution is that the high temperature tempering process is: The forgings are heated to 630-670°C at a rate of no more than 100°C / h, kept warm for 6.4-7.2h / 100mm of effective thickness, and finally cooled in air. Further, the forgings are heated to 640-660°C at a rate of 90-100°C / h.

[0014] The preferred technical solution is that the heating rate of the quenching process is no more than 100°C / h. Furthermore, the heating rate of the quenching process is 90-100°C / h.

[0015] The advantages and beneficial effects of the present invention are: The production method of the flange forging with mandatory low-temperature impact toughness requirements is based on 09Mn2Si low-carbon alloy steel. By strictly controlling the contents of residual phosphorus and sulfur in the forging steel, hot brittleness and cold brittleness are reduced. By adjusting the content of nickel in the forging steel, the cost of the forging is reduced and its performance does not change significantly.

[0016] After forging, the steel billet is rolled into a plurality of connected flange forgings, and after air cooling, the connected plurality of flange forgings are cut and separated to obtain a plurality of independent flange forgings; the impact performance of these independent flange forgings at -60°C ranges from 150 to 171 J. In addition, the difference in mechanical properties between these independent flange forgings is small, especially the difference in impact performance at -60°C is within 20%. DETAILED DESCRIPTION

[0017] The specific implementation of the present invention is further described below in conjunction with the examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the protection scope of the present invention.

[0018] The element composition of low carbon alloy steel with grade 09Mn2Si is: C: ≤0.12%, Si: 0.5%~0.8%, Mn: 1.3%~1.7%, Ni: ≤0.3%, P: ≤0.03%, S: ≤0.035%, Cr: ≤0.3%, V: ≤0.12%, N: ≤0.008%, Cu: ≤0.3%, As: ≤0.08%.

[0019] The mass percentage of an element in forging steel is limited to "≤n", which means that the content of the element in the forging steel is 0~n, excluding the minimum endpoint value "0".

[0020] Upsetting forging ratio The ratio of the larger value to the smaller value of the forging length before and after upsetting is the upsetting forging ratio.

[0021] Drawing forging ratio The ratio of the larger and smaller lengths of the forging before and after drawing is the drawing forging ratio.

[0022] Difference in impact performance at -60℃ The difference between the maximum value and the minimum value in the average value of the impact performance data at -60°C of multiple independent forgings is obtained, and the difference is divided by the maximum value and then multiplied by 100 to obtain the difference in impact performance at -60°C of multiple independent forgings. Example

[0023] Example 1

[0024] Example 1 The production method of flange forgings with mandatory low-temperature impact toughness requirements has the measured values ​​of chemical composition mass percentages as follows: C: 0.1%, Si: 0.65%, Mn: 1.48%, Ni: 0.06%, P: 0.005%, S: 0.005%, Cr: 0.2%, V: 0.03%, N: 0.005%, Cu: 0.03%, As: 0.005%, and the balance is Fe and unavoidable impurities; The production of flange forgings with mandatory low-temperature impact toughness requirements includes sequential forging and post-forging heat treatment steps. The forging steps include sequential upsetting, punching, pre-forming ring rolling, and ring rolling forming. The post-forging heat treatment steps include sequential normalizing heat treatment and quenching and tempering heat treatment steps: S1: heating to 1250℃; S2: The round billet with a length of 2480mm is subjected to three upsetting and two drawing operations, first upsetting to 1400mm, then drawing to 1900mm, then upsetting to 1100mm, then drawing to 1600mm, and finally upsetting to 850mm; The first upsetting forging ratio is 1.77; The first drawing forging ratio is 1.36; The second upsetting forging ratio is 1.73; The second drawing and forging ratio is 1.45; The third upsetting forging ratio is 1.88; S3: Punch a hole of Φ360mm in the middle of the forging to obtain a punched part with an outer diameter of 1230mm and a height of 850mm; S4: The forgings are returned to the furnace for 4 hours at a furnace temperature of 1250°C. During the return to the furnace, the surface temperature of the forgings is 850°C and the core temperature is 900°C. S5: After the remelting is completed, the forging is preformed, specifically, the forging size is rolled to 1268mm in outer diameter, 480mm in inner diameter, and 850mm in length using a ring rolling machine, that is, the preformed ring rolling forging ratio is 1.10; S6: The forgings are returned to the furnace for 4 hours at a furnace temperature of 1250°C. During the return to the furnace, the surface temperature of the forgings is 880°C and the core temperature is 930°C. S7: After the remelting is completed, the forging is rolled into a ring shape using a ring rolling machine, and after air cooling, the forging is cut into two independent flange forgings.

[0025] S8: Normalizing, after the forging is loaded into the furnace, the temperature is raised to 900℃ at a rate of 100℃ / h, kept at this temperature for 7h, and then air-cooled, and rough turning is performed after air-cooling; S9: Tempering, loading the furnace at room temperature, heating to 680℃ at a rate of 100℃ / h, keeping it at that temperature for 2.5h, heating to 920℃ at a rate of 100℃ / h after the end of the heat preservation, keeping it at that temperature for 6.5h, quenching in water, cooling down, and quenching in water after taking out of the furnace; The furnace was loaded at room temperature, and the temperature in the furnace was raised to 650°C at a rate of 100°C / h by high-temperature tempering, kept at that temperature for 12.5h, and then air-cooled.

[0026] Example 1 The performance test results and qualified requirements of flange forgings with mandatory low-temperature impact toughness requirements are as follows: Mechanical properties after quenching and tempering: Flange 1: Hardness HV: 162HV, yield strength ReH: 408N / mm 2 , tensile strength Rm: 533N / mm 2 , elongation δ: 29%, section shrinkage Z: 81%, 20℃ impact performance KCU: 268 / 277 / 294J / cm 2 , -60℃ impact performance KCV: 150 / 169 / 171J / cm 2 .

[0027] Flange 2: Hardness HV: 165HV, yield strength ReH: 448N / mm 2 , tensile strength Rm: 556N / mm 2, elongation δ: 27.5%, section shrinkage Z: 82%, 20℃ impact performance KCU: 265 / 270 / 275J / cm 2 , -60℃ impact performance KCV: 155 / 162 / 167J / cm 2 .

[0028] The qualified requirements of mechanical properties test after quenching and tempering are: hardness HV: ≤240HV, yield strength ReH: ≥245N / mm2, tensile strength Rm: ≥470N / mm2, elongation δ: ≥19%, section shrinkage Z: ≥42%, 20℃ impact performance KCU ≥39J / cm2, -60℃ impact performance KCV ≥24.5J / cm2.

[0029] The difference in impact performance at -60°C between flange 1 and flange 2 is 1.2%.

[0030] Comparative Example 1 Comparative Example 1 The measured values ​​of the chemical composition mass percentages of the flange forging production method with mandatory low-temperature impact toughness requirements are: C: 0.1%, Si: 0.67%, Mn: 1.5%, Ni: 0.16%, P: 0.01%, S: 0.009%, Cr: 0.21%, V: 0.029%, N: 0.005%, Cu: 0.05%, As: 0.0052%, and the balance is Fe and unavoidable impurities; The forging process of Comparative Example 1 is the same as that of Example 1.

[0031] The performance test results of the flange forgings with mandatory low temperature impact toughness requirements in Comparative Example 1 are as follows: Flange 1: Hardness HV: 165HV, yield strength ReH: 398N / mm 2 , tensile strength Rm: 544N / mm 2 , elongation δ: 26%, section shrinkage Z: 84%, 20℃ impact performance KCU: 273 / 282 / 290J / cm 2 , -60℃ impact performance KCV: 160 / 178 / 177J / cm 2 .

[0032] Flange 2: Hardness HV: 175HV, yield strength ReH: 457N / mm 2 , tensile strength Rm: 567N / mm 2 , elongation δ: 24.5%, section shrinkage Z: 83%, 20℃ impact performance KCU: 268 / 271 / 277J / cm 2 , -60℃ impact performance KCV: 157 / 163 / 174J / cm 2 .

[0033] The difference in impact performance at -60°C between flange 1 and flange 2 is 4%.

[0034] The nickel content of comparative example 1 is increased. Compared with example 1, the performance of comparative example 1 remains basically unchanged, the difference in impact performance at -60°C between flange 1 and flange 2 remains basically unchanged, and the cost of comparative example 1 increases after the nickel content is increased.

[0035] Example 2

[0036] Based on the forging steel of Example 1, the forging process of Example 2 is the same as that of Example 1, except that S2-S7 is performed twice: S2: The round billet with a length of 1240mm is processed by three upsetting and two drawing operations, first upsetting to 700mm, then drawing to 952mm, then upsetting to 550mm, then drawing to 798mm, and finally upsetting to 465mm; The first upsetting forging ratio is 1.77; The first drawing forging ratio is 1.36; The second upsetting forging ratio is 1.73; The second drawing and forging ratio is 1.45; The third upsetting forging ratio is 1.72; S3: Punch a hole of Φ360mm in the middle of the forging to obtain a punched part with an outer diameter of 1178mm and a height of 465mm; S4: The forgings are returned to the furnace for 3.5 hours at a furnace temperature of 1250°C. During the return to the furnace, the surface temperature of the forgings is 850°C and the core temperature is 900°C. S5: After the remelting, the forgings are preformed, specifically, the forgings are rolled to an outer diameter of 1220 mm, an inner diameter of 480 mm, and a length of 465 mm using a ring rolling machine, that is, the preformed ring rolling forging ratio is 1.11; S6: The forgings are returned to the furnace for 3.5 hours at a furnace temperature of 1250°C. During the return to the furnace, the surface temperature of the forgings is 880°C and the core temperature is 930°C. S7: After the remelting is completed, the forging is rolled into a ring shape using a ring rolling machine.

[0037] The performance test results of the flange forgings with mandatory low temperature impact toughness requirements in Example 2 are as follows: Flange 1: Hardness HV: 166HV, yield strength ReH: 403N / mm 2 , tensile strength Rm: 521N / mm 2 , elongation δ: 27%, section shrinkage Z: 80%, 20℃ impact performance KCU: 261 / 272 / 283J / cm 2, -60℃ impact performance KCV: 141 / 152 / 166J / cm 2 .

[0038] Flange 2: Hardness HV: 169HV, yield strength ReH: 437N / mm 2 , tensile strength Rm: 547N / mm 2 , elongation δ: 29%, section shrinkage Z: 85%, 20℃ impact performance KCU: 266 / 279 / 283J / cm 2 , -60℃ impact performance KCV: 167 / 171 / 174J / cm 2 .

[0039] The difference in impact performance at -60°C between flange 1 and flange 2 is 10.3%.

[0040] The two flange forgings of Example 2 are forged separately. Compared with Example 1, the performance of Example 2 remains basically unchanged, while the difference in impact performance at -60°C between flange 1 and flange 2 increases to 10.3%, indicating that the combined forging method is beneficial to reducing the difference in impact performance at -60°C between multiple flanges.

[0041] Example 3

[0042] Based on the forging steel of Example 1, the forging process of Example 3 is the same as that of Example 1, except that S9: Tempering, loading the furnace at room temperature, heating to 680℃ at a rate of 100℃ / h, keeping warm for 2.5h, heating to 920℃ at a rate of 100℃ / h after the end of the heat preservation, keeping warm for 6.5h, quenching in water, cooling down, and quenching in water after taking out of the furnace; The furnace was loaded at room temperature, and the temperature in the furnace was raised to 600°C at a rate of 100°C / h by high-temperature tempering, kept at that temperature for 12.5h, and then air-cooled.

[0043] The performance test results of the flange forgings with mandatory low temperature impact toughness requirements in Example 3 are as follows: Flange 1: Hardness HV: 177HV, yield strength ReH: 443N / mm 2 , tensile strength Rm: 571N / mm 2 , elongation δ: 22%, section shrinkage Z: 50%, 20℃ impact performance KCU: 211 / 222 / 223J / cm 2 , -60℃ impact performance KCV:88 / 92 / 96J / cm 2 .

[0044] Flange 2: Hardness HV: 182HV, yield strength ReH: 467N / mm 2, tensile strength Rm: 587N / mm 2 , elongation δ: 21.5%, section shrinkage Z: 55%, 20℃ impact performance KCU: 226 / 229 / 233J / cm 2 , -60℃ impact performance KCV: 90 / 94 / 97J / cm 2 .

[0045] The difference in impact performance at -60°C between flange 1 and flange 2 is 1.8%.

[0046] The high-temperature tempering temperature of Example 3 is lowered. Compared with Example 1, the hardness, yield strength, and tensile strength of Example 3 are increased, while the elongation, cross-sectional shrinkage, and 20°C impact performance are decreased, and the -60°C impact performance is significantly decreased.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for producing flange forgings with mandatory low-temperature impact toughness requirements, comprising the steps of upsetting, punching, ring rolling, normalizing and quenching and tempering in sequence; characterized in that: The forging is made of 09Mn2Si low carbon alloy steel, and the element composition of the 09Mn2Si low carbon alloy steel is as follows by mass percentage: C: ≤0.12%, Si: 0.5%~0.8%, Mn: 1.3% ~1.7%, Ni: ≤0.15%, P: ≤0.02%, S: ≤0.02%, Cr: ≤0.3%, V: ≤0.12%, N: ≤0.008%, Cu: ≤0.3%, As: ≤0.08%, the balance is Fe and unavoidable impurities.

2. The method for producing flange forgings with mandatory low temperature impact toughness requirements according to claim 1, characterized in that: The upsetting and punching steps are the first fire, the ring rolling step is divided into pre-forming ring rolling and ring rolling forming, the pre-forming ring rolling is the second fire, and the ring rolling forming is the third fire; the initial forging temperature of the first, second and third fires is no more than 1220°C, and the final forging temperature of the first, second and third fires is no less than 850°C.

3. The method for producing flange forgings with mandatory low temperature impact toughness requirements according to claim 1, characterized in that: The upsetting step includes three upsetting operations and two drawing operations performed alternately in sequence, and the total product of the upsetting forging ratios of the three upsetting operations and the drawing forging ratios of the two drawing operations is not less than 7.

4. The method for producing flange forgings with mandatory low temperature impact toughness requirements according to claim 3, characterized in that: In the three upsetting and two drawing processes: The first upsetting forging ratio is 1.74~1.8; The first drawing forging ratio is 1.32~1.4; The second upsetting forging ratio is 1.7~1.76; The second drawing forging ratio is 1.41~1.49; The third upsetting forging ratio is 1.85~1.

92.

5. The method for producing flange forgings with mandatory low temperature impact toughness requirements according to claim 1, characterized in that: The ring rolling step includes pre-forming ring rolling, and the ratio of the product of the wall thickness and the length of the forging before and after the pre-forming ring rolling is the pre-forming ring rolling forging ratio, and the pre-forming ring rolling forging ratio is 1.08-1.

12.

6. The method for producing flange forgings with mandatory low temperature impact toughness requirements according to claim 1, characterized in that: The forging is a combined forged flange forging, and the ring rolling step rolls the combined forged flange forging into a plurality of connected flange forgings.

7. The method for producing flange forgings with mandatory low temperature impact toughness requirements according to claim 1, characterized in that: The normalizing process is: After the forgings are hot charged into the furnace, the temperature is raised to 890~910℃ at a heating rate of no more than 100℃ / h, and the temperature is kept at 3.6~4.1h / 100mm according to the effective thickness of the forgings. After the insulation, they are cooled by air.

8. The method for producing flange forgings with mandatory low temperature impact toughness requirements according to claim 1, characterized in that: The quenching and tempering steps are divided into sequential quenching and high temperature tempering, and the quenching process is: The forging is heated to 670-690°C and kept warm for 1.2-1.5h / 100mm according to the effective thickness of the forging. After the insulation, the temperature is raised to 910-930°C and kept warm for 3.3-3.8h / 100mm according to the effective thickness of the forging, and then cooled by water quenching.

9. The method for producing flange forgings with mandatory low temperature impact toughness requirements according to claim 8, characterized in that: The high temperature tempering process is: The forgings are heated to 630-670°C at a rate not exceeding 100°C / h, kept warm for 6.4-7.2h / 100mm of the effective thickness of the forgings, and finally air-cooled.

10. The method for producing flange forgings with mandatory low temperature impact toughness requirements according to claim 8, characterized in that: The heating rate of the quenching process is no more than 100°C / h.