A method of forging a high strength steel

Abstract

The application discloses a forging method for high-strength steel and belongs to the technical field of hot working. The forging method for high-strength steel comprises the following steps: homogenization treatment, continuous upsetting treatment, elongation, continuous upsetting and drawing treatment, and forging to obtain a finished product. The continuous upsetting treatment is performed on the bar, the plastic deformation penetration depth of the large forging bar is increased, the first large plastic deformation is performed on the upsetting, the upper and lower difficult deformation areas are mutually inserted, the subsequent plastic deformation makes the original difficult deformation area effectively deformed, and meanwhile, the homogenization healing at high temperature is performed for multiple times, so that the deformation unevenness is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hot working, and particularly relates to a forging method of high-strength steel. BACKGROUND

[0002] Forging steel can refer to various forgings and forged pieces produced by a forging method, and can also refer to a step in a steel production process, i.e., a forging process.

[0003] In the forging process of steel, the control of temperature and deformation amount has a crucial influence on the quality of finished products. SUMMARY

[0004] The application aims to provide a forging method of high-strength steel to solve the problems of the existing forging method in use.

[0005] To achieve the above-mentioned purpose, the application provides the following technical scheme: a forging method of high-strength steel, comprising:

[0006] homogenizing treatment is performed on the bar;

[0007] the bar after the homogenizing treatment is subjected to continuous upsetting treatment, the relative deformation amount of the height of the bar after the continuous upsetting treatment is not less than 68%, and the total forging ratio of the continuous upsetting treatment is greater than the forging ratio of the defect healing condition of the bar;

[0008] the bar after the continuous upsetting treatment is drawn to obtain a first intermediate blank;

[0009] continuous upsetting and drawing treatment is performed on the first intermediate blank to obtain a second intermediate blank;

[0010] the second intermediate blank is forged into a finished product.

[0011] Preferably, the homogenizing treatment on the bar is performed in a gas-fired heating furnace, and comprises:

[0012] heating to 1190-1210 degrees Celsius and holding, the heating time is greater than 12 hours, and the holding time is not less than 35 hours;

[0013] cooling to 940-960 degrees Celsius and holding, and the cooling rate is less than 50℃ / h, and the holding time is 3 hours;

[0014] heating to 1180-1200 degrees Celsius and holding, the heating rate is less than 100℃ / h, and the holding time is 4-5 hours.

[0015] Preferably, the continuous upsetting treatment on the bar after the homogenizing treatment comprises:

[0016] The rod heated to 1180-1200 degrees Celsius is once upset, and the once-upset rod is high-temperature healed in a furnace, with a healing temperature of 1180-1200 degrees Celsius and a healing time of not less than 3 hours.

[0017] The rod heated to 1180-1200 degrees Celsius is once upset, and the once-upset rod is high-temperature healed in a furnace, with a healing temperature of 1180-1200 degrees Celsius and a healing time of not less than 3 hours.

[0018] Preferably, the relative deformation of the rod height after the first upsetting is 51%, and the forging ratio of the first upsetting is 1.9.

[0019] Preferably, the relative deformation of the rod height after the second upsetting is 37.5%, and the forging ratio of the second upsetting is 1.6.

[0020] Preferably, the continuous upsetting and drawing treatment of the first intermediate blank to obtain the second intermediate blank comprises:

[0021] The first intermediate blank heated to 1140-1160 degrees Celsius is once upset and drawn, and the intermediate body obtained by the once-upset and drawn treatment is high-temperature healed in a furnace, with a healing temperature of 1140-1160 degrees Celsius and a healing time of not less than 3 hours.

[0022] The first intermediate blank heated to 1140-1160 degrees Celsius is once upset and drawn, and the intermediate body obtained by the once-upset and drawn treatment is high-temperature healed in a furnace, with a healing temperature of 1140-1160 degrees Celsius and a healing time of not less than 3 hours.

[0023] Preferably, the forging ratio of the first upsetting and drawing is 1.

[0024] Preferably, the relative deformation of the rod height after the upsetting treatment in the first and second upsetting and drawing processes is 50%.

[0025] Preferably, the forging of the second intermediate blank into a finished product comprises once-pressing the rod into a thick flat blank, turning over 90°, pressing again into a 470mm square blank, chamfering, and rounding into a round rod finished product.

[0026] Preferably, the rounding frequency is 70-120 times / min, and the feed amount is 100-200mm.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] The application firstly performs continuous upsetting treatment on the bar, increases the plastic deformation penetration depth of the large-scale forged bar, and the first large plastic deformation makes the upper and lower difficult deformation regions interpenetrate, and the subsequent plastic deformation makes the original difficult deformation region also effectively deform; meanwhile, the multiple high-temperature homogenization healing makes the deformation unevenness of each time be improved. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a grain size detection diagram of the finished bar of the application at different positions;

[0030] Figure 2 It is a defect detection result diagram of the finished bar of the application;

[0031] Figure 3 It is an impact toughness detection result diagram of the finished bar of the application. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0033] The grain structure of the super-high-strength steel large-scale forged bar for aviation depends on the dynamic recrystallization in the hot working process and the recovery, recrystallization and grain growth mechanism after static recrystallization; the mechanism is realized through the design of forging parameters such as plastic deformation degree, temperature, time and deformation pass and the control of the main processing parameters on an industrial scale.

[0034] In the hot working process, the non-uniform grain structure of the ingot is refined, and a large plastic deformation amount is responsible for closing the internal voids related to the solidification of the ingot; increasing the transverse and longitudinal plastic deformation amount not only enhances the uniformity of the grain size and the closure of the voids, but also helps to refine the non-metallic inclusions, so that they are broken into smaller particles and partially uniformly redistributed; in addition, the high plastic deformation level in multiple directions also helps to eliminate the banded structure after hot working, so the control of the deformation amount is very critical in the production process of the steel, and therefore a forging method of high-strength steel is proposed.

[0035] For the convenience of description, the relative deformation amount of the height before and after upsetting in the subsequent description is calculated by the formula (H1-H2) / H1, wherein H1 represents the height of the bar before upsetting, and H2 represents the height of the bar after upsetting; meanwhile, the forging ratio mentioned in the subsequent description refers to the ratio of the cross-sectional area of the bar before and after upsetting, and meanwhile, when a certain value is mentioned to be between A and B, the value range of the value includes A and B.

[0036] Example one:

[0037] In the embodiment, the forging raw material is a 300M steel bar with a diameter of 920 mm and a height of 1800 mm,

[0038] A forging method of high-strength steel, comprising the following steps:

[0039] S10: homogenizing treatment is performed on the bar;

[0040] Specifically, the homogenizing treatment is performed in a gas cover type heating furnace, and the bar is heated in a double vacuum smelting furnace. The homogenizing treatment process comprises:

[0041] S11: heating to 1190-1210 degrees Celsius and holding, the heating time is greater than 12 hours, and the holding time is greater than 35 hours;

[0042] S12: cooling to 940-960 degrees Celsius and holding, and the cooling rate is less than 50℃ / h, and the holding time is 3 hours;

[0043] S13: heating to 1180-1200 degrees Celsius and holding, the heating rate is less than 100℃ / h, and the holding time is 4-5 hours.

[0044] S20: intermediate blank manufacturing, the upsetting treatment in the intermediate blank manufacturing process is realized by a 45MN press. Specifically, the intermediate blank manufacturing comprises the following steps:

[0045] S21: continuous upsetting treatment is performed on the homogenized bar, the relative deformation amount of the bar height after the continuous upsetting treatment is not less than 68%, and the forging ratio is greater than the forging ratio corresponding to the defect healing condition, and specifically comprises the following steps:

[0046] S211: once upsetting is performed on the bar heated to 1180-1200 degrees Celsius, and the bar after the once upsetting is high-temperature healed by returning to the furnace. The relative deformation amount X1 of the height after the once upsetting is 51%, that is, the height of the bar after the once upsetting is 900 mm, the forging ratio K1 of the once upsetting is 1.9, the high-temperature healing temperature by returning to the furnace is between 1180-1200 degrees Celsius, and the healing time (i.e. holding time) is not less than 3 hours;

[0047] S212: twice upsetting is performed on the bar heated to 1180-1200 degrees Celsius, and the bar after the twice upsetting is high-temperature healed by returning to the furnace. The relative deformation amount X2 of the height of the bar after the twice upsetting is 37.5%, that is, the height of the bar after the twice upsetting is 540 mm, the forging ratio K2 of the twice upsetting is 1.6, the high-temperature healing temperature by returning to the furnace after the twice upsetting is between 1180-1200 degrees Celsius, and the healing time (i.e. holding time) is not less than 3 hours;

[0048] In the continuous upsetting process, the total forging ratio K = K1*K2 = 3.04 of the continuous upsetting process is greater than the forging ratio Ka = 2.875 of the bar defect healing condition, and the total deformation amount X = X1 + (1-X1)*X2 = (1-51%)*37.5% = 70% of the bar height after the continuous upsetting is 70%;

[0049] S22: elongating the bar after the continuous upsetting process to obtain a first intermediate blank with a diameter of 850 mm and a height of 2100 mm, and recycling the elongated bar at a high temperature to heal, the healing temperature being between 1140-1160 degrees Celsius, and the healing time being not less than 3 hours;

[0050] S23: performing continuous upsetting and drawing on the first intermediate blank to obtain a second intermediate blank, and the continuous upsetting and drawing on the first intermediate blank specifically includes the following steps;

[0051] S230: performing one-time upsetting and drawing on the first intermediate blank heated to 1140-1160 degrees Celsius, and recycling the intermediate body obtained by one-time upsetting at a high temperature, specifically elongating the first intermediate blank to obtain an intermediate body with a diameter of 850 mm and a height of 2100 mm after the first intermediate blank is upset to a height of 1050 mm, the healing temperature being between 1140-1160 degrees Celsius, and the healing time being not less than 3 hours;

[0052] S231: performing two-time upsetting and drawing on the intermediate body heated to 1140-1160 degrees Celsius, specifically elongating the intermediate body after the intermediate body is upset, specifically elongating the intermediate body to obtain a second intermediate blank with a diameter of 550 mm and a height of 4800 mm after the intermediate body is upset to a height of 1050 mm, and recycling the second intermediate blank at a high temperature, the healing temperature being between 1050-1070 degrees Celsius, and the healing time (i.e. holding time) being not less than 3 hours.

[0053] S24: product forging, the press used in the product forging being a 31.5 MN press, and specifically including the following steps:

[0054] S241: one-time pressing the second intermediate blank heated to 1050-1070 degrees Celsius to a 420 mm thick flat blank, turning 90°, again pressing to a 420 mm square blank, chamfering, and rounding to a Φ400 mm round bar, the rounding frequency being 70-120 times / min, the feed amount being 50-200 mm, the final forging temperature being greater than 900°C, the deformation amount being greater than 45%, and the complete forging time being less than 10 minutes.

[0055] Example Two:

[0056] The raw material used in the embodiment is also a 300M steel bar with a diameter of φ920 mm and a height of 1800 mm, and a forging method of high-strength steel, the main steps in the embodiment are the same as those in embodiment one, that is, including homogenization treatment, intermediate blank manufacturing and finished product manufacturing steps, wherein the homogenization treatment process of the bar raw material is the same as that in embodiment one, and will not be expanded in the subsequent description. Specifically, the above-mentioned forging method comprises the following steps:

[0057] S10: homogenizing the bar;

[0058] Specifically, the above-mentioned homogenization treatment is carried out in a gas cover type heating furnace, and the bar is preferably heated in a double vacuum melting furnace. The homogenization treatment process comprises:

[0059] S11: heating to 1190-1210 degrees Celsius and holding, the heating time is greater than 12 hours, and the holding time is greater than 35 hours;

[0060] S12: cooling to 940-960 degrees Celsius and holding, and the cooling rate is less than 50℃ / h, and the holding time is 3 hours;

[0061] S13: heating to 1180-1200 degrees Celsius and holding, the heating rate is less than 100℃ / h, and the holding time is 4-5 hours.

[0062] S20: intermediate blank manufacturing, the upsetting treatment in the intermediate blank manufacturing process is realized by a 45MN press. Specifically, the intermediate blank manufacturing comprises the following steps:

[0063] S21, continuously upsetting the homogenized bar, the relative deformation amount of the bar height after continuous upsetting is not less than 68%, and the forging ratio is greater than the forging ratio corresponding to the defect healing condition, and specifically comprises the following steps:

[0064] S211: upsetting the bar heated to 1180-1200 degrees Celsius once, and returning the bar after the first upsetting to high temperature healing, the relative deformation amount X1 of the height after the first upsetting is 51%, that is, the height of the bar after the first upsetting is 900 mm, the forging ratio K1 of the first upsetting is 1.9, the healing temperature of the high temperature healing is between 1180-1200 degrees Celsius, and the healing time (that is, the holding time) is not less than 3 hours;

[0065] S212: the bar heated to 1180-1200 degrees Celsius is subjected to secondary upsetting, and the bar after secondary upsetting is subjected to high-temperature healing in a furnace, the relative deformation amount X2 of the height of the bar after secondary upsetting is 37.5%, that is, the height of the bar after secondary upsetting is 540 mm, the forging ratio K2 of secondary upsetting is 1.6, the high-temperature healing temperature of the bar after secondary upsetting is between 1180-1200 degrees Celsius, and the healing time (i.e. the holding time) is not less than 3 hours;

[0066] In the above continuous upsetting process, the total forging ratio K of the continuous upsetting process is K=K1*K2=3.04, which is greater than the bar forging ratio Ka=2.875 under the defect condition of the bar, and the total deformation amount X of the height of the bar after continuous upsetting is X=X1+(1-X1)*X2=(1-51%)*37.5%=70%;

[0067] S22: the bar after continuous upsetting is drawn to obtain a first intermediate blank with a diameter of 850 mm and a height of 2100 mm, and the drawn bar is subjected to high-temperature healing in a furnace, the healing temperature is between 1140-1160 degrees Celsius, and the healing time is not less than 3 hours;

[0068] S23: the first intermediate blank is subjected to continuous upsetting and drawing to obtain a second intermediate blank, and the continuous upsetting and drawing of the first intermediate blank specifically includes the following steps;

[0069] S230: the first intermediate blank heated to 1140-1160 degrees Celsius is subjected to primary upsetting and drawing, and the intermediate blank obtained after primary upsetting and drawing is subjected to high-temperature healing in a furnace, specifically, the first intermediate blank is upset to a height of 1050 mm and then drawn to obtain an intermediate blank with a diameter of 850 mm and a height of 2100 mm, the healing temperature is between 1140-1160 degrees Celsius, and the healing time is not less than 3 hours;

[0070] S231: the intermediate blank heated to 1140-1160 degrees Celsius is subjected to secondary upsetting and drawing, that is, the intermediate blank is upset and then drawn, specifically, the intermediate blank is upset to a height of 1050 mm and then drawn to obtain a second intermediate blank with a diameter of 600 mm and a height of 4200 mm, and the second intermediate blank is subjected to high-temperature healing in a furnace, the healing temperature is between 1050-1070 degrees Celsius, and the healing time (i.e. the holding time) is not less than 3 hours.

[0071] S24: final forging, the press used in the final forging is a 31.5 MN press, and the final forging specifically includes the following steps:

[0072] The second intermediate blank heated to 1050-1070 degrees Celsius is once pressed to a 470mm thick flat blank, turned 90°, pressed again to a 470mm square blank, chamfered, and rounded to a Φ450mm round bar, with a rounding frequency of 70-120 times / min, a feed amount of 100-200mm, a final forging temperature greater than 900℃, a deformation amount of 50%, and a complete forging time less than 10 minutes.

[0073] Meanwhile, no single point and continuous defects are found in the flaw detection results of the above-mentioned rod product, which meets the requirements of GB / T4162 A level.

[0074] Figure 1 The level of grain size at different positions in the φ400 product is shown, wherein field of view 1 represents the observation of the edge of the finished rod, field of view 2 represents the observation at the 1 / 2 radius position, and field of view 3 represents the observation at the center position. As can be seen from the figure, the grain size level at each field of view position is greater than 8 levels, and the level difference between each position is not greater than 0.5 levels, that is, the difference between the center area and the edge is reduced, the grain size is constructed, and the microstructure is uniformly redistributed. After heat treatment, the mechanical properties meet the specification requirements; meanwhile, it can be seen from the figure that the transverse impact toughness of the rod product is improved by more than 30%, the difference between the transverse and longitudinal impact toughness is within 10%, and the impact toughness difference of the forged rod in each region is within 10%. Figure 3

[0075] Referring to Figure 3 , the standard transverse impact energy is ≥29J, which is 25.6% lower than the longitudinal impact energy of 39J, the transverse and longitudinal impact energy ratio is 0.74, and the toughness anisotropy is large.

[0076] After forging by the method, the average transverse impact energy of the φ400 is 52J, which is 0.07% lower than the average longitudinal impact energy of 56J, the toughness anisotropy is greatly reduced, the transverse and longitudinal impact energy ratio is 0.92, and they are basically equivalent. The longitudinal impact energy is increased by 43% compared with the lower limit of the standard, and the transverse impact energy is increased by 79% compared with the lower limit of the standard.

[0077] After forging by the method, the average transverse impact energy of the φ450 is 46.75J, which is 0.05% lower than the average longitudinal impact energy of 49.05J, the toughness anisotropy is greatly reduced, the transverse and longitudinal impact energy ratio is 0.95, and they are basically equivalent. The longitudinal impact energy is increased by 25.7% compared with the lower limit of the standard, and the transverse impact energy is increased by 61% compared with the lower limit of the standard.

[0078] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the application, the scope of which is defined by the appended claims and their equivalents.​

Claims

1. A method of forging a high strength steel, characterized in that: The application relates to a method for producing a bar product, comprising the following steps: homogenizing the bar product; continuously upsetting the homogenized bar product, wherein the relative deformation of the bar product after the continuous upsetting is not less than 68%, and the total upsetting ratio of the continuous upsetting is greater than the upsetting ratio required for defect healing of the bar product, and the continuous upsetting of the homogenized bar product comprises the following steps: once upsetting the bar product heated to 1180-1200 DEG C, and high-temperature healing of the bar product after the once upsetting in a furnace, wherein the healing temperature is between 1180-1200 DEG C, and the healing time is not less than 3 hours, the relative deformation of the bar product after the once upsetting is 51%, and the upsetting ratio of the once upsetting is 1.9; twice upsetting the bar product heated to 1180-1200 DEG C, and high-temperature healing of the bar product after the twice upsetting in a furnace, wherein the healing temperature is between 1180-1200 DEG C, and the healing time is not less than 3 hours, the relative deformation of the bar product after the twice upsetting is 37.5%, and the upsetting ratio of the twice upsetting is 1.6; stretching the bar product after the continuous upsetting to obtain a first intermediate product; continuously upsetting and stretching the first intermediate product to obtain a second intermediate product; forging the second intermediate product into a finished product.

2. The method of claim 1, wherein: The homogenizing of the bar product is carried out in a gas-fired heating furnace, and comprises the following steps: heating to 1190-1210 DEG C and keeping the temperature, wherein the heating time is greater than 12 hours, and the keeping time is not less than 35 hours; cooling to 940-960 DEG C and keeping the temperature, and the cooling rate is 50 DEG C / h, and the keeping time is 3 hours; heating to 1180-1200 DEG C and keeping the temperature, wherein the heating rate is less than 100 DEG C / h, and the keeping time is 4-5 hours.

3. The method of claim 1, wherein: The continuously upsetting and stretching of the first intermediate product to obtain the second intermediate product comprises the following steps: once upsetting and stretching the first intermediate product heated to 1140-1160 DEG C, and high-temperature healing of the intermediate product after the once upsetting and stretching in a furnace, wherein the healing temperature is between 1140-1160 DEG C, and the healing time is not less than 3 hours; twice upsetting and stretching the intermediate product heated to 1140-1160 DEG C, and high-temperature healing of the second intermediate product after the twice upsetting and stretching in a furnace, wherein the healing temperature is between 1140-1160 DEG C, and the healing time is not less than 3 hours.

4. The method of claim 3, wherein: The upsetting ratio of the once upsetting and stretching is 1.

5. The method of claim 3, wherein: The relative deformation of the bar product after the upsetting in the once upsetting and stretching is 50%.

6. The method of claim 1, wherein: The forging of the second intermediate product into the finished product comprises the following steps: once pressing the bar product to form a thick flat product, turning by 90 DEG, again pressing to form a 470mm square product, chamfering, and rounding to form a round product.

7. The method of claim 6, wherein: ​

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