Hydrogen embrittlement control method for large-size forge piece

Abstract

The invention relates to a large-size forge piece hydrogen embrittlement control method which comprises the following steps that S1, raw materials are prepared, and a forging stock is obtained; s2, heating before forging; s3, first-stage forging is conducted, a forge piece is subjected to upsetting, and the forging ratio range of upsetting is 7: 1-9: 1; s4, primary remelting is conducted, specifically, the forge piece is reheated to 1230-1270 DEG C, and heat preservation is conducted; s5, second-stage forging is conducted, specifically, the forge piece is turned over and then upset, and the forging ratio range of upsetting is 6.5: 1-8.5: 1; s6, secondary remelting is conducted, specifically, the forge piece with the hole is reheated to 1220-1260 DEG C, and heat preservation is conducted; s7, forming, wherein a flange plate and a shaft body which are integrated are formed by the forge piece; s8, upsetting and drawing-out are conducted, specifically, rotary upsetting is conducted on the flange plate, then a shaft body is drawn out, and finally a forge piece is rounded; the method has the advantages that the situation of local hydrogen atom segregation is avoided, the concentration of active hydrogen atoms in the forge piece is reduced, then excessive concentration of local internal stress is avoided, and the hydrogen embrittlement phenomenon of the forge piece is avoided.

Description

Technical Field

[0001] The present invention relates to the field of large-scale forging manufacturing, and in particular to a method for controlling hydrogen embrittlement of large-size forgings. Background Art

[0002] With the popularization and promotion of wind power energy, wind power technology has also been driven to undergo industrial upgrading. The current development trend of wind turbine main engines is large-scale, which also means that wind turbine main engines need to be matched with larger main shafts.

[0003] However, due to the large size of the spindle forging, the traditional one-time forging process is used. The dissolved hydrogen atoms in the forging dissolve in the lattice gaps, which easily lead to specific segregation therein, and the concentration of local active hydrogen atoms becomes higher, that is, the local internal stress increases. At the same time, the uneven deformation during the forging process leads to uneven distribution of external forces, and the temperature difference during the forging cooling process generates thermal stress. Under the influence of the above factors, the stress is excessively concentrated at the active hydrogen atom segregation points, which easily leads to brittle fracture. It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention discloses a method for controlling hydrogen embrittlement of large-size forgings.

[0005] The technical solutions adopted in the present invention are as follows: A method for controlling hydrogen embrittlement of large-size forgings comprises the following steps: step S1, preparing raw materials to obtain a forging blank; step S2, heating the forging blank before forging, heating the forging blank to 1220-1260°C and holding the temperature; step S3, performing a first-stage forging, upsetting the forging, wherein the upsetting ratio ranges from 7:1 to 9:1, and after upsetting, punching the forging downward with a punch; step S4, performing a primary remelting, reheating the forging to 1230-1270°C and holding the temperature; Step S5, second-stage forging, flipping the forging, followed by upsetting with an upsetting ratio ranging from 6.5:1 to 8.5:1. After upsetting, the forging is punched downward with a punch. Step S6, secondary remelting, reheating the perforated forging to 1220-1260°C for insulation. Step S7, forming, placing the heated forging in a mold, inserting a mandrel into the perforated forging, and extruding to form an integrated flange and shaft. Step S8, upsetting and stretching, first performing rotary upsetting on the flange, then stretching the shaft, and finally rounding the forging. Step S9, surface treatment of the forging, first sandblasting the forging surface, then powder spraying the forging, then heating the workpiece to allow powder particles to adhere to the forging surface, and finally cooling the forging to room temperature.

[0006] Further, in step S1, the raw material includes the elements C0.38~0.45%, Si≤0.40%, Mn0.50~0.80%, P≤0.035%, S≤0.020%, Cr0.90~1.20%, Mo0.18~0.36%, Cu≤0.42%, H≤2.0ppm, Ni≤0.60%, and the balance is Fe.

[0007] Furthermore, in step S2, the heating rate is 80-100°C / h, and the holding time ranges from 7 to 8 hours.

[0008] Furthermore, in step S3, the final forging temperature of the forging is controlled at 980-1050°C.

[0009] Furthermore, in step S4, the heating rate is 90-110°C / h, and the holding time ranges from 7 to 8 hours.

[0010] Furthermore, in step S5, the final forging temperature of the forging is controlled at 1020-1080°C.

[0011] Furthermore, in step S6, the heating rate is controlled to be 65-75°C / h, and the holding time range is 5-6h.

[0012] Furthermore, in step S8, the flange is rotated and upset to 8-10% of its original height.

[0013] Furthermore, in step S8, the drawing process parameters are as follows: the anvil angle range is 6~10°, the anvil width ratio range is 0.8~1.2, the downward pressure is 10~13%, the forging adopts 0°, -180° or -90° flipping, the feed range is 0.8~0.9, and the final forging temperature is controlled at 950~980℃.

[0014] Furthermore, in step S9, the powder particles are Teflon powder particles, and the heating temperature of the forging is in the range of 360-450°C.

[0015] The beneficial effects of the present invention are as follows: 1. Multiple forging deformation methods are used to complete large plastic deformation in all directions, so that a large number of grain boundaries and phase sections are generated inside the forging. These grain boundaries and phase sections can accommodate active hydrogen atoms, thereby avoiding the local segregation of hydrogen atoms and reducing the concentration of active hydrogen atoms inside the forging, thereby avoiding excessive concentration of local internal stress and hydrogen embrittlement of the forging.

[0016] 2. Strictly control the degree of forging deformation and deformation temperature window, improve the plasticity of the forging, and allow the inner hole and outer surface of the forging to undergo plastic deformation, forming a directional stress and strain gradient. As the forging temperature decreases, the hydrogen dissolution decreases, causing the active hydrogen to escape outward along the gradient direction, which is beneficial to reducing the concentration of active hydrogen atoms inside the forging.

[0017] 3. Strictly control the ratio of C, Mn, Cr, Mo and Cu. After forging deformation, ultrafine precipitated phases are precipitated in the organization. The precipitated phases are dispersed, and a large number of dislocations and phase interfaces are formed between them, so that the active hydrogen inside the forging can be evenly distributed. In addition, Cr and Cu form a dense oxide film on the outer surface of the forging, which can prevent external hydrogen from entering the forging organization and inhibit hydrogen embrittlement cracking of the forging.

[0018] 4. After each step of forging deformation is completed, the forging is returned to the furnace at low temperature to drive grain refinement and release the accumulated internal stress of the forging.

[0019] 5. Shot peening is used to roughen the surface of the forging, which is conducive to capturing Teflon powder. After the Teflon powder is heated and melted, a protective layer is formed on the outer layer of the forging to prevent corrosion and corrosion extension on the surface of the forging spindle, which is conducive to reducing cracking of the forging.

[0020] 6. Compared with the traditional manufacturing process, there is no need for a 3-5 day normalizing process after forging, which shortens the manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the steps for controlling hydrogen embrittlement of large-size forgings.

[0022] Figure 2 Schematic diagram of the structure for sampling and testing forgings. DETAILED DESCRIPTION

[0023] The specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0024] Example 1: A method for controlling hydrogen embrittlement of large-size forgings, such as Figure 1 As shown, the following steps are included: Step S1: Prepare raw materials to obtain a forging blank. The raw materials include, by weight percentage, C 0.38-0.45%, Si ≤ 0.40%, Mn 0.50-0.80%, P ≤ 0.035%, S ≤ 0.020%, Cr 0.90-1.20%, Mo 0.18-0.36%, Cu ≤ 0.42%, H ≤ 2.0 ppm, Ni ≤ 0.60%, and the balance is Fe.

[0025] Step S2: heating before forging: heating the forging blank to 1230°C and keeping the temperature, controlling the heating rate to 80-100°C / h, and keeping the temperature for 7h.

[0026] Step S3, the first stage forging, upsetting the forging, the upsetting forging ratio range is 7:1, the final forging temperature of the forging is controlled at 980-1050°C, after upsetting, the forging is punched downward with a punch.

[0027] Step S4: Return to the furnace once, use a lifting clamp to remove the punched forging, then return the forging to the furnace, reheat the forging to 1240°C and keep it warm, control the heating rate to 90-110°C / h, and keep it warm for 8h.

[0028] Step S5, second stage forging, turning the forging over, and then upsetting, the upsetting forging ratio range is 6.5:1, the final forging temperature of the forging is controlled at 1020-1080°C, after upsetting, the forging is punched downward with a punch.

[0029] Step S6: Secondary re-melting: Use a lifting clamp to remove the punched forging, then return the forging to the furnace, reheat the forging with holes to 1230°C and keep it warm, with a heating rate of 65-75°C / h and a holding time of 5h.

[0030] Step S7, forming, placing the heated forging into a mold, then inserting a core rod into the holed forging, and then extruding, so that the forging forms an integrated flange and shaft body.

[0031] Step S8, upsetting and drawing: First, the flange is subjected to rotary upsetting, reaching 8-10% of its original height. The shaft is then drawn. Drawing process parameters include: anvil angle range of 6-10°, anvil width ratio range of 0.8-1.2, downward pressure of 10-13%, forging with a turning angle of 0°, -180°, or -90°, feed range of 0.8-0.9, and final forging temperature of 950-980°C. Finally, the forging is rounded.

[0032] Step S9, forging surface treatment, first sandblasting the forging surface to make the forging surface rough, then powder spraying the forging, the powder particles are Teflon powder particles, then heating the workpiece, heating the forging to 380 ° C, so that the powder particles adhere to the forging surface, and finally cooling the forging to room temperature.

[0033] Example 2: A method for controlling hydrogen embrittlement of large-size forgings comprises the following steps: Step S1: Prepare raw materials to obtain a forging blank. The raw materials include, by weight percentage, C 0.38-0.45%, Si ≤ 0.40%, Mn 0.50-0.80%, P ≤ 0.035%, S ≤ 0.020%, Cr 0.90-1.20%, Mo 0.18-0.36%, Cu ≤ 0.42%, H ≤ 2.0 ppm, Ni ≤ 0.60%, and the balance is Fe.

[0034] Step S2: heating before forging: heating the forging blank to 1250°C and keeping the temperature, controlling the heating rate to 80-100°C / h, and keeping the temperature for 8h.

[0035] Step S3, the first stage forging, upsetting the forging, the upsetting forging ratio range is 8:1, the final forging temperature of the forging is controlled at 980-1050°C, after upsetting, the forging is punched downward with a punch.

[0036] Step S4: Return to the furnace once, use a lifting clamp to remove the punched forging, then return the forging to the furnace, reheat the forging to 1250°C and keep it warm, control the heating rate to 90-110°C / h, and keep it warm for 8h.

[0037] Step S5, second stage forging, turning the forging over, and then upsetting, the upsetting forging ratio range is 7.5:1, the final forging temperature of the forging is controlled at 1020~1080℃, after upsetting, the forging is punched downward with a punch.

[0038] Step S6: Secondary re-melting: Use a lifting clamp to remove the punched forging, then return the forging to the furnace, reheat the forging with holes to 1240°C and keep it warm, control the heating rate at 65-75°C / h, and keep it warm for 5h.

[0039] Step S7, forming, placing the heated forging into a mold, then inserting a core rod into the holed forging, and then extruding, so that the forging forms an integrated flange and shaft body.

[0040] Step S8, upsetting and drawing: First, the flange is subjected to rotary upsetting, reaching 8-10% of its original height. The shaft is then drawn. Drawing process parameters include: anvil angle range of 6-10°, anvil width ratio range of 0.8-1.2, downward pressure of 10-13%, forging with a turning angle of 0°, -180°, or -90°, feed range of 0.8-0.9, and final forging temperature of 950-980°C. Finally, the forging is rounded.

[0041] Step S9, forging surface treatment, first sandblasting the forging surface to make the forging surface rough, then powder spraying the forging, the powder particles are Teflon powder particles, then heating the workpiece, heating the forging to 420 ° C, so that the powder particles adhere to the forging surface, and finally cooling the forging to room temperature.

[0042] Example 3: A method for controlling hydrogen embrittlement of large-size forgings comprises the following steps: Step S1: Prepare raw materials to obtain a forging blank. The raw materials include, by weight percentage, C 0.38-0.45%, Si ≤ 0.40%, Mn 0.50-0.80%, P ≤ 0.035%, S ≤ 0.020%, Cr 0.90-1.20%, Mo 0.18-0.36%, Cu ≤ 0.42%, H ≤ 2.0 ppm, Ni ≤ 0.60%, and the balance is Fe.

[0043] Step S2: heating before forging: heating the forging blank to 1260°C and keeping the temperature, controlling the heating rate to 80-100°C / h, and keeping the temperature for 8h.

[0044] Step S3, the first stage forging, upsetting the forging, the forging ratio range of upsetting is 9:1, the final forging temperature of the forging is controlled at 980-1050°C, after upsetting, the forging is punched downward with a punch.

[0045] Step S4: Return to the furnace once, use a lifting clamp to remove the punched forging, then return the forging to the furnace, reheat the forging to 1270°C and keep it warm, control the heating rate to 90-110°C / h, and keep it warm for 8h.

[0046] Step S5, second stage forging, turning the forging over, and then upsetting, the upsetting forging ratio range is 8.5:1, the final forging temperature of the forging is controlled at 1020-1080°C, after upsetting, the forging is punched downward with a punch.

[0047] Step S6: Secondary re-melting: Use a lifting clamp to remove the punched forging, then return the forging to the furnace, reheat the forging with holes to 1260°C and keep it warm, control the heating rate at 65-75°C / h, and keep it warm for 5h.

[0048] Step S7, forming, placing the heated forging into a mold, then inserting a core rod into the holed forging, and then extruding, so that the forging forms an integrated flange and shaft body.

[0049] Step S8, upsetting and drawing: First, the flange is subjected to rotary upsetting, reaching 8-10% of its original height. The shaft is then drawn. Drawing process parameters include: anvil angle range of 6-10°, anvil width ratio range of 0.8-1.2, downward pressure of 10-13%, forging with a turning angle of 0°, -180°, or -90°, feed range of 0.8-0.9, and final forging temperature of 950-980°C. Finally, the forging is rounded.

[0050] Step S9, forging surface treatment, first sandblasting the forging surface to make the forging surface rough, then powder spraying the forging, the powder particles are Teflon powder particles, then heating the workpiece, heating the forging to 450 ° C, so that the powder particles adhere to the forging surface, and finally cooling the forging to room temperature.

[0051] Product performance testing: Experimental group: Samples were taken from the products manufactured in Examples 1 to 3 for mechanical testing and non-destructive testing.

[0052] The location where product samples are taken for testing, such as Figure 2 shown.

[0053] The room temperature mechanical test results of the product are shown in Table 1.

[0054] Table 1 in conclusion: The samples obtained in Examples 1 to 3 have excellent yield strength and tensile strength at room temperature, and the elongation and cross-sectional shrinkage also meet the technical index requirements.

[0055] The samples of Examples 1 to 3 had no breakage or microcracks.

[0056] The technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above-described embodiments only express several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, several variations and improvements can be made, which all fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent of this invention shall be based on the attached claims.

Claims

1. A method for controlling hydrogen embrittlement of large-size forgings, characterized in that: The following steps are involved: Step S1: preparing raw materials to obtain forging blanks; Step S2: heating before forging, heating the forging blank to 1220-1260°C and keeping the temperature; Step S3, first stage forging, upsetting the forging, the upsetting ratio ranges from 7:1 to 9:1, and after upsetting, punching the forging downward with a punch; Step S4: reheat the forging to 1230-1270°C for insulation; Step S5, second stage forging, turning the forging over, and then upsetting, the upsetting forging ratio range is 6.5:1 to 8.5:1, after upsetting, using a punch to punch the forging downward; Step S6: reheating the forged piece to 1220-1260°C for a second time; Step S7: forming, placing the heated forging into a die, inserting a core rod into the holed forging, and then extruding the forging to form an integrated flange and shaft body; Step S8, upsetting and stretching, first performing rotary upsetting on the flange, then stretching the shaft, and finally rounding the forging; Step S9, forging surface treatment, first sandblasting the forging surface, then powder spraying the forging, then heating the workpiece to make the powder particles adhere to the forging surface, and finally cooling the forging to room temperature.

2. A method for controlling hydrogen embrittlement of large-size forgings according to claim 1, characterized in that: In step S1 , the raw material includes the following elements counted in weight percentage: C 0.38-0.45%, Si≤0.40%, Mn 0.50-0.80%, P≤0.035%, S≤0.020%, Cr 0.90-1.20%, Mo 0.18-0.36%, Cu≤0.42%, H≤2.0ppm, Ni≤0.60%, and the balance is Fe.

3. The method for controlling hydrogen embrittlement of large-size forgings according to claim 1, wherein: In step S2, the heating rate is 80-100°C / h, and the holding time ranges from 7 to 8 hours.

4. The method for controlling hydrogen embrittlement of large-size forgings according to claim 1, wherein: In step S3, the final forging temperature of the forging is controlled at 980-1050°C.

5. The method for controlling hydrogen embrittlement of large-size forgings according to claim 1, wherein: In step S4, the heating rate is 90-110°C / h, and the holding time ranges from 7 to 8 hours.

6. The method for controlling hydrogen embrittlement of large-size forgings according to claim 1, wherein: In step S5, the final forging temperature of the forging is controlled at 1020-1080°C.

7. The method for controlling hydrogen embrittlement of large-size forgings according to claim 1, wherein: In step S6, the heating rate is controlled to be 65-75°C / h, and the holding time range is 5-6h.

8. The method for controlling hydrogen embrittlement of large-size forgings according to claim 1, wherein: In step S8, the flange is rotated and upset to 8-10% of its original height.

9. The method for controlling hydrogen embrittlement of large-size forgings according to claim 1, characterized in that: In step S8, the drawing process parameters are as follows: the anvil angle range is 6~10°, the anvil width ratio range is 0.8~1.2, the downward pressure is 10~13%, the forging adopts 0°, -180° or -90° flipping, the feed range is 0.8~0.9, and the final forging temperature is controlled at 950~980℃.

10. The method for controlling hydrogen embrittlement of large-size forgings according to claim 1, characterized in that: In step S9, the powder particles are Teflon powder particles, and the heating temperature of the forging is in the range of 360-450°C.

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