A method for manufacturing a heavy-weight solid wind turbine main shaft made of 42CrMo4 material

Abstract

The invention discloses a method for manufacturing a heavy-weight solid wind turbine main shaft made of 42CrMo4. The technical scheme comprises the following steps: step S1: preparing a steel ingot; step S2: forging, heating the steel ingot to 1225-1235°C, then keeping the temperature for 12-14 hours and taking it out of the furnace, using a hydraulic forging machine to chamfer, draw the eight sides, chop the bottom and chop the riser, and then returning to the furnace to keep the temperature for 6 hours; step S3: performing the first upsetting of the steel ingot, drawing it in eight directions after the first upsetting, performing the second upsetting of the steel ingot, drawing the steel ingot flat, and performing the steel ingot After chamfering to octagonal shape, the steel ingot is returned to the furnace for heat preservation, and the return and heat preservation parameters are that the steel ingot is heated to 1215-1265°C and kept warm for 6 hours; step S4: the steel ingot is upset for the third time; step S5: the steel ingot is stretched to octagonal φ1850mm; step S6: the steel ingot shaft is stretched; step S7: the steel ingot is heated to 1230-1260°C and then kept warm for 6 hours, and the steel ingot is partially upset, partially stretched and formed, partially rounded, and the shaft is straightened. The advantages of the present invention are that the alloy composition is optimized, the forging deformation process is optimized, and the forging quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of manufacturing key parts of wind power equipment, and in particular to a method for manufacturing a heavy-weight solid wind power main shaft made of 42CrMo4 material. Background Art

[0002] With the advancement of science and technology and the deepening of industry, the demand for energy is also increasing, and the gap in traditional fossil energy is also increasing. Wind is one of the pollution-free energy sources, and it is inexhaustible. At present, with the development of technology, wind power equipment is not only widely used in the northwest region of my country. Due to the continuous optimization of construction costs and the increasing maturity of supporting industries, my country's offshore wind power has ushered in an accelerated development period. The planning goal is to ensure 5GW of grid connection by 2020 and strive to start construction of 10GW. As of the end of 2016, my country's cumulative installed capacity of offshore wind power was 1.63GW. It is predicted that in the next three and a half years, the number of newly added offshore wind power grid connections will reach more than 3.37GW, and the number of newly added offshore wind power projects will start construction of more than 8.37GW. In 2016, my country's cumulative installed capacity of offshore wind power exceeded Denmark and ranked third in the global cumulative installed capacity of offshore wind power, following the United Kingdom and Germany.

[0003] At present, offshore wind power equipment has attractive prospects and broad development space. However, opportunities are also accompanied by challenges. Offshore wind power generation faces complex construction geological environment, wave impact, sea ice impact, seawater corrosion, offshore wind force and wind direction changes, and wind turbine main shaft faces unprecedented technical difficulties.

[0004] The current publication number is CN102806291B and its name is a wind turbine main shaft forging method. The specific forging steps are as follows: S1, raw material pretreatment; S2, heating; S3, blank making; S4, upsetting; S5, drawing; S6, flange end upsetting; S7, mandrel drawing; S8, heat treatment; S9, testing. The material used is 42CrMo4. At present, the national standard 42CrMo4 steel ingot is used. With the increase in the size and complex shape of the wind turbine main shaft, after multiple forgings, it is easy to have defects such as looseness in the center of the forging and more non-metallic impurities in the microscopic doping of the metallographic structure, which affects the physical and chemical properties of the wind turbine main shaft on a macro scale and affects the service life of the wind turbine main shaft. Summary of the invention

[0005] In view of the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for manufacturing a heavy-weight solid wind turbine main shaft made of 42CrMo4 material, which has the advantages of optimizing the alloy composition, increasing the proportion of fine strengthening phase in the alloy microstructure, reducing internal defects of the alloy, and cooperating with special deformation tooling and deformation process to achieve high-precision deformation of forgings.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions:

[0007] A method for manufacturing a heavy-weight solid wind turbine main shaft made of 42CrMo4 material, characterized in that it comprises the following steps:

[0008] Step S1: preparing 42CrMo4 steel ingots, first preparing metal raw materials according to the designed formula, and then casting and forming the steel ingots;

[0009] Step S2: Forging, heating the steel ingot to 1225-1235°C, then keeping it warm for 12-14 hours, taking it out of the furnace, chamfering it with a hydraulic forging machine, pulling it into eight directions, then chopping the bottom and the riser, and then returning it to the furnace and keeping it warm for 6 hours;

[0010] Step S3: the steel ingot is subjected to the first upsetting, and then stretched into eight directions after the first upsetting. The steel ingot is subjected to the second upsetting, and then the steel ingot is flattened and squared, and then the steel ingot is chamfered into an octagonal shape, and then the steel ingot is returned to the furnace for heat preservation, and the return and heat preservation parameters are that the steel ingot is heated to 1215-1265° C. and kept warm for 6 hours;

[0011] Step S4: the steel ingot is subjected to a third upsetting;

[0012] Step S5: the steel ingot is drawn to 11850 mm in all directions, and then divided and numbered;

[0013] Step S6: the steel ingot shaft body continues to be stretched;

[0014] Step S7: After the steel ingot is heated to 1230-1260° C., it is kept warm for 6 hours, and then the steel ingot is partially upset, partially stretched, partially rounded, and finally the shaft is straightened.

[0015] Furthermore, the 42CrMo4 steel ingot includes the following components counted in mass percentage: C: 0.36-0.45%; Mn: 1.00-1.30%; Si: 0.15-0.33%; P≤0.02%; S≤0.02%; Cr: 0.95-1.35%; Ni: 0.70-0.95%; Mo: 0.22-0.38%; V: 0.03-0.14%; Cu≤0.25%.

[0016] Further, in step S1, H 2 The concentration is controlled at 1.5ppm.

[0017] Furthermore, in step S2, the heating of the steel ingot is divided into two stages: a preheating stage: heating to 670-930°C at a heating rate of 120-150°C / h; and a rapid heating stage: heating to 1225-1235°C at a heating rate of 250-310°C / h.

[0018] Furthermore, in step S2, the pressure specification of the hydraulic forging machine is 8000T to 10000T, and the drawing size is 1350mm.

[0019] Further, in step S3, the steel ingot is stretched to 1400*φ2900mm in eight directions after the first upsetting, and is flattened to 1100*φ1600mm in square after the first upsetting, and then chamfered to 1400*φ2900mm in eight directions. The final forging temperature of the steel ingot shall not be lower than 850°C.

[0020] Furthermore, in step S4, the third upsetting size of the steel ingot is 1000*φ2450mm.

[0021] Further, in step S5, the steel ingot is divided into processing area A, processing area B, processing area C, processing area D, and processing area E along the axial direction and the corresponding numbers are stamped.

[0022] Furthermore, in step S6, the diameters of the processing areas A and B are rounded to φ1850 mm, the diameter of the processing area C is rounded to φ1550 mm, and the diameters of the processing areas D and E are rounded to φ1325 mm.

[0023] Further, in step S7, processing area C is forged to φ1325mm, and processing equipment includes No. 1 gasket, No. 2 gasket, No. 3 gasket, No. 4 gasket and a rotating worktable. Processing area A and processing area B of the steel ingot are placed on the top of No. 1 gasket for local upsetting, and processing area C, processing area D and processing area E are stretched using No. 2 gasket, No. 3 gasket and No. 4 gasket, and then processing area A is rounded, and finally the shaft body is straightened.

[0024] In summary, the present invention has the following beneficial effects:

[0025] 1. By designing the element ratio in the alloy, the content of Mn and Cr is increased, and the proportion of troostite in the alloy is increased. Since troostite itself has good hardness and toughness, it is beneficial to increase the strength of the alloy. The content of elements such as P and S is strictly controlled. Since the two elements have strong affinity with metal elements, it is easy to cause excessive precipitation of other alloy elements on the grain boundary, which is easy to cause loose defects in the alloy. Adding elements such as Ni and V in the alloy is conducive to the formation of carbides. The formed carbides will be dispersed in the matrix, which plays a strengthening role and improves the shortcomings of the original 42CrMo4.

[0026] 2. Use appropriate forging deformation process and appropriate heat treatment parameters to increase the deformation performance and toughness of the alloy for subsequent multi-stage deformation. By crossing multiple different processing areas and selecting the appropriate deformation amount for each processing area, the deformation and cracking of the steel ingot is greatly reduced, and the forming quality of the forging is improved.

[0027] 3. Due to the different shapes of each processing area, a four-layer gasket tooling is used to adapt to each processing area, which can simultaneously complete the rounding of different radii of the shaft body, greatly improving the processing efficiency of parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the steps of manufacturing a heavy-weight solid wind turbine main shaft made of 42CrMo4 material.

[0029] Figure 2 It is a schematic diagram of the structure of the steel ingot in step S4.

[0030] Figure 3 It is a schematic diagram of the structure of the steel ingot in step S5.

[0031] Figure 4 It is a schematic diagram of the structure of the steel ingot in step S6.

[0032] Figure 5 It is a schematic diagram of the structure of the steel ingot in step S7.

[0033] Figure 6 This is the metallographic image of sample 1.

[0034] Figure 7 This is the metallographic image of sample 2.

[0035] Figure 8 This is the metallographic image of sample 3.

[0036] In the figure, 1, gasket No. 1; 2, gasket No. 2; 3, gasket No. 3; 4, gasket No. 4; 5, rotating worktable. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the present invention clearer, the device proposed by the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings adopt a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, please refer to the accompanying drawings. It should be noted that the structure, proportion, size, etc. illustrated by the accompanying drawings of this specification are only used to match the content disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no technical substantive significance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effect that the present invention can produce and the purpose that can be achieved, should still fall within the scope of the technical content disclosed by the present invention.

[0038] Embodiment 1:

[0039] A method for manufacturing a heavy-weight solid wind turbine main shaft made of 42CrMo4 material, such as Figure 1 As shown, the following steps are included:

[0040] Step S1: Prepare 42CrMo4 steel ingots. First, prepare the metal raw materials according to the designed formula, then cast the steel ingots. 2 The concentration is controlled at 1.5ppm to avoid excessive oxidation of the material during the steelmaking process. The specific 42CrMo4 steel ingot includes the following components counted by mass percentage: C: 0.36-0.45%; Mn: 1.00-1.30%; Si: 0.15-0.33%; P≤0.02%; S≤0.02%; Cr: 0.95-1.35%; Ni: 0.70-0.95%; Mo: 0.22-0.38%; V: 0.03-0.14%; Cu≤0.25%.

[0041] Step S2: Forging, heating the ingot to 1225℃, the ingot heating is divided into two stages, preheating stage: heating to 680℃ at a heating rate of 120~150℃ / h; rapid heating stage: heating to 1230℃ at a heating rate of 250~310℃ / h, and then keeping warm for 12~14h. Due to the large size of the ingot, the ingot needs to be heated evenly inside and outside, so segmented heating is adopted. The first stage is slowly heated to pre-melt the outer surface of the ingot, giving enough time for the heat to penetrate into the core of the ingot. The second stage is quickly heated to complete the transformation of the alloy structure to the sorbite matrix, and maintain good deformation ability. A hydraulic forging machine is used for chamfering. The pressure specification of the hydraulic forging machine is 8000T~10000T, and the ingot size is 1350mm. Then the bottom and riser are chopped, and then the furnace is returned to keep warm for 6h.

[0042] Step S3: The steel ingot is subjected to the first upsetting, and after the first upsetting, it is stretched in eight directions, and the size of the steel ingot is 1400*φ2900mm. The steel ingot is subjected to the second upsetting, and then the steel ingot is flattened and squared, and the size of the steel ingot is 1100*φ1600mm. Then the steel ingot is chamfered to an octagonal shape, and the size of the steel ingot is 1400*φ2900mm. The final forging temperature of the steel ingot shall not be lower than 850℃, and the temperature shall not be lower than the phase change point to avoid the transformation of the structure. After that, the steel ingot is returned to the furnace for heat preservation, and the heat preservation parameters of the return furnace are that the steel ingot is heated to 1215℃ and kept warm for 6h. The steel ingot needs to ensure good deformation performance so that the subsequent steel ingot can be subjected to subsequent complex deformation.

[0043] Step S4: The steel ingot is subjected to a third upsetting, such as Figure 2 As shown, the third upsetting size of the steel ingot is 1000*φ2450mm.

[0044] Step S5: The steel ingot is drawn to 1850 mm in diameter, and then divided and numbered. Figure 3 As shown, the steel ingot is divided into processing area A, processing area B, processing area C, processing area D, and processing area E along the axial direction and the corresponding numbers are stamped.

[0045] Step S6: Figure 4 As shown, the ingot shaft body continues to be drawn, specifically, the diameters of processing areas A and B are rounded to φ1850mm, the diameter of processing area C is rounded to φ1550mm, and the diameters of processing areas D and E are rounded to φ1325mm.

[0046] Step S7: Figure 5 As shown, after the steel ingot is heated to 1235°C, it is kept warm for 6 hours, and then the steel ingot is partially upset, partially stretched, partially rounded, and finally the shaft is straightened.

[0047] Specifically, the specific processing equipment includes a No. 1 gasket, a No. 2 gasket, a No. 3 gasket, a No. 4 gasket and a rotary table. The No. 1 gasket 1, the No. 2 gasket 2, the No. 3 gasket 3, the No. 4 gasket 4 and the rotary table 5 are arranged layer by layer from top to bottom. The size of the No. 1 gasket is φ2470*φ1375*500*R220mm, the size of the No. 2 gasket is φ2630*φ1750*450mm, the size of the No. 3 gasket is φ2650*φ1750*450 mm, the size of the No. 4 gasket is φ2670*φ1750*280mm, and the size of the rotary table is φ3200mm. Working principle: The steel ingot processing area A and processing area B are placed on the top 1 of the No. 1 gasket, and part of the steel ingot itself is inserted into the inner holes of the No. 2 gasket 2, the No. 3 gasket 3, and the No. 4 gasket 4. After that, the drawing work is completed, and the rotating workbench 5 is started to drive all the gaskets to complete the rounding work.

[0048] Embodiment 2:

[0049] The steps different from Example 1 are:

[0050] Step S2: Forging, heating the steel ingot to 1230°C. The heating of the steel ingot is divided into two stages: preheating stage: heating to 800°C at a heating rate of 120-150°C / h; rapid heating stage: heating to 1240°C at a heating rate of 250-310°C / h, and then keeping warm for 12-14h before taking out of the furnace.

[0051] Step S3: The steel ingot is returned to the furnace for heat preservation. The heat preservation parameters are as follows: the steel ingot is heated to 1235° C. and kept warm for 6 hours.

[0052] Step S7: The steel ingot is heated to 1245° C. and then kept at this temperature for 6 hours.

[0053] Embodiment 3:

[0054] The steps different from Example 1 are:

[0055] Step S2: Forging, heating the steel ingot to 1235°C. The heating of the steel ingot is divided into two stages: preheating stage: heating to 850°C at a heating rate of 120-150°C / h; rapid heating stage: heating to 1260°C at a heating rate of 250-310°C / h, and then keeping warm for 12-14h before taking out of the furnace.

[0056] Step S3: The steel ingot is returned to the furnace for heat preservation. The heat preservation parameters are as follows: the steel ingot is heated to 1265° C. and kept at this temperature for 6 hours.

[0057] Step S7: The steel ingot is heated to 1260° C. and then kept at this temperature for 6 hours.

[0058] Comprehensive mechanical properties test of forgings:

[0059] The staff conducted comprehensive mechanical experiments on the two groups of samples. The detailed test results are shown in Table 1.

[0060]

[0061] Table 1

[0062] Metallographic inspection of forgings:

[0063] Experimental preparation: Steel ingot samples were taken from Examples 1 to 3, respectively, and recorded as Samples 1 to 3.

[0064] Detection specification: X1000, 10μm

[0065] Test results:

[0066] Sample 1: The grain size is level 6, the grain structure is fine and dense, and there are no defects such as pitting, looseness, and cracks.

[0067] Sample 2: The grain size is level 6, the grain structure is fine and dense, and there are no defects such as pitting, looseness, and cracks.

[0068] Sample 3: The grain size is level 6, the grain structure is fine and dense, without defects such as pitting, looseness, and cracks.

[0069] The technical features of the above-described embodiments may be arbitrarily combined. 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.

[0070] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof 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, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for manufacturing a heavy-weight solid wind turbine main shaft made of 42CrMo4 material. It is characterized in that The following steps are involved: Step S1: preparing 42CrMo4 steel ingots, first preparing metal raw materials according to the designed formula, and then casting and forming the steel ingots; Step S2: Forging, heating the steel ingot to 1225-1235°C, then keeping it warm for 12-14 hours, taking it out of the furnace, chamfering it with a hydraulic forging machine, pulling it into eight directions, then chopping the bottom and the riser, and then returning it to the furnace and keeping it warm for 6 hours; Step S3: the steel ingot is subjected to the first upsetting, and then stretched into eight directions after the first upsetting. The steel ingot is subjected to the second upsetting, and then the steel ingot is flattened and squared, and then the steel ingot is chamfered into an octagonal shape, and then the steel ingot is returned to the furnace for heat preservation, and the return and heat preservation parameters are that the steel ingot is heated to 1215-1265° C. and kept warm for 6 hours; Step S4: the steel ingot is subjected to a third upsetting; Step S5: the steel ingot is drawn to φ1850mm in all directions, and then divided and numbered; Step S6: the steel ingot shaft body continues to be stretched; Step S7: After the steel ingot is heated to 1230-1260°C, it is kept warm for 6 hours, and then the steel ingot is partially upset, partially stretched and formed, partially rounded, and finally the shaft is straightened; The 42CrMo4 steel ingot includes the following components counted by mass percentage: C: 0.36-0.45%; Mn: 1.00-1.30%; Si: 0.15-0.33%; P≤0.02%; S≤0.02%; Cr: 0.95-1.35%; Ni: 0.70-0.95%; Mo: 0.22-0.38%; V: 0.03-0.14%; Cu≤0.25%; In step S2, the heating of the steel ingot is divided into two stages: a preheating stage: heating to 670-930°C at a heating rate of 120-150°C / h; a rapid heating stage: heating to 1225-1235°C at a heating rate of 250-310°C / h; In step S3, the steel ingot is stretched to 1400*φ2900mm in eight directions after the first upsetting, and the steel ingot is flattened to 1100*φ1600mm in square after the first upsetting, and then chamfered to 1400*φ2900mm in eight directions. The final forging temperature of the steel ingot shall not be lower than 850°C; In step S5, the steel ingot is divided into processing area A, processing area B, processing area C, processing area D, and processing area E along the axial direction and the corresponding numbers are stamped; In step S6, the diameters of the processing areas A and B are rounded to φ1850 mm, the diameter of the processing area C is rounded to φ1550 mm, and the diameters of the processing areas D and E are rounded to φ1325 mm; In step S7, processing area C is forged to φ1325mm, and processing equipment includes No. 1 gasket, No. 2 gasket, No. 3 gasket, No. 4 gasket and a rotating worktable. Processing area A and processing area B of the steel ingot place the top of No. 1 gasket for local upsetting, and No. 2 gasket, No. 3 gasket and No. 4 gasket are used to lengthen processing area C, processing area D and processing area E, and then processing area A is rounded, and finally the shaft body is straightened.

2. According to the method for manufacturing a heavy-weight solid wind turbine main shaft made of 42CrMo4 material as described in claim 1, Features: In step S1, H 2 The concentration is controlled at 1.5ppm.

3. According to the method for manufacturing a heavy-weight solid wind turbine main shaft made of 42CrMo4 material as described in claim 1, Features: In step S2, the pressure specification of the hydraulic forging machine is 8000T to 10000T, and the drawing size is 1350mm.

4. According to the method for manufacturing a heavy-weight solid wind turbine main shaft made of 42CrMo4 material as described in claim 1, Features: In step S4, the third upsetting size of the steel ingot is 1000*φ2450mm.

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