Forming process of large wind power main shaft pipe

Abstract

The application discloses a large wind power main shaft pipe forming process, which solves the problem of high welding quality requirement and multiple welds in the prior art. The process comprises the following steps: punching a steel ingot to obtain a punched blank with a flange hole by using a punch rod and a female die after heating the steel ingot; inserting a top rod into the flange hole of the punched blank after heating the punched blank, so that the punched blank passes through a die ring to obtain a rough-formed wind power main shaft pipe; processing a through center hole in a small-diameter section and a variable-diameter section of the rough-formed wind power main shaft pipe by using a boring cutter on a boring machine to obtain a formed wind power main shaft pipe; and finally obtaining the wind power main shaft pipe by inserting a blank with a hole into the flange hole of the formed wind power main shaft pipe and then performing heat treatment. The process is simple, the production cycle is short, the equipment investment and operation cost are low, the material utilization rate is high, and the product quality is good.

Description

TECHNICAL FIELD

[0001] The present application relates to a large pipe manufacturing process, in particular to a large wind turbine main shaft pipe forming process. BACKGROUND

[0002] With the continuous improvement of wind power technology and the continuous reduction of unit manufacturing cost, the competitiveness of the wind power market will gradually improve, and the development prospect is broad. By improving the mechanical properties of the main shaft, the load capacity and impact resistance of the wind turbine are improved, the service life of the wind turbine is improved, the total power generation of the unit is increased, the energy consumption is reduced, the energy utilization rate is improved, and the wind energy utilization rate is expanded.

[0003] The wind turbine main shaft is large in size and is composed of a small diameter section, a variable diameter section and a flange section. The small diameter section and the variable diameter section have a through center hole for connecting the gear box, and the flange section has a flange hole with a large inner diameter for connecting the flange. Due to the particularity of the use environment of the wind turbine main shaft, the design requirements meet the following technical indicators: the outer diameter of the flange section is φ950-φ970mm, the inner diameter of the shaft body (i.e. the flange hole) is φ650-φ700mm, the outer diameter of the tail gear box connecting section (i.e. the small diameter section) is φ740-φ770mm, and the inner diameter of the center hole is 80-120mm. The product material is usually 21CrMo10 or a material with similar performance, and the final product requires a yield strength of not less than 620MPa, a tensile strength of not less than 760MPa, an impact of not less than 50J at -40℃, a surface hardness of 220-270HB after finishing, and a hardness difference of not more than 20HB between any two points.

[0004] Due to the large size of the wind turbine main shaft, the shape is relatively special, and the forming process is mainly integral free forging or welding type.

[0005] The wind turbine main shaft by integral free forging has solid and hollow types. The solid main shaft has a larger weight, a lower material utilization rate, a larger specification of the forging press, and a higher cost. The hollow shaft also adopts the free forging method, which slightly reduces the weight compared to the solid shaft, but the process is complicated, the machining allowance is large, and the cost is further increased.

[0006] Welding forming mainly divides the wind turbine main shaft into three sections for forging respectively, and then welds them into a whole. In this way, there are inevitable welds between the front flange section and the rear flange section, and between the rear flange section and the variable diameter section. Although this can reduce the process difficulty, equipment investment and cost, due to the existence of two welds, especially the weld between the rear flange section and the variable diameter section, which is close to the gear box and bears a larger torque, the weld is prone to fatigue cracking. Not only is the welding quality high, but also the various strength indicators of the wind turbine main shaft formed by welding are significantly worse than those of the integral formed wind turbine main shaft, resulting in a high scrap rate.

[0007] On the other hand, in the heat treatment step after forming, due to the special shape of the wind power main shaft, the wall thickness of the flange section is much smaller than that of the variable diameter section, which is prone to cause uneven strength and hardness after heat treatment, thereby affecting the overall fatigue strength index of the wind power shaft. SUMMARY

[0008] The purpose of the present application is to solve the above technical problems, and provide a large wind power main shaft pipe forming process which is simple in process, short in production cycle, low in equipment investment and operation cost, high in material utilization rate and good in product quality.

[0009] In the present application, the steel ingot is subjected to riser and bottom sawing, and then subjected to punching, finishing, rough machining and heat treatment steps in sequence,

[0010] In the punching step, the steel ingot is heated and punched on a vertical die forging hydraulic press with a punch rod cooperating with a female die to obtain a punched blank with a flange hole.

[0011] In the finishing step, the punched blank is heated, a top rod is inserted into the flange hole of the punched blank, and the punched blank is finished on a horizontal hydraulic press to obtain a rough formed wind power main shaft pipe.

[0012] In the rough machining step, a through center hole is machined in the small diameter section and variable diameter section of the rough formed wind power main shaft pipe using a boring cutter on a boring machine to obtain a formed wind power main shaft pipe.

[0013] In the heat treatment step, a hole blank is inserted into the flange hole of the formed wind power main shaft pipe before heat treatment to obtain a wind power main shaft pipe.

[0014] In the punching step, the female die has an open top, and the inner cavity is composed of a small diameter section, a variable diameter section and a flange section.

[0015] In the heat treatment step, the outer diameter of the hole blank is the same as the hole diameter of the flange hole of the formed wind power main shaft pipe, and the inner hole diameter of the hole blank is the same as and coaxially arranged with the center hole diameter of the formed wind power main shaft.

[0016] In the heat treatment step, the heat treatment method is normalizing + quenching + tempering, the normalizing temperature is 930-950℃, the holding time is 5-5.5 hours, the quenching temperature is 910-930℃, the holding time is 5-5.5 hours, the tempering temperature is 620-630℃, and the holding time is 10-10.5 hours.

[0017] Preferably, the material of the main shaft of the wind power is 21CrMo10, the flange section in the process of the application refers to the front flange section of the main shaft of the wind power, after the main shaft pipe of the wind power (composed of the small diameter section, the variable diameter section and the front flange section) is obtained by using the forming process of the application, the original rear flange section needs to be welded to form the complete main shaft of the wind power.

[0018] In view of the problems in the background art, the inventors have made the following improvements:

[0019] 1) The weld joint between the rear flange section and the variable diameter section is cancelled, and the rear flange section, the variable diameter section and the small diameter section are integrally formed by using a steel ingot through punching, finishing, rough machining and heat treatment steps. Since the integral forming is adopted, the fiber structure is continuous, the weld joint is reduced compared with the solid welded shaft, the welding cost is reduced, the defect probability caused by welding is reduced, the strength of the main shaft of the wind power is increased, the product life is improved, and the scrap rate is effectively reduced.

[0020] 2) The punching and finishing process is used to replace the traditional integral free forging, which does not need complex processes and large-scale presses, but uses a water pressure machine combined with a female die and a die ring to obtain the main shaft of the wind power with the required inner and outer diameters through two forming fire times. The forming fire times are less, the forming shape and the blank allowance are better controlled, the processes are less, and the production cost and the production cycle can be greatly reduced.

[0021] 3) Considering the special-shaped structure of the main shaft of the wind power, i.e. the small diameter section and the variable diameter section are only provided with a center hole, the wall thickness is large, and the flange section has a large flange hole, the wall thickness is small. During heat treatment, the difference in wall thickness will directly affect the hardness index between any two points (the hardness difference between any two points is not greater than 20 HB). For the above special case, the inventors consider inserting a hole blank into the flange hole of the formed main shaft of the wind power during the heat treatment step, and then performing heat treatment, so as to compensate for the difference in wall thickness by using the hole blank, avoid the problem of uneven strength and hardness caused by uneven wall thickness and inconsistent cooling rate during heat treatment, and meet the index requirement that the hardness difference between two points is not greater than 20 HB. Further, the heat treatment method is normalizing + quenching + tempering, which can further refine the grains and improve the tensile strength and fatigue resistance of the main shaft pipe of the wind power. Preferably, the normalizing temperature is 930-950℃, the holding time is 5-5.5 hours; the quenching temperature is 910-930℃, the holding time is 5-5.5 hours, the tempering temperature is 620-630℃, and the holding time is 10-10.5 hours.

[0022] The hollow wind power shaft meets the requirement of integral forming, reduces welding seams, and is different from free forging, further reduces the excess amount, improves the material utilization rate of the wind power main shaft, reduces the production cost, and the obtained large wind power shaft pipe meets the following performance indexes: the yield strength is not less than 620 MPa, the tensile strength is not less than 760 MPa, the impact at-40 DEG C is not less than 50 J, the surface hardness of the finished product is 220-270 HB, and the hardness difference between any two points is not more than 20 HB. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of a wind power main shaft;

[0024] Figure 2 It is a state schematic diagram of a punching step;

[0025] Figure 3 It is a state schematic diagram of a finishing step;

[0026] Figure 4 It is a state schematic diagram of a rough machining step;

[0027] Figure 5 It is a state schematic diagram of a heat treatment step.

[0028] Among them, A1-small diameter section, A2-diameter changing section, A3-flange front section, A4-flange rear section, A5-center small hole;

[0029] 1-punch, 2-punched blank, 3-flange hole, 4-negative mold, 4.1-small diameter section, 4.2-diameter changing section, 4.3-flange section, 5-ejector rod, 6-die ring, 7-roughly formed wind power main shaft pipe, 8-small diameter section, 9-diameter changing section, 10-center small hole, 11-flange section, 12-hole blank, 12.1-inner hole, 13-wind power main shaft pipe. DETAILED DESCRIPTION

[0030] The forming process of the present application is further explained below in combination with the drawings:

[0031] I. Punching step: see Figure 2 After the steel ingot is heated to 1250±20 DEG C, the punch 1 is used to punch the steel ingot on the 4500T vertical die forging hydraulic press to obtain the punched blank 2 with the flange hole 3, and the cavity size of the negative mold 4 meets the external size requirement of the wind power main shaft pipe, specifically: the negative mold 4 is opened at the top, and the inner cavity is composed of the small diameter section 4.1, the diameter changing section 4.2 and the flange section 4.3.

[0032] II. Finishing step: see Figure 3After the punching blank 2 is heated, the ejector rod 5 is inserted into the flange hole 3 of the punching blank 2, and then the punching blank 2 is placed on a 2000T horizontal hydraulic press for finishing, so that the punching blank 2 passes through a die ring 6 to obtain a roughly formed wind power main shaft pipe 7, an inner diameter of the die ring 6 meets the outer diameter requirement of a flange section of the wind power main shaft pipe, and an outer diameter of the ejector rod 5 meets the size requirement of a flange hole of the wind power main shaft pipe;

[0033] In the rough machining step, referring to Figure 4 , a boring cutter is used on a boring machine to process a through small hole 10 in a small diameter section 8 and a variable diameter section 9 of the roughly formed wind power main shaft pipe 7, so as to obtain a formed wind power main shaft pipe 8;

[0034] In the heat treatment step, referring to Figure 5 , a hole blank 12 is inserted into the flange hole 3 of the formed wind power main shaft pipe 8, and then heat treatment is performed, so as to obtain a wind power main shaft pipe 13, the heat treatment mode is normalizing + quenching + tempering, the normalizing temperature is 930-950℃, the holding time is 5-5.5 hours, the quenching temperature is 910-930℃, the holding time is 5-5.5 hours, the tempering temperature is 620-630℃, and the holding time is 10-10.5 hours. The outer diameter of the hole blank 12 is the same as the hole diameter of the flange hole 3 of the formed wind power main shaft pipe 2, and the inner hole 12.1 of the hole blank 12 has the same hole diameter as the center small hole of the formed wind power main shaft and is coaxially arranged.

[0035] After the finally obtained wind power main shaft pipe 13 is welded with a corresponding matching flange rear section A4, a Figure 1 wind power main shaft is obtained.

[0036] The obtained large wind power shaft pipe meets the following performance indexes: the yield strength is not less than 620MPa, the tensile strength is not less than 760MPa, the impact at-40℃ is not less than 50J, the surface hardness of the finished product is 220-270HB, and the hardness difference between any two points is not more than 20HB.

Claims

1. A process for forming a large windmill main shaft tube, characterized in that, The steel ingot is subjected to riser and bottom sawing, and then subjected to punching, finishing, rough machining and heat treatment steps in sequence, In the punching step, the steel ingot is heated and then punched on a vertical die forging hydraulic press to obtain a punched blank with a flange hole by using a punch rod in cooperation with a female die, the cavity size of the female die meets the external size requirement of the wind power main shaft pipe. In the finishing step, the punched blank is heated, a top rod is inserted into the flange hole of the punched blank, and the punched blank is subjected to finishing on a horizontal hydraulic press to pass through a die ring to obtain a rough-formed wind power main shaft pipe, the inner diameter size of the die ring meets the outer diameter size requirement of the flange section of the wind power main shaft pipe, and the outer diameter size of the top rod meets the flange hole size requirement of the wind power main shaft pipe. In the rough machining step, a through center hole is machined on the small diameter section and the variable diameter section of the rough-formed wind power main shaft pipe by using a boring cutter on a boring machine to obtain a formed wind power main shaft pipe. In the heat treatment step, a hole blank is inserted into the flange hole of the formed wind power main shaft pipe, and then heat treatment is performed to obtain a wind power main shaft pipe.

2. A process for forming large windmill main shaft tubes as claimed in claim 1, characterized in that, In the punching step, the female die is open at the top, and the inner cavity is composed of the small diameter section, the variable diameter section and the flange section of the lower section.

3. The large-scale wind turbine main shaft pipe forming process according to claim 1, characterized in that: In the heat treatment step, the outer diameter of the hole blank is the same as the hole diameter of the flange hole of the formed wind power main shaft pipe, and the inner hole diameter of the hole blank is the same as and coaxially arranged with the center hole diameter of the formed wind power main shaft.

4. The large-scale wind turbine main shaft pipe forming process according to claim 1, characterized in that: In the heat treatment step, the heat treatment mode is normalizing + quenching + tempering, the normalizing temperature is 930-950℃, the holding time is 5-5.5 hours, the quenching temperature is 910-930℃, the holding time is 5-5.5 hours, the tempering temperature is 620-630℃, and the holding time is 10-10.5 hours.

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