Machining method for multi-step abrasion-resistant and corrosion-resistant torque transmission shaft

Abstract

The invention discloses a multi-step wear-resistant and corrosion-resistant torque transmission shaft machining method which comprises the following machining steps of (1) forging machining of a multi-step long shaft, (2) drilling machining, (3) straightening and destressing treatment, (4) laser cladding of a sliding sealing surface section, (5) grinding machining of the sliding sealing surface section, (6) machining of the sliding sealing surface section, (7) machining of the multi-step wear-resistant and corrosion-resistant torque transmission shaft, and (8) machining of the multi-step wear-resistant and corrosion-resistant torque transmission shaft. A spline on the surface of the torque transmission section is machined; seventhly, a taper thread connection section is machined; two step parts with different diameters are formed by forging a raw material blank, and other step structures are formed by machining; moreover, the drilling precision is improved through a three-point one-line drilling process, the problem of wear resistance and corrosion resistance in the using process is solved, and a layer of iron-based alloy powder with the thickness of 0.5 cm is adopted to be subjected to laser cladding on the sealing surface, so that the wear-resistant and corrosion-resistant functions are achieved; and laser cladding and grinding are carried out on the surface of the shaft, so that the problems of non-coaxial assembly and incapability of assembly caused by non-coaxial machining are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of torque transmission shaft processing, in particular to a multi-step wear-resistant and corrosion-resistant torque transmission shaft processing method. BACKGROUND

[0002] The torque transmission shaft is mainly used for the mandrel of a percussion product, and the transmission shaft has the following structural characteristics: the matched percussion device is suitable for an environment of 7000 meters or even up to 10,000 meters deep in the well; the mandrel moves up and down in the percussion device, resists the up and down percussion force of the percussion device, and transmits the rotation of external parts; the mandrel has a stress relief transition surface and a wear-resistant and corrosion-resistant sealing function, and has a tensile strength of 1033 MPa, a material yield strength of more than 965 MPa, and a yield torque of 27 kN / m. At present, the multi-step workpiece of the mandrel of the percussion product is long, and in the process of machining drilling, it is easy to appear deflection and overall bending deformation after machining, which leads to the problems of different shafts and serious wear of the sealing surface in assembly and test, and the need for corrosion resistance of the oilfield well condition. SUMMARY

[0003] The purpose of the present application is to provide a multi-step wear-resistant and corrosion-resistant torque transmission shaft processing method to solve the problem of the existing technology that the multi-step workpiece of the mandrel is long and easy to appear deflection in the process of machining drilling, and overall bending deformation after machining leads to the problems of different shafts and serious wear of the sealing surface in assembly and test.

[0004] The technical scheme of the present application is a multi-step wear-resistant and corrosion-resistant torque transmission shaft processing method, the torque transmission shaft includes a connecting section, a sliding sealing surface section, a torque transmission section, and a connecting sealing surface section and a taper thread connecting section, and the specific method includes the following steps:

[0005] Step one, forging processing of the multi-step long shaft, the selected raw material is a 4145H blank, which is heated and processed to gradually reduce the diameter of the connecting section and the sliding sealing surface section from left to right; the connecting section is the largest diameter section, and the outer diameter processing allowance of the sliding sealing surface section is 15-17mm;

[0006] Step two, drilling processing, when the workpiece is processed, one end is fixed by a four-jaw chuck, the other end is topped by a taper disc, and the middle section is clamped by a supporting method, which effectively improves the accuracy requirement during drilling;

[0007] Step three, straightening and stress relief processing, because the processing allowance is small and the long shaft processing has a length-diameter ratio greater than 15, the cutting heat in the processing process is easy to cause the workpiece to bend and deform, so multiple straightening processes are set in the whole processing process;

[0008] Step four, laser cladding of the sliding sealing surface section, to improve product life and meet the acid and alkali corrosion in the oil field, a deep groove is first machined on the surface of the sliding sealing surface section, and then iron-based powder laser cladding is further carried out on the surface of the formed sliding sealing surface section to prevent loose bonding and falling off;

[0009] Step five, grinding processing of the sliding sealing surface section, the formed sliding sealing surface section is matched with metal parts, and the surface of the sliding sealing surface section needs to be processed and ground to reduce the surface roughness of the sliding sealing surface section;

[0010] Step six, processing of the spline on the surface of the torque transmission section, the spline is the part of the driving torque, to prevent uneven stress on the spline, the spline is symmetrically milled in groups using a milling machine, and the excess amount is controlled by a numerical control machining center for fine milling;

[0011] Step seven, processing of the taper thread connection section, using a numerical control pipe lathe for processing, after processing, the taper, base distance, tooth height and tooth shape of the taper thread are inspected and corrected to be qualified using special measuring tools.

[0012] Further, the connection section and the sliding sealing surface section formed in step one are formed by forging, and the torque transmission section and the connection sealing surface section and the taper thread connection section are formed by machining and turning.

[0013] Further, in step one, the connection section is the largest diameter section, and the machining allowance of the outer diameter of the sliding sealing surface section is 15mm, and a circular transition surface is formed at the step between the two.

[0014] Further, in step three, the straightening process is a three-time straightening process, the first time is the straightening process after rough turning the outer circle step connection section and the sliding sealing surface section of the forged mandrel and heat treatment; the second time is the straightening process after turning the torque transmission section and the connection sealing surface section and the taper thread connection section and drilling; the third time is the straightening process after laser cladding of the sliding sealing surface.

[0015] Further, in step four, the depth of the deep groove is 1mm, the iron-based powder laser cladding is 1.6mm, and the surface of the iron-based powder laser cladding is ground, finally ensuring that the thickness of the cladding layer in the diameter direction is 1mm-1.1mm.

[0016] Further, in step five, the surface roughness of the sliding sealing surface section is less than 0.8.

[0017] Further, in step six, the control allowance of the finishing is 1mm.

[0018] The present application has the beneficial effects compared with the prior art: two workpieces with different diameters are casted and formed by raw material blanks, other step structures are formed by machining, the drilling precision is improved by three-point straight-line drilling process, and the wear-resistant and corrosion-resistant problem in use is solved by laser cladding a layer of 0.5 cm thick iron-based alloy powder on the sealing surface and grinding to achieve the function of wear-resistant and corrosion-resistant, the problems of assembly misalignment and assembly failure caused by different shafts are solved by the whole process of forging, rough turning, three-point straight-line drilling process, finish turning and three straightening treatments. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is the overall structure diagram of the transmission shaft workpiece processed by the present application.

[0020] Figure 2 It is the overall structure diagram of the transmission shaft workpiece processed by the present application. Figure 1 It is the overall structure diagram of the transmission shaft workpiece processed by the present application. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0022] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications will also change accordingly.

[0023] In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of those skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the scope of protection required by the present application.

[0024] Reference Figures 1-2In the present application, the specific structure of the transmission shaft is that the inside is a small diameter hole 6 and the outside is composed of five diameter difference outer cylindrical segments, and the adjacent outer cylindrical segments form steps, and the five outer cylindrical segments form the structure of four stepped shafts, and the segments from large diameter to small diameter are respectively the connection segment 1 of the largest outer diameter segment connecting the upper drill rod, the surface of which is also provided with internal threads 11 for connecting with the drill string, the second outer diameter segment is the stress relieving transition surface and the wear-resistant and corrosion-resistant sliding sealing surface segment 2 (the mandrel moves up and down on the jar tool, and this segment has the functions of wear resistance, corrosion resistance and sealing), the surface roughness value is required to be less than 0.8, the third outer diameter segment is the torque transmission segment 3, the torque transmission segment is connected with the external parts of the jar tool through the spline structure, the mandrel rotates to drive the external parts to rotate together, the fourth outer diameter and the fifth outer diameter segment are the structure of the lower end of the mandrel and the lower end core part of the jar, which is connected by the slightly larger sealing surface segment 4 and the taper thread connection segment 5. The outer diameter of such a mandrel is small, as small as 80mm, and as large as 121mm, the length is greater than 2m, and the length-diameter ratio is more than 15.

[0025] The overall machining sequence is: raw material forging-rough turning outer cylindrical stepped shaft connection segment-heat treatment-straightening and stress relief-semi-finishing machining-deep hole drilling through diameter inner hole-straightening and stress relief-semi-finishing machining of connection segment, sliding sealing surface segment, torque transmission segment, and connecting sealing surface segment and taper thread connection segment-laser cladding of sliding sealing surface segment surface-straightening and stress relief-surface grinding of sliding sealing surface segment-precision machining of outer circle of torque transmission segment and thread of connection segment-milling of spline of torque transmission segment-numerical control pipe thread machining of taper thread connection segment.

[0026] Specifically, the following steps are included:

[0027] Step one, forging processing of the stepped long shaft, the selected raw material is 4145H blank which is heated and then forged from left to right to gradually reduce the diameter of the connection segment, the sliding sealing surface segment, the torque transmission segment, and the connecting sealing surface segment and the taper thread connection segment; the connection segment is the largest diameter segment, and the outer diameter processing allowance of the sliding sealing surface segment is 15mm-17mm; the raw material is 4145H, and the forging process is adopted to save cost and ensure the mechanical properties of the part, that is, the connection segment and the sliding sealing surface segment are formed by forging, the blank is heated, the initial forging temperature of the forged piece is 1180° and the final forging temperature is 900° (the blank is heated to 1180° and taken out to start forging, and when the forged piece material reaches 900℃, the forging is stopped and the furnace is heated again), the blank is forged into a forged piece with one step through multiple heating, that is, the connection segment and the sliding sealing surface segment are formed by forging, and the stepped shaft with a preferred 15mm processing allowance, and the steps of the remaining torque transmission segment and the connecting sealing surface segment and the taper thread connection segment need to be manufactured through later machining.

[0028] The stepped shaft between the connecting section and the sliding sealing surface section is forged with a large arc transition surface 10. During forging, the length of the large end section is more than 80 mm longer than the finished product length, controlled within the range of 150 mm. The total length of the forging is 100 mm to 120 mm longer than the finished product size. The purpose of lengthening is to ensure sufficient length margin in the direction of the workpiece to prevent horseshoe-shaped chipping or local cracks at the end face during the heat treatment of the semi-finished product of the drive shaft. This ensures that the workpiece does not need to be scrapped due to insufficient total length of the workpiece, even if other quality requirements are met, thus guaranteeing the quality and pass rate of the parts. Overheating is not allowed to ensure the uniformity of the internal structure and the mechanical performance requirements. Depending on the material and size of the parts, the holding time must reach 1 to 2 hours, and the workpiece can only be proceeded after observing that the fire color is uniform. This ensures that there are no defects such as cracks, folds, scabs, or slag inclusions on the surface of the forged parts. Annealing treatment is performed after forging.

[0029] Step two, drilling. During machining, one end of the workpiece is clamped by a four-jaw chuck, the other end is sealed with a tapered plate, and the middle section is supported and held in place, effectively improving the accuracy requirements during drilling. Drilling of this type of part is considered deep hole machining. Due to the small size of the hole and the difficulty in chip removal, the drill is prone to jamming. Therefore, the machining parameters need to be better matched. Theoretical calculations show that the optimal feed rate is between 50 and 60 mm / min. The rotational speed is calculated based on the size of the hole. Since the machining allowance for the outer diameter is small, to ensure the smooth completion of all subsequent processes and avoid scrap, The process requires that the wall thickness difference be less than 1.5mm after drilling, as measured by a wall thickness gauge. To ensure this, alignment and support frame references must be machined before drilling. During drilling, dial indicators are used for alignment, and the difference between the two ends is controlled within 0.2mm. During machining, one end is clamped with a four-jaw chuck, and the other end is clamped using a tapered plate top and a support frame in the middle. After the dial indicator is aligned, the three points are in a straight line, ensuring that the workpiece does not deviate during drilling and that the wall thickness difference of the drilled part's inner hole is within the required range. This clamping method significantly reduces the problem of excessive hole deviation and resulting scrap caused by the previous clamping method that only used four jaws and a center frame for alignment.

[0030] Step 3: Straightening and stress relief. Due to the small machining allowance and the machining of a slender shaft, bending deformation is prone to occur during processing. Therefore, multiple straightening processes are implemented throughout the machining process. The required straightness along the entire length varies depending on the machining step, and the three straightening and stress relief processes are interspersed. The first straightening process is performed after heat treatment following rough machining of the outer cylindrical stepped connecting section and sliding sealing surface section of the forged mandrel. After heat treatment, the workpiece undergoes heating and quenching, resulting in bending deformation of 3-4 mm. Due to the small outer cylindrical allowance, straightening and stress relief are necessary to ensure a straightness of 1 mm along the entire length of the part. The second process occurs during semi-finishing. Because the large depth of cut during step machining causes bending (arc or twist), straightening before laser cladding requires a straightness of 0.2 mm along the entire length. The third process occurs during laser cladding. The high temperature of the laser during laser cladding also causes deformation, although the deformation is less than that caused by heat treatment. After straightening, a straightness of 0.2 mm along the entire length is required. Because stress concentration occurs after straightening, which can easily lead to fracture, stress relief is necessary after straightening. The stress relief process involves heating the furnace to 610℃ and holding it at that temperature for 2 to 2.5 hours to achieve the effect of stress relief.

[0031] Step four: Laser cladding of the sliding sealing surface. To improve product lifespan and withstand acid and alkali corrosion in oilfields, the process requires machining a 1mm deep groove on the sliding sealing surface before cladding a 1.6mm thick layer of iron-based powder. Finally, 0.25mm to 0.3mm of the cladding layer is ground off. Only this process can ensure a strong 0.5mm bond between the cladding layer and the substrate; otherwise, the cladding layer is prone to detachment. Since the hardness of the cladding iron-based alloy powder wear-resistant layer reaches HRC52-55, it achieves wear and corrosion resistance, meeting the product's performance requirements.

[0032] Step five involves grinding the sliding sealing surface. The resulting sliding sealing surface mates with a metal part. During operation, friction occurs between the metal part and the sealing surface, easily causing scratches and grooves, leading to product failure. Therefore, grinding is necessary to reduce the surface roughness of the sliding sealing surface. The required surface roughness is ≤0.8, and grinding is incorporated into the process to ensure this. This roughness serves as a benchmark for subsequent processes, ensuring the coaxiality of the entire part, meeting assembly requirements, eliminating misalignment, and improving the assembly pass rate.

[0033] Step six involves machining the splines on the torque transmission section. Since the splines are the torque-transmitting component, to prevent uneven stress on the splines, they are machined symmetrically in groups using a milling machine. The remaining allowance is then controlled by finish milling on a CNC machining center. To prevent spline breakage due to uneven stress, symmetrical milling is required during machining. Roughing is performed symmetrically on a conventional horizontal milling machine, followed by finish milling on a CNC machining center with a 1mm allowance. This ensures the symmetry of the splines.

[0034] Step 7: Machining of the tapered thread connection section is carried out on a CNC pipe lathe. After machining, the taper, base distance, thread height, and thread shape need to be inspected and corrected using special measuring tools until they are qualified. The sealing surface section 4 formed is then precision machined by a CNC machine tool.

[0035] In addition to the preferred embodiments described above, the present invention has other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection claimed by the present invention.

Claims

1. A method for machining a multi-step wear-resistant and corrosion-resistant torsion shaft, characterized in that, The torque transmission shaft includes a connecting section, a sliding sealing surface section, a torque transmission section, a connecting sealing surface section, and a tapered thread connecting section. The specific method includes the following steps: Step 1: Forging of the multi-step long shaft. The selected raw material is 4145H blank. After heat treatment, the connecting section and sliding sealing surface section with gradually decreasing diameter are forged from left to right. The connecting section is the largest diameter section, and the machining allowance of the outer diameter of the sliding sealing surface section is 15mm-17mm. Step 2, drilling: During the workpiece machining, one end is fixed by a four-jaw chuck, the other end is fixed by a tapered plate, and the middle section is supported by a clamping method, which effectively improves the accuracy requirements during drilling. Step 3, straightening and stress relief treatment. Due to the small machining allowance and the fact that it is a slender shaft with a length-to-diameter ratio greater than 15, the cutting heat during the machining process can easily cause the workpiece to bend and deform. Therefore, multiple straightening treatments are set up throughout the machining process. Step four, laser cladding of the sliding sealing surface: In order to improve product life and meet the acid and alkali corrosion requirements of oilfield wells, the process involves first machining a deep groove on the surface of the sliding sealing surface, and then further laser cladding of iron-based powder on the surface of the formed sliding sealing surface to prevent weak adhesion and detachment. Step 5: Grinding of the sliding sealing surface. The resulting sliding sealing surface is mated with the metal part, so the surface of the sliding sealing surface needs to be ground to reduce the surface roughness. Step 6: Machining of the splines on the surface of the torque transmission section. The splines are the part that transmits torque. To prevent uneven stress on the splines, the splines are machined in groups symmetrically using a milling machine, and the allowance is controlled. Finally, the dimensions are ensured by precision milling using a CNC machining center. Step 7: Machining of the tapered thread connection section. This is done on a CNC pipe lathe. After machining, the taper, base distance, thread height, and thread profile of the tapered thread need to be inspected and corrected using special measuring tools until they are qualified.

2. The method for machining a multi-step wear-resistant and corrosion-resistant torsion shaft according to claim 1, characterized in that, The connecting section and sliding sealing surface section formed in step one are formed by forging, while the torsion transmission section, connecting sealing surface section and tapered thread connecting section are formed by machining.

3. The method for machining a multi-step wear-resistant and corrosion-resistant torsion shaft according to claim 2, characterized in that, In step one, the connecting section is the section with the largest diameter, and the machining allowance for the outer diameter of the sliding sealing surface section is 15mm, and an arc transition surface is machined at the step formed between the two.

4. The method for machining a multi-step wear-resistant and corrosion-resistant torsion shaft according to claim 1, characterized in that, In step three, the straightening process consists of three straightening processes. The first is the straightening process after heat treatment following rough turning of the outer cylindrical stepped connecting section and the sliding sealing surface section of the forged mandrel. The second is the straightening process after turning the torque transmission section, the connecting sealing surface section, the tapered thread connecting section, and drilling. The third is the straightening process after laser cladding on the sliding sealing surface.

5. The method for machining a multi-step wear-resistant and corrosion-resistant torsion shaft according to claim 1, characterized in that, In step four, the groove depth is 1 mm, the iron-based powder laser fusion is 1.6 mm, and then the iron-based powder laser fusion surface is ground to ensure that the thickness of the fusion layer in the diameter direction is 1 mm-1.1 mm.

6. The method for machining a multi-step wear-resistant and corrosion-resistant torsion shaft according to claim 1, characterized in that, In step five, the surface roughness of the sliding sealing surface segment is less than 0.

8.

7. The method for machining a multi-step wear-resistant and corrosion-resistant torsion shaft according to claim 1, characterized in that, In step six, the finishing control allowance is 1 mm.

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