A new type of pin shaft and its preparation method and application

Abstract

The application provides a new type of pin shaft, which comprises a hollow shaft and a core shaft embedded in the hollow shaft. The application is obtained by analyzing the working condition of the pin shaft, comprehensively considering the material selection, structure design, heat treatment process and machining process, and selecting 30CrMnSiA high-strength alloy structural steel to redesign the structure. The original Φ380 integral solid structure is optimized into a combined structure, the hollow shaft is installed with the core shaft, the structure of the core shaft is optimized and the machining process is optimized, different heat treatment processes are adopted for the hollow shaft and the core shaft, the two are cold assembled after machining, the interference fit is realized at room temperature, the mechanical properties of the assembled pin shaft are ensured, the problem that the mechanical properties of the material core cannot be reached is effectively avoided, the overall mechanical properties of the combined pin shaft are greatly improved, the strength and toughness of the material are combined, and the fracture toughness and fatigue strength are obviously improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pin shafts, in particular to a new type of pin shaft and a preparation method and application thereof. BACKGROUND

[0002] Shandong Yankuang Intelligent Manufacturing Co., Ltd. is a senior coal machine manufacturing enterprise, and the production of hydraulic support has always played an important role. With the improvement of fully mechanized mining technology, the application of high-end hydraulic support with large mining height is also increasing. As a test and inspection equipment of hydraulic support, the hydraulic support test bench can effectively simulate various working conditions of the support and evaluate the overall performance of the support, and is an indispensable equipment for hydraulic support test and detection. In order to cope with the increasing test and inspection work of high-end hydraulic support, a 50000KN hydraulic support test bench is designed and manufactured. Since this test equipment is designed and manufactured for the first time in China, especially the pin shaft connecting the middle beam and the four columns, the stress is complex, and the pin shaft cannot withstand the test in the process of pressing the support, and the fracture phenomenon occurs.

[0003] The 50000KN hydraulic support test bench is the first set of support test special equipment with the largest pressure in China at present, and its design and manufacture are difficult, the structure design and stress analysis of the key components are very complex, and there is no ready-made experience to refer to, especially the connecting pin shaft of the main bearing component. The support force of the test support is transmitted to the four columns of the test bench through the pin shaft, which bears alternating load. The structure design and manufacturing process should meet the performance requirements to avoid plastic deformation, brittle fracture and other phenomena of the pin shaft, so as to avoid affecting normal use and causing unnecessary loss. The existing pin shaft structure adopts a whole round steel which is heat treated and then turned into use. In the process of pressing the support, the fracture occurs successively, which causes the hydraulic test bench to be unable to work normally. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a new type of pin shaft and a preparation method and application thereof. The new type of pin shaft provided by the present application has good performance.

[0005] The present application provides a new type of pin shaft, which comprises:

[0006] A hollow shaft;

[0007] A core shaft embedded in the hollow shaft.

[0008] Preferably, the material of the hollow shaft and the core shaft is selected from 30CrMnSiA.

[0009] Preferably, a laser cladding layer is arranged on the surface of the hollow shaft.

[0010] The surface roughness of the laser cladding layer is 0.8 μm.

[0011] Preferably, the roughness of the inner surface of the hollow shaft is 0.4 mu m.

[0012] Preferably, the structure of the mandrel is that the two ends are finished fitting surfaces, and the middle is a non-fitting surface.

[0013] Preferably, the tolerance fitting of the hollow shaft and the mandrel is H7 / u6.

[0014] The application provides a preparation method of the novel pin shaft.

[0015] The mandrel is assembled into the hollow shaft by using a cold assembly method.

[0016] Preferably, the preparation method of the mandrel comprises the following steps:

[0017] The round steel is sawed, quenched (the quenching medium is water), low-temperature tempered, heated at a temperature of 880 DEG C, tempered at a temperature of 200 DEG C, air-cooled, turned, and ground to obtain the mandrel.

[0018] Preferably, the preparation method of the hollow shaft comprises the following steps:

[0019] The round steel is sawed, a center through hole is drilled, a quenching and tempering treatment is performed, heating is performed at a temperature of 880 DEG C, tempering is performed at a temperature of 560 DEG C, boring and honing are performed to obtain the hollow shaft.

[0020] The application provides a hydraulic support experiment table, which comprises the novel pin shaft.

[0021] The application finds, through metallographic and stress analysis of the fractured pin shaft, that the pin shaft has problems such as unreasonable structure design, improper heat treatment process and quenching medium selection, and the organizational stress and thermal stress cause the pin shaft to be fractured under alternating loads, thereby affecting the normal use of the pin shaft. Through analysis of the working condition of the pin shaft, the application comprehensively considers aspects such as material selection, structure design, heat treatment process and machining process, selects 30CrMnSiA high-strength alloy structural steel to redesign the structure, optimizes the structure from the original Φ380 integral solid structure to a combined structure, adopts a hollow assembly mandrel type, optimizes the mandrel structure and machining process, adopts different heat treatment processes for the hollow shaft and the mandrel, performs cold assembly after machining, realizes interference fit at room temperature, and the assembled pin shaft guarantees mechanical properties while effectively avoiding the problem that the mechanical properties of the material core cannot be met, so that the overall mechanical properties of the combined pin shaft are greatly improved, the material strength and toughness are combined, and the fracture toughness and fatigue strength are obviously improved. The pressure frame test proves that the pin shaft structure and properties provided by the application are subjected to various working condition tests, meet the expected technical performance requirements, and provide a reference for related large shaft design and machining. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A schematic diagram of a hollow shaft structure of an embodiment of the present application;

[0023] Figure 2 A schematic diagram of a hollow shaft structure of an embodiment of the present application;

[0024] Figure 3 A schematic diagram of a mandrel structure of an embodiment of the present application;

[0025] Figure 4 A schematic diagram of a positioning sleeve structure of an embodiment of the present application;

[0026] Figure 5 A schematic diagram of a mandrel structure with a diameter ranging from Φ250 to Φ380mm of an embodiment of the present application;

[0027] Figure 6 A schematic diagram of a mandrel structure with a diameter ranging from Φ250 to Φ380mm of an embodiment of the present application;

[0028] Figure 7 A schematic diagram of a middle beam structure of the present application;

[0029] Figure 8 A bottom view of a middle beam structure of the present application;

[0030] Figure 9 A schematic diagram of a solid shaft metallographic structure;

[0031] Figure 10 A schematic diagram of a pin shaft metallographic structure prepared in Embodiment 1 of the present application. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work, fall within the protection scope of the present application.

[0033] The present application provides a new type of pin shaft, comprising:

[0034] A hollow shaft;

[0035] A mandrel embedded in the interior of the hollow shaft.

[0036] In this invention, the hole of the hollow shaft is preferably a through hole, the hole diameter of the hollow shaft is preferably 110-130 mm, more preferably 115-125 mm, and most preferably 120 mm; the wall thickness of the hollow shaft is preferably 120-140 mm, more preferably 125-135 mm, and most preferably 130 mm; the length of the hollow shaft is preferably 2100-2200 mm, more preferably 2130-2170 mm, and most preferably 2150 mm.

[0037] In this invention, it is preferable that the hollow shaft has a through hole of the same diameter in the axial direction, preferably Φ118~Φ122mm, more preferably Φ120mm; a positioning sleeve is installed at one end, such as... Figure 4 As shown, the mandrel is used for positioning during cold assembly. Its length is optimized to 60mm while meeting installation requirements, and its inner diameter is optimized to Φ110mm. The mating points of the mandrel and the hollow shaft are the middle parts of the combined shaft that are subjected to shear forces. The mandrel effectively bears the shear force and deflection, enhancing the rigidity and strength of the combined shaft.

[0038] In this invention, the inner surface roughness of the hollow shaft is preferably 0.4 μm, and the coaxiality of the hollow shaft is preferably ≤0.02 mm.

[0039] In this invention, the outer surface of the hollow shaft is preferably provided with a laser cladding layer; the roughness of the outer surface of the hollow shaft (the surface of the laser cladding layer) is preferably 0.8 μm.

[0040] In an embodiment of the present invention, the structural design diagram of the hollow shaft is as follows: Figure 1 and Figure 2 As shown.

[0041] In this invention, the hollow shaft is preferably made of 30CrMnSiA material.

[0042] In this invention, the method for preparing the hollow shaft preferably includes:

[0043] The round steel is sawn into blanks, a center through hole is drilled with a flat-head drill, heat-treated, and then bored and honed to obtain a hollow shaft.

[0044] In this invention, the material of the round steel is preferably 30CrMnSiA; the diameter of the round steel is preferably 385-395mm, more preferably 388-392mm, and most preferably 390mm; the diameter of the drilled center through hole is preferably Φ113-Φ117mm, more preferably Φ114-Φ116mm, and most preferably Φ115mm.

[0045] In this invention, the preferred temperature for the quenching and tempering process is heating to 880°C, holding for 1.5 hours, quenching, followed by tempering at 560°C, and then air cooling to room temperature.

[0046] In the present application, first drill Φ390mm round steel to Φ60mm, in turn to bore to Φ115mm, preferably boring hole to Φ118~Φ122mm, more preferably Φ120mm; preferably honing inner hole Φ1200 +0.035 ; the inner hole surface roughness reaches 0.4μm, coaxiality ≤0.02mm.

[0047] In the present application, the honing preferably further comprises:

[0048] The outer surface of the product after turning and honing is laser cladded, the cladding layer is turned, the cladding layer is ground, and a hollow shaft is obtained.

[0049] In the present application, the outer diameter of the outer surface after turning is preferably Φ380 -0.50 mm.

[0050] In the present application, the cladding powder in the process of laser cladding is preferably cobalt-based self-dissolving alloy powder, such as product Co42A; the laser power is preferably 0.4~0.8kW, more preferably 0.6kW; the scanning speed is preferably 4~6mm / s, more preferably 5mm / s; the cladding layer depth (referring to the thickness of the additive cladding layer formed on the surface of the base layer with metallurgical bonding) is preferably 1.4~1.6mm, more preferably 1.5mm.

[0051] The above laser cladding process parameters adopted in the present application significantly improve the quality of the cladding layer.

[0052] In the present application, the outer diameter after laser cladding is preferably Φ382~Φ383mm, more preferably Φ382.5mm.

[0053] In the present application, the turning of the cladding layer makes the outer diameter to Φ380~Φ381mm, more preferably Φ380.2~Φ380.4mm, and most preferably Φ380.3mm.

[0054] In the present application, the grinding of the cladding layer makes the outer diameter to Φ380 +0.06 mm; the outer surface roughness is 0.8μm.

[0055] In the present application, due to the positioning during cold assembly of the mandrel, a positioning sleeve is designed at one end of the hollow shaft, as shown in the figure, to facilitate the positioning of the mandrel during vertical cold assembly, and the length is optimized to 60mm, and the positioning step after step assembly of the hollow shaft is 5mm. Figure 4

[0056] ​In the present application, the solid pin shaft is optimized to be a hollow shaft with a diameter of 120 mm, and the steel pipe with a wall thickness of 130 mm is subjected to quenching and tempering treatment to obtain a tempered sorbite structure, so that the strength and toughness are organically unified, and the potential performance of the material is fully utilized. Simulation tests prove that under the test pressure of 12500 kN of the rated load, the material of the hollow pin shaft only undergoes elastic deformation, and after the load disappears, the material completely returns to the original state.

[0057] In the present application, the preparation method of the hollow shaft more preferably comprises:

[0058] The round steel with a diameter of 390 mm is sawed and cut, the center through hole is drilled, the hole is bored to a diameter of 115 mm, and after quenching and tempering treatment, better comprehensive mechanical properties are obtained. The inner hole is bored to a diameter of 120 mm, honed to a diameter of 1200 +0.035 , the surface roughness is 0.4 μm, and the coaxiality is ≤0.02 mm. The outer surface is turned to a diameter of 380 -0.50 , the outer surface is subjected to laser cladding to a diameter of 382.5 mm, the cladding layer is turned to a diameter of 380.30 mm, and the cladding layer is ground to a diameter of 380 +0.06 , and the surface roughness is 0.8 μm. The cladding layer mainly increases the wear resistance and deformation resistance of the pin shaft, and prolongs the service life of the pin shaft.

[0059] In the present application, the material of the mandrel is preferably 30CrMnSiA.

[0060] In the present application, the length of the mandrel is preferably 1900-1960 mm, more preferably 1920-1930 mm, and most preferably 1925 mm. According to finite element analysis and test detection analysis, the diameter of the mandrel is preferably Φ110-Φ150 mm, more preferably Φ110-Φ130 mm, and finally preferably Φ120 mm.

[0061] In the present application, the structure of the mandrel is preferably a finish fitting surface at both ends and a non-fitting surface in the middle. In the present application, the structure of the mandrel is optimized to be fitted at both ends and the inner hole, and there is a single-sided gap of 1 mm between the middle and the inner hole. One end has a M16 threaded hole for hoisting during assembly of the cooling mandrel.

[0062] In the present application, the mandrel is preferably divided into three sections in the axial direction, and the diameter of the middle section of the mandrel is preferably Φ117.5-Φ119 mm, more preferably Φ118 mm.

[0063] In the application, the mandrel is divided into three parts, the first segment and the third segment of the mandrel are arranged at the two ends of the mandrel, and the structures are the same, according to the shearing stress and the elastic-plastic deformation of the material during the compression test, the distance between the nearest end surfaces is preferably 140-180 mm, more preferably 150-170 mm, and most preferably 160 mm; and the hole is in interference fit, and the structure is that there is a 1 mm gap between the middle 80 mm length and the hollow shaft, which facilitates assembly without affecting the strength.

[0064] In the application, the two-end mandrel structure is the same and is divided into three segments, in the structural design, the length of the two ends of 160 mm, the length participating in the cooperation is two segments of Φ120*40 mm, according to the finite element simulation analysis and the field test, the distance of the two segments in contact is preferably 35-45 mm, more preferably 40 mm, the middle part is Φ118*80 mm and the hollow shaft has a 1 mm gap, under the premise of not affecting the strength after assembly and fully exerting the performance of the mandrel, the combined area is reduced as much as possible, so that the assembly is easier. The Φ118 mm part of the mandrel is the non-contact surface after assembly, and the surface roughness after processing is 3.2 μm.

[0065] In the application, the surface roughness of the middle segment of the mandrel is preferably 3.2 μm, and the mandrel and the hollow shaft have a 1 mm gap, which can realize the smooth assembly of the mandrel under the premise of ensuring the strength of the mandrel, and also effectively reduces the processing difficulty of the mandrel.

[0066] In the embodiment of the application, the design drawing of the mandrel is as shown in Figure 3 .

[0067] In the application, the preparation method of the mandrel more preferably comprises:

[0068] The round steel is sawed, quenched, low-temperature tempered, turned to the diameter size of the mandrel, and ground to obtain the mandrel.

[0069] In the application, the material of the round steel is preferably 30CrMnSiA; and the diameter of the round steel is preferably Φ120-Φ140 mm, more preferably Φ125-Φ135 mm, and most preferably Φ130 mm.

[0070] In the application, the quenching method preferably comprises:

[0071] The material is sent to the trolley furnace, heated to 880℃ according to the heat treatment heating curve, and kept for 1.5 hours, then quenched after being discharged, and the medium is water.

[0072] In the application, the low-temperature tempering method preferably comprises:

[0073] The tempering furnace is heated to 180-220℃, preferably 200℃, kept for 6-7 hours, preferably 6.5 hours, and then discharged and air-cooled to room temperature.

[0074] In the present application, the surface hardness of the product obtained after the medium-temperature tempering is preferably HB290-HB320, and more preferably HB300.

[0075] In the present application, the first section of the mandrel, the second section of the mandrel and the third section of the mandrel are preferably turned.

[0076] In the present application, the grinding is preferably to the preset tolerance and roughness requirements.

[0077] In the present application, the method for preparing the mandrel preferably further comprises:

[0078] The round steel Φ130 is sawed and cut into pieces, the material is 30CrMnSiA, quenched and low-temperature tempered, the surface hardness is HB290-HB320, Φ118mm and Φ120mm are turned to the size, and Φ120mm is ground to the tolerance and roughness requirements.

[0079] In the present application, the tolerance fit of the hollow shaft and the mandrel is preferably H7 / u6, that is, the tolerance fit of the base hole, The fit of the two places is an interference fit, the grinding tolerance of the fit place of the pin shaft is determined by taking the measured hole diameter tolerance as the reference, considering the reduced size after cooling within the range allowed by the tolerance, and the cold assembly is a clearance fit, and after expansion at room temperature, the interference expansion is integrated.

[0080] The present application provides a preparation method of the novel pin shaft.

[0081] The mandrel is vertically placed into the hollow shaft for assembly by using the cold assembly method.

[0082] In the present application, the cold assembly method preferably comprises placing the mandrel into liquid nitrogen for cooling, and the cooling process is preferably sealed and heat-insulated; the mandrel is slowly pre-cooled in the heat-insulated barrel filled with liquid nitrogen, the mandrel is quickly lifted out after the cold preservation time, the size of the assembly place is quickly measured by using a micrometer, the mandrel is quickly placed into the hollow shaft after the clearance requirement is met.

[0083] In the present application, the preparation method of the pin shaft preferably comprises:

[0084] Check the machining size and roughness of the hollow shaft and mandrel, the interference amount of the hole, shaft joint, adopt cold assembly method, put the mandrel into liquid nitrogen, do good sealing and moisture protection measures, and do good personal protection to avoid frostbite and suffocation danger. Prepare the matching crane, tools, measuring tools and the like, through slow precooling of the mandrel in the heat preservation barrel, after the cold preservation time, quickly lift out the mandrel, and use the micrometer to quickly measure the size of the assembly place, after the clearance requirement is met, quickly put the mandrel into the hollow shaft. The temperature of the mandrel should be controlled below-130 DEG C. Pay attention to prevent violent impact during assembly. Personnel should do safety protection to avoid frostbite.

[0085] In the application, the pin shaft is designed as a hollow hole inlay mandrel combined structure, through simulation stress analysis, the through hole diameter is selected as Φ120mm, which is a relatively ideal state, after the quenching and tempering treatment of the hollow shaft, the organization is more uniform, and good mechanical properties of strength and toughness can be obtained, under the condition of normal stress of 12500kN, the hollow pin shaft is within the elastic deformation range. The mandrel is designed as three sections, the two ends are matched with the hollow shaft to be positioned by the positioning sleeve, and the wide groove structure is adopted at the matching place, which reduces the assembly contact surface while ensuring uniform stress. The assembly adopts cold assembly process, and the tolerance matching is H7 / u6, that is, before assembly, the mandrel is cooled to a certain temperature by using liquid nitrogen as a coolant, so that the outer diameter of the mandrel is slightly cold contracted, and a certain gap is generated between the mandrel and the hollow shaft during assembly, so that the mandrel can be conveniently assembled to the set position. After assembly, due to the expansion of the mandrel, the hole is subjected to uniform radial pressure, and an interference amount of 0.03-0.05mm is generated, and the pin shaft is connected together by relying on the "holding force" and the outer shaft to bear alternating load. The structure form, interference amount, surface roughness, assembly process of the mandrel and the outer shaft all have influence on the holding force and the overall performance of the pin shaft, therefore, the parameter control of the assembly process is very important. In the application, after the cold assembly of the pin shaft, the mandrel and the hollow shaft are tightly combined together to form an integral whole after rising to room temperature due to thermal expansion and cold contraction.

[0086] The application further provides a component of a hydraulic support experiment table, comprising:

[0087] The novel pin shaft in the technical scheme.

[0088] In the application, after the pin shaft body is assembled, the pin shaft body is assembled into the hole of the stand column and the middle beam of the test table, the protrusion of the head of the piston rod of the hydraulic oil cylinder is put into the moving tool, the pin shaft is moved in the pin shaft hole of the stand column and the middle beam by the piston rod, the middle beam has eight pin shaft holes (for example, Figure 7 and Figure 8The four upright columns are connected into one body through the pin shafts passing through the holes in different positions of the four upright columns, the movement and positioning of the middle beam can be accurately controlled by the displacement sensor of the oil cylinder to realize the compression frame test of different height frame types. The disassembly of the pin shafts is realized by moving the oil cylinder on the side to make the pin shafts separate from the hole of the upright column, and the end of the pin shaft is supported in the hole of the front row beam of the middle beam. After the oil cylinder drags the middle beam to move and adjust to the compression frame position, the pin shaft moves, the oil cylinder acts, the pin shaft is inserted into the hole of the upright column and the hole of the rear row beam, and the compression frame test of the support can be realized.

[0089] The present application finds that the structure of the material from the surface to the center changes greatly and the mechanical properties differ greatly through the metallographic analysis of the fracture of the existing broken pin shaft, the hardness gradient change and the mechanical property test, which causes the effective release of the structure stress and thermal stress of the material after processing, and under the action of alternating load, the pin shaft breaks, which is far from the required material performance and service life, affects the normal work of the test equipment, and causes unnecessary loss. It is inevitable to optimize the structure design and processing of the pin shaft to meet the functional requirements.

[0090] The present application finds out the reason for the fracture of the pin shaft through the metallographic structure and mechanical property analysis of the broken pin shaft, optimizes the processing technology from the design, material selection and processing of the pin shaft, improves the strength and toughness of the material, and realizes the organic combination of the comprehensive mechanical properties of the pin shaft to meet the performance and use requirements. According to the problems of the Φ380mm solid pin shaft and the adverse effect of the structure stress formed by heat treatment on the mechanical properties of the material, the structure is redesigned, the appropriate heat treatment, processing and assembly process are selected, and the overall mechanical properties of the pin shaft meet the use requirements.

[0091] The present application has reference significance for the application of the series pin shafts. The inner hole of the Φ350mm-Φ380mm solid shaft is optimized as the combination of Φ120mm through hole and Φ120mm mandrel; the inner hole of the Φ320mm-Φ350mm solid shaft is optimized as the combination of Φ110mm through hole and Φ110mm mandrel, the inner hole of the Φ290mm-Φ320mm solid shaft is optimized as the combination of Φ100mm through hole and Φ100mm mandrel, and the inner hole of the Φ250mm-Φ290mm solid shaft is optimized as the combination of Φ95mm through hole and Φ95mm mandrel. The combined pin shafts of the four forms have no length limit, and the structures subjected to shearing and bending are as shown in Figure 5 and Figure 6 .

[0092] Example 1

[0093] The pin shaft is prepared according to the following method:

[0094] Hollow shaft machining process: round steel Φ390 saw cutting blank, material 30CrMnSiA, flat head drill center hole, bore to Φ115mm, after quenching and tempering treatment, better comprehensive mechanical properties are obtained. Boring inner hole to Φ120mm, honing to Φ1200 +0.035 , surface roughness 0.4μm, coaxiality ≤0.02mm. Turning outer surface Φ380 -0.50 , laser cladding on outer surface to Φ382.5mm, turning cladding layer to Φ380.30mm, grinding cladding layer to Φ380 +0.06 0, surface roughness 0.8μm, the size of hollow shaft is shown in Figure 1 and Figure 2 ; One end of the hollow shaft is installed with a positioning sleeve for positioning the mandrel during cold loading, the length is 60mm, the inner diameter is Φ110mm, and the stepped assembly rear surface is fastened with screws after assembly, the positioning step after assembly is 5mm, the size is shown in Figure 4 .

[0095] Quenching and tempering treatment is: heating at 880℃, holding for 1.5 hours, quenching, then tempering at 560℃, air cooling to room temperature. The cladding powder in the laser cladding process is the product of Co42A, the laser power is 0.6kW, the scanning speed is 5mm / s, and the cladding layer depth is 1.5mm.

[0096] The mandrel is divided into three parts, the first and third segments of the mandrel are arranged at both ends of the mandrel, and the structure is the same, the distance between the nearest end surfaces is 160mm, the structures of the two ends are the same and divided into three segments, in the structural design, the length of the two segments Φ120×40mm participating in cooperation is 160mm in length, the distance between the two segments in contact is 40mm, the middle part is Φ118×80mm, and there is a gap of 1mm between the hollow shaft and the mandrel, the Φ118mm part of the middle part of the mandrel is the non-contact surface after assembly, and the surface roughness after processing is 3.2μm; The surface roughness of the middle segment of the mandrel is preferably 3.2μm, and there is a gap of 1mm between the mandrel and the hollow shaft, and the size is shown in Figure 3 .

[0097] The structure of the mandrel is preferably that the two ends are precisely machined to cooperate, and the middle part is a non-cooperating part, the structural design of the mandrel is that the two ends cooperate with the inner hole, and the middle part has a single-sided gap of 1mm with the inner hole, one end has a M16 screw hole for hoisting during assembly of the cooling mandrel.

[0098] The preparation process of the mandrel is as follows: the round steel Φ130mm is sawed and cut, the material is 30CrMnSiA, quenched and low-temperature tempered, the surface hardness is HB290-320, Φ118mm and Φ120mm are turned to the size, and Φ120mm is ground to the tolerance and roughness requirement. The quenching method comprises the following steps: the material is sent to the trolley furnace, heated to 880℃, kept for 1.5 hours, quenched after being taken out of the furnace, and the medium is water. The low-temperature tempering method comprises the following steps: heated to 200℃ in the tempering furnace, kept for 6.5 hours, and taken out of the furnace and air-cooled to room temperature.

[0099] The tolerance fit of the hollow shaft and the mandrel is H7 / u6, that is, the tolerance fit of the base hole, The fit of the two places is an interference fit, the grinding tolerance of the fit place of the pin shaft is determined by taking the measured hole diameter tolerance as the reference, within the tolerance allowed range, considering the reduced size after cooling, the cold assembly is a clearance fit, and after the room temperature expansion, the interference expansion is integrated.

[0100] The processing size and roughness of the hollow shaft and the mandrel, the interference amount of the hole and the shaft fit place are checked, the mandrel is placed in liquid nitrogen by using the cold assembly method, good sealing and moisturizing measures are taken, and personal protection is done well to avoid the danger of frostbite and suffocation. The matched crane, tools, measuring tools and the like are prepared, the mandrel is slowly pre-cooled in the cold preservation barrel, after 1.5 hours of cold preservation time, the mandrel is quickly lifted out, the size of the fit place is quickly measured by using the micrometer, after the clearance requirement is met, the mandrel is quickly placed in the hollow shaft, the pin shaft is obtained, and the temperature of the mandrel should be controlled below-130℃. Attention should be paid to preventing violent impact during assembly. The personnel should do well in safety protection to avoid frostbite.

[0101] Performance detection

[0102] The metal organization of the pin shaft prepared in Example 1 and the solid pin shaft (obtained by blanking, quenching and tempering treatment and turning forming, and the material and quenching and tempering treatment method are the same as those in Example 1) is analyzed, the metallographic structure of the solid pin shaft is as shown in Figure 9 The metallographic structure of the combined pin shaft prepared in Example 1 is as shown in Figure 10 .

[0103] The mechanical property of the solid pin shaft and the combined pin shaft prepared in Example 1 is detected (GB / T3077-1999), and the detection result is that the tensile strength of the pin shaft near the surface, the radius 1 / 2 and the core is as follows:

[0104] Near surface σb / MPa At 1 / 2 radius σb / MPa Core σb / MPa Solid pin shaft 960 820 690

[0105] Example 1 Hollow shaft surface σb / MPa Hollow shaft mid σb / MPa Hollow shaft inner surface σb / MPa Core σb / MPa 1060 980 1050 1070

[0106] The pin shaft prepared according to the embodiment 1 and the comparative example 1 of the present application is subjected to bending and shearing test, and the detection result is that the combined pin shaft of the embodiment 1 is subjected to 8000kN pressure, the two ends of the shaft are subjected to shearing force, and the geometric size and precision of the two ends of the shaft do not change after unloading; when subjected to 12500kN test pressure, the geometric size and precision of the two ends of the shaft do not change after unloading. The solid pin shaft is subjected to 8000kN pressure, and the pin shaft is brittle broken. Preliminary analysis shows that the thermal stress and organizational stress after heat treatment lead to the failure of the pin shaft, and the main reason is that there is an inherent contradiction between the structure design and the heat treatment, which leads to that the mechanical properties of the material cannot meet the requirements.

[0107] The pin shaft prepared according to the embodiment 1 of the present application is used on a 50000kN hydraulic support test bench, and there are 8 pin shafts of the same specification on the test bench. The old form pin shaft (solid pin shaft) is broken during use, and through analysis, a new combined pin shaft is invented and all the pin shafts are replaced. After the combined pin shaft is used for half a year, the geometric size of the pin shaft is detected, and the results show that the roundness is ≤0.010mm, the straightness is ≤0.02 / 1000, and the surface roughness of the pin shaft does not change. The pin shaft prepared according to the embodiment of the present application fully plays the excellent performance of the combined material, the material is limited to elastic deformation, the strong and tough performance of the pin shaft is better played, and the expected goal of the design is achieved.

[0108] The first 50000kN hydraulic support test bench movable pin shaft in China adopts the pin shaft structure provided by the present application after the solid pin shaft is broken, and the use effect is good. After half a year of use, the precision of the pin shaft is detected, and the results show that the geometric precision of the pin shaft does not change. Under the full load of 50000kN test condition, the pin shaft performance is good after being subjected to various pressure frame working conditions. The upper roller of the three-roller plate bending machine is originally a Φ360×2200mm solid roller shaft, and the bending and straightness tolerance are out of tolerance during use. After being replaced by the combined mandrel provided by the present application, the use performance is stable, and the roundness and straightness are within the manufacturing precision range.

[0109] Through finite element simulation analysis and mechanical property test, the optimized combined pin shaft realizes the organic combination of structure and performance, and the reliability of the design is further verified by subsequent pressure frame test. The combined pin shaft fully meets the functional requirements of the pin shaft, and provides a train of thought and compliance for the optimization of the same type of shaft structure.

[0110] While the application has been described and illustrated with reference to specific embodiments thereof, those skilled in the art will appreciate that various adaptations, changes, modifications, substitutions, developments, improvements, and permutations can be made in the specific embodiments described without departing from the true spirit and scope of the application as defined by the appended claims. All such modifications are intended to be within the scope of the claims. Although methods disclosed herein have been described with reference to particular operations performed in a particular order, it will be understood that these operations can be combined, sub-divided, or re-ordered to form equivalent methods without departing from the teachings of the present application. Accordingly, unless specifically indicated herein, the order and grouping of operations are not a limitation of this application.

Claims

1. A new type of pin shaft characterized by, Comprise: A hollow shaft; A mandrel inlaid inside the hollow shaft; The material of the hollow shaft and the mandrel is selected from 30CrMnSiA; The preparation method of the hollow shaft comprises: Cutting the round steel with a saw, drilling a center through hole, quenching and tempering, boring and honing to obtain the hollow shaft; The quenching and tempering specifically comprises: After the workpiece is heated to 880 DEG C, it is quenched in a 10% mass concentration PAG high polymer quenching liquid, and then tempered at 560 DEG C to obtain a tempered sorbite structure; The preparation method of the mandrel comprises: Cutting the round steel with a saw, quenching and low-temperature tempering, turning and grinding to obtain the mandrel; The quenching and low-temperature tempering specifically comprises: The quenching medium is an aqueous solution, and the workpiece is quenched in the medium after being heated to 880 DEG C, and then low-temperature tempered at 200 DEG C.

2. The novel pin shaft as claimed in claim 1, wherein, The surface of the hollow shaft is provided with a laser cladding layer; The surface roughness of the laser cladding layer is 0.8 μm.

3. The novel pin shaft as claimed in claim 1, wherein, The roughness of the inner surface of the hollow shaft is 0.4 μm.

4. The novel pin shaft as claimed in claim 1, wherein, The structure of the mandrel is a fine machining matching surface at both ends and a non-matching surface in the middle.

5. The novel pin shaft as claimed in claim 1, wherein, The tolerance matching of the hollow shaft and the mandrel is H7 / u6.

6. A method of manufacturing the novel pin shaft as claimed in claim 1, wherein, Comprise: The mandrel is put into the hollow shaft for assembly by using a cold assembly method.

7. A hydraulic support experiment table, characterized in that, Comprise: The novel pin shaft of claim 1.

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