High-hardness stainless steel hydraulic support piston rod machining method and piston rod

Abstract

According to the machining method for the high-hardness stainless steel hydraulic support piston rod and the piston rod, the corrosion resistance effect is improved by optimizing raw materials, the machining frequency is reduced and the machining efficiency is improved through integral forging machining, the structural strength is enhanced by adjusting the heat treatment and surface quenching treatment processes, and the welding blocking process is improved. The welding plug quality is improved; liquid leakage is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic support manufacturing, in particular to a method for processing a high-hardness stainless steel hydraulic support piston rod and the piston rod. Background Art

[0002] Hydraulic supports are essential equipment in coal mining, primarily responsible for mine support. Jacks are one of the primary supporting components during the mining process. The quality of the hydraulic support jacks used in mining determines the stability of the hydraulic support and the actual mining results. The piston rod assembly is a key component of the jack, consisting of a piston and a piston rod body, which are connected by a threaded connection. The piston rod body is a cylindrical rod with a cross hole inside, while the piston is a cylinder with a slightly larger diameter and a shorter length. Existing piston rods for hydraulic support jacks in mining are machined from carbon steel bar stock and are electroplated with a copper-tin alloy to enhance corrosion resistance in emulsions.

[0003] like Figure 1 As shown, the piston and piston rod body of the traditional hydraulic support piston rod are processed separately, with similar procedures. The production process is: cutting → tempering → rough and fine turning → drilling (piston rod body) → electroplating → welding (piston rod body) → installation. The process plan details are shown below.

[0004] Step (1) Cutting: Place the bar material horizontally on the cutting table, and use a saw to cut the parts into blanks according to the drawing dimensions and tolerance requirements. After cutting, check the curvature of the blanks and the verticality of the cut surface, and then proceed to the quenching and tempering process; Step (2) conditioning: The parts to be tempered are subjected to a quenching + high temperature tempering treatment; Step (3) Rough and fine turning of the shape: Use a CNC lathe to perform shape processing. Use a three-jaw chuck to clamp one end of the workpiece. According to the drawing and process, the outer diameter of one end is rough-turned and fine-turned to the required size and tolerance. Then remove the workpiece, change the direction, clamp the processed end, and do rough-turning and fine-turning of the outer diameter first, and then threading. Step (4) Drilling (piston rod body): Fix the piston rod body, draw the hole position line, and use the drilling workbench to drill according to the drawing and process requirements.

[0005] Step (5) Electroplating: Electroplating copper-tin alloy on the outer circle of the workpiece; Step (6) Welding (piston rod body): Fix the workpiece on the welding platform, use a ball grinder to grind the hole to remove the electroplating layer, use a torch to preheat the hole and the area within 20mm around it to 100℃, place a disc plug in the step hole, and use ER50-6 welding wire to fill the hole. After welding, grind it flat and clean the spatter. Step (7) Installation: The piston and the piston rod body are assembled into a piston rod according to process requirements.

[0006] The piston rod products manufactured by the above process have the following problems: (1) The traditional split piston rod adopts copper-tin alloy electroplating on carbon steel surface for corrosion protection. The coating thickness is only about 0.05mm, which has poor corrosion resistance and is easily damaged. At the same time, the internal fluid hole of the piston rod cannot be plated within 20mm of the bottom of the hole. The inside of the hole is prone to rust, polluting the hydraulic system. (2) The traditional piston rod adopts a split structure, and the piston and piston rod body need to be processed separately, which makes the process complicated and the production efficiency low; (3) In order to ensure the plastic toughness of the piston rod, the hardness of the existing workpiece after quenching and tempering can only reach about 240-260HB, which is prone to bending deformation or surface scratches during mine service; (4) The current material has poor weldability, the welding space is narrow during welding, and arc crater cracks are prone to occur, resulting in leakage during service.

[0007] Due to the existence of the above problems, the overall quality of the traditional split piston rod is poor.

[0008] In order to solve the above problems, people have been seeking an ideal technical solution. Summary of the Invention

[0009] The purpose of the present invention is to address the deficiencies of the existing technology and thus provide a high-hardness stainless steel hydraulic support piston rod processing method and piston rod with stronger corrosion resistance, higher one-piece molding efficiency, higher hardness, and strengthened welding blocking weak links.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is: a method for processing a high-hardness stainless steel hydraulic support piston rod, comprising the following steps: Step 1) Cutting: Stainless steel bar raw materials are used for cutting and blanking. The raw material diameter is 10mm larger than the maximum diameter of the piston in the drawing. After blanking, the curvature of the raw material and the verticality of the cutting surface are tested to obtain the stainless steel workpiece to be processed; Step 2) Forging: Heat the stainless steel workpiece to 1250±10℃ and then forge the piston end. Leave at least 5mm machining allowance for the outer diameter and the cylindricity error ≤1.5mm. After the piston end is forged, place the workpiece on the fixture and wait until the temperature drops to 1200±10℃ before forging the piston rod end. Leave at least 5mm machining allowance for the outer diameter and the cylindricity error ≤1mm. The coaxiality error between the piston and the piston rod end is ≤2mm. Step 3) Drilling deep holes: Use deep hole drilling equipment to drill deep holes along the length direction of the workpiece on the piston end face of the stainless steel workpiece according to the requirements of the drawing; Step 4) Heat treatment: First, perform solution treatment: Place the stainless steel workpiece in a heating furnace, set the furnace temperature to 1000-1050℃, set the holding time, and keep the workpiece out of the furnace at ±10℃. After heating, place the workpiece and the fixture in water for cooling. The water temperature should be ≤40℃. When cooling in the pool, first swing it horizontally around, then move it up and down. The water outlet temperature of the part should be controlled at 40-60℃. After the solution treatment is completed, aging treatment is carried out: the stainless steel workpiece is placed in a heating furnace with the furnace temperature not exceeding 350°C, heated to 620±10°C, kept warm for the set time, and then air-cooled to room temperature to ensure a hardness of 280-300HB; Step 5) Processing: First, use the machining center to turn the outer diameter of the piston rod end to the required size, then remove the workpiece, change the direction, use the soft three-grip chuck to clamp the processed piston rod end, and turn the outer diameter of the piston end to the required size; Then the workpiece is transferred to the deep hole drilling machine and re-drilled along the deep hole drilled before heat treatment to remove the oxide scale and other debris generated during heat treatment in the deep hole; Finally, drill the vertical hole that contacts the deep hole according to the drawing requirements; Step 6) Surface quenching: Use laser surface hardening technology to harden the piston rod surface, set the laser power to at least 800W, the scanning speed ≥10mm / s, and perform surface hardening on the outer cylindrical surface of the piston end and the outer cylindrical surface of the piston rod end respectively, ensuring the surface hardness of 350-450HV and the hardened layer thickness of 1-1.5mm; Step 7) Solder plugging: Fix the stainless steel workpiece on the welding platform, grind the piston end hole and the area within 20mm nearby, use a torch to preheat the piston rod hole end within 100mm length, the preheating temperature is at least 120℃, place a stainless steel disc in the step hole to plug it, and use welding wire to weld twice: welding current 200-220A, welding voltage 27-29V, first fill the hole with surfacing welding, and the arc ending point is located in the center of the surfacing weld. After the weld solidifies, grind the weld within at least 5mm around the arc ending point by at least 3mm in the depth direction and completely remove the arc crater defects, and then perform the second surfacing welding. The starting point of the second surfacing welding is at the same position as the first arc ending point. The diameter of the surfacing surface is at least 3mm larger than the hole diameter, the surfacing height is more than 4mm, and the arc ending point is placed at least 5mm outside the hole. After welding, grind it flat and clean up the spatter.

[0011] Based on the above, in step 1), the composition of the stainless steel bar raw material used is controlled: Control C≤0.05%, 0.05%≤Si≤0.07%, 0.06%≤Mn≤0.08%, 16.5%≤Cr≤17.5%, 4%≤Ni≤5%, 0.5%≤Cu≤1%, P≤0.020%, S≤0.005%; In terms of smelting process, LF furnace is used for refining, and RH furnace is used for vacuum degassing. The vacuum degassing time is ≥25min, ensuring that H≤5ppm, N≤10ppm, and O≤10ppm.

[0012] Based on the above, in step 2), the heating temperature before forging the piston end is 1250±10°C, and the heating temperature before forging the piston rod end is 1200±10°C.

[0013] Based on the above, in step 3), the clearance between the drill sleeve and the drill rod of the deep hole drilling equipment is ≤0.05mm, the feed rate is 35mm / min, and the speed is 1600r / min.

[0014] Based on the above, in step 4), the heating furnace temperature for solution treatment is 1040°C, and the furnace outlet temperature is 1040°C±10°C.

[0015] Based on the above, in step 7), manual welding is performed in two steps using φ1.2mm ER309L welding wire.

[0016] Based on the above, in step 7), the wafer plug is a 304 stainless steel wafer plug.

[0017] A high-hardness stainless steel hydraulic support piston rod comprises a piston rod and a piston made of stainless steel and formed in one piece, and is manufactured by the high-hardness stainless steel hydraulic support piston rod processing method.

[0018] The present invention has outstanding substantial features and significant progress compared to the prior art. Specifically, the present invention has the following advantages: (1) The corrosion resistance of the piston rod has been improved, solving the problem of the piston rod being prone to rust during underground service. Specifically, the piston rod is made of stainless steel, and the original chemical composition of the stainless steel is strictly controlled to reduce harmful elements such as P, S, N, and H. This improves the corrosion resistance of the stainless steel and solves the previous problem of the outer cylindrical coating being easy to fall off and the deep hole being unable to effectively perform corrosion protection. It can adapt to a variety of media.

[0019] (2) The piston rod was optimized from a split structure to an integral forged structure, and the two parts were optimized into one part, which reduced the number of processing times and improved the overall processing efficiency of the piston rod by more than 40%.

[0020] (3) The hardness of the piston rod is improved, reducing deformation and surface scratches during underground service. The hardness of the traditional piston rod is 240-260HB, while the internal hardness of the stainless steel piston rod is 280-300HB and the surface hardness can reach 350-450HV, which is not easy to bend and avoids scratches.

[0021] (4) The quality of welding plugging is improved, and leakage of the piston rod during service is avoided. The welding plugging is optimized from one welding to two welding, and the arc end point is placed outside the hole, avoiding leakage caused by arc crater cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The utility model is a schematic diagram of a split piston rod structure in which a piston and a piston rod body are composed of a piston in the prior art.

[0023] Figure 2 It is a structural schematic diagram of the integral piston rod in the present invention.

[0024] Figure 3 It is a processing schematic diagram of the piston rod welding plugging in the present invention.

[0025] Figure 4 It is a schematic diagram of the machining allowance of the integral piston rod in the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below through specific implementation methods.

[0027] like Figure 2 As shown, a high-hardness stainless steel hydraulic support piston rod, whose piston and piston rod are forged as a whole from stainless steel, has two deep holes along the end face of the big end of the piston rod, and two vertical holes intersect with the deep holes at both ends. The deep holes are welded with welding plugs at the end of the big end of the piston rod to serve as a seal.

[0028] The process of machining the high hardness stainless steel hydraulic support piston rod is as follows: First, the stainless steel raw materials and rolling process are adjusted to improve the corrosion resistance. Specifically, in terms of composition, C≤0.05%, 0.05%≤Si≤0.07%, 0.06%≤Mn≤0.08%, 16.5%≤Cr≤17.5%, 4%≤Ni≤5%, 0.5%≤Cu≤1%, P≤0.020%, S≤0.005%. In terms of smelting process, LF furnace is used for refining and RH furnace is used for vacuum degassing. The vacuum degassing time is ≥25min to ensure H≤5ppm, N≤10ppm, and O≤10ppm.

[0029] In this embodiment, the high-hardness stainless steel hydraulic support piston rod adopts a monolithic structure, forged from stainless steel. Its structure is similar to that of a split-piece structure, but without the threaded connection, resulting in a single-piece design. The overall manufacturing process is modified from that of traditional piston rods and includes: blanking → forging → heat treatment → machining → surface hardening → machining → welding and plugging.

[0030] Specifically, it includes: step (1) blanking: Place the stainless steel bar material horizontally on the cutting table and use a CNC disc cutter to cut the parts into blanks. The diameter of the stainless steel bar material is 10mm larger than the maximum diameter of the piston in the drawing. After cutting, check the curvature of the blank and the verticality of the cut surface, and then proceed to the forging process. Step (2) Forging: Heat the stainless steel workpiece to 1250±10℃ and then forge the piston end (big head end). Leave a 5mm machining allowance for the outer diameter and the cylindricity error is ≤1.5mm. After the piston end is forged, place the workpiece on the tooling. When the temperature drops to 1200±10℃, forge the piston rod end (small head end). Leave a 5mm machining allowance for the outer diameter and the cylindricity error is ≤1mm. The coaxiality error between the piston and the piston rod end is ≤2mm.

[0031] Step (3) Drilling deep holes: Use deep hole drilling equipment to drill deep holes along the length of the workpiece on the big end face of the stainless steel workpiece according to the requirements of the drawing. The clearance between the drill sleeve and the drill rod is ≤0.05mm, the feed rate is 35mm / min, and the speed is 1600r / min.

[0032] Step (4) heat treatment: The workpiece is subjected to solution + aging treatment. The workpiece is placed in a heating furnace with the furnace temperature set to 1040℃ and kept warm for 3 hours. The furnace outlet temperature is 1040±10℃. After heating, the workpiece and the tooling are put into water for cooling at the same time. The water temperature is ≤40℃. When cooling in the pool, it is first swung horizontally around and then moved up and down. The water outlet temperature of the parts is controlled at 40-60℃. After the solution is completed, aging is carried out. The parts are placed in a heating furnace with the furnace temperature not exceeding 350℃, heated to 620±10℃, kept warm for 6 hours, and then air-cooled to room temperature to ensure the hardness is 280-300HB. After passing the inspection, they are transferred to the processing procedure.

[0033] Step (5) Processing: First, use the machining center to turn the outer circle of the small head end to the required size, then remove the workpiece, change the direction, use the soft three-grip chuck to clamp the processed small head end, and turn the outer circle of the large head end to the required size.

[0034] The workpiece is then transferred to a deep hole drilling machine and re-drilled along the deep hole drilled before heat treatment to remove the oxide scale and other debris generated during heat treatment in the deep hole.

[0035] Finally, drill the vertical hole that contacts the deep hole according to the drawing requirements.

[0036] Step (6) Surface quenching Use special laser surface quenching equipment to quench the piston rod surface, set the laser power to 800W, the scanning speed to 10mm / s, and perform surface quenching on the outer cylindrical surface of the piston end and the outer cylindrical surface of the piston rod end respectively, ensuring the surface hardness of 350-450HV and the hardened layer thickness of 1-1.5mm.

[0037] Step (7) Soldering Fix the workpiece on the welding platform, use a ball head grinder to grind the hole and the surrounding 20mm range clean, use a torch to preheat the piston rod hole end within 100mm length, the preheating temperature is 120℃, place a 304 disc in the step hole to plug, and use φ1.2mm ER309L welding wire for manual welding in two times: welding current 200-220A, welding voltage 27-29V, first fill the hole with surfacing welding, and the arc ending point is located in the center of the surfacing weld. After the weld solidifies, use an angle grinder to grind the weld within 5mm around the arc ending point by 3mm in the depth direction and completely remove the arc crater defect, and then perform the second surfacing welding. The starting point of the second surfacing welding is at the position of the first arc ending point, the surfacing surface diameter is 3mm larger than the hole diameter, the surfacing height is more than 4mm, and the arc ending point is placed 5mm outside the hole. After welding, grind it flat and clean the spatter.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention. They should all be included in the scope of the technical solution for protection of the present invention.

Claims

1. A method for processing a high-hardness stainless steel hydraulic support piston rod, characterized by: The following steps are involved: Step 1) Cutting: Stainless steel bar raw materials are used for cutting and blanking. The raw material diameter is 10mm larger than the maximum diameter of the piston in the drawing. After blanking, the curvature of the raw material and the verticality of the cutting surface are tested to obtain the stainless steel workpiece to be processed; Step 2) Forging: Heat the stainless steel workpiece to 1250±10℃ and then forge the piston end. Leave at least 5mm machining allowance for the outer diameter and the cylindricity error ≤1.5mm. After the piston end is forged, place the workpiece on the fixture and wait until the temperature drops to 1200±10℃ before forging the piston rod end. Leave at least 5mm machining allowance for the outer diameter and the cylindricity error ≤1mm. The coaxiality error between the piston and the piston rod end is ≤2mm. Step 3) Drilling deep holes: Use deep hole drilling equipment to drill deep holes along the length direction of the workpiece on the piston end face of the stainless steel workpiece according to the requirements of the drawing; Step 4) Heat treatment: First, perform solution treatment: Place the stainless steel workpiece in a heating furnace, set the furnace temperature to 1000-1050℃, set the holding time, and keep the workpiece out of the furnace at ±10℃. After heating, place the workpiece and the fixture in water for cooling. The water temperature should be ≤40℃. When cooling in the pool, first swing it horizontally around, then move it up and down. The water outlet temperature of the part should be controlled at 40-60℃. After solution treatment, aging treatment is carried out: the stainless steel workpiece is placed in a heating furnace with a temperature not exceeding 350°C, heated to 620±10°C, kept at this temperature for a set time, and then air-cooled to room temperature to ensure a hardness of 280-300HB; Step 5) Processing: First, use the machining center to turn the outer diameter of the piston rod end to the required size, then remove the workpiece, change the direction, use the soft three-grip chuck to clamp the processed piston rod end, and turn the outer diameter of the piston end to the required size; Then the workpiece is transferred to the deep hole drilling machine and re-drilled along the deep hole drilled before heat treatment to remove the oxide scale and other debris generated during heat treatment in the deep hole; Finally, drill the vertical hole that contacts the deep hole according to the drawing requirements; Step 6) Surface quenching: Use laser surface hardening technology to harden the piston rod surface, set the laser power to at least 800W, the scanning speed ≥10mm / s, and perform surface hardening on the outer cylindrical surface of the piston end and the outer cylindrical surface of the piston rod end respectively, ensuring the surface hardness of 350-450HV and the hardened layer thickness of 1-1.5mm; Step 7) Solder plugging: Fix the stainless steel workpiece on the welding platform, grind the piston end hole and the area within 20mm nearby, use a torch to preheat the piston rod hole end within 100mm length, the preheating temperature is at least 120℃, place a stainless steel disc in the step hole to plug it, and use welding wire to weld twice: welding current 200-220A, welding voltage 27-29V, first fill the hole with surfacing welding, and the arc ending point is located in the center of the surfacing weld. After the weld solidifies, grind the weld within at least 5mm around the arc ending point by at least 3mm in the depth direction and completely remove the arc crater defects, and then perform the second surfacing welding. The starting point of the second surfacing welding is at the same position as the first arc ending point. The diameter of the surfacing surface is at least 3mm larger than the hole diameter, the surfacing height is more than 4mm, and the arc ending point is placed at least 5mm outside the hole. After welding, grind it flat and clean up the spatter.

2. The method for processing a high-hardness stainless steel hydraulic support piston rod according to claim 1, characterized in that: In step 1), the composition of the stainless steel bar raw material is controlled: Control C≤0.05%, 0.05%≤Si≤0.07%, 0.06%≤Mn≤0.08%, 16.5%≤Cr≤17.5%, 4%≤Ni≤5%, 0.5%≤Cu≤1%, P≤0.020%, S≤0.005%; In terms of smelting process, LF furnace is used for refining, and RH furnace is used for vacuum degassing. The vacuum degassing time is ≥25min, ensuring that H≤5ppm, N≤10ppm, and O≤10ppm.

3. The method for processing a high-hardness stainless steel hydraulic support piston rod according to claim 1, characterized in that: In step 2), the heating temperature before forging the piston end is 1250±10°C, and the heating temperature before forging the piston rod end is 1200±10°C.

4. The method for processing a high-hardness stainless steel hydraulic support piston rod according to claim 1, characterized in that: In step 3), the clearance between the drill sleeve and the drill rod of the deep hole drilling equipment is ≤0.05mm, the feed rate is 35mm / min, and the rotation speed is 1600r / min.

5. The method for processing a high-hardness stainless steel hydraulic support piston rod according to claim 1, characterized in that: In step 4), the heating furnace temperature for solution treatment is 1040°C, and the furnace outlet temperature is 1040°C±10°C.

6. The method for processing a high-hardness stainless steel hydraulic support piston rod according to claim 1, characterized in that: In step 7), manual welding is performed twice using φ1.2mm ER309L welding wire.

7. The method for processing a high-hardness stainless steel hydraulic support piston rod according to claim 1, characterized in that: In step 7), the disc plug is made of 304 stainless steel.

8. A high-hardness stainless steel hydraulic support piston rod, characterized by: The piston rod and piston are made of stainless steel and are integrally formed, and are manufactured by the high-hardness stainless steel hydraulic support piston rod processing method described in any one of claims 1-7.

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