Manufacturing method for stainless steel integral inner liquid inlet piston rod of hydraulic support oil cylinder

Abstract

The invention discloses a manufacturing method of a stainless steel integral inner liquid inlet piston rod of a hydraulic support oil cylinder. The process of sizing, induction heating, local upsetting, thermal refining, rough turning, finish turning, surface quenching, deep hole drilling, liquid through hole drilling, joint hole milling and drilling, sealing and hole blocking, grinding and polishing is adopted, and the problem that a liquid inlet piston rod in a whole of a traditional hydraulic support is poor in corrosion resistance is solved. On the premise that the mechanical property and the corrosion resistance of the piston rod are guaranteed, the machining process is shortened, the machining process is simplified, welding is avoided, and the production efficiency and the corrosion resistance of the hydraulic oil cylinder piston rod are improved, so that the service life of a hydraulic support is prolonged. And the method has very important significance in realizing efficient operation of the fully-mechanized coal mining equipment under the mine.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic oil cylinders, and in particular relates to a method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod. Background Art

[0002] The jack in the hydraulic support is a key component to realize the action function of the hydraulic support, and the piston rod is a key component in the jack. The oil cylinder with an internal liquid inlet piston rod structure can avoid welding of cylinder accessories, reduce cylinder welding, and avoid interference between the cylinder and the structural parts of the hydraulic support. The rod head of the internal liquid inlet piston rod has a joint hole, which connects two deep holes. One deep hole goes straight through the bottom of the rod to supply liquid to the lower cavity, and the other deep hole is connected to the liquid through hole to supply liquid to the upper cavity. The traditional process for improving the corrosion resistance of the piston rod is electroplating the outer circle of the rod. In order to further improve the corrosion resistance of the liquid inlet part of the piston rod inner hole and the outer circumference of the rod, the surface treatment method of the piston rod is copper plating of the piston and the deep liquid inlet hole area, and laser cladding of the outer circumference of the rod. The processing process is: sizing → induction heating → local upsetting → quenching and tempering → rough turning → fine turning before cladding → laser cladding → fine turning → drilling deep holes → drilling through liquid holes → milling and drilling joint holes → copper plating of piston area → polishing of piston area → copper plating of deep holes and through liquid holes → welding plugging → welding plugging flat head → grinding outer circle → polishing outer circle. The following problems exist: (1) The surface treatment method of laser cladding + copper plating has a long process flow, complex process, long production cycle and low production efficiency; (2) The electroplating layer itself has poor corrosion resistance and is prone to rust.

[0003] In order to improve the corrosion resistance of the piston rod, it is necessary to develop a new corrosion-resistant hydraulic support cylinder piston rod processing technology to shorten the processing flow and simplify the processing technology. Stainless steel, as an excellent corrosion-resistant material, is very suitable for manufacturing hydraulic support cylinder piston rods. However, it is necessary to regulate the microstructure of stainless steel, reduce the content of delta ferrite, carbide, and residual austenite, and improve corrosion resistance. On this basis, it is also necessary to improve the uniformity of hardness, thereby improving the accuracy of deep hole processing; ensuring that the outer circle of the rod body has sufficient wear resistance in coal mines. Stainless steel piston rods are not suitable for welding, and crack defects are prone to occur after welding. Due to improper control of welding parameters, welding defects such as welding slag and unfused are prone to occur, which affects the plugging and sealing effect and causes the jack to fail. Therefore, it is necessary to seek a new plugging process to avoid stainless steel welding and ensure plugging and sealing.

[0004] The invention with announcement number CN118835240A discloses a laser cladding process method for a hydraulic cylinder piston rod. The key points of the technical solution include precision turning, laser cladding, and external cylindrical grinding. The laser cladding process is used to firmly attach powder to the piston rod through a laser beam, and various formula contents are developed. An upgraded powder formula is used as the raw material. Through the laser cladding process, it is applied to the piston rod of the hydraulic cylinder, etc. to achieve wear resistance and corrosion resistance requirements; however, this process cannot solve the problem that the piston area and the deep hole area are not corrosion-resistant and are not corrosion-resistant.

[0005] Therefore, it is urgent to explore a new method for manufacturing the piston rod of the hydraulic support cylinder to shorten the processing flow and simplify the processing technology while ensuring the mechanical properties and corrosion resistance of the piston rod. Summary of the invention

[0006] The purpose of the present invention is to provide a method for manufacturing a hydraulic support cylinder stainless steel integral internal liquid inlet piston rod in view of the deficiencies in the above-mentioned prior art, so as to solve the problem of poor corrosion resistance of the traditional hydraulic support integral internal liquid inlet piston rod, as well as the problem of high processing precision of stainless steel deep holes and welding-free hole plugging.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid-inlet piston rod, the internal liquid-inlet piston rod comprising a rod body, a deep hole and a plugging hole, and a ball-expanding high-pressure plug is installed at the plugging hole, and the occlusal surface of the ball-expanding high-pressure plug is used to occlude with the side wall of the plugging hole; The ball expansion type high pressure plug comprises a shell and a steel ball, and the plug end of the shell is closed, and the other end is open and provided with an expansion hole for filling the steel ball, and the inner diameter of the expansion hole is smaller than the diameter of the steel ball, and the steel ball is filled in the expansion hole to have an interference fit with the expansion hole and cause the shell to expand radially; The outer peripheral surface of the shell is provided with an annularly distributed tooth surface structure as an occlusal surface; The processing process includes the following steps: Stainless steel is selected as the raw material, and the process is carried out as follows: sizing → induction heating → local upsetting → quenching and tempering → rough turning → fine turning → surface quenching → deep hole drilling → fluid hole drilling → milling and drilling of joint holes → sealing and plugging holes → grinding → polishing; During the quenching and tempering process, the austenitizing temperature is 1010~1050℃, the austenitizing heating and holding time is: radius*(1.5~1.7)min / mm, and the quenching and tempering process adopts piston rod vertical quenching and circulating water jet impact piston rod; In the process of deep hole drilling, a horizontal deep hole drill is used for deep hole drilling and plugging, which can ensure the straightness of the deep hole to be 0.3~0.4mm / m.

[0008] The depth of the expansion hole in the shell is greater than the diameter of the steel ball, and the plug end of the shell is set to be a frustum; The engaging surface of the ball expansion type high pressure plug is used to engage with the side wall of the plugging hole; The outer diameter of the shell is smaller than the inner diameter of the blocking hole, and the length of the shell is smaller than the depth of the blocking hole.

[0009] During the tempering and quenching process, circulating water is sprayed obliquely on the piston rod along the circumference from the bottom of the piston rod, and cold water moves upward along the surface of the piston rod, with a water flow rate of 1.3~1.8m / s.

[0010] The chemical composition and mass percentage of the stainless steel are: C<0.2%, Si<0.1%, Mn<0.1, Cr is 15-17%, Ni is 2-2.5%, P<0.04%, S<0.03%, and the balance is Fe and unavoidable impurities.

[0011] After quenching and tempering treatment, the surface hardness of the piston rod is 260~265HB, and the hardness of the core of the piston rod is 250~255HB. The hardness is uniform, which is conducive to subsequent machining.

[0012] During the local upsetting process, the initial forging temperature is 1100~1150℃, the final forging temperature is 1030~1080℃, and the cooling rate after forging is 0.5~1.5℃ / s.

[0013] During the surface tempering and quenching process, induction coil heating is used to austenitize the stainless steel, and water spray cooling is used; the moving speed of the induction coil is 90~100mm / min, the quenching temperature is 1020~1040℃, and the water temperature is <40℃; and the surface hardness after quenching is 50~60HRC, and the depth of the hardened layer is 1.5~2mm; the diameter of the induction coil is 3~5mm larger than the diameter of the workpiece.

[0014] After fine turning, the machining allowance of the piston rod surface treatment area is 0.2~0.3mm.

[0015] Carbide drill bits are used in the process of drilling through fluid holes, deep holes, and plugged holes.

[0016] The beneficial effects of the present invention are: (1) The present invention discloses a method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod. By improving the stainless steel piston rod processing process, the process of sizing → induction heating → local upsetting → tempering → rough turning → fine turning → surface quenching → drilling deep holes → drilling through liquid holes → milling and drilling joint holes → sealing and plugging holes → grinding → polishing is adopted to solve the problem of poor corrosion resistance of the traditional hydraulic support integral internal liquid inlet piston rod. Under the premise of ensuring the mechanical properties and corrosion resistance of the piston rod, the processing flow is optimized, and the microstructure of the stainless steel is adjusted to improve the uniformity of the hardness, thereby improving the processing accuracy of the rod body and the hole; the plug ball expansion type stainless steel plug is used to avoid plugging the hole and avoiding welding; the wear resistance of the rod body area is improved by surface quenching. The present invention improves the processing accuracy, production efficiency, and corrosion resistance of the hydraulic cylinder piston rod, thereby improving the service life of the hydraulic support, which is of great significance to the efficient operation of coal comprehensive mining equipment in mines.

[0017] (2) By controlling the Ni content, local upsetting process, and tempering treatment process, the matrix microstructure is controlled to be tempered troostite + δ ferrite, the content of δ ferrite is less than 5%, the tempered troostite has fine grains, the carbides are evenly dispersed, and the δ ferrite is spherical; the comprehensive mechanical properties and corrosion resistance of tempered troostite are better than those of δ ferrite; the content of δ ferrite, carbides, and residual austenite is reduced, the corrosion resistance is improved, and the hardness uniformity is improved, thereby improving the deep hole processing accuracy; ensure that the outer circle of the rod body has sufficient wear resistance in the coal mine, and the surface hardness of the outer circle area of ​​the rod body is not less than 50HRC; therefore, the comprehensive mechanical properties and corrosion resistance of the matrix are good; and the surface hardness of the outer circle of the stainless steel piston rod is improved by surface quenching.

[0018] (3) The method of using a plug-in ball expansion stainless steel plug is adopted to avoid the welding of stainless steel. The ball expansion stainless steel high-pressure plug works according to the principle of pressure expansion. When the steel ball is pressed to the bottom of the sleeve, the steel ball causes a section of the sleeve to expand radially, and the axial stress is converted into the radial expansion response of the sleeve. At this moment, the sharp teeth formed by the annular groove on the outer periphery of the sleeve are forced to press into the surrounding workpiece material, thereby forming an effective high-pressure leak-free seal, which solves the problem that traditional welding plugging holes are prone to welding defects and thus lead to sealing failure. The use of stainless steel materials can avoid the occurrence of sealing failure due to rust, and reduce the difficulty of disassembling and repairing the jack due to unqualified pressure testing after the piston rod and cylinder body are assembled, and the long cycle. Due to the simple structure, the sealing cost is extremely low, which is only the cost of the ball expansion high-pressure sealing plug; with the assembly workstation, it can realize automated precise positioning and installation, improve production efficiency, and no longer require high-level welders to perform plug welding process, reduce the leakage rate and reduce labor costs.

[0019] (4) The microstructure is homogenized by controlling and extending the austenitization time; the quenching is completed by vertical quenching and circulating water jet impact on the piston rod, which improves the quenching uniformity and hardness uniformity, thereby improving the turning efficiency of the piston rod; deep hole drilling is greatly affected by the hardness of the material. When the material is partially hard or soft, it is easy to cause the deep hole drilling to deviate, affecting the straightness of the deep hole. The piston rod produced by this method has good hardness uniformity and also improves the straightness of the deep hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural diagram of a spherical expansion type stainless steel high pressure plug; Figure 2 It is a schematic diagram of the shell structure of a spherical expansion type stainless steel high pressure plug; Figure 3 It is a structural diagram of a stainless steel integral internal liquid inlet piston rod sealed by a ball expansion type stainless steel high pressure plug; In the figure: 1. Shell; 2. Steel ball; 3. Expansion hole; 4. Tooth surface structure; 11. Rod body; 12. Deep hole; 13. Plug hole; 14. Ball expansion type high pressure plug. DETAILED DESCRIPTION

[0021] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0022] The present invention provides a method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod, such as Figures 1 to 3 The liquid inlet piston rod comprises a rod body 11 , a deep hole 12 and a plugging hole 13 , a spherical expansion type high pressure plug 14 is installed at the plugging hole 13 , and the occlusal surface of the spherical expansion type high pressure plug 14 is used to occlude with the side wall of the plugging hole 13 .

[0023] The ball-expansion high-pressure plug 14 includes a shell 1 and a steel ball 2, and the plug end of the shell 1 is closed, and the other end is open and provided with an expansion hole 3 for filling the steel ball 2, and the inner diameter of the expansion hole 3 is smaller than the diameter of the steel ball 2. The steel ball 2 is filled in the expansion hole 3 and has an interference fit with the expansion hole 3 to cause the shell 1 to expand radially.

[0024] The outer peripheral surface of the housing 1 is provided with an annularly distributed tooth surface structure 4 which serves as an occlusal surface; The depth of the expansion hole in the housing 1 is greater than the diameter of the steel ball, and the plug end of the housing 1 is configured to be a frustum, which can facilitate entry into the sealed hole.

[0025] The occlusal surface of the ball expansion type high pressure plug 14 is used to occlude with the side wall of the plugging hole 13; The outer diameter of the shell 1 is smaller than the inner diameter of the blocking hole, and the length of the shell 1 is smaller than the depth of the blocking hole, so as to prevent the steel ball from falling out.

[0026] Preferably, the shell 1 and the steel ball 3 are both made of stainless steel, which is corrosion-resistant, can avoid sealing failure, and extend the service life.

[0027] Working principle: The ball expansion type high-pressure plug can be used for port sealing of various holes. During installation, first ensure that the inner diameter of the hole port is slightly smaller than the outer diameter of the shell 1, and machine a step at a certain depth of the hole. The diameter of the hole further inward from the step is significantly smaller than the outer diameter of the shell 1 to avoid the shell from entering too deep and provide support for the process of knocking in the steel ball 2; then knock the shell 1 into the port of the hole first, and after the shell 1 is completely entered into the hole, continue to knock in the steel ball 2. As the steel ball 2 enters the expansion hole 3, the steel ball 2 drives the shell 1 to expand radially, and the corrugated tooth surface distributed annularly on the outside of the shell 1 bites the inner wall of the hole to achieve high-pressure sealing.

[0028] The processing process is: Stainless steel is selected as the raw material, followed by sizing → induction heating → local upsetting → tempering treatment → rough turning → fine turning → surface quenching → deep hole drilling → fluid hole drilling → milling and drilling joint holes → sealing and plugging holes → grinding → polishing.

[0029] The chemical composition and mass percentage of stainless steel are: C <0.2%, Si <0.1%, Mn <0.1, Cr 15~17%, Ni 2~2.5%, P <0.04%, S <0.03%, and the remainder is Fe and unavoidable impurities.

[0030] Furthermore, the Ni content in the national standard for stainless steel is 1.25-2.5%, and the Ni content of the stainless steel of the present invention takes the upper limit of the national standard.

[0031] Furthermore, during the local upsetting process, the initial forging temperature is 1100~1150°C, the final forging temperature is 1030~1080°C, and the cooling rate after forging is 0.5~1.5°C / s; Furthermore, during the quenching and tempering process, the austenitizing temperature is 1010~1050℃, and the austenitizing heating and holding time is radius*(1.5~1.7)min / mm; the quenching and tempering process is vertical quenching of the piston rod and circulating water jet impact on the piston rod, the circulating water is sprayed obliquely to the piston rod from the circumferential direction below the piston rod, and the cold water on the surface of the piston rod moves upward, and the water flow rate is 1.3~1.8m / s; the tempering temperature is 630~680℃; after quenching and tempering, the surface hardness of the piston rod is 260~265HB, the hardness of the core of the piston rod is 250~255HB, the hardness is uniform, which is conducive to subsequent machining.

[0032] Furthermore, after fine turning, the machining allowance of the surface treatment area of ​​the piston rod is 0.2-0.3 mm.

[0033] Furthermore, during the surface tempering and quenching process, the stainless steel is austenitized by induction coil heating, and water spray is used for cooling; preferably, the induction coil is larger than the workpiece diameter by 5 mm, the oscillating current is 500A, the DC voltage is 550V, the DC current is 200A, the coil moving speed is 90~100mm / min, the quenching temperature is 1020~1040℃, the water temperature is <40℃, and the surface hardness is 50~60HRC and the hardened layer depth is 1.5~2mm.

[0034] Furthermore, the deep hole is located in the core of the piston rod, and a horizontal deep hole drill is used to drill the deep hole. The hardness of the core of the piston rod is uniform, which can ensure the straightness of the deep hole to be 1mm / m, and a countersunk hole with a diameter of Φ10mm and a depth of 12mm is drilled at the opening of one of the deep holes. The countersunk hole needs to block the opening, and a ball-type stainless steel plug is used for sealing.

[0035] Furthermore, a carbide drill bit is used in the process of drilling the fluid hole.

[0036] Among them, by controlling the Ni content, local upsetting process, and tempering treatment process, the matrix microstructure is controlled to be tempered troostite + delta ferrite, the content of delta ferrite is less than 5%, the tempered troostite has fine grains, the carbides are evenly dispersed, and the delta ferrite is spherical; the comprehensive mechanical properties and corrosion resistance of tempered troostite are better than those of delta ferrite, so the comprehensive mechanical properties and corrosion resistance of the matrix are good; the surface hardness of the outer circle of the stainless steel piston rod can be improved by surface quenching. The specific control methods are as follows: ① The microstructure of stainless steel after quenching is martensite + delta ferrite, and the microstructure after quenching + tempering is tempered troostite + delta ferrite. As the content of delta ferrite increases, the strength and hardness of stainless steel decrease. Tempered troostite is more corrosion-resistant than delta ferrite. When the Ni content is less than 2%, the content of delta ferrite increases, which is not conducive to the strength, hardness and corrosion resistance of stainless steel. Therefore, the Ni content is controlled at 2.0~2.5%.

[0037] ② When the forging temperature of stainless steel is too high, it will cause the austenite grains to be coarse, the content of delta ferrite to increase, the comprehensive mechanical properties of the material will decrease, and the corrosion resistance will also decrease. When the forging temperature is lower than the austenite transformation temperature, primary carbides or delta ferrite will precipitate; Cr elements gather around carbides, which are prone to grain boundary corrosion. Delta ferrite is not corrosion-resistant in the environment of coal mines, which will reduce the corrosion resistance of stainless steel; during the cooling process after forging, stainless steel will recover and recrystallize. When the cooling rate is faster, the nucleation rate of recrystallization increases, and the grains are refined. This process is equivalent to residual temperature normalizing after forging.

[0038] ③ If the austenitizing temperature is lower than 1010℃, a large amount of undissolved carbides will be present in the material, which will reduce the strength and hardness of the material and affect the corrosion resistance of the stainless steel. If the austenitizing temperature is higher than 1050℃, the grains will grow and coarsen, and a large amount of δ-ferrite will be formed, which will reduce the toughness, increase the sensitivity to temper brittleness, and reduce the corrosion resistance. The carbides in stainless steel are Cr-containing M 23 C6 or M7C3 carbides are not easy to dissolve during the austenitization process. Therefore, it is necessary to increase the holding time appropriately to dissolve the carbides and diffuse the alloying elements evenly. The austenitization heating holding time is (radius*(1.5~1.7)min / mm), which is slightly longer than the austenitization time of traditional stainless steel. Slightly extending the holding time will not increase delta ferrite, will not cause grain growth, ensure full diffusion of alloying elements, reduce grain boundary segregation, homogenize the organization, and prepare for surface quenching. The microstructure after quenching is martensite + delta ferrite + a small amount of residual austenite, and the content of delta ferrite is less than 5%.

[0039] ④ The tempering temperature of stainless steel is 630~680℃. In this temperature range, the residual austenite gradually decomposes, the delta ferrite gradually spheroidizes, the carbides are dispersed and evenly distributed on the matrix, the surface hardness is 260~265HB, and the comprehensive mechanical properties are good; the decomposition of the residual austenite and the spheroidization of the delta ferrite are conducive to improving the toughness of the material. Tempered troostite is more corrosion-resistant than delta ferrite. The microstructure after quenching and tempering treatment is tempered troostite + delta ferrite, and the content of delta ferrite is less than 5%. Therefore, the stainless steel piston rod of the present invention is more corrosion-resistant in the underground environment of coal mines.

[0040] ⑤ The traditional method of increasing the surface hardness of stainless steel piston rods is rolling. The hardness after rolling is 40~45HRC. However, the falling of coal ore in coal mines can easily scratch the outer surface of the rod. Therefore, it is necessary to increase the surface hardness of the outer circle of the rod. By adopting the surface quenching method, the microstructure of the outer circle of the rod can be transformed into martensite to improve the surface hardness. During the surface quenching and quenching process, the stainless steel is austenitized by induction coil heating. There is a spray water nozzle on the lower side of the coil; the austenitization heating and spray quenching are completed during the movement of the coil. The coil diameter is 5mm larger than the workpiece diameter. This is because the coil is too close to the workpiece and there is a risk of touching the workpiece. The coil is too far from the workpiece and the heating efficiency is low, so the workpiece cannot reach the quenching temperature. The quenching water temperature is less than 40℃ to ensure the quenching intensity. Through the induction heating process parameters, the quenching temperature is controlled to 1020~1040℃, and the surface hardness and the depth of the hardened layer are regulated by controlling the coil movement speed and heating time.

[0041] The technical solution of the present invention is further described in detail below through specific implementation methods.

[0042] Example 1 A method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod, the oil cylinder piston rod is manufactured by the following steps: Step (1) Stainless steel is selected as the raw material. The raw material specification is a diameter of Φ110 mm. Its chemical composition and mass percentage are as follows: C is 0.1%, Si is 0.05%, Mn is 0.05%, Cr is 16%, Ni is 2.4%, P is 0.005%, S is 0.005%, and the balance is Fe and unavoidable impurities.

[0043] Step (2) Determine the size according to the design process requirements.

[0044] Step (3) locally upsetting the sized round steel to obtain an integral piston rod blank.

[0045] Among them, during the local upsetting process, the initial forging temperature is 1120°C, the final forging temperature is 1050°C, and the cooling rate after forging is 0.8°C / s.

[0046] Step (4) performs quenching and tempering treatment on the integral piston rod blank.

[0047] During the tempering treatment, the austenitizing temperature is 1025℃, and the austenitizing heating and holding time is 176min; the tempering quenching process is vertical quenching of the piston rod and circulating water jet impact on the piston rod. The circulating water is sprayed obliquely to the piston rod from the circumferential direction below the piston rod, and the cold water on the surface of the piston rod moves upward, with a water flow rate of 1.5m / s; the tempering temperature is 650℃; the surface hardness of the workpiece after tempering treatment is 269HB.

[0048] Step (5) rough turning and finish turning the tempered integral piston rod blank, with the machining allowance of the surface treatment area being 0.3 mm, to obtain the integral piston rod after finish turning.

[0049] Step (6) surface quenching the integral piston rod after fine turning.

[0050] During the surface quenching and tempering process, the stainless steel is austenitized by induction coil heating and cooled by water spray. The induction coil diameter is Φ110mm, the oscillating current is 500A, the DC voltage is 550V, the DC current is 200A, the coil moving speed is 92mm / min, the quenching temperature is 1030℃, the water temperature is 25℃, and the surface hardness is 55HRC and the hardened layer depth is 1.8mm.

[0051] Step (7) The deep hole is located at the center of the piston rod. A horizontal deep hole drill is used to drill the deep hole. The hardness of the piston rod center is uniform and the straightness of the deep hole is 0.7 mm / m. A countersink with a diameter of Φ10 mm and a depth of 12 mm is drilled at the mouth of one of the deep holes. A carbide drill bit is used during the drilling of the liquid hole.

[0052] Step (8) Grind and polish the surface treatment area of ​​the entire piston rod to the size required by the drawing.

[0053] The microstructure of the matrix is ​​regulated by quenching and tempering, and the microstructure of the surface treatment area is regulated by surface quenching. The mechanical properties of the stainless steel piston rod are shown in Tables 1 and 2. The stainless steel piston rod is subjected to a salt spray test to test its corrosion resistance. In the acid salt spray test, slight corrosion occurs in 60-63 days. However, the electroplated piston rod will be corroded in only 6-7 days in the acid salt spray test.

[0054] Table 1 Mechanical properties of stainless steel piston rod Sampling location Hardness / HB Tensile strength / MPa Yield strength / MPa Sectional shrinkage / % Elongation after break / % Impact energy (-20℃) / J surface 275 1015 876 20 60 41.9 1 / 4 diameter 273 991 862 19 60 40.8 1 / 2 diameter 268 985 847 19 59 39.8 Table 2 Surface quenching hardness of stainless steel piston rod Length from surface / mm 0.2 0.5 0.8 1.3 1.8 2.0 Hardness / HRC 59.3 58.9 57.4 55.3 52.2 45.1 Example 2 This embodiment provides a method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod, and the oil cylinder piston rod is manufactured by the following steps: Step (1) Stainless steel is selected as the raw material. The raw material specification is a diameter of Φ75 mm, and its chemical composition and mass percentage are: C0.09%, Si0.08%, Mn0.07%, Cr 16.5%, Ni 2.2%, P0.005%, S0.005%, and the balance is Fe and unavoidable impurities.

[0055] Step (2) Determine the size according to the design process requirements.

[0056] Step (3) Partially upsetting the round steel after the cut length to obtain the integral piston rod blank Among them, the initial forging temperature is 1110°C, the final forging temperature is 1040°C, and the cooling rate after forging is 0.85°C / s.

[0057] Step (4) performs quenching and tempering treatment on the integral piston rod blank.

[0058] During the tempering treatment, the austenitizing temperature is 1020℃, and the austenitizing heating and holding time is 120min; the tempering quenching process is vertical quenching of the piston rod and circulating water jet impact on the piston rod. The circulating water is sprayed obliquely to the piston rod from the circumferential direction below the piston rod, and the cold water on the surface of the piston rod moves upward, with a water flow rate of 1.4m / s; the tempering temperature is 660℃; the surface hardness of the workpiece after tempering treatment is 273HB.

[0059] Step (5) rough turning and finish turning the tempered integral piston rod blank, with the machining allowance of the surface treatment area being 0.3 mm, to obtain the integral piston rod after finish turning.

[0060] Step (6) surface quenching the integral piston rod after fine turning.

[0061] During the surface quenching and tempering process, the stainless steel is austenitized by induction coil heating and cooled by water spray. The induction coil diameter is Φ75mm, the oscillating current is 500A, the DC voltage is 550V, the DC current is 200A, the coil moving speed is 98mm / min, the quenching temperature is 1030℃, the water temperature is 26℃, and the surface hardness is 56.3HRC and the hardened layer depth is 1.8mm.

[0062] Step (7) The deep hole is located at the center of the piston rod. A horizontal deep hole drill is used to drill the deep hole. The hardness of the piston rod center is uniform and the straightness of the deep hole is 0.6 mm / m. A countersink with a diameter of Φ10 mm and a depth of 12 mm is drilled at the mouth of one of the deep holes. In the process of drilling the liquid hole, a carbide drill bit is used.

[0063] Step (8) Grind and polish the surface treatment area of ​​the entire piston rod to the size required by the drawing.

[0064] The microstructure of the matrix is ​​regulated by quenching and tempering, and the microstructure of the surface treatment area is regulated by surface quenching. The mechanical properties of the stainless steel piston rod are shown in Tables 3 and 4. The stainless steel piston rod is subjected to a salt spray test to test its corrosion resistance. In the acid salt spray test, slight corrosion occurs in 60-62 days. However, the electroplated piston rod will be corroded in only 6-7 days in the acid salt spray test.

[0065] Table 3 Mechanical properties of stainless steel piston rod Sampling location Hardness / HB Tensile strength / MPa Yield strength / MPa Sectional shrinkage / % Elongation after break / % Impact energy (-20℃) / J surface 273 1012 871 20 60 43.7 1 / 4 diameter 271 988 859 20 60 41.1 1 / 2 diameter 266 981 843 19 59 39.6 Table 4 Surface quenching hardness of stainless steel piston rod Length from surface / mm 0.2 0.5 0.8 1.3 1.8 2.0 Hardness / HRC 58.9 58.1 56.8 54.5 51.5 44.3 If the words "first", "second" and the like are used in this patent to limit components, those skilled in the art should know that the use of "first" and "second" is only for the convenience of describing the present invention and simplifying the description, and the above words have no special meaning.

[0066] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the invention claimed for protection. The scope of protection claimed for the present invention is defined by the attached claims and their equivalents.

[0067] In the description of the present invention, it is necessary to understand that the terms "front", "rear", "left", "right", "center", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the protection content of the present invention.

Claims

1. A method for manufacturing a hydraulic support cylinder stainless steel integral internal liquid inlet piston rod, characterized in that: The liquid inlet piston rod comprises a rod body, a deep hole and a plugging hole, and a ball-expanding high-pressure plug is installed at the plugging hole, and the engaging surface of the ball-expanding high-pressure plug is used to engage with the side wall of the plugging hole; The ball expansion type high pressure plug comprises a shell and a steel ball, and the plug end of the shell is closed, and the other end is open and provided with an expansion hole for filling the steel ball, and the inner diameter of the expansion hole is smaller than the diameter of the steel ball, and the steel ball is filled in the expansion hole to have an interference fit with the expansion hole and cause the shell to expand radially; The outer peripheral surface of the shell is provided with an annularly distributed tooth surface structure as an occlusal surface; The processing process includes the following steps: Stainless steel is selected as the raw material, and the process is carried out as follows: sizing → induction heating → local upsetting → quenching and tempering → rough turning → fine turning → surface quenching → deep hole drilling → fluid hole drilling → milling and drilling of joint holes → sealing and plugging holes → grinding → polishing; During the quenching and tempering process, the austenitizing temperature is 1010~1050℃, the austenitizing heating and holding time is: radius*(1.5~1.7)min / mm, and the quenching and tempering process adopts piston rod vertical quenching and circulating water jet impact piston rod; During the deep hole drilling process, a horizontal deep hole drill is used to drill deep holes and plug holes.

2. The method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod according to claim 1, characterized in that: The depth of the expansion hole in the shell is greater than the diameter of the steel ball, and the plug end of the shell is set to be a frustum; The engaging surface of the ball expansion type high pressure plug engages with the side wall of the plugging hole; The outer diameter of the shell is smaller than the inner diameter of the blocking hole, and the length of the shell is smaller than the depth of the blocking hole.

3. The method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod according to claim 1, characterized in that: During the tempering and quenching process, circulating water is sprayed obliquely on the piston rod along the circumference from the bottom of the piston rod, and cold water moves upward along the surface of the piston rod, with a water flow rate of 1.3~1.8m / s.

4. The method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod according to claim 1, characterized in that: The chemical composition and mass percentage of the stainless steel are: C<0.2%, Si<0.1%, Mn<0.1, Cr is 15-17%, Ni is 2-2.5%, P<0.04%, S<0.03%, and the balance is Fe and unavoidable impurities.

5. The method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod according to claim 1, characterized in that: After quenching and tempering treatment, the surface hardness of the piston rod is 260~265HB, and the hardness of the core of the piston rod is 250~255HB.

6. The method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod according to claim 1, characterized in that: During the local upsetting process, the initial forging temperature is 1100~1150℃, the final forging temperature is 1030~1080℃, and the cooling rate after forging is 0.5~1.5℃ / s.

7. The method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod according to claim 1, characterized in that: During the surface quenching and tempering process, the stainless steel is austenitized by induction coil heating and cooled by water spray; the induction coil moving speed is 90~100mm / min, the quenching temperature is 1020~1040℃, and the water temperature is <40℃; After quenching, the surface hardness is 50~60HRC and the depth of the hardened layer is 1.5~2mm.

8. The method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod according to claim 6, characterized in that: The diameter of the induction coil is 3-5 mm larger than the diameter of the workpiece.

9. The method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod according to claim 1, characterized in that: After fine turning, the machining allowance of the piston rod surface treatment area is 0.2~0.3mm.

10. The method for manufacturing a hydraulic support oil cylinder stainless steel integral internal liquid inlet piston rod according to claim 1, characterized in that: Carbide drill bits are used in the process of drilling through fluid holes, deep holes, and plugged holes.

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