A manufacturing method of a stainless steel integral inner liquid inlet piston rod of a hydraulic support oil cylinder

Abstract

The application discloses a manufacturing method of a stainless steel integral inner liquid inlet piston rod of a hydraulic support oil cylinder, and solves the problems of poor corrosion resistance of a traditional integral inner liquid inlet piston rod of a hydraulic support, high machining precision of a stainless steel deep hole, and welding-free hole plugging by improving a stainless steel piston rod machining process flow and adopting a process of fixed size, induction heating, local upsetting, quenching and tempering treatment, rough turning, fine turning, surface quenching, deep hole drilling, through hole drilling, joint hole milling, sealing hole plugging, grinding and polishing. The method shortens a machining process, simplifies a machining process, and is free of welding under the premise of guaranteeing mechanical properties and corrosion resistance of the piston rod, has important significance for improving production efficiency and corrosion resistance of the hydraulic oil cylinder piston rod, prolonging service life of the hydraulic support, and realizing efficient operation of coal fully-mechanized mining equipment in a mine.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydraulic oil cylinders, and particularly relates to a manufacturing method of a stainless steel integral inner-liquid-inlet piston rod of a hydraulic support oil cylinder. BACKGROUND

[0002] The jack in the hydraulic support is a key component for realizing the action function of the hydraulic support, and the piston rod in the jack is a key component in the jack. The oil cylinder with the inner-liquid-inlet piston rod structure can avoid welding of the cylinder body accessories, reduce welding of the oil cylinder, and avoid interference between the oil cylinder and the structural member of the hydraulic support. The rod head of the inner-liquid-inlet piston rod has a joint hole, the joint hole is connected with two deep holes, one of the deep holes directly penetrates the bottom of the rod to supply liquid to the lower cavity, and the other deep hole is connected with a liquid passage hole to supply liquid to the upper cavity. The traditional process for improving the corrosion resistance of the piston rod is electroplating on the outer circle of the rod body. In order to further improve the corrosion resistance of the inner hole liquid inlet part and the outer circle part of the rod body of the piston rod, the surface treatment method of the piston rod is to plate copper in the piston and the liquid inlet deep hole area and to perform laser cladding on the outer circle of the rod body. The processing process is as follows: sizing, induction heating, local upsetting, quenching and tempering, rough turning, fine turning before cladding, laser cladding, fine turning, drilling deep holes, drilling liquid passage holes, milling and drilling joint holes, plating copper in the piston area, polishing the piston area, plating copper in the deep holes and the liquid passage holes, welding plugs, welding plug flat heads, grinding the outer circle, and polishing the outer circle. The following problems exist.

[0003] (1) The surface treatment method of laser cladding + copper plating has a long process flow, a complex process, a long production cycle, and low production efficiency.

[0004] (2) The electroplated layer itself has poor corrosion resistance and is prone to rust.

[0005] In order to improve the corrosion resistance of the piston rod, a new corrosion-resistant hydraulic support oil cylinder piston rod processing process needs to be developed to shorten the processing flow and simplify the processing process. Stainless steel is a good corrosion-resistant material and is very suitable for manufacturing hydraulic support oil cylinder piston rods. However, the microstructure of the stainless steel needs to be controlled to reduce the content of delta ferrite, carbide, and residual austenite and to improve the corrosion resistance. On this basis, the hardness uniformity needs to be improved to further improve the deep hole machining precision, and the outer circle of the rod body needs to have sufficient wear resistance in the coal mine. The stainless steel piston rod is not suitable for welding, and cracks are prone to occur after welding. If the welding parameters are not properly controlled, welding defects such as slag and incomplete fusion are prone to occur, which affects the sealing effect of the plug and causes the jack to fail. Therefore, a new plug process needs to be sought to avoid welding of the stainless steel and ensure the sealing of the plug.

[0006] The invention of the publication number CN118835240A discloses a kind of laser cladding process method of hydraulic oil cylinder piston rod, and its technical scheme points include finish turning, laser cladding, cylindrical grinding, and laser cladding process is used to firmly adhere powder on piston rod by laser beam, various formula content is developed, upgrading powder formula is used as raw material, through the process mode of laser cladding, it is applied to the piston rod of hydraulic press oil cylinder, etc., to achieve wear resistance, corrosion resistance requirements;However, this process cannot solve the problem of no corrosion resistance treatment in the piston area and deep hole area.

[0007] Therefore, it is urgent to explore a new hydraulic support oil cylinder piston rod manufacturing method to shorten the processing flow and simplify the processing technology under the premise of ensuring the mechanical properties and corrosion resistance of the piston rod. SUMMARY

[0008] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a manufacturing method for a stainless steel integral internal liquid inlet piston rod of a hydraulic support oil cylinder, which solves the problem of poor corrosion resistance of traditional hydraulic support integral internal liquid inlet piston rod, as well as the problems of stainless steel deep hole high machining precision and plug hole welding-free.

[0009] To solve the above technical problems, the technical scheme adopted by the present application is:

[0010] A manufacturing method for a stainless steel integral internal liquid inlet piston rod of a hydraulic support oil cylinder, the internal liquid inlet piston rod comprising a rod body, a deep hole and a plug hole, and a ball expansion high-pressure plug head is installed at the plug hole, and the engagement surface of the ball expansion high-pressure plug head is used to engage with the side wall of the plug hole.

[0011] The ball expansion high-pressure plug head comprises a shell and a steel ball, the plug head end of the shell is closed, the other end is open and provided with an expansion hole for filling the steel ball, the inner diameter of the expansion hole is smaller than the diameter of the steel ball, the steel ball is filled into the expansion hole in interference fit with the expansion hole and makes the shell radially expand;

[0012] The outer peripheral surface of the shell is provided with an annularly distributed tooth surface structure and serves as an engagement surface;

[0013] The processing flow comprises the following steps:

[0014] Stainless steel is selected as raw material, and the following steps are carried out: sizing → induction heating → local upsetting → quenching and tempering treatment → rough turning → finish turning → surface quenching → drilling deep hole → drilling through hole → milling joint hole → sealing plug hole → grinding → polishing;

[0015] During the quenching and tempering treatment, 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;

[0016] During drilling deep hole, the horizontal deep hole drill is used to drill deep hole and plug hole, so that the straightness of the deep hole can be ensured to be 0.3-0.4mm / m.

[0017] The depth of the hole in the shell is greater than the diameter of the steel ball, and the plug end of the shell is provided with a conical frustum type;

[0018] The occlusal surface of the ball-expanding high-pressure plug is used for occlusion with the side wall of the plugged hole.

[0019] The outer diameter of the shell is smaller than the inner diameter of the plugged hole, and the length of the shell is smaller than the depth of the plugged hole.

[0020] During quenching and tempering, the circulating water is sprayed to the piston rod from below along the circumference, and the cold water moves upward along the surface of the piston rod, and the water flow speed is 1.3-1.8m / s.

[0021] The chemical composition and mass percentage of the stainless steel are as follows: 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 inevitable impurities.

[0022] After the quenching and tempering treatment, the surface hardness of the piston rod is 260-265HB, and the core hardness of the piston rod is 250-255HB, so that the hardness is uniform, and the subsequent machining is facilitated.

[0023] 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.

[0024] During the surface quenching process, the austenitizing of the stainless steel is carried out by using an induction coil, and water spraying cooling is used; the moving speed of the induction coil is 90-100mm / min, the quenching temperature is 1020-1040℃, the water temperature is <40℃; and after quenching, the surface hardness is 50-60HRC, and the quenching layer depth is 1.5-2mm; the diameter of the induction coil is greater than the diameter of the workpiece by 3-5mm.

[0025] After the finish turning, the machining allowance of the surface treatment area of the piston rod is 0.2-0.3mm.

[0026] During drilling through the liquid hole, the deep hole and the plugged hole, a hard alloy drill bit is used.

[0027] The beneficial effects of the present application are:

[0028] (1) The application discloses a manufacturing method of a stainless steel integral inner-liquid inlet piston rod of a hydraulic support oil cylinder, and solves the problem of poor corrosion resistance of a traditional integral inner-liquid inlet piston rod of a hydraulic support by improving the processing technological procedure of the stainless steel piston rod, adopting the process of fixed size, induction heating, local upsetting, quenching and tempering treatment, rough turning, finish turning, surface quenching, drilling deep holes, drilling through liquid holes, milling joint hole, sealing hole plugging, grinding and polishing, and the like.

[0029] (2) By controlling the content of Ni, the local upsetting process and the quenching and tempering treatment process, the microstructure of the base body is controlled to be tempered sorbite + delta ferrite, the content of the delta ferrite is less than 5%, the tempered sorbite has small grains and uniformly dispersed carbides, and the delta ferrite is in a spherical shape; the comprehensive mechanical properties and corrosion resistance of the tempered sorbite are better than those of the delta ferrite; the content of the delta ferrite, carbide and residual austenite is reduced, the corrosion resistance and hardness uniformity are improved, and the deep hole machining precision is further improved; the surface hardness of the outer circle of the rod body is not less than 50HRC, so that the comprehensive mechanical properties and corrosion resistance of the base body are good; and the surface hardness of the outer circle of the stainless steel piston rod body is improved by the surface quenching method.

[0030] (3) The method of the plug ball expansion type stainless steel plug is adopted to avoid welding of the stainless steel, and the plug is operated according to the pressure expansion principle; when the steel ball is pressed to the bottom of the sleeve, the steel ball causes radial expansion of a section of the sleeve, axial stress is converted into radial expansion response of the sleeve, at this moment, the sharp teeth formed by the annular groove on the periphery of the sleeve are forced to press into the surrounding workpiece material, thereby forming an effective high-pressure leak-free seal, solving the problem that the traditional welded hole sealing port is prone to welding defects and thus causes sealing failure. The stainless steel material can avoid sealing failure caused by rust, reduce the difficulty of disassembly and repair of the jack due to unqualified pressure test after assembly of the piston rod and the cylinder, and reduce the cycle time. Due to the simple structure, the sealing cost is extremely low, only the cost of the plug ball expansion type high-pressure sealing plug; the assembly workstation can realize automatic and accurate positioning and installation, improve the production efficiency, and no longer need high-level welders for plug welding process, thereby reducing the liquid leakage rate and labor cost.

[0031] (4) By controlling the extension of austenitizing time, the homogenization of the structure is achieved; by vertical quenching and circulating water jet impact on the piston rod, quenching is completed, the uniformity of quenching and hardness is improved, and the turning machining efficiency of the piston rod is improved; the deep hole drill is greatly affected by the hardness of the material, and when the material is locally hard or soft, the deep hole drill is easily deviated, which affects the straightness of the deep hole, and the hardness uniformity of the piston rod prepared by the method is good, and the straightness of the deep hole is also improved. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a structural schematic diagram of a ball expansion type stainless steel high pressure plug;

[0033] Figure 2 is a structural schematic diagram of a shell of a ball expansion type stainless steel high pressure plug;

[0034] Figure 3 is a structural schematic diagram of a stainless steel integrated inner liquid inlet piston rod of a ball expansion type stainless steel high pressure plug;

[0035] In the figure: 1. Shell; 2. Steel ball; 3. Expansion hole; 4. Tooth surface structure; 11. Rod body; 12. Deep hole; 13. Plugging hole; 14. Ball expansion type high pressure plug. DETAILED DESCRIPTION

[0036] The following specific embodiments illustrate the embodiments of the present application, and those skilled in the art can easily understand other advantages and effects of the present application from the disclosure.

[0037] The present application provides a manufacturing method of a hydraulic support oil cylinder stainless steel integrated inner liquid inlet piston rod, as shown in Figures 1 to 3 The liquid inlet piston rod includes a rod body 11, a deep hole 12 and a plugging hole 13, a ball expansion type high pressure plug 14 is installed at the plugging hole 13, and the engagement surface of the ball expansion type high pressure plug 14 is used to engage with the side wall of the plugging hole 13.

[0038] The ball expansion type high pressure plug 14 includes a shell 1 and a steel ball 2, and the plug end of the shell 1 is closed, the other end is open and provided with an expansion hole 3 for filling the steel ball 2, 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 is in interference fit with the expansion hole 3 and makes the shell 1 radially expand.

[0039] The outer peripheral surface of the shell 1 is provided with annularly distributed tooth surface structure 4 and is used as the engagement surface;

[0040] The depth of the expansion hole in the shell 1 is greater than the diameter of the steel ball, and the plug end of the shell 1 is provided in a conical frustum type, which can conveniently enter the sealed hole.

[0041] The engagement surface of the ball expansion type high pressure plug 14 is used to engage with the side wall of the plugging hole 13;

[0042] The shell 1 has an outer diameter smaller than the inner diameter of the hole, and the length of the shell 1 is smaller than the depth of the hole, so that the steel ball is prevented from being pulled out.

[0043] Preferably, the shell 1 and the steel ball 3 are made of stainless steel, which has the characteristics of corrosion resistance, so that the sealing failure is avoided and the service life is prolonged.

[0044] Working principle:

[0045] The ball expansion type high-pressure plug can be used for port sealing of various holes. When installing, first, it is necessary to ensure that the inner diameter of the hole is slightly smaller than the outer diameter of the shell 1, and a step is processed at a certain depth of the hole, the inner diameter of the step is greatly smaller than the outer diameter of the shell 1, so that the shell is prevented from entering too deep, and support is provided for the process of knocking the steel ball 2 into the hole; then the shell 1 is knocked into the hole, and after the shell 1 is completely entered into the hole, the steel ball 2 is continuously knocked in, and 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 on the outer part of the shell 1 engages the inner wall surface of the hole, so that high-pressure sealing is achieved.

[0046] The machining process flow is as follows:

[0047] The stainless steel material is selected as the raw material, and then the following processes are performed: sizing, induction heating, local upsetting, quenching and tempering, rough turning, fine turning, surface quenching, drilling deep holes, drilling through liquid holes, milling and drilling joint holes, sealing hole blocking, grinding and polishing.

[0048] The chemical composition and mass percentage of the stainless steel are as follows: C < 0.2%, Si < 0.1%, Mn < 0.1, Cr 15-17%, Ni 2-2.5%, P < 0.04%, S < 0.03%, and the balance of Fe and unavoidable impurities.

[0049] Further, the Ni content in the stainless steel standard is 1.25-2.5%, and the Ni content of the stainless steel in the present application is the upper limit in the standard.

[0050] Further, in 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.

[0051] Further, in 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; the quenching process is piston rod vertical quenching and circulating water jet impact on the piston rod, the circulating water is sprayed from the lower circumference of the piston rod to the piston rod obliquely, and the cold water on the surface of the piston rod moves upward, the water flow speed is 1.3-1.8m / s; the tempering temperature is 630-680℃; after the quenching and tempering treatment, the surface hardness of the piston rod is 260-265HB, and the core hardness of the piston rod is 250-255HB, the hardness is uniform, which is beneficial to subsequent machining.

[0052] Further, the machining allowance of the surface treatment area of the piston rod is 0.2-0.3 mm after finish machining.

[0053] Further, austenitizing of the stainless steel is performed by using an induction coil heating method during surface quenching, and water spraying is used for cooling; preferably, the induction coil is greater than the workpiece diameter by 5 mm, the oscillation current is 500 A, the direct current voltage is 550 V, the direct current is 200 A, the coil moving speed is 90-100 mm / min, the quenching temperature is 1020-1040℃, the water temperature is <40℃, the surface hardness is 50-60 HRC, and the hardening layer depth is 1.5-2 mm.

[0054] Further, the deep hole is located in the center of the piston rod, a horizontal deep hole drill is used to drill the deep hole, the hardness of the center of the piston rod is uniform, the straightness of the deep hole can be guaranteed to be 1 mm / m, and a counterbore with a diameter of Φ10 mm and a depth of 12 mm is drilled at one of the deep hole orifices, and the counterbore needs to be plugged, a plug ball expansion type stainless steel plug is used for plugging.

[0055] Further, a carbide drill bit is used during drilling the through hole.

[0056] The microstructure of the base body is controlled to be tempered sorbite + δ ferrite by controlling the content of Ni, local upsetting process and quenching and tempering process, the content of δ ferrite is less than 5%, the tempered sorbite grains are small, the carbides are uniformly and dispersedly distributed, and the δ ferrite is spherical; the comprehensive mechanical properties and corrosion resistance of the tempered sorbite are better than those of the δ ferrite, so the comprehensive mechanical properties and corrosion resistance of the base body are good; the surface hardness of the outer circle of the stainless steel piston rod body can be improved by surface quenching. The specific control method is as follows:

[0057] ①The microstructure of the stainless steel after quenching is martensite + δ ferrite, and the microstructure after quenching + tempering is tempered sorbite + δ ferrite. The increase of the content of δ ferrite reduces the strength and hardness of the stainless steel. The tempered sorbite is more corrosion resistant than the δ ferrite, and when the content of Ni is less than 2%, the increase of the content of δ ferrite is not conducive to the strength, hardness and corrosion resistance of the stainless steel. Therefore, the content of Ni is controlled to be 2.0-2.5%.

[0058] ②When the forging temperature of the stainless steel is too high, the austenite grain will be coarse, the content of the δ-ferrite will increase, the comprehensive mechanical property of the material will decrease, and the corrosion resistance will also decrease. When the forging temperature is lower than the austenite transformation temperature, the primary carbide or the δ-ferrite will be precipitated; the Cr element will gather around the carbide, and the grain boundary corrosion will easily occur; the δ-ferrite is not resistant to corrosion in the environment of the coal mine underground, and the corrosion resistance of the stainless steel will decrease; the stainless steel will occur recovery recrystallization in the cooling process after forging, the nucleation rate of the recrystallization will increase, and the grain will be refined. The process is equivalent to normalizing after forging.

[0059] ③When the austenitizing temperature is lower than 1010℃, a large amount of unsolved carbide will exist in the material, so that the strength and hardness of the material will decrease, and the corrosion resistance of the stainless steel will also be affected. When the austenitizing temperature is higher than 1050℃, the grain will grow and coarsen, a large amount of δ-ferrite will be formed, the toughness will decrease, the sensitivity of temper brittleness will increase, and the corrosion resistance will also decrease. The carbide in the stainless steel is the Cr-containing M 23 C6 or M7C3 carbide, which is not easy to dissolve in the austenitizing process, therefore, the holding time needs to be appropriately increased, so that the carbide is dissolved and the alloy elements are uniformly diffused. The austenitizing heating holding time is (radius * (1.5~1.7) min / mm), compared with the austenitizing time of the traditional stainless steel, the time is slightly increased. The slightly prolonged holding time will not increase the δ-ferrite, will not cause the grain growth, will ensure the full diffusion of the alloy elements, will reduce the grain boundary segregation, will homogenize the structure, and will prepare for the surface quenching. The microstructure after quenching is martensite + δ-ferrite + a small amount of residual austenite, and the content of the δ-ferrite is less than 5%.

[0060] ④The tempering temperature of the stainless steel is 630~680℃, in this temperature range, the residual austenite is gradually decomposed, the δ-ferrite is gradually spheroidized, the carbide is uniformly distributed on the matrix, the surface hardness is 260~265HB, the comprehensive mechanical property is good, the decomposition of the residual austenite and the spheroidization of the δ-ferrite are beneficial to improve the toughness of the material. The tempered sorbite is more resistant to corrosion than the δ-ferrite, the microstructure after the quenching and tempering treatment is tempered sorbite + δ-ferrite, and the content of the δ-ferrite is less than 5%, therefore, the stainless steel piston rod of the present application is more resistant to corrosion in the environment of the coal mine underground.

[0061] 5. The method for improving the surface hardness of the traditional stainless steel piston rod by rolling, and the hardness after rolling is 40-45 HRC, but the coal ore falling in the coal mine can easily scratch the outer surface of the rod body, and therefore, the surface hardness of the outer circle of the rod body needs to be improved. The surface quenching method can change the microstructure of the outer surface of the rod body into martensite and improve the surface hardness. In the surface quenching and tempering process, the induction coil is used for austenitizing the stainless steel, and the lower side of the coil has a water spraying nozzle; the coil is moved to complete the austenitizing heating and the water spraying quenching. The diameter of the coil is greater than the diameter of the workpiece by 5 mm, because if the coil is too close to the workpiece, there is a risk of touching the workpiece, and if the coil is too far from the workpiece, the heating efficiency is low and the workpiece cannot reach the quenching temperature. The quenching water temperature is less than 40℃ to ensure the quenching intensity. The quenching temperature is controlled to be 1020-1040℃ by the induction heating process parameters, the heating time is controlled by controlling the moving speed of the coil, and the surface hardness and the depth of the hardened layer are regulated.

[0062] The technical solutions of the present application will be further described in detail through the specific embodiments.

[0063] Embodiment 1

[0064] A manufacturing method of a stainless steel integral inner-liquid hydraulic support oil cylinder piston rod, the oil cylinder piston rod is prepared by the following steps:

[0065] Step (1) selecting stainless steel as the raw material, the specification of the raw material is diameter Φ110mm, and the chemical composition and mass percentage content 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.

[0066] Step (2) sizing according to the size required by the design process.

[0067] Step (3) locally upsetting the sized round steel to obtain an integral piston rod blank.

[0068] In the local upsetting process, the initial forging temperature is 1120℃, the final forging temperature is 1050℃, and the cooling rate after forging is 0.8℃ / s.

[0069] Step (4) performing a quenching and tempering treatment on the integral piston rod blank.

[0070] In the quenching and tempering treatment process, the austenitizing temperature is 1025℃, the austenitizing heating holding time is 176min; the quenching and tempering process is piston rod vertical quenching and circulating water jet impact on the piston rod, the circulating water is sprayed from the lower side of the piston rod in the circumferential direction and obliquely to the piston rod, the surface cold water of the piston rod moves upward, and the water flow speed is 1.5m / s; the tempering temperature is 650℃; and the surface hardness of the workpiece after the quenching and tempering treatment is 269HB.

[0071] Step (5) rough turning and finish turning are performed on the quenched and tempered whole piston rod blank, the machining allowance of the surface treatment area is 0.3 mm, and a finished whole piston rod is obtained.

[0072] Step (6) surface quenching is performed on the finished whole piston rod.

[0073] In the surface quenching process, austenitizing of the stainless steel is performed by using an induction coil heating method, and cooling is performed by using water spraying. The induction coil has a diameter of Φ110 mm, an oscillation current of 500 A, a direct current voltage of 550 V, a direct current of 200 A, a coil moving speed of 92 mm / min, a quenching temperature of 1030 °C, and a water temperature of 25 °C. The surface hardness is 55 HRC, and the hardening layer depth is 1.8 mm.

[0074] Step (7) deep holes are located in the center of the piston rod, and deep holes are drilled by using a horizontal deep hole drill. The hardness of the center of the piston rod is uniform, and the straightness of the deep hole is 0.7 mm / m. One of the deep hole orifices is drilled with a diameter of Φ10 mm and a depth of 12 mm. During the drilling of the through hole, a carbide drill bit is used.

[0075] Step (8) the surface treatment area of the whole piston rod is ground and polished to the size required by the drawing.

[0076] Through the quenching and tempering treatment, the microstructure of the base body is controlled, and through the surface quenching, the microstructure of the surface treatment area is controlled. The mechanical properties of the stainless steel piston rod are shown in Tables 1 and 2. The salt spray test is performed on the stainless steel piston rod to test its corrosion resistance. The acid salt spray test is performed for 60-63 days, and slight corrosion occurs. However, the electroplated piston rod is corroded after only 6-7 days of acid salt spray test.

[0077] Table 1 Mechanical properties of the stainless steel piston rod

[0078] Sampling location Hardness / HB Tensile strength / MPa Yield strength / MPa % reduction of area % elongation after break Impact work (-20°C) / 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

[0079] Table 2 Surface quenching hardness of the stainless steel piston rod

[0080] Distance from surface length / 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

[0081] Example 2

[0082] The embodiment provides a manufacturing method of a whole inner-liquid-inlet piston rod of a hydraulic support oil cylinder.

[0083] Step (1) selects stainless steel as raw material, the raw material specification is diameter Φ75mm, its chemical composition and mass percentage content are: C 0.09%, Si 0.08%, Mn 0.07%, Cr 16.5%, Ni 2.2%, P 0.005%, S 0.005%, the balance is Fe and inevitable impurities.

[0084] Step (2) according to the size required by the design process, sizing is carried out.

[0085] Step (3) the sized round steel is partially upset to obtain an overall piston rod blank

[0086] Wherein, the initial forging temperature is 1110℃, the final forging temperature is 1040℃, and the cooling rate after forging is 0.85℃ / s.

[0087] Step (4) the overall piston rod blank is subjected to quenching and tempering treatment.

[0088] During the quenching and tempering treatment, the austenitizing temperature is 1020℃, the austenitizing heating and holding time is 120min; the quenching process is piston rod vertical quenching, and the piston rod is impacted by circulating water jet, the circulating water is sprayed from the lower circumference of the piston rod to the piston rod obliquely, the surface cold water of the piston rod moves upward, and the water flow speed is 1.4m / s; the tempering temperature is 660℃; the surface hardness of the workpiece after the quenching and tempering treatment is 273HB.

[0089] Step (5) the overall piston rod blank in the quenched and tempered state is subjected to rough turning and finish turning, the machining allowance of the surface treatment area is 0.3mm, and a finished overall piston rod is obtained.

[0090] Step (6) the finished overall piston rod is subjected to surface quenching.

[0091] During the surface quenching process, the austenitizing of the stainless steel is carried out by adopting the induction coil heating mode, and the cooling is carried out by adopting water spraying. The induction coil diameter is Φ75mm, the oscillation current is 500A, the direct current voltage is 550V, the direct current is 200A, the coil moving speed is 98mm / min, the quenching temperature is 1030℃, and the water temperature is 26℃, so that the surface hardness is 56.3HRC, and the hardening layer depth is 1.8mm.

[0092] Step (7) the deep hole is located at the center of the piston rod, the horizontal deep hole drilling is adopted to drill the deep hole, the hardness of the center of the piston rod is uniform, and the straightness of the deep hole is 0.6mm / m. One of the deep hole orifices is drilled to be a counterbore with a diameter of Φ10mm and a depth of 12mm. During the process of drilling the through hole, the carbide drill bit is used.

[0093] Step (8) the surface treatment area of the overall piston rod is ground and polished to the size required by the drawing.

[0094] The mechanical properties of the stainless steel piston rod are shown in Table 3 and Table 4 by adjusting the microstructure of the base body through the quenching and tempering treatment and by adjusting the microstructure of the surface treatment area through the surface quenching. The salt spray test is performed on the stainless steel piston rod to test its corrosion resistance. The acid salt spray test shows that the piston rod is slightly corroded after 60-62 days. However, the electroplated piston rod is corroded after only 6-7 days of acid salt spray test.

[0095] Table 3 Mechanical properties of the stainless steel piston rod

[0096] Sampling location Hardness / HB Tensile strength / MPa Yield strength / MPa % reduction of area % elongation after break Impact work (-20°C) / 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

[0097] Table 4 Surface quenching hardness of the stainless steel piston rod

[0098] Distance from surface length / 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

[0099] In the patent, the terms "first", "second", etc. are used to limit the components. Those skilled in the art should know that the use of "first", "second" is only for the convenience of describing the invention and simplifying the description, and the above terms do not have special meanings.

[0100] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed invention. The scope of protection of the present application is defined by the appended claims and their equivalents.

[0101] In the description of the present application, it should be understood that the terms "front", "back", "left", "right", "center", etc. indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the scope of protection of the present application.

Claims

1. A manufacturing method of a hydraulic support oil cylinder stainless steel integrated inner liquid inlet piston rod, characterized in that, The liquid inlet piston rod comprises a rod body, a deep hole and a blocked hole, and a ball expansion high-pressure plug is installed at the blocked hole, and the engagement surface of the ball expansion high-pressure plug is used to engage with the side wall of the blocked hole; The ball expansion 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 and is in interference fit with the expansion hole to make the shell radially expand; The outer peripheral surface of the shell is provided with a tooth surface structure distributed in a ring shape and used as the engagement surface; The machining process flow comprises the following steps: Stainless steel is selected as the raw material, and the following steps are performed: sizing, induction heating, local upsetting, quenching and tempering, rough turning, finish turning, surface quenching, drilling a deep hole, drilling a through hole, milling a joint hole, sealing a blocked hole, grinding and polishing; In the quenching and tempering process, the austenitizing temperature is 1010-1050 DEG C, the austenitizing heating and holding time is radius*(1.5-1.7)min / mm, and the piston rod is vertically quenched and impacted by circulating water jet. In the deep hole drilling process, a horizontal deep hole drill is used to drill the deep hole and the blocked hole.

2. The manufacturing method of the hydraulic support oil cylinder stainless steel integrated inner 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 provided in a conical frustum shape. The engagement surface of the ball expansion high-pressure plug engages with the side wall of the blocked hole. The outer diameter of the shell is smaller than the inner diameter of the blocked hole, and the length of the shell is smaller than the depth of the blocked hole.

3. The manufacturing method of the hydraulic support oil cylinder stainless steel integrated inner liquid inlet piston rod according to claim 1, characterized in that: In the quenching and tempering process, the circulating water is sprayed from below the piston rod along the circumference and obliquely to the piston rod, and the cold water moves upward along the surface of the piston rod at a speed of 1.3-1.8 m / s.

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

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

6. The manufacturing method of a hydraulic support oil cylinder stainless steel integrated inner liquid inlet piston rod according to claim 1, characterized in that: In the local upsetting process, the initial forging temperature is 1100-1150 DEG C, the final forging temperature is 1030-1080 DEG C, and the cooling rate after forging is 0.5-1.5 DEG C / s.

7. The manufacturing method of the hydraulic support oil cylinder stainless steel integrated inner liquid inlet piston rod according to claim 1, characterized in that: In the surface quenching process, the austenitizing of the stainless steel is performed by using an induction coil, and the water spray cooling is used; the moving speed of the induction coil is 90-100 mm / min, the quenching temperature is 1020-1040 DEG C, and the water temperature is <40 DEG C. After quenching, the surface hardness is 50-60 HRC, and the depth of the hardened layer is 1.5-2 mm.

8. The manufacturing method of the hydraulic support oil cylinder stainless steel integrated inner liquid inlet piston rod according to claim 7, characterized in that: The diameter of the induction coil is 3-5 mm larger than the diameter of the workpiece.

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

10. The manufacturing method of a hydraulic support oil cylinder stainless steel integrated inner liquid inlet piston rod according to claim 1, characterized in that: In the processes of drilling the through hole, the deep hole and the blocked hole, a carbide drill bit is used.

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