Special die for medical hip joint integrated femoral stem and forging method

Abstract

According to the special mold for the medical hip joint integrated femoral stem, a femoral stem finished product is obtained through machining of the mold, machining is not needed except for subsequent machining holes of a stem body, the machining amount, difficulty and cost are reduced, the appearance shape and surface quality are good, and the mechanical property and abrasion resistance are high; the service life is long. The invention further provides a forging method of the femoral stem. The special die comprises an extrusion die, a bending die, a pre-forging die and a finish-forging die, and is characterized in that an upper die cavity of the bending die is subjected to profiling according to the shape of a workpiece needing to be bent, a head cavity does not interfere with the workpiece, the cavity keeps 2-10 mm away from the cavity, the contact positions of the upper die and the lower die of the bending die and the extrusion workpiece are switched through smooth and large smooth surfaces, and the fillet radius is R25-R70; the method comprises the steps of blanking, coating spraying treatment, heating, extrusion, bending, cooling treatment, coating spraying treatment, heating, pre-forging, cooling treatment, coating spraying treatment, heating, finish forging, cooling treatment, edge cutting, annealing and chemical milling.

Description

Technical Field

[0001] The present invention relates to the field of precision forging processing of medical orthopedic implants, and in particular to a method for manufacturing an integrated femoral stem of a hip joint forging, specifically a special mold and a forging method for an integrated femoral stem of a medical hip joint. Background Art

[0002] In medical hip replacement surgery, the femoral stem is an important implant, and its quality and performance are directly related to the patient's rehabilitation effect and the success rate of the operation. Therefore, how to manufacture a high-precision, high-performance femoral stem has always been an important issue in the field of medical device manufacturing. Hip joint forging cup-handle integrated femoral stems were widely used in the 1980s and 1990s. Most of them were produced by casting, which required a lot of machining and was difficult. The mechanical properties of the hip joint femoral stems were poor and the surface quality was poor.

[0003] Compared with the widely used acetabular cup and femoral stem which are forged separately and then assembled for use, the integrated femoral stem for hip joint is used non-assembled. Summary of the invention

[0004] In view of the above problems, the present invention provides a special mold for a medical hip joint integrated femoral stem. The finished hip joint integrated femoral stem is obtained by processing the mold. Except for the subsequent processing holes of the stem body, no further machining is required, which reduces the machining amount, difficulty and cost. The obtained hip joint integrated femoral stem has good appearance and surface quality, high mechanical properties and wear resistance, long product life, and is suitable for large quantities. For this purpose, the present invention also provides a forging method for a medical hip joint integrated femoral stem.

[0005] The technical solution is as follows: A special mold for integrated femoral stem of medical hip joint It includes an extrusion die, a bending die, a pre-forging die, and a final forging die, and is characterized in that: the upper mold cavity of the bending die is shaped according to the shape of the required bending workpiece, the head cavity does not interfere with the workpiece, and the cavity is 2mm-10mm away from the air. At the same time, the upper and lower dies of the bending die are connected to the extruded workpiece at a contact position with a smooth large round surface, and the fillet radius is R25-R70; It is further characterized by: The lower die of the pre-forging die is located at the stem of the integrated femoral stem of the hip joint and is provided with three stop blocks, two of which are located on both sides of the tail of the femoral stem, and one stop block is located at the middle back arc of the femoral stem. The three stop blocks are 10-20mm high from the bridge portion, and the stop blocks are 8mm-15mm away from the lower model cavity of the pre-forging die. A slope is used to connect the back arc of the stem and one of the two tail stop blocks, and the slope angle is 30°-45°. The transition is R-angled with a fillet radius of R3-R8. The upper die of the pre-forging die is treated with corresponding air avoidance, and the upper die of the pre-forging die avoids 2mm-10mm.

[0006] The pre-forging die is provided with a profiling groove at the position where the upper and lower cup ball heads contact the bending part. The shape of the profiling groove is similar to the shape of the part of the bending part squeezed by the upper and lower dies. The depth of the profiling groove at the bridge part of the pre-forging die is 1 mm-2 mm. The transition between the profiling groove and the pre-forging die is R-angled, and the fillet radius is R1-R1.5.

[0007] A forging method for an integrated femoral stem for medical hip joints, characterized in that it comprises the following steps: (1) Select Ti6Al4V bar for cutting; (2) Spray the blanks with paint. Before spraying the paint, clean the surface of the blanks. Use glass lubricant for the paint, keep it at 100℃-200℃ for 30 min-240 min, and control the coating thickness to 0.08 mm-0.1 mm. (3) Heating and extruding the sprayed blanks; the heating temperature is 920℃-980℃, and the cooling is carried out by air cooling at room temperature. Graphite is used for lubrication during the forming process; (4) The extruded part is bent according to the shape of the integrated femoral stem and cooled to obtain a hip joint femoral stem blank; in the bending process, the heating temperature is 900°C-950°C, and the room temperature air cooling method is used for cooling, and graphite is used for lubrication during the forming process; (5) Spray coating on the blank; before spraying the coating, clean the surface of the blank; the coating uses glass lubricant and is kept at 100℃-200℃ for 30min-240min, and the coating thickness is controlled at 0.05mm-0.07mm; (6) The sprayed blank is heated, pre-forged and cooled to obtain a pre-forged part; the heating temperature is 920°C-980°C, and the cooling is carried out by air cooling at room temperature. Graphite is used for lubrication during the forming process; (7) Spray coating on the pre-forged parts; before spraying the coating, clean the surface of the pre-forged parts; the coating uses glass lubricant, keeps the temperature at 100℃-200℃ for 30min-240min, and the coating thickness is controlled at 0.02mm-0.05mm; (8) The pre-forged parts after finishing are heated, final forged and cooled; the heating temperature is 900℃-980℃, and the cooling is carried out by air cooling at room temperature. Graphite is used for lubrication during the forming process; (9) The final forging is subjected to post-process operations such as trimming, annealing, and chemical milling to finally obtain the finished forging of the one-piece femoral stem. The flash of the final forging is cut by a laser trimming machine; the annealing temperature is 740℃-760℃, the annealing holding time is 60min-75min, and the workpiece is cooled to below 60℃ after being filled with argon gas and then taken out of the furnace and cooled to room temperature; the annealed workpiece is chemically milled using HNO3 and HF, and the chemical milling amount is 0.06mm-0.10mm.

[0008] It is further characterized in that the heating time t min =k*h max +(2-5) min, where k is the thermal conductivity of the heated part, in min / mm, h max The thickest dimension of the heated part, in mm; t max =t min +(5-15)min, the k value of Ti6Al4V material is 0.4 min / mm -0.5min / mm.

[0009] Through the mold and forging method of the present invention, Ti6Al4V rod is used as raw material, and the finished product of hip joint integrated femoral stem is obtained in sequence through the subsequent steps of blanking, spraying, extrusion, bending and blanking, spraying, pre-forging, spraying, final forging, trimming, annealing, chemical milling, etc., except for the subsequent processing holes of the stem body, no further mechanical processing is required, which reduces the machining amount, difficulty and cost, and improves the utilization rate of raw materials. The obtained hip joint integrated femoral stem has good appearance and surface quality, no pits, pits, folds, etc. on the surface, roughness Ra≤1.6, high mechanical properties and wear resistance, the mechanical properties of the forgings meet the requirements of ASTM 620, the product has a long service life, and is suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of a hip joint integrated femoral stem forging; Reference numerals: head 1, neck 2, handle 3, tail 4; Figure 2 A schematic diagram of the femoral stem and acetabular cup forgings that are currently widely used; Reference numerals: femoral stem 5, acetabular cup 6; Figure 3 It is a schematic diagram of bending forming; Reference numerals: bending upper die 7, bending lower die 8; Figure 4 It is a schematic diagram of the upper die of the bending die; Figure 5 It is a schematic diagram of the lower die of the bending die; Figure 6 This is a schematic diagram of the existing bending die; Reference numerals: bending upper die 13, bending lower die 14; Figure 7 It is a schematic diagram of pre-forging; Reference numerals: pre-forging upper die 15, pre-forging lower die 16; Figure 8 It is a schematic diagram of the lower die of the pre-forging die; Fig. 9 It is a schematic diagram of the upper die of the pre-forging die; Fig.10 This is a schematic diagram of an existing pre-forging die. DETAILED DESCRIPTION

[0011] See Figure 3 and Figure 7 The mold design of the hip joint integrated femoral stem of the present invention includes a bending mold and a pre-forging mold.

[0012] Depend on Figure 1 and Figure 2 By comparison, it is found that the head size of the one-piece femoral stem is much larger than that of the modular femoral stem 5. The existing modular femoral stem raw materials are generally selected from φ16 mm-φ24 mm, and the blanks are made through the top forging and bending processes of the flat forging machine. However, the maximum cross-sectional size of the head of the one-piece femoral stem is φ40 mm-60 mm. The top forging of small-sized bars will result in large deformation, poor surface quality of the top forging, and insufficient pre-forging. Therefore, the top forging process is changed to the extrusion process, and large-sized bars of φ40 mm-φ55 mm are selected for production. 6 is the acetabular cup.

[0013] See Figure 3 , Figure 4 , Figure 5 , Figure 6The bending die consists of two parts: the upper die 7 and the lower die 8. The convex part of the upper die 7 is processed by profiling. The contact position between the bending die and the extruded workpiece adopts smooth large smooth surface transitions 9 and 11, and the fillet radius is R25-70. The upper bending model cavity 10 and the lower bending model cavity 12 are designed to be shaped like the extruded workpiece, and the cavity avoids 2 mm-10 mm. The advantage of such a design is that the contact position between the bending die and the extruded workpiece adopts smooth large smooth surface transitions 9 and 11, which can reduce the crushing of the bending workpiece and reduce the workload of subsequent polishing and repair; at the same time, since the diameter of the ball head part of the cup-handle integrated hip joint forging is 40mm-60mm, the bending angle is 45°~55°, the upper bending model cavity 10 and the lower bending model cavity 12 are designed to be shaped like the extruded workpiece, and the cavity avoids 2mm-10mm, which can better meet the requirements of multiple specifications, multiple types, and multiple angles of the cup-handle integrated hip joint forging. Compared with the currently used bending dies 13 and 14, the newly designed bending die has no flash due to the previous process of extrusion, and there is no need to open a flash groove on the die, which greatly saves processing time.

[0014] See Figure 7 , Figure 8 , Fig. 9 The pre-forging die consists of two parts: the upper pre-forging die 15 and the lower pre-forging die 16. After numerical simulation analysis and on-site production conditions, the existing pre-forging dies 25 and 26 ( Fig.10 ) Only adding a positioning block to the bridge cannot meet the pre-forging requirements of the integrated femoral stem of the hip joint. Therefore, three stopper blocks 18, 20 and 21 are set at the handle of the lower die 16 of the pre-forging die. The stopper blocks 20 and 21 are located on both sides of the handle tail 4, and the stopper block 18 is located at the back arc in the middle of the handle. The three stopper blocks are 10mm-20mm high from the bridge, and the stopper blocks are 8mm-15mm away from the lower model cavity. The stopper blocks 18 and 20 are connected by a slope 19 with a slope angle of 30°-45°. The transition is treated with an R angle with a fillet radius of R3-R8, and the upper die of the pre-forging die is treated with corresponding air avoidance. The advantage of such a design is that during pre-forging, the bent workpiece is first subjected to stress in the cavity at the ball head 1, and the bent workpiece will rotate around the ball head. Placing the stopper blocks 20 and 21 can prevent the bent workpiece from rotating and ensure the forming of the tail of the handle body; placing the stopper block 18 can prevent the bent workpiece from generating secondary bending under the rotation of the stopper block 20 and the ball head during pre-forging, avoid the tearing of the flash on the handle body, and ensure product performance; the stopper block 18 and the stopper block 20 are connected by a slope 19, and the slope angle is 30°-45°. The slope design is adopted instead of a stopper table or no obstruction, which can avoid the setting of the stopper table causing all the metal to flow to the other side of the cavity, ensuring the reliability of the internal organizational performance of the product, and can also avoid the bending workpiece being subjected to stress at the bridge of the mold due to the lack of design obstruction at 19, causing a large amount of metal to flow out of the cavity, resulting in a waste of raw materials. The slope design at 19 is also convenient for demolding of the pre-forged workpiece. The corresponding position of the upper die 15 of the pre-forging die is avoided.

[0015] The upper die 15 ball head cavity and the lower die 16 ball head cavity of the pre-forging die are provided with profiling grooves 17 and 22. The shape of the profiling grooves is similar to the shape of the part of the bent piece squeezed by the upper and lower dies. The profiling grooves are 1 mm to 2 mm deep at the bridge of the pre-forging die. The profiling grooves and the pre-forging die are R-angled at the transition point, and the fillet radius is R1-R1.5. The advantage of such a design is that the profiling grooves 17 and 22 can fix the placement of the bent piece in advance, reduce the rotation amplitude of the bent workpiece during pre-forging, and reduce the risk of forming.

[0016] 1 is the head, 2 is the neck, 3 is the handle, 4 is the tail, 23 is the clearance of the material block of the lower die 21, and 24 is the clearance of the lower die 19; A forging method for an integrated femoral stem for medical hip joints, characterized in that it comprises the following steps: (1) Select Ti6Al4V bar for cutting; (2) Spray the blanks with paint. Before spraying the paint, clean the surface of the blanks. Use glass lubricant for the paint, keep it at 100℃-200℃ for 30 min-240 min, and control the coating thickness at 0.08 mm-0.1 mm. The best insulation temperature is 150℃, the best insulation time is 135 min, and the best coating thickness is controlled at 0.09 mm. (3) Heat and extrude the sprayed blanks; the heating temperature is 920℃-980℃, the optimal heating temperature is 950℃, and the blanks are cooled by air cooling at room temperature. Graphite is used for lubrication during the forming process; (4) The extruded part is bent according to the shape of the one-piece femoral stem and cooled to obtain a hip joint femoral stem blank; in the bending process, the heating temperature is 900°C-950°C, the optimal heating temperature is 925°C, and the room temperature air cooling method is used for cooling, and graphite is used for lubrication during the forming process; (5) Spraying the coating on the blank; before spraying the coating, clean the surface of the blank; the coating uses glass lubricant, keeps the temperature at 100℃-200℃ for 30min-240min, and the coating thickness is controlled at 0.05mm-0.07mm. The optimal insulation temperature is 150℃, the optimal insulation time is 135min, and the optimal coating thickness is controlled at 0.06mm; (6) The sprayed blank is heated, pre-forged and cooled to obtain a pre-forged part; the heating temperature is 920°C-980°C, the optimal heating temperature is 950°C, and the blank is cooled by air cooling at room temperature. Graphite is used for lubrication during the forming process; (7) Spray coating on the pre-forged parts; before spraying the coating, clean the surface of the pre-forged parts; the coating uses glass lubricant, keeps warm at 100℃-200℃ for 30min-240min, and the coating thickness is controlled at 0.02mm-0.05mm; the optimal insulation temperature is 150℃, the optimal insulation time is 135min, and the optimal coating thickness is controlled at 0.035mm; (8) The pre-forged parts after finishing are heated, final forged and cooled; the heating temperature is 900℃-980℃, the optimal heating temperature is 940℃, and the cooling is carried out by air cooling at room temperature. Graphite is used for lubrication during the forming process; (9) The final forging is subjected to post-process operations such as trimming, annealing, and chemical milling to finally obtain the finished forging of the one-piece femoral stem. The flash of the final forging is cut by a laser trimming machine; the annealing temperature is 740℃-760℃, the optimal annealing temperature is 750℃, the annealing holding time is 60min-75min, and the optimal annealing holding time is 67.5min. After cooling to below 60℃ with argon gas, it is taken out of the furnace and cooled to room temperature; HNO3 and HF are used to chemically mill the annealed workpiece, and the chemical milling amount is 0.06mm-0.10mm, and the optimal chemical milling amount is 0.08mm.

[0017] In this case, the heating time t min =k*h max +(2-5) min, where k is the thermal conductivity of the heated part, in min / mm, h max The thickest dimension of the heated part, in mm; t max =t min +(5-15)min, the k value of Ti6Al4V material is 0.4 min / mm -0.5min / mm.

[0018] The forging process of the present invention is further described in detail below through examples. It is necessary to point out that the examples are only used to further illustrate the present invention and cannot be understood as any limitation on the scope of protection of the present invention. Technical personnel skilled in the art can make some non-essential improvements and adjustments to implement the present invention according to the above content, but such implementation should still fall within the scope of protection of the present invention.

[0019] In this example, the forging process of the medical orthopedic implant hip joint integrated femoral stem based on Ti6Al4V material is operated according to the forging process described above: 1) Cutting: Select Ti6Al4V bars of appropriate specifications according to the size of the integrated hip stem and the maximum cross-sectional area of ​​the head; 2) Spray coating: clean the surface of the unloaded parts to ensure that there are no pollutants on the surface; keep the temperature at 150℃ for 80 minutes, and the coating thickness is 0.086mm; 3) Extrusion: After spraying, the blank is heated, extruded and cooled to obtain an extruded part that meets the length of the one-piece femoral stem. The heating temperature is 950°C. The cooling is carried out by air cooling at room temperature, and graphite is used for lubrication during the forming process. 4) Bending: The extruded part is bent according to the shape of the integrated femoral stem and cooled to obtain a hip joint femoral stem blank, wherein the heating temperature is 900°C. The blank is cooled by air cooling at room temperature, and graphite is used for lubrication during the forming process; 5) Spray coating: clean the surface of the bent part to ensure that there are no pollutants on the surface; keep it at 150℃ for 76 minutes, and the coating thickness is 0.062mm; 6) Pre-forging: The sprayed blank is heated, pre-forged and cooled to obtain a pre-forged part, wherein the heating temperature is 950°C. The blank is cooled by air cooling at room temperature, and graphite is used for lubrication during the forming process; 7) Spray coating: clean the pre-forging surface to ensure that there are no pollutants on the surface; keep it at 150℃ for 94 minutes, and the coating thickness is 0.047mm; 8) Final forging: The sprayed pre-forged parts are heated, final forged and cooled to obtain the final forged products. The heating temperature is 900℃. The cooling is carried out by air cooling at room temperature, and graphite is used for lubrication during the forming process; 9) Use laser trimming machine to cut the flash of the final forging; the annealing temperature is 750℃, the annealing holding time is 62min, and the workpiece is cooled to below 60℃ after being filled with argon gas and then cooled to room temperature; use HNO3 and HF to chemically mill the annealed workpiece, and the milling amount is 0.072mm; In steps 3), 4), 6) and 8), the shortest heating time t min =k*h max +(2-5) min, where k is the thermal conductivity of the heated part, in min / mm, h max The thickest dimension of the heated part, in mm; t max =t min + (5-15) min. The k value of Ti6Al4V material is 0.5 min / mm.

[0020] The finished forgings are surface treated to obtain the finished hip joint integrated femoral stem. Except for the subsequent processing holes of the stem body, no further machining is required, which reduces the machining volume, difficulty and cost. The obtained hip joint integrated femoral stem has good appearance and surface quality, high mechanical properties and wear resistance, long product life, and is suitable for large quantities. The following table shows the results of mechanical property tests for three batches with the same process flow.

Claims

1. A special mold for a medical hip joint integrated femoral stem, comprising an extrusion die, a bending die, a pre-forging die, and a final forging die, characterized in that: The upper mold cavity of the bending die is shaped according to the shape of the required bending workpiece, the head cavity does not interfere with the workpiece, and the cavity is free of 2mm-10mm. At the same time, the contact position between the upper and lower dies of the bending die and the extruded workpiece adopts a smooth large smooth surface transition, and the fillet radius is R25-R70.

2. A special mold for a medical hip joint integrated femoral stem according to claim 1, characterized in that The lower die of the pre-forging die is located at the stem of the integrated femoral stem of the hip joint and is provided with three stop blocks, two of which are located on both sides of the tail of the femoral stem, and the last stop block is located at the middle back arc of the femoral stem. The stop block is 10-20mm high from the bridge portion, and the stop block is 8mm-15mm away from the lower model cavity of the pre-forging die. A slope is used to connect the back arc of the stem and one of the two tail stop blocks, and the slope angle is 30°-45°. The transition is R-angled with a fillet radius of R3-R8. The upper die of the pre-forging die is treated with corresponding air avoidance, and the upper die of the pre-forging die avoids 2mm-10mm.

3. A special mold for a medical hip joint integrated femoral stem according to claim 2, characterized in that The pre-forging die is provided with a profiling groove at the position where the upper and lower cup ball heads contact the bending part. The shape of the profiling groove is similar to the shape of the part of the bending part squeezed by the upper and lower dies. The profiling groove is 1 mm-2 mm deep at the bridge of the pre-forging die. The transition between the profiling groove and the pre-forging die is R-angled, and the fillet radius is R1-R1.

5.

4. A forging method for an integrated femoral stem for medical hip joint, characterized in that: It includes the following steps: (1) Select Ti6Al4V bar for cutting; (2) Spray coating on the blanks; Before spraying the paint, clean the surface of the unloaded parts; The coating uses glass lubricant and is kept at 100℃-200℃ for 30 min-240 min. The coating thickness is controlled at 0.08 mm-0.1 mm. (3) Heating and extruding the sprayed blanks; the heating temperature is 920℃-980℃, and the cooling is carried out by air cooling at room temperature. Graphite is used for lubrication during the forming process; (4) The extruded part is bent according to the shape of the integrated femoral stem and cooled to obtain a hip joint femoral stem blank; during the extrusion process, the heating temperature is 900°C-950°C, and the room temperature air cooling method is used for cooling, and graphite is used for lubrication during the forming process; (5) spraying the blank with paint; Before spraying the paint, clean the surface of the blank; The coating uses glass lubricant and is kept at 100℃-200℃ for 30min-240min. The coating thickness is controlled at 0.05mm-0.07mm. (6) The sprayed blank is heated, pre-forged and cooled to obtain a pre-forged part; the heating temperature is 920°C-980°C, and the cooling is carried out by air cooling at room temperature. Graphite is used for lubrication during the forming process; (7) Spray coating on pre-forged parts; Before spraying the paint, clean the surface of the pre-forging; The coating uses glass lubricant and is kept at 100℃-200℃ for 30min-240min. The coating thickness is controlled at 0.02mm-0.05mm. (8) The pre-forged parts after finishing are heated, final forged and cooled; the heating temperature is 900℃-980℃, and the cooling is carried out by air cooling at room temperature. Graphite is used for lubrication during the forming process; (9) The final forging is subjected to post-process operations such as trimming, annealing, and chemical milling to finally obtain the finished forging of the one-piece femoral stem. The flash of the final forging is cut by a laser trimming machine; the annealing temperature is 740℃-760℃, the annealing holding time is 60min-75min, and the workpiece is cooled to below 60℃ after being filled with argon gas and then taken out of the furnace and cooled to room temperature; the annealed workpiece is chemically milled using HNO3 and HF, and the chemical milling amount is 0.06mm-0.10mm.

5. A forging method for an integrated femoral stem for medical hip joint according to claim 4, characterized in that: Heating time t min =k*h max +(2-5) min, where k is the thermal conductivity of the heated part, in min / mm, h max The thickest dimension of the heated part, in mm; t max =t min +(5-15)min, the k value of Ti6Al4V material is 0.4-0.5min / mm.

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