KR20190134047A - Method for producing cobalt-chromium-molybdenum artificial joint using vacuum precision casting and HIP process - Google Patents

Abstract

The present invention relates to a method for producing a cobalt-chromium-molybdenum artificial joint using vacuum precision casting and HIP process. More particularly, the present invention relates to a method for producing a cobalt-chromium-molybdenum artificial joint using vacuum precision casting and HIP process, the method capable of commercializing an artificial knee joint whose quality variation is reduced to ensure quality reliability. The present invention has the advantage that the commercialization of various artificial joints is possible.

Description

Method for producing cobalt-chromium-molybdenum artificial joint using vacuum precision casting and HIP process

The present invention relates to a cobalt-chromium-molybdenum-based artificial joint manufacturing method using vacuum precision casting and HIP process, more specifically vacuum precision based on orthopedic Co-Cr-Mo alloy having excellent biocompatibility as a basic composition (Centrifugal) Optimized aftertreatment process conditions specialized in castings and castings, and by securing the homogeneity of microstructures through securing the microstructure control technology of castings, finally, the variation of physical properties is finally reduced The present invention relates to a cobalt-chromium-molybdenum artificial joint manufacturing method using vacuum precision casting and HIP process that can commercialize a knee joint.

Artificial joints are a representative joint replacement product for patients with advanced degenerative arthritis, and are expected to expand rapidly due to the aging of the population and the increase in the degenerative arthritis of the obese population.

The global market size of artificial joints is estimated to be about $ 14.4 billion in 2014 and about $ 11.8 billion in 2021, and the domestic market size is KRW111.3 billion in 2014, of which the knee joints account for 64% of the total market.

Currently, some artificial joints are being localized, but there are only two domestic artificial joint manufacturers, and most of the artificial joints have high import dependence (91%) depending on imports. Joint products are the second largest importers.

In order to commercialize artificial joints, optimal design and analysis of artificial knee joints through anatomical considerations, precision casting and post-treatment processes for uniform casting quality, and production through surface precision machining / polishing processes are required.

Despite the recent surge in demand, localization is difficult because of lack of experience in precision casting of medical products using cobalt-chromium-based alloys, and lack of heat treatment technology for securing a certain quality of medical precision castings.

Co-28Cr-6Mo alloy (ASTM F75) is the most commonly used casting alloy for artificial knee joints. As it is difficult to cut, it is manufactured as an implant through precision casting method. Co-Cr-Mo casting alloys can minimize mechanical ion and metal ion dissolution, such as excellent biocompatibility, tensile strength, elongation and wear resistance, which are not cytotoxic and do not react with biological tissues when inserted into the body for a long time. Has excellent corrosion resistance.

However, this alloy necessarily forms defects such as porosity or solidification shrinkage, segregation of alloying elements, and uneven carbides during casting, and if it cannot be controlled through post-treatment such as proper heat treatment, ductility and fatigue Although it is known to reduce mechanical properties such as strength, in Korea, research on post-treatment process technology for micropore control and homogenization of microstructures is very poor, and thus the quality characteristics of cast products are severely deformed and commercialization is limited.

Casting defects (solidification shrinkage, pores) generated during casting are difficult to obtain a healthy casting due to the formation of the inside of the casting, and during the solidification, process carbide having M23C6 composition is formed along the grain boundary due to the reaction of chromium and solid solution carbon. This acts as a point of breakdown of the material, which is the primary material against external stress, along with coagulation shrinkage and porosity, which reduces the quality uniformity of the artificial joint. In particular, the residual pores that are not removed are exposed to the surface after surface polishing, resulting in a decrease in product yield and a serious adverse effect on wear characteristics.

Castings can improve ductility, tensile strength and average fatigue failure through heat treatment annealing, but the fatigue fracture strength is dispersed due to residual pores that are difficult to remove through heat treatment alone. There is a limit in improving product yield and predictable fatigue failure alone.

Therefore, in order to produce products with excellent fatigue failure characteristics and consistency of quality characteristics, we have secured post-treatment process technology (Hot Isostatic Pressing (HIP), Solution Annealing (SA) process, etc.) specialized for the Co-Cr-Mo alloy castings. Is necessary.

Republic of Korea Patent Publication 10-2008-0107554 Republic of Korea Patent Publication 10-2016-0078583 Republic of Korea Patent Registration 10-1184905

The present invention is to solve the conventional problems as described above, a series of post-treatment process conditions specialized in vacuum precision (centrifugal) casting and castings with a basic composition of orthopedic Co-Cr-Mo alloy with excellent biocompatibility By optimizing (temperature, time, pressure, etc.) and securing the homogeneity of microstructures through securing the microstructure control technology of the cast product, artificial knee joints with quality reliability can be commercialized by finally reducing the physical property deviation. An object of the present invention is to provide a cobalt-chromium-molybdenum artificial joint manufacturing method using vacuum precision casting and HIP process.

In addition, the present invention eliminates pores in the microstructure and uniformity of the microstructure, while maintaining the hardness and wear resistance of the cast product, while maintaining the hardness and wear resistance cobalt-chromium- using vacuum precision casting and HIP process that can be developed The purpose is to provide a molybdenum artificial joint manufacturing method.

Cobalt-chromium-molybdenum-based artificial joint manufacturing method using the vacuum precision casting and HIP process according to the present invention for achieving the above object comprises a mold manufacturing step of manufacturing a mold using wax for casting the artificial joint; A coating layer forming step of forming a coating layer on the surface of the mold prepared in the mold manufacturing step; A heating step of heating the mold to form a cavity in the mold to melt wax in the coating layer and discharge the wax to the outside; An alloy casting step of injecting an artificial joint casting alloy into a cavity formed in the mold through the heating step; A coating layer removing step of removing the coating layer after the alloy injected in the alloy casting step is hardened; A first heat treatment step of treating the cast product from which the coating layer has been removed in the coating layer removing step by hot isostatic pressing; And a second heat treatment step of treating the cast product treated in the first heat treatment step by a solid solution heat treatment method.

The casting alloy is composed of a cobalt-chromium-molybdenum-based alloy, and is preferably characterized in that Co28Cr6Mo.

The first heat treatment step is characterized in that after the heat treatment at a pressure of 1000 bar or more for 1 to 8 hours at a temperature of 1170 ℃ ~ 1225 ℃, it is cooled to 5 ℃ ~ 13 ℃ per minute.

The second heat treatment step is characterized by rapidly cooling using Ar gas after heat treatment in a vacuum atmosphere for 3 to 4 hours at a temperature of 1170 ℃ ~ 1230 ℃.

The coating layer includes a first coating layer formed on the surface of the mold to a predetermined thickness, and a second coating layer formed on the surface of the first coating layer to a predetermined thickness, wherein the first coating layer is a zirconia or alumina-based fireproof material. Characterized in that formed.

The cobalt-chromium-molybdenum artificial joint manufacturing method using vacuum precision casting and HIP process according to the present invention is a technical know-how for the post-treatment (HIP, heat treatment) process is the most important process for determining the mechanical and chemical properties / characteristics of the cast product It is possible to secure, as well as the localization of high-quality cast material of Co-Cr-Mo-based alloy, as well as the source manufacturing technology applicable to a variety of bio-implants, there is an advantage that can be commercialized a variety of artificial joints.

Post-treatment process technologies such as HIP (Hot Isostatic Pressing), SA (Solution Annealing), etc., included in the artificial joint manufacturing method according to the present invention, as well as Co-Cr-Mo alloys, Ti-based main alloys, metal 3D printing implants It can be used for manufacturing, there is an advantage that can be applied to the coating of bioabsorbable material, porous material.

It is expected that HIP and Solution Annealing technologies will become an essential process in the MIM (Metal Injection Molding) and CIM (Metal Injection Molding) processes using metal and ceramic powder materials. It can also be extended to other industries.

1 to 9 are views showing a cobalt-chromium-molybdenum-based artificial joint manufacturing method using vacuum precision casting and HIP process according to the present invention.
10 is a photograph of the surface of the cast product after the alloy casting step of the cobalt-chromium-molybdenum artificial joint manufacturing method using the vacuum precision casting and HIP process according to the present invention.
11 is a photograph of the interior of the cast product after the alloy casting step of the cobalt-chromium-molybdenum artificial joint manufacturing method using the vacuum precision casting and HIP process according to the present invention.
12 is a photograph of the surface of the cast product after the first heat treatment step of the cobalt-chromium-molybdenum artificial joint manufacturing method using vacuum precision casting and HIP process according to the present invention.
Figure 13 is a photograph of the interior of the cast product after the first heat treatment step of the cobalt-chromium-molybdenum artificial joint manufacturing method using vacuum precision casting and HIP process according to the present invention.
14 is a photograph of the surface of the cast product after the second heat treatment step of the cobalt-chromium-molybdenum artificial joint manufacturing method using vacuum precision casting and HIP process according to the present invention.
Figure 15 is a photograph of the interior of the cast product after the second heat treatment step of the cobalt-chromium-molybdenum artificial joint manufacturing method using the vacuum precision casting and HIP process according to the present invention.

Hereinafter, a cobalt-chromium-molybdenum artificial joint manufacturing method using vacuum precision casting and HIP process according to a preferred embodiment of the present invention with reference to the accompanying drawings will be described in detail.

1 to 12 show a cobalt-chromium-molybdenum artificial joint manufacturing method using vacuum precision casting and HIP process according to the present invention. 1 to 12, the cobalt-chromium-molybdenum artificial joint manufacturing method using the vacuum precision casting and HIP process according to the present invention is a mold manufacturing step (S100), coating layer forming step (S200), and heating step S300, the alloy casting step S400, the coating layer removing step S500, the first heat treatment step S600, and the second heat treatment step S700.

As shown in FIG. 1, the mold manufacturing step (S100) manufactures a mold using wax for casting an artificial joint, and manufactures the first mold 11 and the second mold 12.

The first mold 11 is formed by injecting wax W into the die 10 and is formed to have a shape and size corresponding to that of the artificial joint. The second mold 12 melts and discharges the wax W in the heating step S300 to be described later, and then melts the artificial mold with a cavity in the first mold 11 formed by melting and discharging the wax W. An alloy injection passage is formed in the longitudinal direction therein to inject the alloy 31 therein.

In addition, in the mold manufacturing step (S100), as shown in FIG. 2, not only the manufacture of the first mold 11 and the second mold 12, but also a plurality of manufactured first molds 11 are applied to the second mold 12. The process of assembling and coupling apart from each other is included. At this time, since the first mold 11 and the second mold 12 are made of wax W, a portion of the second mold 12 to which the first mold 11 is to be coupled is melted to form a first mold ( 11) can be joined by bonding.

After the mold manufacturing step (S100), the first mold 11 and the second mold 12 are first washed with an industrial detergent, alcohol, etc., and secondly washed with alcohol and hot water.

Coating layer forming step (S200) forms a coating layer on the surface of the mold manufactured in the mold manufacturing step (S100) as shown in FIG. Coating layer formed in the coating layer forming step (S200) is the first coating layer 21 is formed to a predetermined thickness on the surface of the mold, and the second coating layer 22 is formed to a predetermined thickness on the surface of the first coating layer 21. It includes.

Since the first coating layer 21 is in direct contact with the hot molten metal injected into the cavity in the alloy casting step S400 after the heating step S300 described later, that is, the molten alloy 31, the reactivity with the molten metal 31 is considered. Therefore, it is preferable to be formed of a zirconia or alumina-based refractory material.

The first coating layer 21 is formed by depositing a slurry (colloidal silica + surfactant + zircon flower + antifoaming agent) on the first mold 11 and the second mold 12 having been cleaned, and then removing air bubbles from the surface of the air. can do. When the first coating layer 21 is divided into primary and secondary, it is naturally dried for at least 5 hours after the primary coating, and is naturally dried for at least 16 hours after the secondary coating.

In addition, prior to the first coating of the first coating layer 21, it is preferable to reduce the viscosity of the slurry to coat the slot portions and the hole portions of the first mold 11 and the second mold 12 by air spraying.

On the other hand, the second coating layer 22 is the first to sixth coating process is carried out, the first to fifth coating process is coated with a refractory coating sequentially REMASIL48 and RG30, the fifth coating is Upon completion, the mixture is immersed in the slurry, coated with sixth layers, and then dried naturally. After that, put in the air dryer and forced to dry for more than 12 hours.

The second coating layer 22 is preferably applied to a material excellent in permeability and heat transfer to prevent trapping of gas.

The heating step (S300) is a step of dissolving wax in the coating layer by heating the mold to form a cavity in the first mold 11 and the second mold 12 as shown in FIG. In the first mold (11) and the second mold (12) formed of wax is melted and removed, both inside the coating layer surrounding the first mold (11) and the second mold (12) molten alloy for the formation of artificial joints ( The cavity is formed so that 31) can be injected. Heating step (S300) is carried out for 20 (± 5) minutes at a temperature of 145 ℃ (± 5) under a steam pressure of 5 ~ 7kg.

Alloy casting step (S400) is a step of injecting the artificial alloy casting molten alloy 31 as shown in Figure 5, the cavity formed in the mold (11, 12) through the heating step (S300), gravity of the molten metal The vacuum precision casting method which is the pressure casting method by the action, and the vacuum centrifugal casting method which is the pressure casting method by the centrifugal force can be applied.

During precision casting, the microstructure (grain size, porosity, segregation, etc.) of the as-cast cast 30 is greatly changed depending on the process conditions such as mold temperature, melt temperature, injection time, and the like. affect. Therefore, it is desirable to establish an optimal casting process and to analyze the microstructure characteristics of the as-cast casting 30 to perform post-processing process optimization.

The casting alloy 31 used in the alloy casting step S400 of FIG. 5 is made of a cobalt-chromium-molybdenum-based alloy. In the present embodiment, the casting alloy 31 applies Co28Cr6Mo (ASTM F75) approved for medical use.

Coating layer removal step (S500) is a step of forming a cast product 30 consisting of a casting alloy by crushing and removing the coating layer as shown in Figure 6 after the alloy injected in the alloy casting step (S400) is completely hardened, The coating layer is crushed to remove the coating layer.

After the coating layer removal step, as shown in Figure 7 and 8 is injected into the mold 2 and the hardened portion and injected into the mold 1 to produce a cast product by cutting the hardened portion.

The first heat treatment step (S600) is a step of treating the cast product 30 from which the coating layer has been removed and cut in the coating layer removing step (S500) by hot isostatic pressing, that is, by HIP (Hot Isostatic Pressing) method, 1170 ° C. After heat treatment at a pressure of 1000 bar or more for 1 to 8 hours at a temperature of ~ 1225 ℃, it is cooled to 5 ℃ ~ 13 ℃.

HIP is fired by high temperature and high pressure (isotropic pressurization) when HIP processing the casting by raising the pressure of the chamber by heating in the high pressure containment container and applying high temperature / high pressure to the material in all directions using inert Ar gas. Deformation and diffusion bonding improve the removal of internal micropore and the isotropy of grains. HIP has been proven to be effective in castings in various industries. Especially, it is effective in removing micropores and homogenizing crystal grains, but it is necessary to establish fine process conditions according to the type and composition of alloy.

The eutectic transformation temperature of cobalt main alloy is around 1235 ° C. When the alloy is heated above this temperature, local areas where process segregation exists, such as dendritic and grain boundaries, are re-dissolved and then cooled by sigma, gamma, M23C6. Phases that degrade mechanical properties, such as carbides, are formed, which greatly reduce ductility as well as reduce corrosion resistance. Therefore, the HIP process temperature is set to be less than the Eutetic transformation temperature, the process holding time is secured by the time that the internal pores and precipitates can be sufficiently diffused, it is desirable to derive the most ideal HIP method.

The second heat treatment step S700 is configured to include a 2-1 treatment step and a 2-2 treatment step.

The 2-1th treatment step is a step of treating the cast product treated in the first heat treatment step S600 by the solid solution heat treatment method, that is, SA (Solution Annealing) method, for 3 to 4 hours at a temperature of 1170 ° C to 1230 ° C. After heat treatment in a vacuum atmosphere, and then rapidly cooled using Ar gas.

In addition, the second step 2-2 is a process of performing the precipitation hardening heat treatment, which is a heat treatment process, and is rapidly cooled using Ar gas after heat treatment in a vacuum atmosphere at a temperature of 780 ° C. to 830 ° C. for 3 to 4 hours.

In the heat treatment process performed in the second step 2-2, precipitates are formed in the stabilized microstructure to improve the physical properties of the metal, thereby confirming the hardness (improved from 25 HRc to 36 HRc) and strength (improved from 680 MPa to 870 MPa). Can be.

SA (Solution annealing) is carried out in a vacuum atmosphere by vacuum heat treatment, and is carried out in a vacuum or high temperature atmosphere to remove segregation due to non-uniformity of local chemical composition and difference in solidification rate of the cast product, and is generally a homogenization heat treatment furnace. Known. In particular, in order to maintain the homogenized microstructure at high temperature, rapid cooling is applied.

The general process variables of SA are similar to HIP, but the ductility and fracture strength can be improved while maintaining the tensile strength through the homogenization of microstructures that are not homogenized through the HIP process and the refinement and homogenization of segregation deposited at grain boundaries.

Through SA, the Cr, Mo, and C atoms segregated in the grain boundary and resin phase near the eutectic process temperature are dissolved and dissolved, non-equilibrium solidification during rapid quenching, and some fine segregation uniformly in the matirx. Will be distributed.

Longer SA process times allow full reassembly of segregation, but grain coarsening reduces mechanical properties. Therefore, it is necessary to select an appropriate process time.

The amount and shape of precipitated segregation is determined by the cooling rate after SA. The faster the cooling rate, the more precipitated segregation is fine and evenly distributed within the matrix rather than grain boundaries. Therefore, it is possible to control the microstructure by controlling the cooling rate, thereby controlling the physical properties of the casting.

10 and 11 are surface and fine for pore analysis of the cast product 30 immediately after the alloy casting step (S400) of the cobalt-chromium-molybdenum artificial joint manufacturing method using the vacuum precision casting and HIP process according to the present invention 12 shows a photograph taken inside for tissue analysis, and FIGS. 12 and 13 after the first heat treatment step (S600) of the cobalt-chromium-molybdenum artificial joint manufacturing method using vacuum precision casting and HIP process according to the present invention. Photographs are taken of the surface and the microstructure analysis for pore analysis of the cast product 30 of Figure 14 and Figure 15 shows the cobalt-chromium-molybdenum using the vacuum precision casting and HIP process according to the present invention Photographs showing the inside of the surface and the microstructure analysis for pore analysis of the cast product 30 after the second heat treatment step (S700) of the artificial joint manufacturing method is shown.

10 and 11, defects due to internal pores appear on the inner surface of the alloy ingot before applying the cobalt-chromium-molybdenum artificial joint manufacturing method using vacuum precision casting and HIP process according to the present invention, In the cast structure, the physical properties are deteriorated and the uniform properties are insignificant.

On the other hand, referring to Figures 12 and 13 after the first heat treatment step (S600) () of the cobalt-chromium-molybdenum artificial joint manufacturing method using the vacuum precision casting and HIP process according to the present invention that the internal pores completely disappeared It can be confirmed, it can be confirmed that the microstructure is broken down and refined.

In addition, referring to Figure 14 and 15, after the second heat treatment step (S700) of the cobalt-chromium-molybdenum artificial joint manufacturing method using the vacuum precision casting and HIP process according to the present invention confirmed that the cast structure is homogenized This indicates that the physical properties are improved.

The cobalt-chromium-molybdenum-based artificial joint manufacturing method using the vacuum precision casting and the HIP process according to the present invention described above has been described with reference to the accompanying drawings, which are merely exemplary, and have ordinary knowledge in the art. It will be understood that various modifications and equivalent other embodiments are possible from this.

Therefore, the true technical protection scope of the present invention should be defined only by the technical spirit of the appended claims.

10: formwork
11: 1st frame
12: Frame 2
21: first coating layer
22: second coating layer
30: casting products
31: molten alloy
S100: mold manufacturing stage
S200: coating layer forming step
S300: heating step
S400: Alloy casting step
S500: coating layer removal step
S600: first heat treatment step
S700: second heat treatment step

Claims (5)

A mold manufacturing step of manufacturing a mold using wax for casting artificial joints;
A coating layer forming step of forming a coating layer on the surface of the mold prepared in the mold manufacturing step;
A heating step of heating the mold to form a cavity in the mold to melt wax in the coating layer and discharge the wax to the outside;
An alloy casting step of injecting an artificial joint casting alloy into a cavity formed in the mold through the heating step;
A coating layer removing step of removing the coating layer after the alloy injected in the alloy casting step is hardened;
A first heat treatment step of treating the cast product from which the coating layer has been removed in the coating layer removing step by hot isostatic pressing;
And a second heat treatment step of treating the cast product treated in the first heat treatment step by a solid solution heat treatment method. The method of manufacturing a cobalt-chromium-molybdenum artificial joint using vacuum precision casting and a HIP process.
The method of claim 1,
The casting alloy is a cobalt-chromium-molybdenum-based alloy, characterized in that the cobalt-chromium-molybdenum artificial joint manufacturing method using a vacuum precision casting and HIP process.
The method of claim 2,
The first heat treatment step is heat treatment at a pressure of 1000 bar or more for 1 to 8 hours at a temperature of 1170 ℃ ~ 1225 ℃, and then cooled to 5 ℃ ~ 13 ℃ per minute cobalt-chromium using vacuum precision casting and HIP process -Molybdenum artificial joint manufacturing method.
The method of claim 2,
The second heat treatment step is a cobalt-chromium-molybdenum using a vacuum precision casting and HIP process characterized in that the heat treatment in a vacuum atmosphere for 3 to 4 hours at a temperature of 1170 ℃ ~ 1230 ℃ rapidly cooled using Ar gas Method of manufacturing artificial joints.
The method of claim 1,
The coating layer includes a first coating layer formed to a predetermined thickness on the surface of the mold, and a second coating layer formed to a predetermined thickness on the surface of the first coating layer,
The first coating layer is a cobalt-chromium-molybdenum artificial joint manufacturing method using a vacuum precision casting and HIP process, characterized in that formed of a zirconia or alumina-based refractory material.

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