Metal powder injection molding optimization method for 17-4PH stainless steel SIM card holder blank

Abstract

The invention discloses a metal powder injection molding optimization method for a 17-4PH stainless steel SIM card holder blank, which comprises the following steps: feeding a feed composed of 17-4PH stainless steel metal powder and an optimization binder into an injection machine, the optimization binder being composed of 90-99% by mass of polyformaldehyde and 1-10% by mass of carnauba wax; the 17-4PH stainless steel SIM card holder blank is obtained by adopting Box-Behnken response surface analysis and carrying out metal powder injection molding under the conditions that the injection pressure is 100-110 MPa, the injection temperature is 190-200 DEG C, the mold temperature is 70-90 DEG C and the injection speed is 10-60 mm / s and the pressure holding time is 1-10 seconds through shear stress minimization optimization process parameters, so that the molding defects can be reduced, the mold testing cost can be remarkably reduced, the production efficiency can be improved, and the production cost can be reduced. And the mechanical property and the surface quality of a metal powder injection molding product are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of metal powder injection molding, and in particular relates to a metal powder injection molding optimization method for a 17-4PH stainless steel SIM card holder blank. Background Art

[0002] Metal Injection Molding (MIM) is a process that heats and injects a mixture of metal powder and a binder into a mold. It is widely used to produce complex, precisely sized metal parts. Combining the efficiency of plastic injection molding with the high precision of metalworking, MIM is particularly well-suited for the mass production of small, high-precision metal parts, such as 17-4PH stainless steel trays, medical device components, and electronic components.

[0003] In the metal powder injection molding process, traditional binders are usually materials such as polyoxymethylene. Although they have good molding properties, they are prone to problems such as poor fluidity and incomplete filling during the injection molding process. Under high shear forces, the final product may have defects such as under-injection and deformation. Although the molding quality can be improved to a certain extent by optimizing process parameters such as injection temperature, injection pressure, and mold temperature, existing methods are still unable to completely solve the problems caused by the poor fluidity of the binder. In addition, the interaction between complex process parameters means that traditional optimization methods often cannot achieve the optimal effect, resulting in high mold trial costs and unstable quality of molded parts. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to propose a metal powder injection molding optimization method for 17-4PH stainless steel SIM card holder blanks. Aiming at the defects of the metal powder injection molding process of 17-4PH stainless steel SIM card holder blanks, by introducing a binder for metal powder injection molding based on polyformaldehyde and carnauba wax, combined with the injection molding process parameters optimized by computer simulation, the fluidity of the binder and the coupling of the metal powder and the binder are effectively improved, thereby improving the compatibility of the metal powder and the binder. It can not only reduce molding defects, but also significantly reduce the trial mold cost and improve production efficiency, thereby achieving the mechanical properties and surface quality of metal powder injection molded products, and solving the molding defect problem caused by poor binder fluidity and shear heating in the traditional MIM process.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A metal powder injection molding optimization method for a 17-4PH stainless steel SIM card holder blank comprises the following steps:

[0007] (1) feeding a feed material into an injection molding machine, wherein the feed material comprises 17-4PH stainless steel metal powder and an optimized binder, wherein the optimized binder is composed of 90% to 99% polyoxymethylene and 1% to 10% carnauba wax by mass percentage;

[0008] (2) The Box-Behnken response surface analysis was used to construct a response surface model of shear stress and injection pressure, injection temperature, and mold temperature. The process parameters were optimized by minimizing the shear stress, and the optimized process parameters for metal powder injection molding of 17-4PH stainless steel SIM card holder blanks were obtained, including injection pressure of 100-110 MPa, injection temperature of 190-200 °C, and mold temperature of 70-90 °C.

[0009] (3) Metal powder injection molding is performed under the optimized process parameters of metal powder injection molding set in step (2), with an injection speed of 10 to 60 mm / s and a holding time of 1 to 10 s to obtain a 17-4PH stainless steel SIM card holder blank.

[0010] Preferably, in step (1), the polyoxymethylene is at least one of homopolyoxymethylene and copolymer polyoxymethylene.

[0011] Preferably, in step (1), the mass content of the 17-4PH stainless steel powder in the feed is 60% to 70%, and the mass content of the optimized binder is 30% to 40%.

[0012] Preferably, in step (1), the optimized adhesive consists of 95% polyoxymethylene and 5% carnauba wax by mass percentage.

[0013] Preferably, in step (1), the method for preparing the feed comprises:

[0014] (a) Batching: Weigh 17-4PH stainless steel metal powder and optimized binder and mix according to the ratio;

[0015] (b) Granulation: 17-4PH stainless steel metal powder and optimized binder are added into an internal mixer and mixed. After mixing, the mixture is extruded and pelletized to obtain the product.

[0016] More preferably, in step (b), the 17-4PH stainless steel metal powder and the optimized binder are mixed at 165-220° C. for 0.5-2 hours.

[0017] Preferably, in step (2), the injection pressure is 105 MPa, the injection temperature is 195° C., and the mold temperature is 80° C. The shear stress of the molded part is minimized, the filling effect is optimal, and the molding quality is significantly improved.

[0018] Preferably, in step (3), the injection speed is 20 to 50 mm / s, and the holding time is 2 to 5 s.

[0019] The present invention starts from both material modification and process optimization. First, carnauba wax is introduced into the binder as a modifying component, and its excellent fluidity and low shear viscosity characteristics are used to improve the overall rheological properties of the polyformaldehyde-based binder, thereby improving the uniformity and stability of the metal powder feeding. Through rheological property tests and melt index experiments, it is determined that when the addition amount is 5wt%, the feeding exhibits excellent fluidity and shape stability. Secondly, the Box-Behnken response surface method is used to establish a response surface model to optimize and analyze the interaction between injection pressure, injection temperature and mold temperature on shear stress, and the process parameters are optimized by minimizing shear stress. In the molding process, the shear stress is effectively reduced, shear heat generation is controlled, defect generation is reduced, filling quality is improved, and trial mold costs are reduced, thereby achieving improved molding quality and optimized preparation efficiency of 17-4PH stainless steel trays in the MIM process.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. By introducing carnauba wax into the polyoxymethylene-based binder, the fluidity and shear-thinning properties of the feed are effectively improved, the shear heat generated during the molding process is reduced, and the coupling between the metal powder and the binder is improved, thereby significantly reducing injection molding defects.

[0022] 2. Compared to traditional binders, carnauba wax is a natural plant wax. Its gradient decomposition during the degreasing stage can precisely control gas diffusion paths, reducing the risk of microcracks and stress concentration. Furthermore, carnauba wax offers the advantage of environmental compatibility, significantly reducing VOC emissions compared to traditional binders.

[0023] 3. The Box-Behnken response surface method is used to establish a response model of shear stress and injection pressure, injection temperature, and mold temperature, and scientifically and systematically optimize the combination of process parameters. Through the dual optimization of materials and processes, the trial mold cost is significantly reduced, molding defects are reduced, and the consistency and mechanical properties of the molded products are improved. It is suitable for the production process of stainless steel SIM card trays prepared by metal powder injection molding and has significant application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a dimensional diagram of the 17-4PH stainless steel SIM card holder blank in the embodiment.

[0025] Figure 2 This is a diagram of the under-injection defect of the 17-4PH stainless steel SIM card holder blank in the embodiment.

[0026] Figure 3This is a diagram showing the deformation defects of the 17-4PH stainless steel SIM card holder blank in the embodiment.

[0027] Figure 4 This is an SEM image of the defect location of the 17-4PH stainless steel SIM card holder blank in the embodiment.

[0028] Figure 5 This is the SEM image of the 17-4PH stainless steel powder in the embodiment.

[0029] Figure 6 is a picture of carnauba wax in the examples.

[0030] Figure 7 This is a relationship diagram between viscosity and shear rate at 190°C for three feeds with addition amounts of carnauba wax of 0wt% (A0), 5wt% (A1), and 10wt% (A2) in the embodiment.

[0031] Figure 8 The melt index diagrams of three feeds with addition amounts of carnauba wax of 0 wt% (A0), 5 wt% (A1), and 10 wt% (A2) at different temperatures are shown in the examples.

[0032] Figure 9 Response surface diagram of the interaction between injection pressure and injection temperature on shear stress in the embodiment.

[0033] Figure 10 Response surface diagram of the interaction between injection pressure and mold temperature on shear stress in the embodiment.

[0034] Figure 11 Response surface diagram of the interaction between injection temperature and mold temperature on shear stress in the embodiment.

[0035] Figure 12 This is the shear stress result under the optimized process parameters of metal powder injection molding in the embodiment.

[0036] Figure 13 This is the appearance of the optimized 17-4PH stainless steel SIM card holder blank in the embodiment. DETAILED DESCRIPTION

[0037] In order to more fully understand and demonstrate the technical solutions, objectives, and advantages of the present invention, the following is a further detailed and complete description of the technical effects produced by the present invention in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present invention, and not all of them. It should be pointed out that for those skilled in the art, other embodiments obtained without departing from the concept of the present invention are all within the scope of protection of the present invention.

[0038] The following embodiment proposes a metal powder injection molding optimization method for a 17-4PH stainless steel SIM card holder blank, comprising the following steps:

[0039] (1) feeding a feed into an injection molding machine, wherein the feed comprises 17-4PH stainless steel metal powder and an optimized binder, wherein the optimized binder is composed of 90% to 99% polyoxymethylene and 1% to 10% carnauba wax by mass percentage;

[0040] (2) The Box-Behnken response surface analysis was used to construct a response surface model of shear stress and injection pressure, injection temperature, and mold temperature. The process parameters were optimized by minimizing the shear stress, and the optimized process parameters for metal powder injection molding of 17-4PH stainless steel SIM card holder blanks were obtained, including injection pressure of 100-110 MPa, injection temperature of 190-200 °C, and mold temperature of 70-90 °C.

[0041] (3) Metal powder injection molding is performed under the optimized process parameters of metal powder injection molding set in step (2), with an injection speed of 10 to 60 mm / s and a holding time of 1 to 10 s to obtain a 17-4PH stainless steel SIM card holder blank.

[0042] In some embodiments, in step (1), the polyoxymethylene is at least one of homopolyoxymethylene and copolymer polyoxymethylene.

[0043] In some embodiments, in step (1), the mass content of 17-4PH stainless steel powder in the feed is 60% to 70%, and the mass content of the optimized binder is 30% to 40%.

[0044] In some embodiments, in step (1), the optimized binder is composed of 95% polyoxymethylene and 5% carnauba wax by mass.

[0045] In some embodiments, in step (1), the preparation method of the feed comprises: weighing 17-4PH stainless steel metal powder and an optimized binder, and mixing them according to a ratio; adding the 17-4PH stainless steel metal powder and the optimized binder into an internal mixer, mixing them, and extruding and pelletizing them after mixing; in some embodiments, the 17-4PH stainless steel metal powder and the optimized binder are mixed at 165-220° C. for 0.5-2 hours.

[0046] In some embodiments, in step (2), the injection pressure is 105 MPa, the injection temperature is 195° C., and the mold temperature is 80° C. The shear stress of the molded part is minimized, the filling effect is optimal, and the molding quality is significantly improved.

[0047] In some embodiments, in step (3), the injection speed is 20 to 50 mm / s, and the holding time is 2 to 5 s.

[0048] Example 1

[0049] This embodiment proposes a metal powder injection molding optimization method for a 17-4PH stainless steel SIM card holder blank, and the steps are as follows:

[0050] (1) A feedstock is added to an injection molding machine. The feedstock is composed of 65% 17-4PH stainless steel powder and 35% binder by mass, wherein the binder is polyoxymethylene (homopolyoxymethylene or copolymer). The 17-4PH stainless steel powder and the binder are weighed and added to an internal mixer and mixed at 165-220° C. for 1 hour. After mixing, the mixture is extruded and pelletized to obtain the feedstock.

[0051] (2) The Box-Behnken response surface analysis was used to construct a response surface model of shear stress and injection pressure, injection temperature, and mold temperature. The metal powder injection molding process parameters were optimized by minimizing the shear stress, that is, the injection pressure was 105 MPa, the injection temperature was 195 °C, and the mold temperature was 80 °C.

[0052] (3) Metal powder injection molding is performed under the optimized process parameters of metal powder injection molding set in step (2), with an injection speed of 20 to 50 mm / s and a holding time of 2 to 5 s to obtain a 17-4PH stainless steel SIM card holder blank.

[0053] Example 2

[0054] This embodiment proposes a metal powder injection molding optimization method for a 17-4PH stainless steel SIM card holder blank, and the steps are as follows:

[0055] (1) Feed the material into the injection molding machine. The feed material is composed of 65% 17-4PH stainless steel metal powder ( Figure 5 ) and 35% optimized binder, which is composed of 95% polyoxymethylene and 5% carnauba wax ( Figure 6 ), wherein the polyoxymethylene is homopolyoxymethylene or copolymer polyoxymethylene. 17-4PH stainless steel powder and an optimized binder are weighed and added to an internal mixer, mixed at 165-220° C. for 1 hour, and then extruded and pelletized to obtain a feed material.

[0056] (2) The Box-Behnken response surface analysis was used to construct a response surface model of shear stress and injection pressure, injection temperature, and mold temperature. The metal powder injection molding process parameters were optimized by minimizing the shear stress. The injection pressure was 105 MPa, the injection temperature was 195 °C, and the mold temperature was 80 °C.

[0057] (3) Metal powder injection molding is performed under the optimized process parameters of metal powder injection molding set in step (2), with an injection speed of 20 to 50 mm / s and a holding time of 2 to 5 s to obtain a 17-4PH stainless steel SIM card holder blank.

[0058] In this embodiment, the size of the 17-4PH stainless steel SIM card holder blank is as follows: Figure 1 As shown, the short shot defect is as follows Figure 2 As shown, the deformation defect is Figure 3 As shown, the microstructure of the defect location is as follows Figure 4 As shown, 17-4PH stainless steel powder is Figure 5 As shown, the appearance of the optimized 17-4PH stainless steel SIM card holder blank is as follows Figure 13 As shown;

[0059] Figure 9-11 They are the response surface diagrams of the interaction between injection pressure and injection temperature on shear stress, the response surface diagrams of the interaction between injection pressure and mold temperature on shear stress, and the response surface diagrams of the interaction between injection temperature and mold temperature on shear stress in this embodiment; the shear stress under the optimal process parameters of metal powder injection molding after optimization in this embodiment is as follows: Figure 12 shown.

[0060] Example 3

[0061] This embodiment proposes a metal powder injection molding optimization method for a 17-4PH stainless steel SIM card holder blank, and the steps are as follows:

[0062] (1) A feedstock is added to an injection molding machine. The feedstock is composed of 65% by mass of 17-4PH stainless steel powder and 35% of an optimized binder. The optimized binder is composed of 90% by mass of polyoxymethylene and 10% by mass of carnauba wax. The polyoxymethylene is a homopolyoxymethylene or a copolymer of polyoxymethylene. The 17-4PH stainless steel powder and the optimized binder are weighed and added to an internal mixer. The mixture is mixed at 165-220° C. for 1 hour. After mixing, the mixture is extruded and pelletized to obtain the feedstock.

[0063] (2) The Box-Behnken response surface analysis was used to construct a response surface model of shear stress and injection pressure, injection temperature, and mold temperature. The metal powder injection molding process parameters were optimized by minimizing the shear stress. The injection pressure was 105 MPa, the injection temperature was 195 °C, and the mold temperature was 80 °C.

[0064] (3) Metal powder injection molding is performed under the optimized process parameters of metal powder injection molding set in step (2), with an injection speed of 20 to 50 mm / s and a holding time of 2 to 5 s to obtain a 17-4PH stainless steel SIM card holder blank.

[0065] In summary, the present invention simultaneously approaches material modification and process optimization, introduces carnauba wax into the binder, and utilizes its excellent fluidity and low shear viscosity characteristics to improve the overall rheological properties of the polyformaldehyde-based binder, thereby improving the uniformity and stability of the metal powder feeding. Secondly, the Box-Behnken response surface optimization is used to analyze the interaction between injection pressure, injection temperature and mold temperature on shear stress, establish a response surface model, and optimize process parameters by minimizing shear stress (shear stress is less than 1.5MPa during the forming process to reduce defects and improve filling quality). In this way, shear stress is effectively reduced during the forming process, shear heat generation is controlled, defect generation is reduced, and the quality of the molded parts is improved and the preparation efficiency is optimized.

[0066] The relationship between viscosity and shear rate of the three feeds with the addition amount of carnauba wax of 0wt% (A0), 5wt% (A1) and 10wt% (A2) at 190°C is as follows: Figure 7 As shown, the addition amount of carnauba wax in Examples 1-3 is 0wt% (A0), 5wt% (A1), and 10wt% (A2). The melt index of the three feeds at different temperatures is as follows: Figure 8 shown.

[0067] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A metal powder injection molding optimization method for 17-4PH stainless steel SIM card holder blank, characterized in that: The following steps are involved: (1) feeding a feed material into an injection molding machine, wherein the feed material comprises 17-4PH stainless steel metal powder and an optimized binder, wherein the optimized binder is composed of 90% to 99% polyoxymethylene and 1% to 10% carnauba wax by mass percentage; (2) The Box-Behnken response surface analysis was used to construct a response surface model of shear stress and injection pressure, injection temperature, and mold temperature. The metal powder injection molding process parameters of 17-4PH stainless steel SIM card holder blanks were optimized by minimizing shear stress, including injection pressure of 100-110 MPa, injection temperature of 190-200 °C, and mold temperature of 70-90 °C. (3) Metal powder injection molding is performed under the optimized process parameters of metal powder injection molding set in step (2), with an injection speed of 10 to 60 mm / s and a holding time of 1 to 10 s to obtain a 17-4PH stainless steel SIM card holder blank.

2. The metal powder injection molding optimization method of the 17-4PH stainless steel SIM card holder blank according to claim 1 is characterized in that: In step (1), the polyoxymethylene is at least one of homopolyoxymethylene and copolymer polyoxymethylene.

3. The metal powder injection molding optimization method of the 17-4PH stainless steel SIM card holder blank according to claim 1 is characterized in that: In step (1), the mass content of 17-4PH stainless steel powder in the feed is 60% to 70%, and the mass content of the optimized binder is 30% to 40%.

4. The metal powder injection molding optimization method of the 17-4PH stainless steel SIM card holder blank according to claim 1 is characterized in that: In step (1), the optimized adhesive consists of 95% polyoxymethylene and 5% carnauba wax by mass percentage.

5. The metal powder injection molding optimization method of the 17-4PH stainless steel SIM card holder blank according to claim 1 is characterized in that: In step (1), the preparation method of the feed comprises: (a) Batching: Weigh 17-4PH stainless steel metal powder and optimized binder and mix according to the ratio; (b) Granulation: 17-4PH stainless steel metal powder and optimized binder are added into an internal mixer and mixed. After mixing, the mixture is extruded and pelletized to obtain the product.

6. The metal powder injection molding optimization method of the 17-4PH stainless steel SIM card holder blank according to claim 5, characterized in that: In step (b), the 17-4PH stainless steel metal powder and the optimized binder are mixed at 165-220° C. for 0.5-2 hours.

7. The metal powder injection molding optimization method of the 17-4PH stainless steel SIM card holder blank according to claim 1, characterized in that: In step (2), the injection pressure is 105 MPa, the injection temperature is 195°C, and the mold temperature is 80°C.

8. The metal powder injection molding optimization method of the 17-4PH stainless steel SIM card holder blank according to claim 1, characterized in that: In step (3), the injection speed is 20 to 50 mm / s, and the holding time is 2 to 5 s.

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