A method of transferring a swing arm member metal powder injection molding

Abstract

The application discloses a kind of conveying swing arm piece metal powder injection molding method, comprising the following steps: step S01: selecting raw material, raw material includes percentage by weight: 74.2% to 78.95% iron powder, 12% to 14% chromium powder, 0.3% to 0.6% nickel powder, 0.35% to 0.45% carbon powder, 0.2% to 0.5% manganese powder, 0.3% to 0.65% molybdenum powder, 0.2% to 0.5% silicon powder, 7.7% to 9.1% binder;Raw material is mixed;Step S02: select the mold corresponding to conveying swing arm piece, the mixed raw material is transported to the mold in molding machine and injection molding blank;Step S03: the blank is sandblasted once;Step S04: blank is placed on ceramic plate, and adjacent two blanks are arranged with interval;Step S05: blank is transferred to defatting furnace and is subjected to segmented defatting;Step S06: blank is transferred to sintering furnace and is subjected to segmented sintering;Step S07: the finished product is sandblasted twice;The application can reduce the deformation of finished product, without additional shaping process and making shaping mold, improve production efficiency and reduce production cost.

Description

Technical Field

[0001] This invention relates to the technical field of manufacturing methods for conveyor swing arms, and in particular to a metal powder injection molding method for conveyor swing arms. Background Technology

[0002] The conveyor swing arm is a core transmission and actuation component of automated material conveying equipment, mainly responsible for key actions such as material feeding, reversing transfer, and stroke limiting. The part has a triangular overall structure, with an assembly shaft hole on one corner of the main body for transmission with the equipment's power shaft; the other two corners extend outward to form a cantilevered swing section. In operation, the torque output by the power shaft drives the main body of the swing arm to reciprocate around the axis of the shaft hole, and the transmission and actuation functions are achieved through the synchronous swing of the two swing sections. This type of part has stringent requirements for the accuracy of the shaft hole fit, the positional accuracy of the swing section, the structural strength, and the wear and corrosion resistance. Its processing and forming quality directly determines the operational stability and overall service life of the conveying equipment.

[0003] The current mainstream manufacturing method for conveyor swing arm components is still based on traditional subtractive machining. Most of them use stainless steel bars or plates as blanks and are processed into shape through multiple processes such as blanking, contour milling, shaft hole drilling, deburring and grinding. Due to the triangular irregular structure of the parts, the cutting allowance in the machining process is large and the utilization rate of metal materials is low, which significantly increases the production and manufacturing cost.

[0004] Existing technologies include traditional molding powder metallurgy processes for manufacturing swing arm-type parts. However, this process has limited forming capabilities and is only suitable for simple axisymmetric structural parts. For triangular conveyor swing arms with cantilever swing sections, it is difficult to control the uniformity of powder filling during the molding stage, and the demolding process can easily cause chipping and damage to the edges and corners. At the same time, the density of the blank is unevenly distributed along the thickness direction, resulting in large shrinkage deformation after sintering. The roundness of the shaft hole and the positional accuracy of the swing section are difficult to meet the assembly accuracy requirements, requiring additional shaping and secondary machining processes for correction. This process route not only has limited improvement in production efficiency, but also generally results in low density and mechanical properties of the finished product, making it difficult to withstand alternating contact loads under reciprocating swing conditions, and posing a high risk of wear and impact failure.

[0005] Metal powder injection molding, as a one-piece molding technology, has the capability to manufacture complex and irregularly shaped metal parts. However, under conventional processes, the deformation of the finished product after sintering is relatively large, requiring additional shaping molds to meet precision requirements. This increases process complexity, raises production costs, and reduces production efficiency. Furthermore, conventional processes only perform surface treatment after sintering, failing to eliminate initial defects such as parting lines and release agent residues on the blank surface during pre-processing. These defects can further evolve during debinding and sintering, developing into permanent quality problems such as surface pits and oxide spots, ultimately resulting in low-quality finished products. Summary of the Invention

[0006] The purpose of this invention is to provide a metal powder injection molding method for conveyor swing arm components, which can reduce the deformation of the finished product, eliminate the need for additional shaping processes and the manufacture of shaping molds, and improve production efficiency and reduce production costs while ensuring product quality.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for metal powder injection molding of a conveyor swing arm includes the following steps:

[0009] Step S01: Select raw materials, which include the following by weight percentages: 74.2%-78.95% iron powder, 12.0%-14.0% chromium powder, 0.3%-0.6% nickel powder, 0.35%-0.45% carbon powder, 0.2%-0.5% manganese powder, 0.3%-0.65% molybdenum powder, 0.2%-0.5% silicon powder, and 7.7%-9.1% binder; mix the raw materials.

[0010] Step S02: Select the mold corresponding to the conveying swing arm component, and convey the mixed raw materials to the mold in the molding machine to inject and mold the blank;

[0011] Step S03: Perform a sandblasting on the blank;

[0012] Step S04: Place the blanks on the ceramic plate, with adjacent blanks spaced apart;

[0013] Step S05: Transfer the blank to the degreasing furnace for segmented degreasing;

[0014] Step S06: Transfer the billet to the sintering furnace for segmented sintering;

[0015] Step S07: Perform secondary sandblasting on the finished product.

[0016] Based on the above technical solution, the present invention can be improved as follows:

[0017] Furthermore, in step S02, the mold temperature is 90-120℃, and the injection speed is 5-10cm. 3 / s, molding pressure 74-76MPa; holding time 1-4s, holding pressure 74-76MPa.

[0018] Furthermore, in step S03, the blank is sandblasted with glass sand with a particle size of 0.125-0.180 mm and a sandblasting pressure of 0.13-0.15 MPa.

[0019] Furthermore, in step S05, oxalic acid and nitrogen are introduced into the degreasing furnace, and the temperature of the oxalic acid is 100-130℃.

[0020] Further, in step S05, the segmented degreasing includes:

[0021] The first stage of degreasing takes 90 minutes, the degreasing oven temperature is 110-120℃, the nitrogen flow rate is 65-75L / min, and the acid flow rate is 0.8-2.3g / min.

[0022] The second stage of degreasing takes 480 minutes, with the degreasing oven temperature at 115-125℃, nitrogen flow rate at 65-75L / min, and acid flow rate at 1.2-3.2g / min.

[0023] The third stage of degreasing takes 60 minutes, with the degreasing oven temperature at 120-130℃, nitrogen flow rate at 75-85L / min, and acid flow rate at 0.8-2.3g / min.

[0024] Furthermore, in step S05, a pretreatment is performed before the first stage of degreasing, and a posttreatment is performed after the third stage of degreasing;

[0025] The pretreatment time is 150 min, the degreasing oven temperature is 105-115℃, and the nitrogen flow rate is 85-95 L / min;

[0026] The post-treatment time is 90 minutes, the degreasing oven temperature is 120-130℃, and the nitrogen flow rate is 70-90 L / min.

[0027] Further, in step S06, segmented sintering includes:

[0028] The first sintering time is 90 minutes, the sintering furnace temperature is 1040-1060℃, and the pressure is 0MPa.

[0029] The second sintering time is 120 minutes, the sintering furnace temperature is 1040-1060℃, and the pressure is 0MPa.

[0030] The third sintering time is 100 min, the sintering furnace temperature is 1350-1370℃, the pressure is 15-25MPa, and argon gas is introduced at a flow rate of 25-35L / min.

[0031] The fourth sintering time is 180 min, the sintering furnace temperature is 1350-1370℃, the pressure is 15-25 MPa, and argon gas is introduced at a flow rate of 25-35 L / min.

[0032] The fifth sintering time is 60 minutes, the sintering furnace temperature is 890-910℃, the pressure is 15-25MPa, and argon gas is introduced at a flow rate of 25-36L / min.

[0033] Furthermore, in step S06, after the fifth stage of sintering is completed, the system is forced to cool for 6 minutes and then the argon gas supply is stopped.

[0034] Furthermore, in step S07, the secondary sandblasting uses glass sand with a particle size of 0.125-0.180 mm and a sandblasting pressure of 0.20-0.25 MPa.

[0035] Furthermore, after sandblasting, a spray gun is used to remove the glass sand remaining on the blank. The compressed air pressure sprayed from the spray gun is 0.3-0.5 MPa.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] This invention is based on a conveyor swing arm structure and is integrally formed using metal powder injection molding. It can directly form a complete three-dimensional structure without the need for multiple milling and drilling processes in traditional machining. By performing a sandblasting before segmented degreasing and a second sandblasting after segmented sintering, it is possible to remove parting lines and release agent residues and optimize the surface pore structure before degreasing, and to eliminate oxide deposits and surface micro-defects after sintering. This works synergistically with segmented degreasing and segmented sintering to reduce the amount of deformation of the finished product. It eliminates the need for additional shaping processes and the manufacture of shaping molds, thereby improving production efficiency and reducing production costs while ensuring product quality. Attached Figure Description

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0039] Figure 1 This is a schematic diagram of the structure of the conveyor swing arm component manufactured in this embodiment;

[0040] Figure 2 This is a flowchart of the metal powder injection molding method for conveying the swing arm component in this embodiment;

[0041] Figure 3 This is a metallographic diagram of the finished conveyor swing arm component after five sintering stages in this embodiment.

[0042] The markings on the attached diagram are: 1. Main body of the swing arm; 2. Swinging part; 3. Shaft hole. Detailed Implementation

[0043] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. These descriptions are intended to aid in understanding the present invention but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0044] See Figure 1This embodiment relates to a metal powder injection molding method for a conveyor swing arm component. The manufactured conveyor swing arm component includes a triangular swing arm body 1. The swing arm body 1 forms swing parts 2 at two of its corners, and the swing arm body 1 has a shaft hole 3 at the other corner. The shaft hole 3 is used to cooperate with the power shaft of the installed conveyor equipment. When the power shaft rotates, it drives the swing arm body 1 to rotate around the axis, and correspondingly drives the two swing parts 2 on the swing arm body 1 to swing.

[0045] See Figure 2 This embodiment describes a method for metal powder injection molding of a swing arm component, which includes the following steps:

[0046] Step S01: Select raw materials, which include the following by weight percentages: 74.2%-78.95% iron powder, 12%-14% chromium powder, 0.3%-0.6% nickel powder, 0.35%-0.45% carbon powder, 0.2%-0.5% manganese powder, 0.3%-0.65% molybdenum powder, 0.2%-0.5% silicon powder, and 7.7%-9.1% binder; mix the raw materials.

[0047] Step S02: Select the mold corresponding to the conveying swing arm component, and convey the mixed raw materials to the mold in the molding machine to inject and mold the blank;

[0048] Step S03: Perform a sandblasting on the blank;

[0049] Step S04: Place the blanks on the ceramic plate, with adjacent blanks spaced apart;

[0050] Step S05: Transfer the blank to the degreasing furnace for segmented degreasing;

[0051] Step S06: Transfer the billet to the sintering furnace for segmented sintering;

[0052] Step S07: Perform secondary sandblasting on the finished product;

[0053] Step S08: Conduct a full inspection of the finished products and screen out the unqualified finished products;

[0054] Step S09: Package the qualified finished products.

[0055] In step S01 of this embodiment, the iron powder is 500-625 mesh, the chromium powder is 500-625 mesh, the carbon powder is 325-500 mesh, and the particle size of the remaining powders matches the particle size range of the iron powder; the binder is polyoxymethylene binder; the mixing equipment is an internal mixer, with a set speed of 55-70 r / min and a mixing time of 85-90 min, to ensure that the metal powder and binder are fully coated and uniformly fused, without agglomeration or stratification; the composite raw material after mixing must be sealed immediately and stored in a constant temperature and dry silo to isolate it from air and moisture, prevent the powder from oxidizing and absorbing moisture, and avoid affecting the subsequent injection molding and sintering quality.

[0056] In step S02 of this embodiment, the molding machine is a horizontal injection molding machine, on which a mold with a cavity size matching that of the conveying swing arm is installed. The mold temperature is 90-120℃, and the injection speed is 5-10cm. 3 The forming pressure is 74-76 MPa per second; the holding time is 1-4 seconds, and the holding pressure is 74-76 MPa to compensate for cooling shrinkage and ensure uniform density of the blank; the density of the formed blank is 5.05-5.15 g / cm³. 3 This density range can balance the structural strength and porosity of the blank, which not only avoids deformation and damage during transportation and degreasing due to excessively low blank strength, but also retains pores to provide channels for subsequent binder decomposition and gas escape.

[0057] In step S03 of this embodiment, the blank is sandblasted with glass sand with a particle size of 0.125-0.180 mm and a sandblasting pressure of 0.13-0.15 MPa. After sandblasting, the glass sand remaining on the blank is removed with a spray gun with a compressed air pressure of 0.3-0.5 MPa. Due to the low hardness of the blank, the glass sand can remove the parting line, gate residue and release agent residue. At the same time, the slightly roughened surface increases the contact area of ​​oxalic acid, accelerates the degreasing rate, eliminates the surface internal stress generated by injection, and reduces the risk of cracking during the degreasing and sintering process.

[0058] In step S04 of this embodiment, the spacing between two adjacent blanks on the ceramic plate is 1-3mm. This spacing can ensure that the airflow and temperature in the furnace act uniformly on each blank, realize the synchronous decomposition of the binder, and uniform heating and shrinkage of the blanks, and avoid defects such as incomplete degreasing, sintering deformation, and adhesion damage caused by the bonding of blanks.

[0059] In step S05 of this embodiment, oxalic acid and nitrogen gas are introduced into the degreasing furnace, and the temperature of the oxalic acid is 100-130°C; wherein,

[0060] The first stage of degreasing takes 90 minutes, with the degreasing furnace temperature at 110-120℃, nitrogen flow rate at 65-75L / min, and acid flow rate at 0.8-2.3g / min. Degreasing is started slowly with a low acid flow rate, which can controllably reduce the decomposition rate of the binder, prevent the binder on the surface of the blank from rapidly decomposing and forming a crust, and form a tightly sealed layer to prevent the internal gas from escaping, thus preventing the blank from bubbling and surface cracking from the root.

[0061] The second stage of degreasing takes 480 minutes, with the degreasing furnace temperature at 115-125℃, nitrogen flow rate at 65-75L / min, and acid flow rate at 1.2-3.2g / min. The amount of catalyst is gradually increased to accelerate the decomposition and removal of most of the binders inside the blank, completing the main degreasing operation while maintaining a stable decomposition rate to ensure that the degreasing of the blank inside and out is carried out simultaneously.

[0062] The third stage of degreasing takes 60 minutes, with the degreasing furnace temperature at 120-130℃, nitrogen flow rate at 75-85L / min, and acid flow rate at 0.8-2.3g / min; this ensures that the binder inside the blank is completely decomposed, and that a small amount of binder remaining on the surface of the blank maintains the shape and strength of the blank.

[0063] In the 100-130℃ range, gaseous oxalic acid acts as a catalyst to penetrate into the interior of the blank, causing the polyoxymethylene molecular chains to break and decompose into formaldehyde gas that escapes from the pores of the blank. The initial low acid flow rate avoids the rapid decomposition on the surface to form a dense layer that hinders the escape of internal gas, while the mid-term high acid flow rate ensures complete internal degreasing, thus preventing the blank from bubbling and cracking at the source.

[0064] Furthermore, in step S05 of this embodiment, the blanks in the degreasing furnace are pretreated and posttreated before and after the three-stage degreasing process, respectively; wherein,

[0065] The pretreatment time is 150 minutes, the degreasing furnace temperature is 105-115℃, and the nitrogen flow rate is 85-95L / min. The air and water vapor in the furnace are thoroughly removed by continuous nitrogen purging, while the billet is heated slowly and evenly to avoid thermal shock caused by rapid temperature rise and effectively prevent low-temperature thermal cracking defects.

[0066] The post-treatment time is 90 minutes, the degreasing furnace temperature is 120-130℃, and the nitrogen flow rate is 70-90L / min. By continuously purging with a large flow rate of nitrogen, the residual oxalic acid vapor and harmful formaldehyde gas produced by the decomposition of binder in the furnace are thoroughly removed, preventing the blanks from adsorbing residual acid liquid and impurities, and avoiding oxidation and impurities during subsequent sintering.

[0067] Oxalic acid is not introduced during pretreatment and posttreatment. By purging with nitrogen gas during pretreatment and posttreatment, oxidation of the blanks is prevented and residual acid gas and decomposition products are completely discharged, thus avoiding affecting the subsequent sintering quality.

[0068] In step S06 of this embodiment, the sintering furnace is a horizontal vacuum sintering furnace.

[0069] In step S06, the first sintering time is 90 minutes, the sintering furnace temperature is 1040-1060℃, and the pressure is 0 MPa.

[0070] Since the 1040-1060℃ range is far above the thermal decomposition temperature of polymer materials, under vacuum negative pressure, the residual binder gradually undergoes thermal decomposition and vaporization, decomposing into small molecule hydrocarbon gases, which are quickly extracted from the furnace cavity by the vacuum system. The vacuum environment can lower the boiling point of the decomposition products, enhance the removal efficiency, and isolate oxygen to avoid local overheating and deformation of the blank caused by the exothermic oxidation of the binder. At the same time, it can prevent the binder from coking at high temperatures and remaining in the pores of the blank, causing defects such as excessive carbon content and internal porosity. This temperature is in the early stage of solid-state sintering of the alloy. Metal atoms migrate mainly through surface diffusion and grain boundary diffusion, gradually accumulating at the contact interface of adjacent powder particles to form a sintering neck structure that connects the particles. The appearance of the sintering neck enables the powder particles that are only physically bonded by the binder to establish a metallurgical bond. After the binder is completely removed, the blank can still maintain its complete geometric shape and basic structural strength, avoiding problems such as collapse, sagging edges and corners, and deformation of shaft holes when the temperature is raised to a high temperature range above 1350℃ due to the loss of internal support caused by high temperature.

[0071] In step S06, the second sintering time is 120 min, the sintering furnace temperature is 1040-1060℃, and the pressure is 0 MPa.

[0072] After the first 90-minute pre-sintering stage, the low-molecular-weight binder in the surface layer and shallow pores of the blank has been largely removed. However, the high-molecular-weight binder in the internal pores and interparticle spaces has a higher pyrolysis activation energy and remains. The second 120-minute sintering stage provides sufficient pyrolysis time for the internal binder, allowing it to fully decompose into small-molecule hydrocarbons. Combined with a vacuum negative pressure environment to reduce the partial pressure of the decomposition products, the small-molecule gas is driven to diffuse outward through the still-connected pores inside the blank, ultimately achieving complete removal of residual adhesive across the entire thickness range. This avoids defects such as excessive carbon content, internal porosity, and carbon spots caused by binder coking residue, and allows atoms to continuously deposit at the particle contact interface, enabling the first sintering stage to be completed. The initial sintering neck formed by dots gradually coarsens and expands, evolving from point contact to planar bonding. As the sintering neck gradually increases in size, a continuous three-dimensional metallurgical network skeleton is gradually built between the originally discrete powder particles, enabling the blank to obtain strength far exceeding that of the degreased state. When the temperature is subsequently raised to a high temperature range above 1350℃, this three-dimensional metallurgical network skeleton can resist the deformation trend caused by the high-temperature softening of the material, maintaining the contour shape of the triangular swing arm, the roundness of the shaft hole, and the structural integrity of the thin-walled swing part. If the temperature is directly raised to a higher temperature at this stage, the surface of the blank will preferentially undergo sintering densification, sealing the internal pores, causing the gas generated by the decomposition of the binder to be unable to escape, ultimately forming internal pores, blistering, or even cracking defects.

[0073] In step S06, the sintering time for the third stage is 100 min, the sintering furnace temperature is 1350-1370℃, the pressure is 15-25 MPa, and argon gas is introduced at a flow rate of 25-35 L / min.

[0074] Due to the high saturated vapor pressure of elements such as chromium and manganese in a high-temperature vacuum environment, they are prone to sublimation and volatilization, leading to the depletion of alloy elements on the surface of the billet and directly reducing the corrosion resistance and phase transformation strengthening effect of the matrix. After argon gas is introduced to form a positive pressure of 15-25 MPa, the total gas phase pressure in the furnace increases significantly. According to Raoult's law, the driving force for the volatilization of alloy elements decreases significantly with the increase of total pressure. At the same time, argon molecules can form a gas phase barrier, preventing the volatilized metal atoms from escaping outward, reducing the loss of alloy elements, and ensuring the uniformity of composition of the billet from the surface to the interior. In the 370℃ temperature range, compared to the first and second sintering stages, the atomic diffusion rate in the third sintering stage is significantly increased, and the mass transfer mode changes from mainly surface diffusion to mainly grain boundary diffusion and volume diffusion. The third sintering stage lasts for 100 minutes, which allows the irregularly shaped blank to be fully heated as a whole. The sintering neck rapidly coarsens and fills the gaps between particles. The pores gradually shrink and break into isolated closed pores. The blank undergoes significant volume shrinkage, which avoids excessive shrinkage difference between the surface and the interior caused by rapid heating and effectively reduces sintering defects such as edge warping, out-of-roundness of shaft holes, and thin-wall cracking.

[0075] In step S06, the fourth sintering time is 180 min, the sintering furnace temperature is 1350-1370℃, the pressure is 15-25 MPa, and argon gas is introduced at a flow rate of 25-35 L / min.

[0076] Due to the fourth stage sintering of 180 minutes, the isolated closed pores inside the blank gradually become spheroidized, the small pores are gradually filled and eliminated through atomic migration, the size of the large pores continues to shrink and the number of large pores decreases, and the blank undergoes uniform volume shrinkage, thus forming a continuous and dense metal matrix.

[0077] In step S06, the sintering time for the fifth stage is 60 minutes, the sintering furnace temperature is 890-910℃, the pressure is 15-25MPa, and argon gas is introduced at a flow rate of 25-36L / min.

[0078] After the fourth stage of long-term high-temperature sintering, the billet is cooled to enter the fifth stage sintering temperature range. Short-term cooling sintering can eliminate the intragranular composition segregation caused by high-temperature sintering, allowing alloying elements such as carbon, chromium, molybdenum, and nickel to fully diffuse and uniformly distribute in the austenitic matrix, avoiding the problem of local uneven hardness after phase transformation. At the same time, 890-910℃ is the optimal precipitation temperature range for chromium-rich carbides. Supersaturated carbon and chromium elements that are completely dissolved in austenite during the high-temperature sintering stage precipitate in the form of nanoscale second phases at austenite grain boundaries and intragranular dislocations during the holding process at this temperature. The precipitated carbides can pin the austenite grain boundaries, inhibit abnormal grain enlargement during the holding process, and improve the toughness of the matrix through fine grain strengthening. At the same time, the second phase particles themselves can further improve the hardness and wear resistance of the material.

[0079] After the fifth stage of sintering, forced cooling was performed for 6 minutes, and the argon gas supply was stopped. The homogenized austenite underwent a non-diffusion shear transformation, transforming into a metallographic structure of acicular martensite and lath martensite (see...). Figure 3 Among them, lath martensite has high fracture toughness and impact resistance, while acicular martensite has high matrix hardness, which enables the finished product to achieve a balance between hardness and toughness, avoiding the defects of a single martensite morphology being too hard and brittle or too soft and not wear-resistant.

[0080] As the furnace temperature continues to drop during the forced cooling phase, the saturated vapor pressure of alloying elements such as chromium and manganese is significantly reduced, and the risk of high-temperature volatilization is completely eliminated. There is no need to continuously introduce argon gas for partial pressure protection. Stopping the introduction of argon gas can reduce the interference of gas convection in the furnace on the cooling uniformity of parts, ensure the consistent cooling rate of parts throughout the furnace, reduce the consumption of inert gas, and balance product quality stability and process economy.

[0081] In this embodiment, the first and second stages of sintering are vacuum sintering, while the third to fifth stages are partial pressure sintering. The density of the finished product after completing the five stages of sintering is greater than 7.6 g / cm³.3 .

[0082] In step S07 of this embodiment, glass sand is used for secondary sandblasting. The glass sand particle size is 0.125-0.180 mm, and the sandblasting pressure is 0.20-0.25 MPa. After sandblasting, a spray gun is used to remove the glass sand remaining on the blank. The compressed air pressure sprayed by the spray gun is 0.3-0.5 MPa, which can thoroughly remove the surface oxide layer, sintering deposits, particle protrusions, and fine adhesion marks generated during sintering, unify the surface roughness of the finished product, and improve the appearance quality and assembly compatibility of the finished product. During the secondary sandblasting process, a uniform compressive stress will be formed on the surface of the finished product, which can effectively offset the internal tensile stress generated during sintering, repair sintering stress defects, and significantly improve the fatigue life and operational stability of the conveyor swing arm under high-frequency reciprocating swing conditions.

[0083] In step S08 of this embodiment, a dual inspection method of visual inspection and dimensional accuracy verification is adopted to screen for defects such as surface cracks, chipped edges, burrs, scratches, out-of-tolerance dimensions, and eccentricity of shaft holes. This distinguishes between qualified and unqualified finished products, prevents defective finished products from entering the assembly process, and ensures the quality stability of batch finished products.

[0084] This embodiment is based on a conveyor swing arm structure and is integrally formed using metal powder injection molding. It can directly form a complete three-dimensional structure without the need for multiple milling and drilling processes in traditional machining. By performing a sandblasting before segmented degreasing and a second sandblasting after segmented sintering, it is possible to remove parting lines and release agent residues and optimize the surface pore structure before degreasing, and to eliminate oxide deposits and surface micro-defects after sintering. This works synergistically with segmented degreasing and segmented sintering to reduce the amount of deformation of the finished product. No additional shaping process or shaping mold is required throughout the process, which improves production efficiency and reduces production costs while ensuring product quality.

[0085] The above embodiments of the present invention are not intended to limit the scope of protection of the present invention. The implementation of the present invention is not limited thereto. All other modifications, substitutions or alterations made to the above structure of the present invention based on the above content of the present invention, in accordance with ordinary technical knowledge and common practice in the field, without departing from the basic technical idea of ​​the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A method for metal powder injection molding of a conveyor swing arm component, characterized in that, Includes the following steps: Step S01: Select raw materials, which include the following by weight percentages: 74.2%-78.95% iron powder, 12%-14% chromium powder, 0.3%-0.6% nickel powder, 0.35%-0.45% carbon powder, 0.2%-0.5% manganese powder, 0.3%-0.65% molybdenum powder, 0.2%-0.5% silicon powder, and 7.7%-9.1% binder; mix the raw materials. Step S02: Select the mold corresponding to the conveying swing arm component, and convey the mixed raw materials to the mold in the molding machine to inject and mold the blank; Step S03: Perform a sandblasting on the blank; Step S04: Place the blanks on the ceramic plate, with adjacent blanks spaced apart; Step S05: Transfer the blank to the degreasing furnace for segmented degreasing; Step S06: Transfer the billet to the sintering furnace for segmented sintering; Step S07: Perform secondary sandblasting on the finished product.

2. The metal powder injection molding method for the conveyor swing arm component according to claim 1, characterized in that, In step S02, the mold temperature is 90-120℃ and the injection speed is 5-10cm. 3 / s, molding pressure 74-76MPa; holding time 1-4s, holding pressure 74-76MPa.

3. The metal powder injection molding method for the conveyor swing arm component according to claim 1, characterized in that, In step S03, the blank is sandblasted with glass sand with a particle size of 0.125-0.180 mm and a sandblasting pressure of 0.13-0.15 MPa.

4. The metal powder injection molding method for the conveyor swing arm component according to claim 1, characterized in that, In step S05, oxalic acid and nitrogen are introduced into the degreasing furnace, and the temperature of the oxalic acid is 100-130℃.

5. The metal powder injection molding method for the conveyor swing arm component according to claim 4, characterized in that, In step S05, segmented degreasing includes: The first stage of degreasing takes 90 minutes, the degreasing oven temperature is 110-120℃, the nitrogen flow rate is 65-75L / min, and the acid flow rate is 0.8-2.3g / min. The second stage of degreasing takes 480 minutes, with the degreasing oven temperature at 115-125℃, nitrogen flow rate at 65-75L / min, and acid flow rate at 1.2-3.2g / min. The third stage of degreasing takes 60 minutes, with the degreasing oven temperature at 120-130℃, nitrogen flow rate at 75-85L / min, and acid flow rate at 0.8-2.3g / min.

6. The metal powder injection molding method for the conveyor swing arm component according to claim 5, characterized in that, In step S05, pretreatment is performed before the first stage of degreasing, and posttreatment is performed after the third stage of degreasing. The pretreatment time is 150 min, the degreasing oven temperature is 105-115℃, and the nitrogen flow rate is 85-95 L / min; The post-treatment time is 90 minutes, the degreasing oven temperature is 120-130℃, and the nitrogen flow rate is 70-90 L / min.

7. The method for metal powder injection molding of the conveyor swing arm component according to claim 1, characterized in that, In step S06, segmented sintering includes: The first sintering time is 90 minutes, the sintering furnace temperature is 1040-1060℃, and the pressure is 0MPa. The second sintering time is 120 minutes, the sintering furnace temperature is 1040-1060℃, and the pressure is 0MPa. The third sintering time is 100 min, the sintering furnace temperature is 1350-1370℃, the pressure is 15-25MPa, and argon gas is introduced at a flow rate of 25-35L / min. The fourth sintering time is 180 min, the sintering furnace temperature is 1350-1370℃, the pressure is 15-25 MPa, and argon gas is introduced at a flow rate of 25-35 L / min. The fifth sintering time is 60 minutes, the sintering furnace temperature is 890-910℃, the pressure is 15-25MPa, and argon gas is introduced at a flow rate of 25-36L / min.

8. The method for metal powder injection molding of the conveyor swing arm component according to claim 7, characterized in that, In step S06, after the fifth stage of sintering is completed, the mixture is forced to cool for 6 minutes and the argon gas supply is stopped.

9. The method for metal powder injection molding of a conveyor swing arm according to claim 1, characterized in that, In step S07, the secondary sandblasting uses glass sand with a particle size of 0.125-0.180 mm and a sandblasting pressure of 0.20-0.25 MPa.

10. The method for metal powder injection molding of a conveyor swing arm according to claim 3 or 9, characterized in that, After sandblasting, use a spray gun to remove any remaining glass sand. The compressed air pressure from the spray gun should be 0.3-0.5 MPa.

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