Partitioned reinforced composite structure triangle for composite needle circular weft knitting machine and forming method thereof

Abstract

The invention belongs to the technical field of textile machinery, and discloses a partitioned reinforced composite structure triangle for a composite needle circular weft knitting machine and a forming method thereof.The partitioned reinforced composite structure triangle for the composite needle circular weft knitting machine comprises a working face area, a toughness transition area and an installation base body area; the working face area, the toughness transition area and the installation base body area are made of high-carbon and high-chromium free-cutting steel, medium-carbon and medium-chromium free-cutting steel and low-carbon and low-chromium free-cutting steel respectively. The preparation method comprises the following steps: firstly, designing a precise pressing die according to a triangular three-dimensional model, partitioning a die cavity into a working surface region, a toughness transition region and a mounting base body region according to function regions, and accurately filling each powder cavity with free-cutting steel powder with corresponding components; and performing cold isostatic pressing, high-temperature vacuum sintering, heat treatment and finish machining to obtain the partitioned reinforced composite structure triangle for the composite needle circular weft knitting machine. The technical problem that high wear resistance, high impact resistance and excellent machining manufacturability of a traditional triangle are difficult to consider at the same time is systematically solved, the service life of the triangle is remarkably prolonged, and the reliability of the triangle is remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of textile machinery and relates to a partition-strengthened composite structure cam for a composite needle circular weft knitting machine and a forming method thereof. BACKGROUND

[0002] As a key loop-forming component, the performance of the cam of a weft knitting large circular machine directly affects the speed, efficiency and fabric quality of the knitting machine. With the development of knitting equipment towards high gauge and high speed, the working environment of the cam is increasingly harsh. On the one hand, the speed of the knitting needle on the cam track can reach 30-40 m / s, and the knitting needle needs to bear thousands of high-frequency and high-strain cyclic impact loads per minute, which is prone to generate fatigue cracks at stress concentration sites. On the other hand, the severe friction between the knitting needle and the working surface of the cam can cause serious wear. Especially under the condition of high gauge, the machining precision of the working surface of the cam is required to be extremely high (the tolerance is usually controlled within ±0.01 mm), and micron-level wear can cause the dynamic trajectory of the needle hook to deviate, resulting in needle collision, needle missing and other problems, which seriously affect the fabric quality.

[0003] In the prior art, related patents provide various technical solutions, but all have certain limitations.

[0004] The patent application with the application publication number CN120624882A discloses a copper-based powder metallurgy friction material and a preparation method thereof. The method significantly improves the friction stability, wear resistance and heat decay resistance of the copper-based friction material under high-speed heavy-load conditions (such as 400 km / h braking) through unique multi-component design (such as adding chromium iron, nickel-coated tungsten disulfide, etc.) and process optimization. However, the overall composition of the material is single and uniform, which cannot realize functional partitioning (such as high wear resistance on the friction surface and high thermal conductivity in the matrix), limiting the performance breakthrough under more complex working conditions. This "one-size-fits-all" design approach cannot meet the evolutionary needs of modern high-end equipment for gradient and multi-functional integration of friction materials.

[0005] The patent with the authorization publication number CN104384503B discloses an iron-copper-based powder metallurgy antifriction material and a preparation method thereof. The method prepares a composite material with wear resistance and low friction coefficient by adding various components (such as bronze powder, aluminum oxide, fluorinated graphite, etc.). The method shows the flexibility of powder metallurgy technology in material composition design, but the composition design is uniformly mixed, resulting in isotropic homogeneous material. Moreover, the material does not involve the technology of realizing composition gradient change through partition powder loading, so it cannot manufacture integrated cam components with significant performance differences in different areas of the same part, and cannot fundamentally solve the problem of differentiated needs of different functional areas of the cam for material performance.

[0006] Patent with authorization announcement No. CN101755060B discloses a functionally segmented powder metal component, which realizes lightweight and performance optimization of the part and avoids cost and process problems caused by using multiple materials or complex assembly by manufacturing functionally segmented, performance different regions such as high strength region and high wear resistance region on the same powder metallurgical component through single material powder and differential subsequent processing such as selective cooling or heat treatment. However, it also has limitations: process control is complex, precision of heat treatment or cooling is extremely high, and it is difficult to ensure uniformity and stability of performance of different regions; and it may not be suitable for occasions requiring extreme performance difference.

[0007] Patent with authorization announcement No. CN104017965B discloses a strengthening and toughening heat treatment method of Cr12MoV steel, which aims to improve hardness, impact toughness and wear resistance of the steel by optimizing quenching temperature and adopting deep cryogenic treatment and subsequent tempering process. The method improves the problem of insufficient toughness of traditional Cr12MoV steel to some extent, but its essence is still the overall heat treatment of single homogeneous material. For the triangular structure with complex structure and different performance requirements of different parts, the method cannot realize the coordination of ultra-high wear resistance of the working surface and high impact resistance of the matrix, and the performance improvement is limited.

[0008] Patent application with application announcement No. CN103882370A discloses a soft nitriding surface treatment method of 42CrMo steel rotary drive part, which forms a high-hardness compound layer on the surface of the part by nitrocarburizing to improve the surface wear resistance and fatigue strength. However, the surface strengthening layer is usually thin (usually only a few microns to tens of microns), and under the condition of continuous strong impact and wear of high-speed knitting needles, there is a risk of peeling of the layer and insufficient durability. Once the protective layer fails, the wear resistance will decrease sharply, and the process cannot improve the toughness and processing performance of the core of the part.

[0009] Therefore, there is an urgent need for a partitioned reinforced composite structure triangular for a compound needle circular weft knitting machine and a forming method thereof, which can break through the performance limitations of a single material system, realize the coordinated optimization of high wear resistance of the working surface, high toughness of the transition zone and excellent processing performance of the installation zone, and fundamentally solve the harsh requirements of high-speed weft knitting large circular machines on the comprehensive performance of the triangular part. SUMMARY

[0010] The purpose of the present application is to solve the problems existing in the prior art and provide a partitioned reinforced composite structure triangular for a compound needle circular weft knitting machine and a forming method thereof.

[0011] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0012] A triangular composite structure with partitioned reinforcement for a composite needle circular weft knitting machine includes a working surface area, a toughness transition area, and an installation base area;

[0013] The working surface area directly withstands the impact and friction of the knitting needles. It is made of high-carbon, high-chromium free-cutting steel, ensuring the formation of a sufficient number of hard carbides (such as M7C3 and MC type carbides) to provide excellent wear resistance. The toughness transition zone surrounds and supports the working surface area, using medium-carbon, medium-chromium free-cutting steel. With a moderate number of carbides and improved matrix toughness, it effectively absorbs the impact energy of the knitting needles, preventing cracks from propagating from the high-hardness working surface area. The mounting base area forms the triangular main frame and mounting fixing parts, using low-carbon, low-chromium free-cutting steel. This significantly improves the material's machinability, facilitating drilling, tapping, and other machining operations, thus improving manufacturing efficiency. The high-carbon, high-chromium free-cutting steel contains Mo and S elements, and the appropriate amount of sulfur improves the material's machinability, facilitating final precision grinding and preventing machining cracks. The medium-carbon, medium-chromium free-cutting steel contains Mo; the low-carbon, low-chromium free-cutting steel contains Ca and S elements, significantly improving machinability while ensuring a strong bond with the transition zone through sintering.

[0014] The working surface area, the toughness transition area, and the mounting substrate area are formed by integrated molding. These three functional areas are not simply mechanical combinations, but rather metallurgical bonding is achieved at the atomic diffusion level through a powder metallurgy process of partitioned powder loading and precision sintering. This results in an integrated structure with a continuous gradient transition in composition and properties at the bonding interface, avoiding stress concentration caused by abrupt performance changes and improving the overall structural reliability, thereby fundamentally resolving the performance contradictions in each area. Near the interface between the working surface area and the toughness transition area (i.e., the transition zone within a certain width on both sides of the interface), the contents of C, Cr, and Mo show a continuous gradient distribution from high to low. Near the interface between the toughness transition area and the mounting substrate area, the contents of C and Cr show a continuous gradient distribution from high to low.

[0015] The triangular shape of this invention is the same as that of existing technologies, comprising three functional parts: a working surface, a transition zone, and an installation zone. This is determined by the basic requirements of the circular knitting machine needle movement trajectory and fixed installation. However, existing triangular shapes are often treated as a homogeneous whole, using a single material (such as Cr12MoV steel) and improving performance through overall heat treatment or surface treatment (such as nitriding). This results in performance bottlenecks. The unique feature of this invention lies in the "zonal reinforcement" design of the internal material structure and the integrated molding process. Based on the understanding of the stress state and failure mechanism of different functional areas within the triangular shape, this invention creatively proposes a "functional adaptation and gradient transition" design concept at the material design and manufacturing level. It precisely divides the traditional triangular shape into functional zones, resulting in a continuous gradient in the internal material distribution and performance, thereby achieving performance improvement.

[0016] In traditional triangular alloys, increasing hardness often sacrifices toughness, leading to brittle fracture. In this invention, the working surface hardness reaches HRC 62-64, while the impact toughness in the transition zone is no less than 25 J (good impact resistance). Bench tests show that the wear resistance is more than 2.5 times that of the traditional Cr12MoV triangular alloy, and the impact fatigue resistance is improved by more than 50%. This simultaneous achievement of high hardness and high toughness is difficult to attain with existing technologies.

[0017] The superior machinability of the mounting area in this invention (increasing machining efficiency by 40%) reduces manufacturing costs, while the gradient transition combined with the high-toughness zone avoids interface cracking caused by machining stress. The overall structure exhibits no stress concentration under high-speed impact, significantly improving reliability.

[0018] As a preferred technical solution:

[0019] The composite needle circular knitting machine with a triangular reinforced composite structure as described above uses high-carbon, high-chromium free-cutting steel with the following chemical composition by mass percentage: C: 0.95~1.10%, Cr: 5.5~6.5%, Mo: 0.8~1.2%, V: 0.2~0.4%, Mn: ≤0.6%, Si: ≤0.6%, S: 0.10~0.14%, with the balance being Fe and unavoidable impurities. The high-carbon, high-chromium free-cutting steel used in the working area, after vacuum oil quenching and multiple deep cryogenic tempering treatments, has a metallographic structure consisting of a tempered martensitic matrix with uniformly distributed M7C3 and MC type carbides. Its macroscopic hardness can reach HRC 62~64, and its impact toughness (AKU) is not less than 8J.

[0020] The composite needle circular knitting machine with a triangular partitioned reinforced composite structure, as described above, uses medium-carbon, medium-chromium free-cutting steel with the following chemical composition by mass percentage: C: 0.45~0.55%, Cr: 2.5~3.5%, Mo: 0.4~0.6%, Mn: 0.6~0.9%, Si: 0.2~0.4%, S: 0.06~0.09%, with the balance being Fe and unavoidable impurities. The medium-carbon, medium-chromium free-cutting steel used in the toughness transition zone has a hardness controlled at HRC 52~54 after heat treatment, and its impact toughness (AKU) is significantly higher than that of the working surface zone, not less than 25J, effectively acting as a resistance zone for crack propagation.

[0021] The composite needle circular knitting machine with a partitioned reinforced composite triangular structure, as described above, uses low-carbon, low-chromium free-cutting steel with the following chemical composition by mass percentage: C: 0.15~0.25%, Cr: 0.8~1.2%, Mn: 0.9~1.2%, S: 0.24~0.28%, Ca: 0.002~0.006%, with the balance being Fe and unavoidable impurities. The low-carbon, low-chromium free-cutting steel used in the mounting base area has a hardness of HRC 28~32 after heat treatment, and its relative machinability (with 45 steel as 100%) can reach 150~180%, making it extremely easy to perform subsequent machining such as drilling and tapping.

[0022] As described above, in a composite needle circular knitting machine, a triangular composite structure with partitioned reinforcement has a C content that gradually decreases from 0.95-1.10% to 0.45-0.55%, a Cr content that gradually decreases from 5.5-6.5% to 2.5-3.5%, and a Mo content that gradually decreases from 0.8-1.2% to 0.4-0.6% along a transition zone 50-200 micrometers wide from the interface between the working surface area and the toughness transition zone.

[0023] Along the interface between the tough transition zone and the mounting substrate zone, along a transition zone 50-200 micrometers wide, the C content gradually decreases from 0.45-0.55% to 0.15-0.25%, and the Cr content gradually decreases from 2.5-3.5% to 0.8-1.2%.

[0024] The present invention also provides a method for forming a partitioned reinforced composite triangular structure for a composite needle circular knitting machine as described above. First, a precision mold is designed based on the three-dimensional model of the triangle. The mold cavity is divided into three independent powder cavities according to functional partitions: a working surface area, a toughness transition area, and an installation base area. Each powder cavity is precisely filled with free-cutting steel powder of the corresponding composition. Then, the triangle is subjected to cold isostatic pressing, high-temperature vacuum sintering, heat treatment, and precision machining to obtain the partitioned reinforced composite triangular structure for a composite needle circular knitting machine.

[0025] The temperature for high-temperature vacuum sintering is above 1250℃.

[0026] First, free-cutting steel powders with different formulations are separated and compacted using partitions, and then the partitions are removed for high-temperature sintering. In an environment above 1250℃, the metal atoms (such as Cr) and C atoms on both sides will actively permeate and migrate to each other. After a long period of heat preservation, a fusion zone with continuously and gradually changing composition and properties is generated on the original interface, so that the different parts are truly metallurgically combined into a whole.

[0027] As a preferred technical solution:

[0028] The forming method of a triangular composite structure with partition reinforcement for a composite needle circular knitting machine, as described above, includes the following specific steps:

[0029] (1) Mold design and powder filling: Based on the three-dimensional model of the triangle, a precision mold is designed. The mold cavity is divided into three independent powder cavities in sequence according to the functional area: the working surface area, the toughness transition area and the mounting base area. Each powder cavity is precisely filled with free-cutting steel powder of the corresponding composition, and the powder stacking density of each area is ensured to be uniform.

[0030] (2) Cold isostatic pressing: Bidirectional pressing is performed under a pressure of 300~600 MPa to obtain a high-density, high-strength triangular green blank;

[0031] (3) High temperature vacuum sintering: The triangular green billet is placed in a vacuum sintering furnace at 1250~1280℃ and held for 90~120 minutes. During this process, since the composition of the free-cutting steel in each region is not selected independently, but is based on the overall performance matching, the powder in different regions achieves a strong metallurgical bond through atomic diffusion (i.e., the powder in each region will interact and atomic diffusion behavior), and a composition gradient transition zone with a width of 50~200μm is formed at the interface, achieving a perfect composition gradient transition and metallurgical bond. After effectively eliminating the stress concentration caused by the sudden change in performance, the sintered billet is obtained.

[0032] (4) Heat treatment and finishing: First, heat treatment is performed on the sintered blank, and then the working track of the working surface of the heat-treated sintered blank is ground and polished to make the surface roughness Ra ≤ 0.2 μm. After meeting the running requirements of high-gauge knitting needles, the triangular composite structure of the composite needle circular weft machine with partition reinforcement is obtained.

[0033] As described above, in the forming method of a composite needle circular knitting machine with partitioned reinforcement of a composite triangular structure, in step (1), the mold cavity is precisely divided into three independent powder cavities: the working surface area, the transition area, and the installation area by an embedded partition.

[0034] As described above, in the forming method of a composite needle circular knitting machine with partitioned reinforcement of a composite triangular structure, in step (2), the density of the triangular green blank is 85-92% of the theoretical density and the compressive strength is 150-250 MPa.

[0035] Theoretical density = 1 / Σ (Wi / ρi);

[0036] Where Wi is the mass fraction of the i-th component in the free-cutting steel, ρi is the density of the i-th component in its pure form, and Σ represents the summation over all components.

[0037] As described above, in the method for forming a triangular composite structure with partition reinforcement for a composite needle circular knitting machine, the heat treatment process in step (4) is as follows: first, heat the sintered blank to 1030°C and hold it for 30-60 minutes, then immerse it in oil and quench it to room temperature, then heat the quenched sintered blank to 520°C, hold it for 90-120 minutes and then cool it to room temperature, then heat it again to 520°C, hold it for 90-120 minutes and then cool it to room temperature.

[0038] Beneficial effects:

[0039] (1) This invention systematically solves the technical problem that traditional triangles cannot simultaneously achieve high wear resistance, high impact resistance and excellent processing performance through precise partitioning design of material composition, significantly improving the service life and reliability of triangles, and is especially suitable for high-gauge, high-speed weft knitting circular knitting machines.

[0040] (2) In the manufacturing of triangles, the present invention adopts a partitioned component design and optimizes the material formula according to the functional requirements of different parts, achieving the best combination of wear resistance, toughness and machinability (i.e., the working surface has high hardness and good wear resistance; the transition area has sufficient toughness and impact resistance; the installation area is easy to process and has low cost).

[0041] (3) The present invention adopts a partitioned powder metallurgy process to achieve integrated molding of complex composition structures, avoiding the bonding strength problem caused by secondary processing such as welding and inlay.

[0042] (4) The present invention uses high alloy materials only on the working surface, which reduces the consumption of precious elements; near-net-shape forming reduces material waste; excellent machinability improves production efficiency and reduces overall cost by more than 30%.

[0043] (5) Due to the stress buffering effect of the gradient transition zone, the vibration and noise of the triangular composite structure of the composite needle circular knitting machine under high-speed operation (knitting needle speed 30~40 m / s) are reduced, the dynamic balance level reaches G2.5 level, and the radial runout is less than 0.015 mm, ensuring the stable operation of high-gauge knitting needles. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the triangular partitioned reinforced composite structure for the composite needle circular weft machine of the present invention;

[0045] Figure 2 The composite needle circular weft machine of this invention uses a triangular partitioned reinforced composite structure that is different from the triangular structure of the present invention. Figure 1 A diagram illustrating the angle;

[0046] In the figure, 1-working surface area, 2-toughness transition area, 3-installation substrate area. Detailed Implementation

[0047] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0048] To ensure that the performance of the substances used in each embodiment and comparative example is fully disclosed, the manufacturers and brands of the substances are specified. Other products from manufacturers and brands that conform to the limitations of this invention are also feasible.

[0049] The test methods for the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0050] Surface roughness: The composite needle circular knitting machine with partitioned reinforced composite triangular structure prepared in each embodiment was used as a sample. Then, referring to GB / T 1031-2009 "Product Geometric Specification (GPS) Surface Structure Profile Method Surface Roughness Parameters and Values", a contact surface roughness measuring instrument (model MarSurf M 300 C, German MarSurf, equipped with a diamond stylus with a tip radius of 2μm and a cone angle of 90°) was used to test the surface roughness of the five samples prepared in the same embodiment. Finally, the average value was calculated, and Ra was expressed in μm. The length (lr) of each sample was 0.8 mm. During the test, measurements were taken at five different positions evenly distributed on each working surface track, and the arithmetic mean was taken as the final result.

[0051] Hardness: The composite needle circular knitting machine triangular structures with partitioned reinforcement prepared in each embodiment were used as samples. Then, in accordance with GB / T 230.1-2018 "Metallic materials Rockwell hardness test - Part 1: Test method", the hardness of the working surface area, toughness transition area and mounting base area of ​​the sample were tested by Rockwell hardness tester. The results were read directly on the Rockwell hardness tester according to the depth difference. The initial test force was 98.07 N, the main test force was 1471 N, the indenter type was diamond conical indenter (apex angle 120°), and the ambient temperature was 20℃.

[0052] Impact toughness: Using the same raw material formulation for the triangular composite structure with partitioned reinforcement for the composite needle circular knitting machine prepared in each embodiment, independent standard specimens (55mm×10mm×10mm) were prepared for the working surface area, toughness transition area, and mounting base area using the process corresponding to the embodiment. These specimens were then used as samples. The impact toughness (i.e., impact energy absorption) of the working surface area and toughness transition area of ​​each specimen was tested according to GB / T 229-2020 "Charpy Impact Test for Metallic Materials". The test involved a pendulum impacting a standard notched specimen once, and the energy absorbed when the specimen fractured was measured. The notch type of the specimen was a standard V-notch (2mm deep), the test temperature was 25℃, the instantaneous impact velocity of the pendulum was 5.3 m / s, and the radius of curvature of the pendulum edge was 8mm.

[0053] Wear resistance: The composite needle circular knitting machine triangular structures with partitioned reinforcement prepared in each embodiment were used as samples. The wear resistance of the samples was then tested according to GB / T 12444-2006 "Metallic Materials Wear Test Method - Test Ring-Block Sliding Wear Test". The test was conducted by measuring the wear mark width at the middle and both ends (1 mm from the edge), taking the average of three measurements, and calculating the volumetric wear (in mm). 3 The wear resistance of the sample is denoted as 12.32 mm (width) × 19.05 mm (length), and the ambient temperature is 25℃.

[0054] Impact fatigue life: The composite needle circular knitting machine with partitioned reinforced composite triangular structure prepared in each embodiment was used as a sample. The impact fatigue life of the samples was then tested using a DC-150 impact testing machine until macroscopic cracks exceeding 1 mm in length appeared. The number of impact cycles the sample endured from the start to failure was recorded; this number represents the impact fatigue life. The impact energy was 5 J, and the impact frequency was 2 Hz.

[0055] Dynamic balance grade: The composite needle circular knitting machine with partitioned reinforced composite triangular structure prepared in each embodiment was used as a sample. Then, the dynamic balance grade of the sample was tested using a single-sided vertical balancing machine (model YYW-300, balancing accuracy grade G6.3) in accordance with GB / T 9239.11-2025 "Mechanical vibration rotor balancing Part 11: Balancing methods and tolerances for rigid rotors"; the test speed was 80% of the rated speed.

[0056] Radial runout: The composite needle circular knitting machine triangular structures with partitioned reinforcement prepared in each embodiment were used as samples. The samples were first reliably mounted on the mandrel, and then the position of the indicator of the measuring frame (MarStand 818 series) was adjusted so that the probe was perpendicular to and in contact with the working surface area (i.e., the needle travel surface) of the sample. Then, the mandrel was slowly and evenly rotated one revolution, and the maximum and minimum values ​​of the indicator pointer were recorded. The radial runout of the sample was calculated (i.e., radial runout = maximum reading of indicator – minimum reading of indicator). The obtained radial runout of the sample was compared with the line profile tolerance of 0.05 mm of the triangular needle travel curve relative to the positioning reference specified in FZ / T97010-2016 "General Technical Conditions for Triangular Structures of Circular Knitting Machines". If the radial runout of the sample was less than this tolerance, the composite needle circular knitting machine triangular structure of the present invention was deemed qualified. The measurement reference was the positioning reference surface (i.e., the positioning pin hole) of the triangular.

[0057] Machining efficiency: The composite needle circular knitting machine triangular structures with partitioned reinforcement prepared in each embodiment were used as samples. The samples were weighed using a precision balance (0.1g accuracy, model: Sartorius Quintix35-1S), and then cut using a CNC machining center (Haas VF-2 series). After cutting, the samples were weighed again using a precision balance. The cutting volume (mass difference / material density) was obtained based on the weight of the samples before and after cutting. Finally, the machining efficiency was quantitatively evaluated using the material removal rate (MRR, unit: cm³ / min). The formula for calculating the material removal rate is: Material removal rate = Cutting volume / Effective cutting time. The cutting tool was a 3-flute carbide end mill with a diameter of Φ10 mm, a cutting speed (Vc): 80 m / min, a feed per tooth (fz): 0.1 mm / tooth, an axial depth of cut (ap): 2 mm, and a radial depth of cut (ae): 10 mm (full cutting). The cooling method was a pressure of 0.5... Cooling was performed using a water-based emulsion (concentration 8wt%) at a pressure of MPa and a flow rate of 50 L / min.

[0058] Example 1

[0059] A composite needle circular knitting machine uses a partitioned reinforced composite structure triangle, such as... Figure 1 , Figure 2 As shown, it includes a working surface area 1, a tough transition area 2, and an installation substrate area 3;

[0060] Working area 1 is made of high-carbon, high-chromium free-cutting steel. The chemical composition of the high-carbon, high-chromium free-cutting steel by mass percentage is: C: 0.95%, Cr: 6%, Mo: 1%, V: 0.3%, Mn: 0.6%, Si: 0.5%, S: 0.1%, with the balance being Fe and unavoidable impurities.

[0061] The toughness transition zone 2 uses medium carbon medium chromium free-cutting steel. The chemical composition of the medium carbon medium chromium free-cutting steel by mass percentage is: C: 0.5%, Cr: 3%, Mo: 0.5%, Mn: 0.6%, Si: 0.2%, S: 0.06%, with the balance being Fe and unavoidable impurities.

[0062] The mounting base area 3 is made of low-carbon, low-chromium free-cutting steel. The chemical composition of the low-carbon, low-chromium free-cutting steel by mass percentage is: C: 0.2%, Cr: 1%, Mn: 0.9%, S: 0.24%, Ca: 0.002%, with the balance being Fe and unavoidable impurities.

[0063] The working surface area 1, the toughness transition area 2, and the mounting base area 3 are obtained by integral molding;

[0064] Along a 50-micrometer-wide transition zone from the interface between working area 1 and toughness transition zone 2, the C content gradually decreases from 0.95% to 0.45%, the Cr content gradually decreases from 5.5% to 2.5%, and the Mo content gradually decreases from 0.8% to 0.4%.

[0065] Along the interface from the tough transition zone 2 to the mounting substrate zone 3, along a 50-micrometer-wide transition band, the C content gradually decreases from 0.45% to 0.15%, and the Cr content gradually decreases from 2.5% to 0.8%.

[0066] The forming method for the triangular composite structure reinforced by partitioning in a composite needle circular knitting machine, as described above, includes the following steps:

[0067] (1) Mold design and powder filling: Based on the three-dimensional model of the triangle, a precision mold is designed. The mold cavity is divided into three independent powder cavities in sequence by embedded partitions: working surface area, toughness transition area and mounting base area. Each powder cavity is precisely filled with free-cutting steel powder of the corresponding composition.

[0068] (2) Cold isostatic pressing: bidirectional pressing is performed under a pressure of 300MPa to obtain a triangular green blank;

[0069] The obtained triangular green body has a compressive strength of 150 MPa and a theoretical density of 7.5 g / cm³. 3The density is 85% of the theoretical density; where the theoretical density is calculated by the formula: theoretical density = 1 / Σ (Wi / ρi), where Wi is the mass fraction of the i-th component in the free-cutting steel, and ρi is the density of the i-th component in its pure form.

[0070] (3) High-temperature vacuum sintering: The triangular green body is placed in a vacuum of 1.0×10⁻⁶. -1 The sintered billet was obtained by holding it in a vacuum sintering furnace at 1250°C for 90 minutes.

[0071] (4) Heat treatment and finishing: First, heat the sintered blank to 1030℃ and hold for 30 minutes. Then, immerse it in oil and quench it to 20℃. Then, heat the quenched sintered blank to 520℃, hold for 90 minutes and cool it to 20℃. Then, heat it to 520℃ again, hold for 90 minutes and cool it to 20℃. Then, grind and polish the working track of the working surface of the cooled sintered blank to make the surface roughness Ra 0.1μm, thus obtaining the triangular composite structure with partition reinforcement for the composite needle circular weft machine.

[0072] The final composite needle circular knitting machine has a triangular working surface area hardness of HRC 62, a toughness transition area hardness of HRC 52, a mounting base area hardness of HRC 28, an impact toughness of 8J in the working surface area, and an impact toughness of 25J in the toughness transition area.

[0073] The wear resistance of the triangular composite structure with partitioned reinforcement used in composite needle circular knitting machines is 0.3mm. 3 It has an impact fatigue life of 75,000 cycles, a dynamic balance grade of G2.5, and a machining efficiency of 11 cm. 3 / min; The radial runout of the working surface area of ​​the triangular composite structure of the composite needle circular weft machine is 0.005mm.

[0074] The composite needle circular knitting machine with partitioned reinforced composite structure triangle obtained above can be used in composite triangles for high-speed single-sided circular knitting machines with a cylinder diameter of 46 inches and a machine size of E44.

[0075] Example 2

[0076] A triangular composite structure with partitioned reinforcement for a composite needle circular weft knitting machine includes a working surface area, a toughness transition area, and an installation base area;

[0077] The working surface area is made of high-carbon, high-chromium free-cutting steel. The chemical composition of the high-carbon, high-chromium free-cutting steel by mass percentage is: C: 1%, Cr: 5.5%, Mo: 0.8%, V: 0.2%, Mn: 0.55%, Si: 0.55%, S: 0.12%, with the balance being Fe and unavoidable impurities.

[0078] The toughness transition zone uses medium-carbon, medium-chromium free-cutting steel. The chemical composition of the medium-carbon, medium-chromium free-cutting steel, by mass percentage, is: C: 0.45%, Cr: 2.5%, Mo: 0.4%, Mn: 0.75%, Si: 0.3%, S: 0.075%, with the balance being Fe and unavoidable impurities.

[0079] The mounting base area is made of low-carbon, low-chromium free-cutting steel. The chemical composition of the low-carbon, low-chromium free-cutting steel by mass percentage is: C: 0.15%, Cr: 0.8%, Mn: 1.05%, S: 0.28%, Ca: 0.004%, with the balance being Fe and unavoidable impurities.

[0080] The working surface area, the toughness transition area, and the mounting base area are obtained through integrated molding;

[0081] Along a 125-micrometer-wide transition zone on both sides of the interface between the working surface area and the tough transition zone, the C content gradually decreases from 1.025% to 0.5%, the Cr content gradually decreases from 6% to 3%, and the Mo content gradually decreases from 1% to 0.5%.

[0082] Along the interface between the tough transition zone and the mounting substrate zone, along a 125-micrometer-wide transition band, the C content gradually decreases from 0.5% to 0.2%, and the Cr content gradually decreases from 3% to 1%.

[0083] The forming method for the triangular composite structure reinforced by partitioning in a composite needle circular knitting machine, as described above, includes the following steps:

[0084] (1) Mold design and powder filling: Based on the three-dimensional model of the triangle, a precision mold is designed. The mold cavity is divided into three independent powder cavities in sequence by embedded partitions: working surface area, toughness transition area and mounting base area. Each powder cavity is precisely filled with free-cutting steel powder of the corresponding composition.

[0085] (2) Cold isostatic pressing: bidirectional pressing is performed under a pressure of 400MPa to obtain a triangular green blank;

[0086] The obtained triangular green body has a compressive strength of 200 MPa and a theoretical density of 7.75 g / cm³. 3 The density is 88.5% of the theoretical density; the theoretical density is calculated by the formula: theoretical density = 1 / Σ (Wi / ρi), where Wi is the mass fraction of the i-th component in the free-cutting steel, and ρi is the density of the i-th component in its pure form.

[0087] (3) High-temperature vacuum sintering: The triangular green body is placed in a vacuum of 5.0×10⁻⁶. -2 The sintered billet was obtained by holding it in a vacuum sintering furnace at 1260°C for 100 minutes.

[0088] (4) Heat treatment and finishing: First, heat the sintered blank to 1030℃ and hold for 50 minutes, then immerse it in oil and quench it to 22.5℃. Then heat the quenched sintered blank to 520℃, hold for 105 minutes and cool it to 22.5℃. Then heat it to 520℃ again, hold for 105 minutes and cool it to 22.5℃. Then grind and polish the working track of the working surface of the cooled sintered blank to make the surface roughness Ra 0.15μm, thus obtaining the triangular composite structure with partition reinforcement for the composite needle circular weft machine.

[0089] The final composite needle circular weft machine has a working surface area hardness of HRC 63, a toughness transition area hardness of HRC 53, a mounting base area hardness of HRC 30, an impact toughness of 9J in the working surface area, and an impact toughness of 26J in the toughness transition area.

[0090] The wear resistance of the triangular composite structure with partitioned reinforcement used in composite needle circular knitting machines is 0.4mm. 3 It has an impact fatigue life of 97,500 cycles, a dynamic balance grade of G3.7, and a machining efficiency of 14 cm. 3 / min; The radial runout of the working surface area of ​​the triangular composite structure of the composite needle circular weft machine is 0.01mm.

[0091] The composite needle circular knitting machine with partitioned reinforced composite structure triangle obtained above can be used in composite triangles for high-speed single-sided circular knitting machines with a cylinder diameter of 46 inches and a machine size of E44.

[0092] Example 3

[0093] A triangular composite structure with partitioned reinforcement for a composite needle circular weft knitting machine includes a working surface area, a toughness transition area, and an installation base area;

[0094] The working surface area is made of high-carbon, high-chromium free-cutting steel. The chemical composition of the high-carbon, high-chromium free-cutting steel by mass percentage is: C: 1.1%, Cr: 6.5%, Mo: 1.2%, V: 0.4%, Mn: 0.5%, Si: 0.6%, S: 0.14%, with the balance being Fe and unavoidable impurities.

[0095] The toughness transition zone uses medium-carbon, medium-chromium free-cutting steel. The chemical composition of the medium-carbon, medium-chromium free-cutting steel, by mass percentage, is: C: 0.55%, Cr: 3.5%, Mo: 0.6%, Mn: 0.9%, Si: 0.4%, S: 0.09%, with the balance being Fe and unavoidable impurities.

[0096] The mounting base area is made of low-carbon, low-chromium free-cutting steel. The chemical composition of the low-carbon, low-chromium free-cutting steel by mass percentage is: C: 0.25%, Cr: 1.2%, Mn: 1.2%, S: 0.25%, Ca: 0.006%, with the balance being Fe and unavoidable impurities.

[0097] The working surface area, the toughness transition area, and the mounting base area are obtained through integrated molding;

[0098] Along a 200-micrometer-wide transition zone from the working surface area to the tough transition zone, the C content gradually decreases from 1.1% to 0.55%, the Cr content gradually decreases from 6.5% to 3.5%, and the Mo content gradually decreases from 1.2% to 0.6%.

[0099] Along a 200-micrometer-wide transition zone from the tough transition zone to the mounting substrate zone, the C content gradually decreases from 0.55% to 0.25%, and the Cr content gradually decreases from 3.5% to 1.2%.

[0100] The forming method for the triangular composite structure reinforced by partitioning in a composite needle circular knitting machine, as described above, includes the following steps:

[0101] (1) Mold design and powder filling: Based on the three-dimensional model of the triangle, a precision mold is designed. The mold cavity is divided into three independent powder cavities in sequence by embedded partitions: working surface area, toughness transition area and mounting base area. Each powder cavity is precisely filled with free-cutting steel powder of the corresponding composition.

[0102] (2) Cold isostatic pressing: bidirectional pressing is performed under a pressure of 600MPa to obtain a triangular green blank;

[0103] The obtained triangular green body has a compressive strength of 250 MPa and a theoretical density of 8 g / cm³. 3 The density is 92% of the theoretical density; the theoretical density is calculated by the formula: theoretical density = 1 / Σ (Wi / ρi), where Wi is the mass fraction of the i-th component in the free-cutting steel, and ρi is the density of the i-th component in its pure form.

[0104] (3) High-temperature vacuum sintering: The triangular green body is placed in a vacuum of 1.0×10⁻⁶. -3 The sintered billet was obtained by holding it in a vacuum sintering furnace at 1280°C for 110 minutes.

[0105] (4) Heat treatment and finishing: First, heat the sintered blank to 1030℃ and hold for 60 minutes. Then, immerse it in oil and quench it to 25℃. Then, heat the quenched sintered blank to 520℃, hold for 120 minutes and cool it to 25℃. Then, heat it to 520℃ again, hold for 120 minutes and cool it to 25℃. Then, grind and polish the working track of the working surface of the cooled sintered blank to make the surface roughness Ra 0.2μm, thus obtaining the triangular composite structure with partition reinforcement for the composite needle circular weft machine.

[0106] The hardness HRC of the working surface area of ​​the composite needle circular weft knitting machine triangular reinforced composite structure is 64, the hardness HRC of the toughness transition area is 54, the hardness HRC of the mounting base area is 32, the impact toughness of the working surface area is 10J, and the impact toughness of the toughness transition area is 27J.

[0107] The wear resistance of the triangular composite structure with partitioned reinforcement used in composite needle circular knitting machines is 0.5mm. 3 It has an impact fatigue life of 120,000 cycles, a dynamic balance grade of G5.0, and a machining efficiency of 17 cm. 3 / min; The radial runout of the working surface area of ​​the triangular composite structure of the composite needle circular weft machine is 0.015mm.

[0108] The composite needle circular knitting machine with partitioned reinforced composite structure triangle obtained above can be used in composite triangles for high-speed single-sided circular knitting machines with a cylinder diameter of 46 inches and a machine size of E44.

[0109] Example 4

[0110] A triangular composite structure with partitioned reinforcement for a composite needle circular weft knitting machine includes a working surface area, a toughness transition area, and an installation base area;

[0111] The working surface area is made of high-carbon, high-chromium free-cutting steel. The chemical composition of the high-carbon, high-chromium free-cutting steel by mass percentage is: C: 1.05%, Cr: 5.8%, Mo: 1.1%, V: 0.25%, Mn: 0.58%, Si: 0.52%, S: 0.11%, with the balance being Fe and unavoidable impurities.

[0112] The toughness transition zone uses medium-carbon, medium-chromium free-cutting steel. The chemical composition of the medium-carbon, medium-chromium free-cutting steel, by mass percentage, is: C: 0.52%, Cr: 2.8%, Mo: 0.55%, Mn: 0.8%, Si: 0.25%, S: 0.07%, with the balance being Fe and unavoidable impurities.

[0113] The mounting base area is made of low-carbon, low-chromium free-cutting steel. The chemical composition of the low-carbon, low-chromium free-cutting steel by mass percentage is: C: 0.23%, Cr: 0.9%, Mn: 1%, S: 0.26%, Ca: 0.003%, with the balance being Fe and unavoidable impurities.

[0114] The working surface area, the toughness transition area, and the mounting base area are obtained through integrated molding;

[0115] Along an 80-micrometer-wide transition zone from the working surface area to the tough transition zone, the C content gradually decreases from 1.05% to 0.48%, the Cr content gradually decreases from 5.8% to 2.8%, and the Mo content gradually decreases from 0.9% to 0.45%.

[0116] Along a 150-micrometer-wide transition zone from the tough transition zone to the mounting substrate zone, the C content gradually decreases from 0.51% to 0.18%, and the Cr content gradually decreases from 2.75% to 0.9%.

[0117] The forming method for the triangular composite structure reinforced by partitioning in a composite needle circular knitting machine, as described above, includes the following steps:

[0118] (1) Mold design and powder filling: Based on the three-dimensional model of the triangle, a precision mold is designed. The mold cavity is divided into three independent powder cavities in sequence by embedded partitions: working surface area, toughness transition area and mounting base area. Each powder cavity is precisely filled with free-cutting steel powder of the corresponding composition.

[0119] (2) Cold isostatic pressing: bidirectional pressing is performed under a pressure of 500MPa to obtain a triangular green blank;

[0120] The obtained triangular green body has a compressive strength of 175 MPa and a theoretical density of 7.6 g / cm³. 3 The density is 87% of the theoretical density; the theoretical density is calculated by the formula: theoretical density = 1 / Σ (Wi / ρi), where Wi is the mass fraction of the i-th component in the free-cutting steel, and ρi is the density of the i-th component in its pure form.

[0121] (3) High-temperature vacuum sintering: The triangular green body is placed in a vacuum of 7.5×10 -2 The sintered billet was obtained by holding it in a vacuum sintering furnace at 1270°C for 120 minutes.

[0122] (4) Heat treatment and finishing: First, heat the sintered blank to 1030℃ and hold for 40 minutes. Then, immerse it in oil and quench it to 23℃. Then, heat the quenched sintered blank to 520℃, hold for 100 minutes and cool it to 23℃. Then, heat it to 520℃ again, hold for 98 minutes and cool it to 23℃. Then, grind and polish the working track of the working surface of the cooled sintered blank to make the surface roughness Ra 0.16μm, thus obtaining the triangular composite structure with partition reinforcement for the composite needle circular weft machine.

[0123] The final composite needle circular knitting machine has a triangular working surface area hardness of HRC 62.5, a toughness transition area hardness of HRC 53.5, a mounting base area hardness of HRC 31, an impact toughness of 9J in the working surface area, and an impact toughness of 26J in the toughness transition area.

[0124] The wear resistance of the triangular composite structure with partitioned reinforcement used in composite needle circular knitting machines is 0.35mm. 3 It has an impact fatigue life of 85,000 cycles, a dynamic balance grade of G3, a radial runout of 0.008 mm, and a machining efficiency of 13 cm². 3 / min; The radial runout of the working surface area of ​​the triangular composite structure of the composite needle circular weft machine is 0.008mm.

[0125] The composite needle circular knitting machine with partitioned reinforced composite structure triangle obtained above can be used in composite triangles for high-speed single-sided circular knitting machines with a cylinder diameter of 46 inches and a machine size of E44.

[0126] Example 5

[0127] A triangular composite structure with partitioned reinforcement for a composite needle circular weft knitting machine includes a working surface area, a toughness transition area, and an installation base area;

[0128] The working surface area is made of high-carbon, high-chromium free-cutting steel. The chemical composition of the high-carbon, high-chromium free-cutting steel by mass percentage is: C: 0.98%, Cr: 6.2%, Mo: 0.9%, V: 0.32%, Mn: 0.6%, Si: 0.58%, S: 0.13%, with the balance being Fe and unavoidable impurities.

[0129] The toughness transition zone uses medium-carbon, medium-chromium free-cutting steel. The chemical composition of the medium-carbon, medium-chromium free-cutting steel, by mass percentage, is: C: 0.47%, Cr: 3.2%, Mo: 0.46%, Mn: 0.7%, Si: 0.35%, S: 0.08%, with the balance being Fe and unavoidable impurities.

[0130] The mounting base area is made of low-carbon, low-chromium free-cutting steel. The chemical composition of the low-carbon, low-chromium free-cutting steel by mass percentage is: C: 0.18%, Cr: 1.1%, Mn: 1.1%, S: 0.27%, Ca: 0.005%, with the balance being Fe and unavoidable impurities.

[0131] The working surface area, the toughness transition area, and the mounting base area are obtained through integrated molding;

[0132] Along a 150-micrometer-wide transition zone from the working surface area to the tough transition zone, the C content gradually decreases from 1% to 0.53%, the Cr content gradually decreases from 6.3% to 3.2%, and the Mo content gradually decreases from 1.1% to 0.55%.

[0133] Along a 75-micrometer-wide transition zone from the tough transition zone to the mounting substrate zone, the C content gradually decreases from 0.47% to 0.22%, and the Cr content gradually decreases from 3.25% to 1.1%.

[0134] The forming method for the triangular composite structure reinforced by partitioning in a composite needle circular knitting machine, as described above, includes the following steps:

[0135] (1) Mold design and powder filling: Based on the three-dimensional model of the triangle, a precision mold is designed. The mold cavity is divided into three independent powder cavities in sequence by embedded partitions: working surface area, toughness transition area and mounting base area. Each powder cavity is precisely filled with free-cutting steel powder of the corresponding composition.

[0136] (2) Cold isostatic pressing: bidirectional pressing is performed under a pressure of 450MPa to obtain a triangular green blank;

[0137] The obtained triangular green body has a compressive strength of 225 MPa and a theoretical density of 7.9 g / cm³. 3 The density is 91% of the theoretical density; where the theoretical density is calculated by the formula: theoretical density = 1 / Σ (Wi / ρi), where Wi is the mass fraction of the i-th component in the free-cutting steel, and ρi is the density of the i-th component in its pure form.

[0138] (3) High-temperature vacuum sintering: The triangular green body is placed in a vacuum of 2.5×10 -2 The sintered billet was obtained by holding it in a vacuum sintering furnace at 1265°C for 105 minutes.

[0139] (4) Heat treatment and finishing: First, heat the sintered blank to 1030℃ and hold for 45 minutes. Then, immerse it in oil and quench it to 24℃. Then, heat the quenched sintered blank to 520℃, hold for 110 minutes and cool it to 24℃. Then, heat it to 520℃ again, hold for 112 minutes and cool it to 24℃. Then, grind and polish the working track of the working surface of the cooled sintered blank to make the surface roughness Ra 0.18μm, thus obtaining the triangular composite structure with partition reinforcement for the composite needle circular weft machine.

[0140] The final composite needle circular knitting machine has a triangular working surface area hardness of HRC 63.5, a toughness transition area hardness of HRC 54.6, a mounting base area hardness of HRC 29, an impact toughness of 10J in the working surface area, and an impact toughness of 27J in the toughness transition area.

[0141] The wear resistance of the triangular composite structure with partitioned reinforcement used in composite needle circular knitting machines is 0.45mm. 3 It has an impact fatigue life of 105,000 cycles, a dynamic balance grade of G4, and a machining efficiency of 16 cm. 3 / min; The radial runout of the working surface area of ​​the triangular composite structure of the composite needle circular weft machine is 0.012mm.

[0142] The composite needle circular knitting machine with partitioned reinforced composite structure triangle obtained above can be used in composite triangles for high-speed single-sided circular knitting machines with a cylinder diameter of 46 inches and a machine size of E44.

Claims

1. A zoned reinforced composite structure cam for a compound needle circular weft knitting machine, characterized by: The working face area, the ductile transition area and the installation base area are obtained by integrated forming. The contents of C, Cr and Mo are continuously distributed from high to low near the interface from the working face area to the ductile transition area. The chemical composition of the high-carbon high-chromium free-cutting steel is as follows in terms of mass percentage: C: 0.95-1.10%, Cr: 5.5-6.5%, Mo: 0.8-1.2%, V: 0.2-0.4%, Mn: ≤0.6%, Si: ≤0.6%, S: 0.10-0.14%, and the balance of Fe and inevitable impurities.

2. A partitioned reinforced composite structure cam for a compound needle circular weft knitting machine according to claim 1, characterized in that, The chemical composition of the medium-carbon medium-chromium free-cutting steel is as follows in terms of mass percentage: C: 0.45-0.55%, Cr: 2.5-3.5%, Mo: 0.4-0.6%, Mn: 0.6-0.9%, Si: 0.2-0.4%, S: 0.06-0.09%, and the balance of Fe and inevitable impurities.

3. A partitioned reinforced composite structure cam for a compound needle circular weft knitting machine according to claim 2, characterized in that, The chemical composition of the low-carbon low-chromium free-cutting steel is as follows in terms of mass percentage: C: 0.15-0.25%, Cr: 0.8-1.2%, Mn: 0.9-1.2%, S: 0.24-0.28%, Ca: 0.002-0.006%, and the balance of Fe and inevitable impurities.

4. A partitioned reinforced composite structure cam for a compound needle circular weft knitting machine according to claim 3, characterized in that, The contents of C, Cr and Mo are continuously distributed from high to low near the interface from the working face area to the ductile transition area.

5. A zoned reinforced composite structure cam for a compound needle circular weft knitting machine according to claim 4, characterized in that, The contents of C, Cr and Mo are continuously distributed from high to low near the interface from the working face area to the ductile transition area. First, a precision die is designed according to the three-dimensional model of the triangle, and the die cavity is isolated into three independent powder cavities of the working face area, the ductile transition area and the installation base area in sequence according to the function, and the corresponding composition of free-cutting steel powder is accurately filled into each powder cavity.

6. A method of forming a partitioned reinforced cam structure for a compound needle circular weft knitting machine according to any one of claims 1 to 5, characterized in that: The temperature of the high-temperature vacuum sintering is above 1250℃. The specific steps are as follows:

7. The method of claim 6, wherein the method further comprises the steps of: providing a plurality of reinforcing elements; and positioning the plurality of reinforcing elements in the mold. ​ (1) Mould design and powder filling: according to the three-dimensional model of the triangular, a precision mould is designed, the mould cavity is isolated into three independent powder cavities, i.e. the working surface area, the ductile transition area and the installation base area in sequence according to the function, and the corresponding composition of the free-cutting steel powder is accurately filled into each powder cavity; (2) Cold isostatic pressing: two-way pressing is carried out under the pressure of 300-600 MPa to obtain the triangular green body; (3) High-temperature vacuum sintering: the triangular green body is placed in a vacuum sintering furnace at 1250-1280℃, and heat preservation is carried out for 90-120 minutes to obtain the sintered body; (4) Heat treatment and finishing: the sintered body is first heat treated, and then the working track of the working surface of the sintered body after heat treatment is ground and polished to make the surface roughness Ra ≤ 0.2 μm, thereby obtaining the partition-strengthened composite structure triangular for the compound needle circular weft knitting machine.

8. The method for forming a triangular composite structure with partitioned reinforcement for a composite needle circular knitting machine according to claim 7, characterized in that, In step (1), the mould cavity is accurately divided into three independent powder cavities, i.e. the working surface area, the transition area and the installation area, by the embedded partition plate.

9. The method of claim 7, wherein the method further comprises: forming the composite structure by: providing a first layer of a first material; providing a second layer of a second material; and providing a third layer of a third material; and bonding the first, second, and third layers together to form the composite structure. In step (2), the density of the triangular green body is 85-92% of the theoretical density, and the compressive strength is 150-250 MPa; Theoretical density = 1 / Σ (Wi / ρi); Wherein, Wi is the mass fraction of the i-th component in the free-cutting steel, and ρi is the density of the pure substance of the i-th component.

10. A method of forming a partitioned reinforced composite structure cam for a compound needle circular weft knitting machine according to claim 7, characterized in that, In step (4), the heat treatment process is as follows: first, the sintered body is heated to 1030℃ and heat preserved for 30-60 minutes, then immersed in oil for quenching to room temperature, then the sintered body after quenching is heated to 520℃, heat preserved for 90-120 minutes and then cooled to room temperature, then heated to 520℃ again, heat preserved for 90-120 minutes and then cooled to room temperature.

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