A method for forming and preparing a high-temperature iron-based self-lubricating and anti-friction composite material

Abstract

The present invention discloses a method for constructing and forming a high-temperature iron-based self-lubricating and anti-friction composite material, which belongs to the technical field of high-temperature anti-friction composite material preparation. The preparation method comprises the following steps: preparation of an iron-based preform, pretreatment of graphite fibers, and construction and forming; currently, graphite is widely used in matrix materials as a lubricating medium, but the addition of graphite leads to an increase in carbon content, which causes the plasticity and forgeability of iron-based metals to drop sharply, affecting the service performance of the material; the method of the present invention adds micron-sized graphite fibers to the iron-based material for construction and forming, and controls the amount of fiber added by nickel plating the fiber surface to prepare a graphite / iron-based composite material with good bonding strength; the presence of uniform graphite inside the matrix forms a lubricating film during wear, thereby exerting a good anti-friction effect, improving the service life and working stability of hot-processed parts, and improving production efficiency.

Description

Technical Field

[0001] The invention relates to a method for constructing and forming a high-temperature iron-based self-lubricating anti-friction composite material, belonging to the technical field of high-temperature anti-friction composite material preparation. Background Art

[0002] Thermal processing machinery and parts play a very key role in my country's economic construction. They are widely used in various industries such as chemical industry, construction, aerospace, electricity, natural gas, metallurgy, etc., and are also the fields where wear and tear occurs most frequently. According to statistics, about 80% of the failure of mechanical parts in the world is related to wear and tear, resulting in material losses of up to 10 million tons, and direct or indirect economic losses of hundreds of billions of dollars; due to its extremely harsh working environment, it needs to withstand working environments such as thermal shock, strong friction, heavy load, extrusion, and cooling water quenching, which places relatively high requirements on the comprehensive performance of materials, especially in terms of wear resistance.

[0003] Nowadays, with the continuous development and innovation in the field of materials, the wear resistance of equipment and parts is improved from two aspects. On the one hand, a large amount of wear-resistant elements such as Cr and Ni are added to the materials. However, from the perspective of my country's sustainable development: nickel and chromium are strategic resources with relatively small resource reserves. At the same time, from the perspective of corporate economic benefits, the cost of raw materials is too high and it is not suitable to be used to manufacture equipment and parts. On the other hand, graphite is widely used in matrix materials as a lubricating medium. When the matrix material is continuously squeezed and rubbed by external forces, the evenly distributed graphite can form a lubricating film on its surface to help it resist severe wear from the outside. However, as the graphite content increases, the bonding strength between the inside of the matrix decreases, and at the same time, the carbon content increases, which reduces the performance of the matrix material, especially the sharp decrease in plastic toughness, making the matrix material very brittle, affecting the service performance of the material; therefore, considering adding appropriate graphite to the matrix material is one of the effective ways to solve the failure of the guide plate material.

[0004] According to the above problems, we replaced the high-content nickel-chromium alloy with iron-based composite materials, so that the cost of raw materials was effectively controlled. The iron-based raw materials were melted and cast into a slab with uniform composition and prefabricated with micron-sized graphite fibers. After stacking, solid metallurgical bonding was performed using diffusion welding under a vacuum environment, and free forging process was performed under a forging press to obtain graphite / iron-based composite material components. In the hot-processed parts made by this method, the graphite fibers are evenly distributed in the matrix, which solves the problem of uneven graphite addition in large-size castings. In addition, the graphite fibers can increase the bonding strength with the matrix after nickel plating. When it works under high temperature, heavy load, and strong friction, the graphite fibers evenly distributed in the matrix will form a layer of graphite lubricating film on its surface, which can play a good anti-friction effect, reduce the severe wear of the hot-processed parts and the outside world, and effectively extend the service life and working stability of the hot-processed parts, thereby improving production efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide a method for constructing and forming a high-temperature iron-based self-lubricating and anti-friction composite material, wherein the iron-based composite material after alloy design is prefabricated, and graphite fibers after chemical nickel plating are added to a homogeneous plate blank for construction and forming. The hot-processed component prepared by the method has uniform micron-level graphite fibers distributed in its matrix. When facing high temperature, heavy load, and strong friction, the graphite lubricating film formed on the surface can play a good anti-friction effect, reduce the wear rate of the guide plate, increase the service life and working stability of the hot-processed component, and improve production efficiency. The method specifically comprises the following steps:

[0006] (1) Preparation of iron-based preform: The iron-based preform is prepared by vacuum melting and casting methods; the size and volume of the iron-based preform should match the subsequent construction and final product volume.

[0007] (2) Graphite fiber pretreatment: After the graphite fiber is sensitized and activated, it is placed in a solution composed of nickel salt, chelating agent, reducing agent, stabilizer and buffer in a certain proportion, and heated in a water bath and kept warm so that a uniformly distributed and firm nickel layer is obtained on the fiber surface.

[0008] (3) Construction and forming: The iron-based blank after cooling and forming is polished to be smooth and flat, and then the surface is cleaned with an organic solvent to ensure that the surface is highly clean and fresh metal is exposed. The nickel-plated graphite fibers are placed in the evenly distributed through holes on the blank, compacted and stacked to form; then placed in a vacuum environment, heated and pressurized to make the weldments in close contact, and kept warm for a period of time to achieve solid metallurgical bonding between the weldment joints, and then the welded blank is placed under a forging press for free forging process.

[0009] Preferably, the mass percentages of the iron-based components in step (1) of the present invention are: Cr: 32% to 34%, Ni: 3% to 5%, Si: 0.5% to 1.5%, C: 0.2% to 0.5%, Mn: 0.2% to 0.6%, Ti: 0.2% to 0.4%, V: 0.1% to 0.8%, Mo: 1% to 2%, Cu: 0.3% to 0.8%. Except for the above-mentioned elemental components, the rest are unavoidable impurities.

[0010] Preferably, the Cr and Ni elements in the iron-based component described in step (1) of the present invention are key wear-resistant elements of the matrix material, which play a role of solid solution strengthening in the matrix, thereby improving the corrosion resistance and high temperature resistance of the material. When the content of these two elements in the material composition is small, the matrix is ​​softer during contact with the outside world, and the wear amount is too large, so that the material fails prematurely and affects the working stability of the equipment and the production efficiency of the product. At the same time, from the perspective of economic benefits and my country's resource reserves, Cr and Ni elements should not be too much, so the content of Cr and Ni elements is controlled at 32% to 34% and 3% to 5% respectively; Si and Mn elements are used as reducing agents and deoxidizers to remove impurities during the smelting process. An appropriate amount of silicon can significantly improve the tensile strength of the matrix, and can effectively improve the antioxidant ability when combined with alloy elements such as molybdenum; the addition of Ti, Mo, and V elements can play a role in refining grains and improving the density of the matrix, and at the same time have good comprehensive mechanical properties under high temperature environment; the addition of an appropriate amount of Cu element is to improve the strength and ductility of the matrix, and its content is controlled at 0.3% to 0.8%; the content of C element in the matrix should not be too much, and too high C content will cause the matrix to become brittle, affecting the subsequent forging and other treatments of the present invention, so the content of C element is controlled at 0.2% to 0.5%.

[0011] Preferably, the vacuum melting in step (1) of the present invention is carried out in a vacuum induction melting furnace, the melting temperature is 1550°C to 1650°C, the argon pressure is 0.05 to 2 MPa, and the vacuum degree in the vacuum induction melting furnace is (1 to 5)×(10 -1 ~10 -3 )Pa.

[0012] Preferably, the sensitizing solution in step (2) of the present invention is hydrochloric acid + stannous chloride, with concentrations of 25 ml / L and 20 g / L respectively; the activating solution is silver nitrate, with a concentration of 4 g / L.

[0013] Preferably, the nickel salt of the present invention is nickel sulfate with a concentration of 35-40 g / L; the complexing agent is sodium citrate with a concentration of 30-34 g / L; the reducing agent is sodium hypophosphite with a concentration of 27-30 g / L; the stabilizer is boric acid with a concentration of 8-10 g / L; the buffer is sodium hydroxide with a concentration of 20-25 g / L; the heating temperature is 60-70°C, and the insulation time is 1-1.5 h.

[0014] Preferably, the graphite fiber in step (2) of the present invention has a diameter of 5 to 50 μm, a length of 1 to 20 mm, and a density of 1.77 to 1.82 g / cm 3 .

[0015] Preferably, the organic solvent described in step (3) of the present invention is alcohol or acetone, the through-hole area on the slab accounts for 1 / 24 of the slab area, the hole depth of the top and bottom slabs is 1 / 2 of the slab, and the volume fraction of graphite fiber is 10% to 25% of the slab preform after stacking.

[0016] Preferably, the stacking forming in step (3) of the present invention is to overlap and stack the slabs together to form a cubic structure; the advantage of this method is that it solves the problem of uneven addition of reinforcements to large-sized castings, and the evenly distributed through holes in the slabs can be well filled with reinforcements, and then after stacking, the reinforcements can be evenly distributed in the matrix, which provides more operability and convenience for subsequent process treatment.

[0017] Preferably, the vacuum degree in step (3) of the present invention is (1-20)×10 -3 Pa, heated to 900-1050°C at a heating rate of 85-95°C / min, with a pressure of 0.5-50MPa and a holding time of 2h-5h.

[0018] Preferably, the specific steps of the free forging process of the present invention are as follows:

[0019] ① Heat the slab to 850℃ at a rate of 80-90℃ / min, keep it warm for 0.5-1h, then heat it to 1050-1150℃, keep it warm for 1-2h, and then put it into the forging press for the first upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to the original size of the forging, and the final forging temperature is 800-900℃.

[0020] ② Heat the slab to 850℃ at a rate of 80-90℃ / min, keep it warm for 0.5-1h, then reheat it to 1050-1150℃, keep it warm for 1-2h, and then put it into the forging press for the second upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to the original size of the forging, and the final forging temperature is 800-900℃.

[0021] ③ Heat the slab to 850℃ at a rate of 80-90℃ / min, keep it warm for 0.5-1h, then heat the slab to 1050-1150℃ again, keep it warm for 1-2h, and then put it into the forging press for the third upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to 0.3-0.4 of the original height of the forging.

[0022] ④ After forging, heat the slab to 850°C at a heating rate of 100-120°C / min and air cool to room temperature.

[0023] Preferably, the free forging process described in step (3) of the present invention has the advantage over conventional forging in that after the free forging process is implemented, the density of the matrix structure is greatly improved compared with the conventional forging process, and the internal defects become less; repeated upsetting and drawing operations significantly improve the mechanical properties, enhance the internal compaction effect of the material, and make the metallurgical bonding ability between the stacked slabs better; at the same time, the material is fully deformed in all directions, the graphite fiber reinforcement in the matrix is ​​more evenly distributed, and the bonding with the matrix interface is more firm; appropriate heating after the forging is completed eliminates the internal stress generated during the forging process, and at the same time plays a role in refining the grains and uniformizing the structure for subsequent processing.

[0024] Beneficial effects of the present invention:

[0025] (1) Currently, graphite has been widely used as a lubricating medium in hot processing machinery. However, the increase in carbon content caused by the addition of graphite seriously reduces the forming properties of iron-based metals, causing a sharp drop in plasticity and forgeability, affecting the service performance of the material. The present invention designs an alloy with an iron-based component and prefabricates it with nickel-plated graphite fibers. After stacking and forming, diffusion welding is used for solid-state metallurgical bonding in a vacuum environment, thereby effectively solving the technical problem of difficult processing. The present invention also uniformly distributes the graphite fibers in the matrix through a free forging process. This method solves the problem of uneven graphite addition in large-size castings.

[0026] (2) Nickel-plated micron-sized graphite fibers are added to the iron matrix to act as a lubricating medium, and the amount of graphite fibers added is controlled to enhance the bonding strength between the graphite fibers and the matrix. The graphite / iron-based composite material components made by this method take into account the performance of the material itself and when facing high temperature, high speed, and high pressure wear, the graphite lubricating film formed on the surface can exert a good wear-reducing effect, reduce the wear rate of the material, increase the service life and working stability of the hot processing parts, and improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a comparison chart of the friction coefficient of guide plate materials made by two different methods when in service at 750℃;

[0028] Figure 2 This is a schematic diagram of preparing a high-temperature iron-based self-lubricating and anti-friction composite material using a building forming method according to the present invention;

[0029] Figure 3 It is a schematic diagram of the forging process of the present invention;

[0030] Figure 4 Schematic diagram of graphite fibers distributed in the matrix after forging. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but the protection scope of the present invention is not limited to the contents.

[0032] Example 1

[0033] A method for constructing and forming a high-temperature iron-based self-lubricating and anti-friction composite material comprises the following steps:

[0034] (1) Preparation of iron-based preform: raw materials such as ferrochrome, ferronickel, carbon, ferrotitanium, ferromolybdenum, copper, ferrovanadium or other alloys or iron ore are added into a vacuum furnace in a certain proportion; the raw materials are heated to 1650°C by the high temperature of the electric arc; argon gas is introduced as a protective gas with an argon pressure of 2 MPa and the vacuum degree is 6.7×10 -3 Pa, ferrosilicon, ferromanganese and other alloying elements are added as deoxidizers. After the impurities and oxides in the steel are gradually removed, the molten metal is poured into a graphite mold with a size of 150×150×25 mm, wherein the depth of the holes in the top and bottom slabs is 12.5 mm, and the molten metal is naturally cooled to room temperature. The mass percentages of the iron-based components in this embodiment are: Cr: 34%, Ni: 5%, Si: 1.5%, C: 0.5%, Mn: 0.6%, Ti: 0.4%, V: 0.8%, Cu: 0.8%, Mo: 2%, and the balance is Fe. In addition to the above-mentioned elemental components, the rest are unavoidable impurities.

[0035] (2) Graphite fiber pretreatment: Graphite fibers with a length of 20 mm, a diameter of 50 μm, and a volume fraction of 10% of the matrix were sensitized in a mixed solution of 20 g / L anhydrous stannous chloride and 25 ml / L hydrochloric acid, then activated with a 4 g / L silver nitrate solution, and finally placed in a mixed solution of 40 g / L nickel sulfate, 34 g / L sodium citrate, 30 g / L sodium hypophosphite, 10 g / L boric acid, and 25 g / L sodium hydroxide, and kept warm in water at 70°C for 1 h.

[0036] (3) Construction and forming: The homogeneous iron-based blank after cooling and forming is polished and smoothed, and the surface is cleaned with alcohol to ensure that the surface is highly clean and fresh metal is exposed. Then, the nickel-plated graphite fibers are evenly distributed in the holes on each blank, compacted and stacked to form a size of 150×150×150 mm; then, a vacuum of 1.5×10 -3 Pa environment, the heating temperature is 950 ° C, the pressure is 30 MPa to make the weldments close contact, and the heat preservation is 1.5 hours to achieve solid metallurgical bonding between the weldment joints; the welded slab adopts free forging process, and the specific steps are as follows:

[0037] ① Heat the slab to 800℃ at 80℃ / min, keep it warm for 0.5h, then quickly heat it to 1100℃, keep it warm for 1.5h, and then put it into the forging press for the first upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to the original size of the forging, and the final forging temperature is 850℃.

[0038] ② Reheat the slab to 800℃ at 80℃ / min, keep it warm for 0.5h, then quickly heat it to 1100℃, keep it warm for 1.5h, and then put it into the forging press for the second upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to the original size of the forging, and the final forging temperature is 850℃.

[0039] ③ Heat the slab to 800℃ at 80℃ / min again, keep it warm for 0.5h, then quickly heat it to 1100℃, keep it warm for 1.5h, and then put it into the forging press for the third upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to 0.35 of the original height of the forging.

[0040] ④ After forging, heat the slab to 850℃ at 100℃ / min and air cool to room temperature.

[0041] In this embodiment, the amount of graphite fiber added is 10% of the volume fraction of the matrix. The graphite / iron-based composite guide plate made by this method has a nickel-plated surface of the graphite fiber, which improves the bonding strength between the graphite fiber and the matrix. At the same time, it is evenly dispersed in the matrix through diffusion welding and forging processes, and the hardness is improved. However, the wear reduction effect of a small amount of graphite fiber added during service is not obvious enough.

[0042] Example 2

[0043] A method for constructing and forming a high-temperature iron-based self-lubricating and anti-friction composite material comprises the following steps:

[0044] (1) Preparation of iron-based preform: raw materials such as ferrochrome, ferronickel, carbon, ferrotitanium, ferromolybdenum, copper, ferrovanadium or other alloys or iron ore are added into a vacuum furnace in a certain proportion; the raw materials are heated to 1600°C by the high temperature of the electric arc; argon is introduced as a protective gas with an argon pressure of 1 MPa and the vacuum degree is 6.7×10 -3Pa, ferrosilicon, ferromanganese and other alloying elements are added as deoxidizers. After the impurities and oxides in the steel are gradually removed, the molten metal is poured into a graphite mold with a size of 150×150×25 mm, wherein the depth of the holes in the top and bottom slabs is 12.5 mm, and the molten metal is naturally cooled to room temperature; the mass percentages of the iron-based components in this embodiment are: Cr: 33%, Ni: 4%, Si: 1.0%, C: 0.35%, Mn: 0.4%, Ti: 0.3%, V: 0.45%, Cu: 0.55%, Mo: 1.5%, and the balance is Fe. In addition to the above-mentioned elemental components, the rest are unavoidable impurities.

[0045] (2) Graphite fiber pretreatment: Graphite fibers with a length of 10 mm, a diameter of 25 μm, and a volume fraction of 20% of the matrix were sensitized in a mixed solution of 20 g / L anhydrous stannous chloride and 25 ml / L hydrochloric acid, then activated with a 4 g / L silver nitrate solution, and finally placed in a mixed solution of 38 g / L nickel sulfate, 32 g / L sodium citrate, 28 g / L sodium hypophosphite, 9 g / L boric acid, and 22 g / L sodium hydroxide, and kept warm in water at 65 ° C for 1 h.

[0046] (3) Construction and forming: The homogeneous iron-based blank after cooling and forming is polished and smoothed, and the surface is cleaned with alcohol to ensure that the surface is highly clean and fresh metal is exposed. Then, the nickel-plated graphite fibers are evenly distributed in the holes on each blank, compacted and stacked to form a size of 150×150×150 mm; then, a vacuum of 1.5×10 -3 Pa environment, the heating temperature is 950 ° C, the pressure is 30 MPa to make the weldments close contact, and the heat preservation is 1.5 hours to achieve solid metallurgical bonding between the weldment joints; the welded slab adopts free forging process, and the specific steps are as follows:

[0047] ① Heat the slab to 800℃ at 80℃ / min, keep it warm for 0.5h, then quickly heat it to 1100℃, keep it warm for 1.5h, and then put it into the forging press for the first upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to the original size of the forging, and the final forging temperature is 850℃.

[0048] ② Reheat the slab to 800℃ at 80℃ / min, keep it warm for 0.5h, then quickly heat it to 1100℃, keep it warm for 1.5h, and then put it into the forging press for the second upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to the original size of the forging, and the final forging temperature is 850℃.

[0049] ③ Heat the slab to 800℃ at 80℃ / min again, keep it warm for 0.5h, then quickly heat it to 1100℃, keep it warm for 1.5h, and then put it into the forging press for the third upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to 0.35 of the original height of the forging.

[0050] In this embodiment, the amount of graphite fiber added is 20% of the volume fraction of the matrix. The guide plate made by this method has a fully clean surface and the blank is close to the range of atomic gravity to form a strong metal bond. A small amount of residual microscopic holes and interface oxides gradually disappear under the action of diffusion, so that the interface and the matrix are completely consistent in composition, organization, and performance, and metallurgical connection is achieved; through the forging process, the graphite fiber is evenly dispersed in the matrix, and its hardness is greatly improved. At the same time, after the appropriate amount of graphite fiber is added, the effect of reducing wear during service is more significant, which can greatly increase the service life of the guide plate and greatly improve the production efficiency of the product during service.

[0051] Example 3

[0052] A method for constructing and forming a high-temperature iron-based self-lubricating and anti-friction composite material comprises the following steps:

[0053] (1) Preparation of iron-based preform: Raw materials such as ferrochrome, ferronickel, carbon, ferrotitanium, ferromolybdenum, copper, ferrovanadium and other alloys or iron ore are added into a vacuum furnace in a certain proportion. The raw materials are heated to 1550°C by the high temperature of the electric arc. Argon is introduced as a protective gas with a pressure of 0.05 MPa. At a vacuum degree of 6.7×10 -3 Pa, ferrosilicon, ferromanganese and other alloying elements are added as deoxidizers. After the impurities and oxides in the steel are gradually removed, the molten metal is poured into a graphite mold with a size of 150×150×25 mm, wherein the depth of the holes in the top and bottom slabs is 12.5 mm, and the molten metal is naturally cooled to room temperature; the mass percentages of the iron-based components in this embodiment are: Cr: 32%, Ni: 3%, Si: 0.5%, C: 0.2%, Mn: 0.2%, Ti: 0.2%, V: 0.1%, Cu: 0.3%, Mo: 1%, and the balance is Fe. In addition to the above-mentioned elemental components, the rest are unavoidable impurities.

[0054] (2) Graphite fiber pretreatment: Graphite fibers with a length of 1 mm, a diameter of 5 μm, and a volume fraction of 25% of the matrix were sensitized in a mixed solution of 20 g / L anhydrous stannous chloride and 25 ml / L hydrochloric acid, then activated with a 4 g / L silver nitrate solution, and finally placed in a mixed solution of 35 g / L nickel sulfate, 30 g / L sodium citrate, 27 g / L sodium hypophosphite, 8 g / L boric acid, and 20 g / L sodium hydroxide, and kept warm in water at 60 ° C for 1 h.

[0055] (3) Construction and forming: The homogeneous iron-based blank after cooling and forming is polished and smoothed, and the surface is cleaned with alcohol to ensure that the surface is highly clean and fresh metal is exposed. Then, the nickel-plated graphite fibers are evenly distributed in the holes on each blank, compacted and stacked to form a size of 150×150×150 mm; then, a vacuum of 1.5×10 -3 Pa environment, the heating temperature is 950 ° C, the pressure is 30 MPa to make the weldments close contact, and the heat preservation is 1.5 hours to achieve solid metallurgical bonding between the weldment joints; the welded slab adopts free forging process, and the specific steps are as follows:

[0056] ① Heat the slab to 800℃ at 80℃ / min, keep it warm for 0.5h, then quickly heat it to 1100℃, keep it warm for 1.5h, and then put it into the forging press for the first upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to the original size of the forging, and the final forging temperature is 850℃.

[0057] ② Reheat the slab to 800℃ at 80℃ / min, keep it warm for 0.5h, then quickly heat it to 1100℃, keep it warm for 1.5h, and then put it into the forging press for the second upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to the original size of the forging, and the final forging temperature is 850℃.

[0058] ③ Heat the slab to 800℃ at 80℃ / min again, keep it warm for 0.5h, then quickly heat it to 1100℃, keep it warm for 1.5h, and then put it into the forging press for the third upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to 0.35 of the original height of the forging.

[0059] In this embodiment, the amount of graphite fiber added is 25% of the volume fraction of the matrix. Nickel plating on the surface of the graphite fiber improves the bonding strength between the graphite fiber and the matrix. When the amount of graphite fiber added reaches 30% of the volume fraction of the matrix, the matrix becomes very brittle due to the excessively high carbon content, which aggravates the wear of the guide plate during service and has an adverse effect on product quality and production efficiency.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 2 is that the process adopts the traditional powder metallurgy sample preparation process; the specific steps are as follows:

[0062] (1) Weigh Ni powder, Fe powder, Cr powder, Si powder and other metal element powders according to the mass ratio, and then weigh the grinding balls according to the ratio of grinding balls to abrasives of 3:1. The diameter of the grinding balls is The mesh number of Ni powder is 300 mesh, the mesh number of Cr powder is 200 mesh, the mesh number of C powder is 200 mesh, the mesh number of Fe powder is 300 mesh, the mesh number of Si powder is 300 mesh, the mesh number of V powder is 300 mesh, and the mesh number of other metal powders is 250 mesh.

[0063] (2) Pour the mixed powder into a stainless steel ball mill, add nickel-plated graphite fiber with a length of 3 mm and a volume fraction of 20% of the matrix, evacuate the jar, and then inject argon as a protective gas. Repeat this operation three times; the speed of the ordinary ball mill is 350 r / min, and the mixing time is 3 h; finally, use an ordinary ball mill to fully mix the mixture to obtain a mixed powder.

[0064] (3) Preparation of composite materials: Pour the fully mixed graphite fiber and metal powder into a 150×150×200mm graphite mold, the prefabricated block pressure is 50MPa, and the pressure is maintained for 3h to obtain a prefabricated block size of 150×150×150mm; then put the prefabricated module sample into a vacuum tube furnace for high-temperature sintering at a sintering temperature of 1200℃, keep warm for 4h, and naturally cool to room temperature.

[0065] The guide plate sample in this comparative example is made by powder metallurgy process. After the powder is compressed, the pores inside the product cannot be completely eliminated. The addition of a proper amount of graphite fiber increases the defects inside the guide plate, making its overall performance poor.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Example 2 is that the process adopts a conventional forging method; the specific steps are as follows:

[0068] (1) Preparation of iron-based preform: raw materials such as ferrochrome, ferronickel, carbon, ferrotitanium, ferromolybdenum, copper, ferrovanadium or other alloys or iron ore are added into a vacuum furnace in a certain proportion; the raw materials are heated to 1600°C by the high temperature of the electric arc; argon is introduced as a protective gas with an argon pressure of 1 MPa and the vacuum degree is 6.7×10 -3 Pa, ferrosilicon, ferromanganese and other alloying elements are added as deoxidizers. After the impurities and oxides in the steel are gradually removed, the molten metal is poured into a graphite mold with a size of 150×150×25 mm, wherein the depth of the holes in the top and bottom slabs is 12.5 mm, and the molten metal is naturally cooled to room temperature; the mass percentages of the iron-based components in this embodiment are: Cr: 33%, Ni: 4%, Si: 1.0%, C: 0.35%, Mn: 0.4%, Ti: 0.3%, V: 0.45%, Cu: 0.55%, Mo: 1.5%, and the balance is Fe. In addition to the above-mentioned elemental components, the rest are unavoidable impurities.

[0069] (2) Graphite fiber pretreatment: Graphite fibers with a length of 10 mm, a diameter of 25 μm, and a volume fraction of 20% of the matrix were sensitized in a mixed solution of 20 g / L anhydrous stannous chloride and 25 ml / L hydrochloric acid, then activated with a 4 g / L silver nitrate solution, and finally placed in a mixed solution of 38 g / L nickel sulfate, 32 g / L sodium citrate, 28 g / L sodium hypophosphite, 9 g / L boric acid, and 22 g / L sodium hydroxide, and kept warm in water at 65 ° C for 1 h.

[0070] (3) Construction and forming: The homogeneous iron-based blank after cooling and forming is polished and smoothed, and the surface is cleaned with alcohol to ensure that the surface is highly clean and fresh metal is exposed. Then, the nickel-plated graphite fibers are evenly distributed in the holes on each blank, compacted and stacked to form a size of 150×150×150 mm; then, a vacuum of 1.5×10 -3 Pa environment, the heating temperature is 950℃, the pressure is 30MPa to make the weldments in close contact, and the temperature is kept for 1.5h to achieve solid metallurgical bonding between the weldment joints; the welded slab adopts conventional forging process, and the specific steps are as follows:

[0071] The slab was heated to 800°C at 80°C / min, kept warm for 0.5h, then quickly heated to 1100°C, kept warm for 1.5h, and then placed in a forging press for upsetting and drawing; the upsetting reduction was 1 / 2 of the original height of the slab, and then the slab was drawn to 0.35 of the original height of the forging.

[0072] This comparative example adopts conventional forging method. Compared with Example 2, the iron-based composite material guide plate forged by this method has poor density, internal voids cannot be completely removed, and the grains are relatively coarse. At the same time, the graphite fibers cannot be better distributed inside the matrix. The overall performance is poor during service and the service life is short.

[0073] The following table is a comparison of the performance parameters of the examples and the comparative examples.

[0074] Table 1 Performance parameters comparison between examples and comparative examples

[0075] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Average friction coefficient (μ) 0.57 0.32 0.69 0.78 0.73 Brinell hardness (HB) 273 289 300 264 269

[0076] It can be seen from the data in the above charts that the friction coefficient of the iron-based composite material guide plate obtained by the construction forming method is much lower than the friction coefficient of the iron-based composite material guide plate obtained by powder metallurgy and conventional forging process. By comparison, it can be seen that the iron-based composite material obtained by the construction forming method has a better effect in reducing wear.

Claims

1. A method for constructing and forming a high-temperature iron-based self-lubricating and anti-friction composite material, It is characterized in that The iron base after alloy design is composite prefabricated, and graphite fiber after chemical nickel plating is added to the homogeneous slab to form a structure, which specifically includes the following steps: (1) Preparation of iron-based preform: The iron-based preform is prepared by vacuum melting and casting. The size and volume of the iron-based preform should match the subsequent construction and final product volume. (2) Graphite fiber pretreatment: After sensitization and activation, the graphite fiber is placed in a solution composed of nickel salt, complexing agent, reducing agent, stabilizer and buffer in a certain proportion, and heated in a water bath and kept warm so that a uniformly distributed and firm nickel layer is formed on the fiber surface; (3) Construction and forming: The iron-based blank after cooling and forming is polished to be smooth and flat, and then the surface is cleaned with an organic solvent to ensure that the surface is highly clean and fresh metal is exposed. The nickel-plated graphite fibers are placed in the evenly distributed through holes on the blank, compacted and stacked to form; then placed in a vacuum environment, heated and pressurized to make the weldments in close contact, kept warm for a period of time to achieve solid metallurgical bonding between the weldment joints, and then the welded blank is placed under a forging press for free forging process; The mass percentage of the iron-based component ratio in step (1) is: Cr: 32% ~ 34%, Ni: 3% ~ 5%, Si: 0.5% ~ 1.5%, C: 0.2% ~ 0.5%, Mn: 0.2% ~ 0.6%, Ti: 0.2% ~ 0.4%, V: 0.1% ~ 0.8%, Mo: 1% ~ 2%, Cu: 0.3% ~ 0.8%. In addition to the above-mentioned elemental components, the rest are unavoidable impurities; The graphite fiber in step (2) has a diameter of 5-50 μm, a length of 1-20 mm, and a density of 1.77-1.82 g / cm 3 ; The specific steps of free forging process are as follows: ① The slab is heated to 850℃ at a rate of 80~90℃ / min, kept warm for 0.5~1h, then heated to 1050~1150℃, kept warm for 1~2h, and then placed in a forging press for the first upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to the original size of the forging, and the final forging temperature is 800~900℃; ② The slab is heated to 850℃ at a rate of 80~90℃ / min, kept warm for 0.5~1h, then reheated to 1050~1150℃, kept warm for 1~2h, and then placed in a forging press for a second upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to the original size of the forging, and the final forging temperature is 800~900℃; ③ The slab is heated to 850℃ at a rate of 80~90℃ / min, kept warm for 0.5~1h, then heated to 1050~1150℃ again, kept warm for 1~2h, and then put into the forging press for the third upsetting and drawing; the upsetting reduction is 1 / 2 of the original height of the slab, and then the slab is drawn to 0.3~0.4 of the original height of the forging; ④ After forging, heat the slab to 850℃ at a heating rate of 100~120℃ / min and air cool to room temperature.

2. The method for preparing a high-temperature iron-based self-lubricating and anti-friction composite material by forming and molding according to claim 1, Features: In step (1), vacuum melting is carried out in a vacuum induction melting furnace, the melting temperature is 1550°C to 1650°C, the argon pressure is 0.05 to 2 MPa, and the vacuum degree in the vacuum induction melting furnace is (1 to 5)×(10 -1 ~ 10 -3 ) Pa.

3. The method for preparing a high-temperature iron-based self-lubricating and anti-friction composite material by forming and molding according to claim 1, Features: The sensitizing solution in step (2) is hydrochloric acid + stannous chloride, with concentrations of 25 ml / L and 20 g / L respectively; the activating solution is silver nitrate, with a concentration of 4 g / L.

4. The method for preparing a high-temperature iron-based self-lubricating and anti-friction composite material by forming and molding according to claim 1, Features: The nickel salt is nickel sulfate with a concentration of 35 to 40 g / L; the complexing agent is sodium citrate with a concentration of 30 to 34 g / L; the reducing agent is sodium hypophosphite with a concentration of 27 to 30 g / L; the stabilizer is boric acid with a concentration of 8 to 10 g / L; the buffer is sodium hydroxide with a concentration of 20 to 25 g / L; the heating temperature is 60 to 70°C, and the insulation time is 1 to 1.5 hours.

5. The method for preparing a high-temperature iron-based self-lubricating and anti-friction composite material by forming and molding according to claim 1, Features: The organic solvent in step (3) is alcohol or acetone, the through hole area on the slab accounts for 1 / 24 of the slab area, the hole depth of the top and bottom slabs is 1 / 2 of the slab, and the volume fraction of the graphite fiber is 10% to 25% of the slab preform after stacking.

6. The method for forming and preparing a high-temperature iron-based self-lubricating and anti-friction composite material according to claim 1, Features: The vacuum degree in step (3) is (1~20)×10 -3 Pa, heated to 900~1050℃ at a heating rate of 85~95℃ / min, pressure of 0.5~50MPa, and holding time of 2h~5h.

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