Preparation method of material for self-lubricating weather-resistant metal fittings

Abstract

The invention discloses a preparation method of a material for self-lubricating weather-resistant hardware fittings, which is composed of the following raw material components according to mass percentage: C 3.0% - 3.9%, Si 1.5% - 2.0%, Al 0.5% - 1.5%, Cu 0.1% - 0.5%, Mn 0.1% - 0.2%, P ≤ 0.1%, S ≤ 0.015%, other alloying elements ≤ 1.0%, and the balance is Fe. The sum of the contents of the above components should be 100%. The invention also discloses a preparation method of the material: Step 1, weigh raw materials such as carburized pig iron, ferrosilicon, ferromanganese, pig iron, pure copper, and pure aluminum according to the components, and melt the weighed materials at high temperature in an induction furnace to obtain a first liquid; Step 2, add an inoculant and a nodulizer to the first liquid; Step 3, obtain a casting by horizontal continuous casting; Step 4, forge after heat preservation, then carry out heat preservation and air cooling, and finally carry out salt bath heat preservation and air cooling. The invention solves the problem of poor corrosion resistance of the existing hardware fitting materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of fitting materials, and particularly relates to a material for self-lubricating weather-resistant fittings. The present invention also relates to a preparation method of the material for self-lubricating weather-resistant fittings. Background Art

[0002] Electric power fittings are various metal accessories that play a role in connection, fixation and protection in overhead transmission lines, and they play an important role in power transmission and transformation projects. With the development of China's social economy, the demand for electric power in industrial production and daily life is increasing day by day. The state puts forward higher requirements for the safety and stability of the power grid. The quality stability and reliability of electric power fittings directly determine the safe operation of the power grid system. The long-distance span of the overhead power transmission line requires the fittings that play a connecting and fixing role to have a certain strength and toughness. The current Q235B material for preparing fittings can meet the requirements of its strength and toughness indexes. However, as fittings for connecting overhead power transmission lines, they may suffer from wear failure due to reciprocating relative friction movement with transmission wires or corrosion and aging due to harsh environments, which greatly reduces their service life. Therefore, improving their anti-wear and corrosion resistance on the premise of meeting the mechanical property indexes such as strength and toughness of electric power fittings is the key to improving their service life.

[0003] The commonly used materials for current electric power fittings include malleable cast iron, steel, aluminum and aluminum alloys. The excellent mechanical properties of ferrous metals can meet the requirements of electric power fittings for strength and toughness, and their low price makes them widely used in electric power fittings. However, ferrous metals have poor corrosion resistance. To improve the corrosion resistance of ferrous metals, they are often hot-dip galvanized. However, the galvanized layer is prone to peeling off during the reciprocating friction process between the fittings and the wires, exposing the base metal to the air and significantly reducing its corrosion resistance. In addition, the waste liquid generated by hot-dip galvanizing causes serious environmental pollution. To solve the problems of poor corrosion resistance and environmental pollution in ferrous metals, electric power fittings made of aluminum and aluminum alloys have been applied in a certain range. Aluminum electric power fittings have a smaller density, and their density is only 1 / 3 of that of iron; and a dense aluminum oxide passivation film is easily formed on the surface of aluminum and aluminum alloys to improve their corrosion resistance. However, problems such as the high price and low strength of aluminum fittings have limited their application in the electric power metal industry. Summary of the Invention

[0004] The purpose of the present invention is to provide a material for self-lubricating weather-resistant fittings, which solves the problem of low service life of existing fitting materials due to wear or corrosion.

[0005] Another purpose of the present invention is to provide a preparation method of the material for self-lubricating weather-resistant fittings.

[0006] The technical solution adopted by the present invention is that the material for self-lubricating weather-resistant metal fittings is composed of the following raw materials by mass percentage: C 3.0% - 3.9%, Si 1.5% - 2.0%, Al 0.5% - 1.5%, Cu 0.2%, Mn 0.1% - 0.2%, P 0.1%, S ≤ 0.015%, other alloying elements ≤ 1.0%, and the balance is Fe. The sum of the contents of each component should be 100%.

[0007] Another technical solution adopted by the present invention is the preparation method of the material for self-lubricating weather-resistant metal fittings, which is specifically implemented according to the following steps:

[0008] Step 1: According to the following material mass percentages: C 3.0% - 3.9%, Si 1.5% - 2.0%, Al 0.5% - 1.5%, Cu 0.2%, Mn 0.1% - 0.2%, P 0.1%, S ≤ 0.015%, other alloying elements ≤ 1.0%, and the balance is Fe. The sum of the contents of each component should be 100%. Weigh the raw materials of carburizing pig iron, ferrosilicon, ferromanganese, pig iron, pure copper, and pure aluminum, and melt the weighed materials at high temperature in an induction furnace to obtain a first liquid;

[0009] Step 2: Add an inoculant and a spheroidizing agent to the first liquid in Step 1 to obtain a second liquid;

[0010] Step 3: Inject the second liquid in Step 2 into the hearth of a preheated horizontal continuous casting furnace, and obtain a casting by the horizontal continuous casting method;

[0011] Step 4: Place the casting in Step 3 in a muffle furnace at 900°C - 1000°C and keep it warm for 1 - 3 hours, then cool it to room temperature with the furnace, to obtain a first metal part;

[0012] Step 5: Forge the first metal at high temperature into the shape of a metal fitting to obtain a second metal;

[0013] Step 6: Place the second metal in a muffle furnace at 1000°C - 1100°C and keep it warm for 2 - 5 hours, then take it out and air-cool it to obtain a third metal;

[0014] Step 7: Place the third metal in a muffle furnace to keep it warm, then quench it in a salt bath furnace at 250°C - 350°C and keep it warm for 1 - 3 hours, then take it out and air-cool it to obtain the self-lubricating weather-resistant metal fitting.

[0015] The characteristics of another technical solution of the present invention also lie in:

[0016] In Step 2, the inoculant is ferrosilicon, and its addition amount is 1.1% - 1.5% of the mass of the first liquid. The spheroidizing agent is rare earth magnesium, and its addition amount is 1.0% - 1.8% of the mass of the first liquid.

[0017] The forging temperature in Step 5 is 700°C - 900°C.

[0018] In Step 7, the holding temperature in the muffle furnace is 850°C to 950°C, and the holding time is 1 - 2 h.

[0019] In Step 7, the interval time from taking out the third metal from the muffle furnace to entering the salt bath is not more than 50 s.

[0020] The beneficial effects of the present invention are as follows:

[0021] 1) Free graphite with a volume fraction of not less than 15% in the self-lubricating weather-resistant fitting material provides self-lubricating properties for the fitting and improves its wear resistance;

[0022] 2) Low silicon and a small amount of aluminum in the self-lubricating weather-resistant fitting material improve the plasticity of the material and provide conditions for its plastic forming;

[0023] 3) A small amount of copper in the self-lubricating weather-resistant fitting material exists in the form of free copper on the material surface, improving the corrosion resistance of the material;

[0024] 4) A small amount of phosphorus in the self-lubricating weather-resistant fitting material can form phosphates on the material surface during salt bath quenching to improve the corrosion resistance;

[0025] 5) The sub-micron scale phase and supersaturated high-carbon phase in the self-lubricating weather-resistant fitting material ensure the strength of the fitting (hardness not less than 45 HRC);

[0026] 6) After the self-lubricating weather-resistant fitting material is forged and formed, certain heat treatment is carried out to make the spheroidal graphite undergo re-spheroidization, ensuring the strength and toughness of the fitting material after subsequent heat treatment. Description of the Drawings

[0027] Figure 1 is a micrograph of the spheroidal graphite distribution state in the cast iron material prepared in Example 1 of the preparation method of the self-lubricating weather-resistant fitting material of the present invention;

[0028] Figure 2 is a micrograph of the spheroidal graphite state after Step 5 in Example 2 of the preparation method of the self-lubricating weather-resistant fitting material of the present invention;

[0029] Figure 3 is a micrograph of the spheroidal graphite state after Step 6 in Example 3 of the preparation method of the self-lubricating weather-resistant fitting material of the present invention;

[0030] Figure 4 is a micrograph of the self-lubricating weather-resistant fitting material prepared in Example 4 of the preparation method of the self-lubricating weather-resistant fitting material of the present invention;

[0031] Figure 5It is the macroscopic view of the self-lubricating weather-resistant fitting prepared in Example 5 of the preparation method of the material for self-lubricating weather-resistant fitting of the present invention. Detailed implementation manners

[0032] The present invention will be described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0033] The material for self-lubricating weather-resistant fitting is composed of the following raw materials by mass percentage: C 3.0% - 3.9%, Si 1.5% - 2.0%, Al 0.5% - 1.5%, Cu 0.2%, Mn 0.1% - 0.2%, P 0.1%, S ≤ 0.015%, other alloying elements ≤ 1.0%, and the balance is Fe. The sum of the contents of the above components should be 100%.

[0034] The preparation method of the material for self-lubricating weather-resistant fitting is specifically implemented according to the following steps:

[0035] Step 1: According to the following material mass percentages: C 3.0% - 3.9%, Si 1.5% - 2.0%, Al 0.5% - 1.5%, Cu 0.2%, Mn 0.1% - 0.2%, P 0.1%, S ≤ 0.015%, other alloying elements ≤ 1.0%, and the balance is Fe. The sum of the contents of the above components should be 100%. Weigh raw materials such as carburizing pig iron, ferrosilicon, ferromanganese, pig iron, pure copper, and pure aluminum, and melt the weighed materials at high temperature in an induction furnace to obtain a first liquid.

[0036] Step 2: Add an inoculant and a spheroidizing agent to the first liquid in Step 1 to obtain a second liquid;

[0037] The inoculant is selected as ferrosilicon, and the spheroidizing agent is selected as rare earth magnesium. The addition amount of the inoculant is 1.1% - 1.5% of the mass of the first liquid, and the addition amount of the spheroidizing agent is 1.0% - 1.8% of the mass of the first liquid. The purpose of adding the spheroidizing agent and the inoculant is to promote graphitization, reduce the white mouth tendency, improve the graphite morphology and distribution, and obtain spherical graphite;

[0038] Step 3: Inject the second liquid in Step 2 into the hearth of a preheated horizontal continuous casting furnace, and obtain a casting by the horizontal continuous casting method;

[0039] Step 4: Place the casting in Step 3 in a muffle furnace at 900°C - 1000°C and keep it warm for 1 - 3 hours, and then cool it to room temperature with the furnace to obtain a first metal part;

[0040] This is to obtain an austenite structure, and the subsequent cooling with the furnace is to obtain a ferrite matrix to improve the workability and formability of the material;

[0041] Step 5: Forge the first metal into the shape of a fitting at 700°C - 900°C to obtain a second metal;

[0042] Among them, during the forging process of the first metal at 700°C - 900°C, the matrix structure can be ferrite or austenite, both of which maintain good plastic forming properties;

[0043] Step 6: Place the second metal in a muffle furnace at 1000°C - 1100°C, keep it warm for 2 - 5 hours, then take it out and air-cool it to obtain the third metal;

[0044] The purpose of keeping it warm in the muffle furnace is to make the deformed graphite become spherical during the forging process, providing material preparation for regulating its mechanical properties in subsequent heat treatment;

[0045] Step 7: Place the third metal in a muffle furnace to keep it warm, then quench it in a salt bath furnace at 250°C - 350°C for 1 - 3 hours, and then take it out and air-cool it to obtain the self-lubricating weather-resistant hardware;

[0046] Among them, the casting is kept warm in a muffle furnace at 850°C - 950°C for 1 - 2 hours to obtain an austenite matrix structure with uniform carbon content. The salt bath temperature of the casting is 250°C - 350°C to obtain nano-scale phase and high-carbon phase. The interval from taking the casting out of the muffle furnace to entering the salt bath does not exceed 50 s to prevent the carbon dissolved in the phase from precipitating.

[0047] Example 1

[0048] The preparation method of the material for self-lubricating weather-resistant hardware is specifically implemented according to the following steps:

[0049] Step 1: According to the mass percentage of the special material for self-lubricating weather-resistant hardware, C 3.0%, Si 2.0%, Al 1.0%, Cu 0.2%, Mn 0.1%, P 0.1%, S 0.015%, other alloying elements ≤ 1.0%, and the balance is Fe. The sum of the contents of the above components should be 100%. Weigh the raw materials, such as carburized pig iron, ferrosilicon, ferromanganese, pig iron, pure copper, and pure aluminum, and melt the weighed raw materials at high temperature in an induction furnace to obtain the first liquid;

[0050] Step 2: Add an inoculant and a nodulizer to the first liquid to obtain the second liquid;

[0051] Among them, the addition amount of the inoculant is 1.2% of the mass of the first liquid, and the addition amount of the nodulizer is 1.5% of the mass of the first liquid.

[0052] Step 3: Pour the second liquid into the preheated hearth of a horizontal continuous casting furnace and obtain a casting by the horizontal continuous casting method;

[0053] Step 4: Place the casting in a muffle furnace at 900°C, keep it warm for 2 hours, and then cool it to room temperature with the furnace to obtain the first metal;

[0054] Step 5: Forge the first metal at 700 °C into the shape of a fitting to obtain the second metal;

[0055] Step 6: Place the second metal in a muffle furnace at 1000 °C and keep it warm for 2 hours, then take it out and air-cool it to obtain the third metal;

[0056] Step 7: Place the third metal in a muffle furnace at 900 °C and keep it warm for 1 hour, then quench it in a salt bath furnace at 300 °C and keep it warm for 1 hour, then take it out and air-cool it to obtain the product.

[0057] Example 2

[0058] The preparation method of the material for self-lubricating and weather-resistant fittings is specifically implemented according to the following steps:

[0059] Step 1: According to the mass percentages of the special material for self-lubricating and weather-resistant fittings: C 3.9%, Si 1.5%, Al 1.5%, Cu 0.2%, Mn 0.1%, P 0.1%, S 0.015%, other alloying elements 1.0%, and the balance is Fe, and the sum of the contents of the above components should be 100%. Weigh the raw materials of carburizing pig iron, ferrosilicon, ferromanganese, pig iron, pure copper, and pure aluminum, and melt the weighed raw materials at high temperature in an induction furnace to obtain the first liquid;

[0060] Step 2: Add an inoculant and a spheroidizing agent to the first liquid to obtain the second liquid;

[0061] Among them, the addition amount of the inoculant is 1.2% of the mass of the first liquid, and the addition amount of the spheroidizing agent is 1.5% of the mass of the first liquid.

[0062] Step 3: Pour the second liquid into the preheated hearth of a horizontal continuous casting furnace and obtain a casting by the horizontal continuous casting method;

[0063] Step 4: Place the casting in a muffle furnace at 900 °C and keep it warm for 2 hours, then cool it to room temperature with the furnace to obtain the first metal;

[0064] Step 5: Forge the first metal at 700 °C into the shape of a fitting to obtain the second metal;

[0065] Step 6: Place the second metal in a muffle furnace at 1000 °C and keep it warm for 2 hours, then take it out and air-cool it to obtain the third metal;

[0066] Step 7: Place the third metal in a muffle furnace at 900 °C and keep it warm for 1 hour, then quench it in a salt bath furnace at 300 °C and keep it warm for 1 hour, then take it out and air-cool it to obtain the product.

[0067] Example 3

[0068] The preparation method of the material for self-lubricating and weather-resistant fittings is specifically implemented according to the following steps:

[0069] Step 1: According to the mass percentages of the special material for self-lubricating weather-resistant metal fittings: C 3.0%, Si 2.0%, Al 1.0%, Cu 0.2%, Mn 0.1%, P 0.1%, S 0.015%, other alloying elements 1.0%, and the balance being Fe, with the sum of the contents of each component being 100%, weigh the raw materials including carburized pig iron, ferrosilicon, ferromanganese, pig iron, pure copper, and pure aluminum, and melt the weighed raw materials at high temperature in an induction furnace to obtain a first liquid;

[0070] Step 2: Add an inoculant and a nodulizer to the first liquid to obtain a second liquid;

[0071] Among them, the addition amount of the inoculant is 1.2% of the mass of the first liquid, and the addition amount of the nodulizer is 1.5% of the mass of the first liquid.

[0072] Step 3: Pour the second liquid into the preheated hearth of a horizontal continuous casting furnace and obtain a casting by using the horizontal continuous casting method;

[0073] Step 4: Place the casting in a muffle furnace at 950 °C and keep it warm for 2 hours, then cool it in the furnace to room temperature to obtain a first metal;

[0074] Step 5: Forge the first metal at 800 °C into the shape of a metal fitting to obtain a second metal;

[0075] Step 6: Place the second metal in a muffle furnace at 1100 °C and keep it warm for 2 hours, then take it out and air-cool it to obtain a third metal;

[0076] Step 7: Place the third metal in a muffle furnace at 900 °C and keep it warm for 1 hour, then quench it in a salt bath furnace at 300 °C and keep it warm for 1 hour, then take it out and air-cool it to obtain the product.

[0077] Example 4

[0078] A preparation method of a material for self-lubricating weather-resistant metal fittings is specifically implemented according to the following steps:

[0079] Step 1: According to the mass percentages of the special material for self-lubricating weather-resistant metal fittings: C 3.0%, Si 2.0%, Al 1.0%, Cu 0.2%, Mn 0.1%, P 0.1%, S 0.015%, other alloying elements 1.0%, and the balance being Fe, with the sum of the contents of each component being 100%, weigh the raw materials including carburized pig iron, ferrosilicon, ferromanganese, pig iron, pure copper, and pure aluminum, and melt the weighed raw materials at high temperature in an induction furnace to obtain a first liquid;

[0080] Step 2: Add an inoculant and a nodulizer to the first liquid to obtain a second liquid;

[0081] Among them, the addition amount of the inoculant is 1.2% of the mass of the first liquid, and the addition amount of the nodulizer is 1.5% of the mass of the first liquid.

[0082] Step 3: Pour the second liquid into the hearth of a preheated horizontal continuous casting furnace, and obtain a casting by using the horizontal continuous casting method;

[0083] Step 4: Place the casting in a muffle furnace at 900 °C and keep it warm for 2 hours, then cool it to room temperature with the furnace, to obtain the first metal;

[0084] Step 5: Forge the first metal at 700 °C into the shape of a fitting, to obtain the second metal;

[0085] Step 6: Place the second metal in a muffle furnace at 1000 °C and keep it warm for 5 hours, then take it out and air-cool it, to obtain the third metal;

[0086] Step 7: Place the third metal in a muffle furnace at 900 °C and keep it warm for 1 hour, then quench it in a salt bath furnace at 300 °C and keep it warm for 1 hour, then take it out and air-cool it, thus obtaining the product.

[0087] Example 5

[0088] A preparation method of a material for a self-lubricating weather-resistant fitting is specifically implemented according to the following steps:

[0089] Step 1: According to the mass percentages of the special material for the self-lubricating weather-resistant fitting: C 3.0%, Si 2.0%, Al 1.0%, Cu 0.2%, Mn 0.1%, P 0.1%, S 0.015%, other alloying elements 1.0%, and the balance is Fe, and the sum of the contents of the above components should be 100%, weigh raw materials such as carburized pig iron, ferrosilicon, ferromanganese, pig iron, pure copper, and pure aluminum, and melt the weighed raw materials at high temperature in an induction furnace to obtain the first liquid;

[0090] Step 2: Add an inoculant and a nodulizer to the first liquid to obtain the second liquid;

[0091] Among them, the addition amount of the inoculant is 1.2% of the mass of the first liquid, and the addition amount of the nodulizer is 1.5% of the mass of the first liquid.

[0092] Step 3: Pour the second liquid into the hearth of a preheated horizontal continuous casting furnace, and obtain a casting by using the horizontal continuous casting method;

[0093] Step 4: Place the casting in a muffle furnace at 900 °C and keep it warm for 2 hours, then cool it to room temperature with the furnace, to obtain the first metal;

[0094] Step 5: Forge the first metal at 900 °C into the shape of a fitting, to obtain the second metal;

[0095] Step 6: Place the second metal in a muffle furnace at 1100 °C and keep it warm for 5 hours, then take it out and air-cool it, to obtain the third metal;

[0096] Step 7: Place the third metal in a muffle furnace at 900 °C and hold for 2 hours, then quench in a salt bath furnace at 350 °C and hold for 3 hours, and then take it out and air cool to obtain it.

[0097] Example 6

[0098] The preparation method of the material for self-lubricating weather-resistant metal fittings is specifically implemented according to the following steps:

[0099] Step 1: According to the mass percentage of the special material for self-lubricating weather-resistant metal fittings, C 3.9%, Si 1.5%, Al 1.5%, Cu 0.2%, Mn 0.1%, P 0.1%, S 0.015%, other alloying elements 1.0%, and the balance is Fe. The sum of the contents of each component should be 100%. Weigh raw materials such as carburized pig iron, ferrosilicon, ferromanganese, pig iron, pure copper, and pure aluminum, and melt the weighed raw materials at high temperature in an induction furnace to obtain a first liquid;

[0100] Step 2: Add an inoculant and a nodulizer to the first liquid to obtain a second liquid;

[0101] Among them, the addition amount of the inoculant is 1.2% of the mass of the first liquid, and the addition amount of the nodulizer is 1.5% of the mass of the first liquid.

[0102] Step 3: Pour the second liquid into the preheated hearth of a horizontal continuous casting furnace and obtain a casting by the horizontal continuous casting method;

[0103] Step 4: Place the casting in a muffle furnace at 900 °C and hold for 2 hours, and then cool it to room temperature with the furnace to obtain a first metal;

[0104] Step 5: Forge the first metal into the shape of a metal fitting at 800 °C to obtain a second metal;

[0105] Step 6: Place the second metal in a muffle furnace at 1050 °C and hold for 2 hours, and then take it out and air cool to obtain a third metal;

[0106] Step 7: Place the third metal in a muffle furnace at 900 °C and hold for 1 hour, then quench in a salt bath furnace at 250 °C and hold for 1 hour, and then take it out and air cool to obtain it.

[0107] For the material prepared by the preparation method of the material for self-lubricating weather-resistant metal fittings of the present invention, the low silicon and a small amount of aluminum improve the plasticity of the material, providing conditions for its plastic forming. A small amount of copper exists in the form of free copper on the surface of the material to improve the corrosion resistance of the material. The sub-micron scale phase and the supersaturated high-carbon phase ensure the strength of the metal fitting.

Claims

1. The material for self-lubricating weather-resistant hardware fittings, characterized in that, It consists of the following raw material components by mass percentage: C 3.0% - 3.9%, Si 1.5% - 2.0%, Al 0.5% - 1.5%, Cu 0.2%, Mn 0.1% - 0.2%, P 0.1%, S ≤ 0.015%, other alloying elements ≤ 1.0%, and the balance is Fe. The sum of the contents of each component above should be 100%; The preparation method of the self-lubricating and weather-resistant fitting material is specifically implemented according to the following steps: Step 1: According to the following material mass percentages: C 3.0% - 3.9%, Si 1.5% - 2.0%, Al 0.5% - 1.5%, Cu 0.2%, Mn 0.1% - 0.2%, P 0.1%, S ≤ 0.015%, other alloying elements ≤ 1.0%, and the balance is Fe. The sum of the contents of each component above should be 100%. Weigh the raw materials of carburizing pig iron, ferrosilicon, ferromanganese, pig iron, pure copper, and pure aluminum, and melt the weighed materials at high temperature in an induction furnace to obtain the first liquid; Step 2: Add an inoculant and a nodulizer to the first liquid in Step 1 to obtain the second liquid; In Step 2, the inoculant is ferrosilicon, and its addition amount is 1.1% - 1.5% of the mass of the first liquid. The nodulizer is rare earth magnesium, and its addition amount is 1.0% - 1.8% of the mass of the first liquid; Step 3: Inject the second liquid in Step 2 into the hearth of a preheated horizontal continuous casting furnace, and obtain a casting by the horizontal continuous casting method; Step 4: Place the casting in Step 3 in a muffle furnace at 900°C - 1000°C and keep it warm for 1 - 3 hours, and then cool it to room temperature with the furnace to obtain the first metal part; Step 5: Forge the first metal at high temperature into the shape of a fitting to obtain the second metal; The forging temperature in Step 5 is 700°C - 900°C; Step 6: Place the second metal in a muffle furnace at 1000°C - 1100°C and keep it warm for 2 - 5 hours, then take it out and air-cool to obtain the third metal; Step 7: Place the third metal in a muffle furnace for heat preservation, then quench it in a salt bath furnace at 250°C - 350°C and keep it warm for 1 - 3 hours, and then take it out and air-cool to obtain the self-lubricating and weather-resistant fitting; In Step 7, the heat preservation temperature in the muffle furnace is 850°C - 950°C, and the heat preservation time is 1 - 2 hours; In Step 7, the interval time from taking out the third metal from the muffle furnace to entering the salt bath is not more than 50 s; The casting is kept in a muffle furnace at 850°C - 950°C for 1 - 2 hours to obtain an austenite matrix structure with uniform carbon content. The salt bath temperature of the casting is 250°C - 350°C to obtain nano-scale phases and high-carbon phases. The interval between the casting being taken out of the muffle furnace and entering the salt bath does not exceed 50 s to prevent the precipitation of carbon dissolved in the phases; Free graphite with a volume fraction of not less than 15% in the self-lubricating and weather-resistant fitting material provides the self-lubricating property for the fitting.

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