阅读说明：本技术 一种高强度紧固件的表面镀层处理工艺 (Surface coating treatment process of high-strength fastener ) 是由 胡宗山 屈东东 胡宗海 廖美忠 龚盼 于 2020-05-19 设计创作，主要内容包括：一种高强度紧固件的表面镀层处理工艺,属于机械基础件及制造技术领域,S1：基材制作；S2：热镦紧固件基材；S3：螺纹加工；S4：第一次热处理；S5：第二次热处理；S6：表面处理；S7：电镀后进行水洗；S8：除去紧固件表面多余的液体；S9：将紧固件浸入钝化溶液中；S10：将钝化后的紧固件使用45～65℃的清水进行清洗,将水洗后的紧固件采用热风吹干；S11：在紧固件表面涂覆PTFE防腐蚀涂层。本发明所述的高强度紧固件的表面镀层处理工艺,开发高强度的紧固件,能够解决汽车紧固件长期使用后松动脱落的问题,紧固件的镀层梳理工艺获得的紧固件,具有高耐腐蚀性和经济性较好的镀层,提高了紧固件的防腐寿命,对于保证汽车的正常行驶本具有重要意义。(A surface coating treatment process of a high-strength fastener belongs to the technical field of mechanical basic parts and manufacturing, and comprises the following steps of S1: manufacturing a base material; s2: hot heading the fastener base material; s3: processing threads; s4: carrying out first heat treatment; s5: carrying out secondary heat treatment; s6: surface treatment; s7: washing with water after electroplating; s8: removing excess liquid from the surface of the fastener; s9: immersing the fastener in a passivating solution; s10: cleaning the passivated fastener with clear water at 45-65 ℃, and drying the cleaned fastener with hot air; s11: and coating a PTFE anti-corrosion coating on the surface of the fastener. The surface coating treatment process for the high-strength fastener disclosed by the invention is used for developing the high-strength fastener, and can solve the problem that the automobile fastener loosens and falls off after being used for a long time.)

1. A surface coating treatment process of a high-strength fastener is characterized by comprising the following steps: the method comprises the following steps:

s1: manufacturing a base material: selecting high-strength steel, putting the steel into automatic cutting equipment, and cutting the steel into a plurality of fastener base materials by the automatic cutting equipment;

s2: hot heading fastener base material: heating the fastener base material by a high-frequency heating machine until the surface of the fastener base material is heated to 900-950 ℃, controlling the heating time to be 5-6 seconds, placing the fastener base material subjected to the hot heading treatment in a forming die, and then controlling a piston rod of a hydraulic cylinder to extend out, wherein the piston rod drives a punch to impact the fastener base material subjected to the hot heading treatment;

s3: and (3) thread machining: manufacturing the external thread of the fastener base material by using a thread rolling machine, and forming a thread on the outer wall of the fastener base material;

s4: first heat treatment: placing the fastener semi-finished product prepared in the step S3 into a high-temperature heating furnace for heating, placing the heated fastener semi-finished product into an organic silicon medium for cooling treatment until the temperature of the metal workpiece is reduced to 350-450 ℃, taking out the fastener semi-finished product and placing the fastener semi-finished product into deionized water for water bath cooling;

s5: and (3) second heat treatment: carrying out secondary heat treatment on the fastener semi-finished product cooled and cooled in the step S4;

s6: surface treatment: completely immersing a semi-finished product of the fastener in a zinc plating solution at the temperature of 35-40 ℃ for electroplating, wherein each liter of the zinc plating solution contains 60-70 g of zinc chloride, 280-360 g of ammonium chloride, 30-35 g of potassium chloride, 30-38 g of sodium hydroxide, 55-65 g of triethanolamine, 28-30 g of boric acid, 15-20 ml of organic solvent, 1-2 g of softener, 5-8 ml of main brightener and 20-25 ml of auxiliary brightener, which are water; the main brightening agent is 50-100 mg/L of benzalacetone, 200-250 mg/L of sodium benzoate, 5-10 mg/L of nicotinic acid and 10-20 mg/L of nonylphenol polyoxyethylene ether; the auxiliary brightening agent is imidazole propoxy condensed 40-90 mg/L; the softening agent is a rare earth additive which is lanthanum chloride or cerium chloride; the organic solvent is any one or combination of ethanol, butyl ether and ethylene glycol monomethyl ether; electroplating time is 3-5 minutes, and cathode current density is as follows: 2.0-3A/dm 2;

s7: washing with water after electroplating, then immersing the fastener into an activating solution, soaking at room temperature for 3-5 seconds, and washing with water again;

s8: removing redundant liquid on the surface of the fastener, placing the fastener in a dryer for drying at the temperature of 65-75 ℃, placing the fastener after galvanization and cooling in an oven for heating to 230-260 ℃, and preserving heat for 3-4 hours;

s9: immersing the fastener in a passivating solution;

s10: cleaning the passivated fastener with clear water at 45-65 ℃, and drying the cleaned fastener with hot air;

s11: and coating a PTFE (polytetrafluoroethylene) anti-corrosion coating on the surface of the fastener, and baking the fastener at the baking temperature of 65-70 ℃ for 60-70 min.

2. The surface coating treatment process for a high-strength fastener according to claim 1, characterized in that: the step S2 further includes shot blasting treatment of the fastener base material, and specifically includes the following steps:

performing shot blasting treatment on the surface of the base material of the fastener by using a through type shot blasting machine, wherein the shot blasting time is 15-25 min, so that the surface of the fastener is steel gray, removing iron scales, and spraying the surface of the raw material of the fastener subjected to shot blasting treatment.

3. The surface coating treatment process for a high-strength fastener according to claim 1, characterized in that: in the step S11, a PTFE corrosion protection coating is applied, and the PTFE corrosion protection coating is sprayed on the surface of the fastener by using a plasma spraying method.

4. The surface coating treatment process for a high-strength fastener according to claim 1, characterized in that: the second heat treatment in the above step S5 includes the steps of:

and (3) moving the semi-finished product of the fastener into a heating furnace, heating to 400-450 ℃, preserving heat for 15-20 minutes, then continuing heating to 550-600 ℃, preserving heat for 45-50 minutes, moving the semi-finished product of the fastener out of the heating furnace, naturally cooling to 120-140 ℃ in air, and performing carburizing and quenching treatment on the semi-finished product of the fastener.

5. The surface coating treatment process for a high-strength fastener according to claim 4, characterized in that: the quenching treatment comprises the following steps:

a heating procedure, namely moving the heated fastener semi-finished product into a heating furnace to be heated to 820-860 ℃, preserving heat for 25-30 min, keeping the temperature of the fastener semi-finished product between 720 ℃ and the upper temperature limit for not less than 15min, and keeping the heating rate of the heating process to be not more than 2 ℃/s; when the temperature is raised to 650 ℃, methanol is introduced into the heating furnace, and the introduction amount is 25-35 ml/min; pre-cooling the heated fastener semi-finished product to ensure that the temperature of the fastener semi-finished product is reduced to 760-780 ℃, then carrying out water cooling, controlling the temperature of the fastener semi-finished product to 70-80 ℃ after the water cooling is finished, and then carrying out tempering treatment.

6. The surface coating treatment process for a high-strength fastener according to claim 5, characterized in that: the tempering treatment comprises the following steps:

transferring the quenched semi-finished product of the fastener into a tempering furnace, heating the tempering furnace to 540-560 ℃, preserving heat for 50-60 min, naturally cooling the semi-finished product of the fastener to 220-240 ℃ along with the furnace after heat preservation, taking out the semi-finished product of the fastener, and naturally cooling the semi-finished product of the fastener in the air to room temperature; and cooling to 65 ℃ in air cooling, performing primary high-temperature tempering, heating to 600-650 ℃ at a heating speed of 300-400 ℃/h, keeping the temperature for 40min, and cooling in air after discharging.

7. The surface coating treatment process for a high-strength fastener according to claim 1, characterized in that: the passivation solution in the step S9 is:

lithium carbonate: 5-20 g/L, fluoride salt: 1-10 g/L, meta-aluminate: 2-15 g/L, and casein: 2-15 g/L, silicate: 5-15 g/L.

8. The surface coating treatment process for a high-strength fastener according to claim 1, characterized in that: the activating solution in the step S7 is:

H₃PO₄：5.0～14g/L、CaH₂PO₄：5.4～10.2g/L、ZnH₂PO₄：0.8～3.8 g/L、NaNO₃：1～3g/L、NaNO₂：2～6g/L。

9. the surface coating treatment process for a high-strength fastener according to claim 1, characterized in that: in the step S1, the weight ratio of the high-strength steel is selected as follows:

c: 0.08 to 0.12, Si: 0.6-0.8, P is less than or equal to 0.015, S is less than or equal to 0.015, Ni: 15-20, Cr: 15-18, V: 0.15 to 0.55, Mo: 1.4-1.8, Ti: 3-4.5, Mn: 0.12 to 0.25, W: 0.01 to 0.03, Nb: 0.05-0.10 wt% and Fe for the rest.

10. The surface coating treatment process for a high-strength fastener according to claim 1, characterized in that: the PTFE anti-corrosion coating in the step S11 comprises the following components in parts by weight:

12 parts of phenolic resin, 4 parts of polyethylene, 4 parts of organic silicon resin, 8 parts of aluminum powder, 5 parts of anticorrosive filler, 2 parts of lubricant, 5 parts of thixotropic agent, 2 parts of plasticizer, 2 parts of dispersant and 8 parts of solvent.

Technical Field

The invention belongs to the technical field of mechanical basic parts and manufacturing, and particularly relates to a surface coating treatment process of a high-strength fastener.

Background

The fastener is a mechanical basic member with large quantity and wide range, and the product quality and the reliability of the fastener play an important role in the working performance and the structural safety of a host machine. With the increasing deterioration of the natural environment, the corrosion resistance of the surface of the fastener is required to be high, so that the surface treatment of the fastener is more and more emphasized.

The fasteners comprise bolts, screws, studs, nuts, self-tapping screws, wood screws, washers, check rings, pins, rivets, connecting pairs and assemblies and the like, and the galvanization of the surfaces of the fasteners is required for two reasons: corrosion prevention and decoration. The zinc coating is a typical anode coating for steel fasteners, plays an electrochemical protection role for a substrate, and is widely applied to corrosion prevention of the fasteners due to stability in the atmosphere and low cost. The traditional galvanizing process comprises electrogalvanizing, hot-dip galvanizing and zinc impregnation, the galvanizing multi-selection hot-dip galvanizing process of the prior domestic and foreign outdoor fastener is that molten metal reacts with an iron substrate to generate an alloy layer, so that the substrate and the plating layer are combined, the hot-dip galvanizing has the advantages of uniform plating layer, strong adhesive force, long service life and the like, the fastener in the prior art is generally subjected to acid pickling before the hot-dip galvanizing, in order to remove iron oxide on the surface of the fastener, after the acid pickling, cleaning by ammonium chloride or zinc chloride aqueous solution or ammonium chloride and zinc chloride mixed aqueous solution, then the steel is sent into a hot galvanizing bath, the surface of the fastener is easily corroded by the acid washing process, so that the fastener has the crisp and fracture phenomena, meanwhile, the pickling process can generate a large amount of pickling waste liquid to be treated, which is not beneficial to environmental protection and greatly increases the production cost.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a surface coating treatment process of a high-strength fastener, which solves the problems that the coating treatment process of the fastener in the prior art is easy to cause environmental pollution and the coating of the fastener is not firm and is easy to wear.

The technical scheme is as follows: the invention provides a surface coating treatment process of a high-strength fastener, which comprises the following steps:

s1: manufacturing a base material: selecting high-strength steel, putting the steel into automatic cutting equipment, and cutting the steel into a plurality of fastener base materials by the automatic cutting equipment;

s2: hot heading fastener base material: heating the fastener base material by a high-frequency heating machine until the surface of the fastener base material is heated to 900-950 ℃, controlling the heating time to be 5-6 seconds, placing the fastener base material subjected to the hot heading treatment in a forming die, and then controlling a piston rod of a hydraulic cylinder to extend out, wherein the piston rod drives a punch to impact the fastener base material subjected to the hot heading treatment;

s3: and (3) thread machining: manufacturing the external thread of the fastener base material by using a thread rolling machine, and forming a thread on the outer wall of the fastener base material;

s4: first heat treatment: placing the fastener semi-finished product prepared in the step S3 into a high-temperature heating furnace for heating, placing the heated fastener semi-finished product into an organic silicon medium for cooling treatment until the temperature of the metal workpiece is reduced to 350-450 ℃, taking out the fastener semi-finished product and placing the fastener semi-finished product into deionized water for water bath cooling;

s5: and (3) second heat treatment: carrying out secondary heat treatment on the fastener semi-finished product cooled and cooled in the step S4;

s6: surface treatment: completely immersing a semi-finished product of the fastener in a zinc plating solution at the temperature of 35-40 ℃ for electroplating, wherein each liter of the zinc plating solution contains 60-70 g of zinc chloride, 280-360 g of ammonium chloride, 30-35 g of potassium chloride, 30-38 g of sodium hydroxide, 55-65 g of triethanolamine, 28-30 g of boric acid, 15-20 ml of organic solvent, 1-2 g of softener, 5-8 ml of main brightener and 20-25 ml of auxiliary brightener, which are water; the main brightening agent is 50-100 mg/L of benzalacetone, 200-250 mg/L of sodium benzoate, 5-10 mg/L of nicotinic acid and 10-20 mg/L of nonylphenol polyoxyethylene ether; the auxiliary brightening agent is imidazole propoxy condensed 40-90 mg/L; the softening agent is a rare earth additive which is lanthanum chloride or cerium chloride; the organic solvent is any one or combination of ethanol, butyl ether and ethylene glycol monomethyl ether; electroplating time is 3-5 minutes, and cathode current density is as follows: 2.0-3A/dm 2;

s7: washing with water after electroplating, then immersing the fastener into an activating solution, soaking at room temperature for 3-5 seconds, and washing with water again;

s8: removing redundant liquid on the surface of the fastener, placing the fastener in a dryer for drying at the temperature of 65-75 ℃, placing the fastener after galvanization and cooling in an oven for heating to 230-260 ℃, and preserving heat for 3-4 hours;

s9: immersing the fastener in a passivating solution;

s10: cleaning the passivated fastener with clear water at 45-65 ℃, and drying the cleaned fastener with hot air;

s11: and coating a PTFE (polytetrafluoroethylene) anti-corrosion coating on the surface of the fastener, and baking the fastener at the baking temperature of 65-70 ℃ for 60-70 min.

Further, the surface plating treatment process of the high-strength fastener further includes shot blasting treatment of a fastener base material in the step S2, and specifically includes the following steps:

performing shot blasting treatment on the surface of the base material of the fastener by using a through type shot blasting machine, wherein the shot blasting time is 15-25 min, so that the surface of the fastener is steel gray, removing iron scales, and spraying the surface of the raw material of the fastener subjected to shot blasting treatment.

Further, in the surface plating treatment process of the high-strength fastener, the PTFE corrosion protection coating is applied in step S11, and the PTFE corrosion protection coating is sprayed on the surface of the fastener by using a plasma spraying method.

Further, in the surface coating treatment process of the high-strength fastener, the second heat treatment in the step S5 includes the following steps:

and (3) moving the semi-finished product of the fastener into a heating furnace, heating to 400-450 ℃, preserving heat for 15-20 minutes, then continuing heating to 550-600 ℃, preserving heat for 45-50 minutes, moving the semi-finished product of the fastener out of the heating furnace, naturally cooling to 120-140 ℃ in air, and performing carburizing and quenching treatment on the semi-finished product of the fastener.

Further, the surface coating treatment process of the high-strength fastener comprises the following steps:

a heating procedure, namely moving the heated fastener semi-finished product into a heating furnace to be heated to 820-860 ℃, preserving heat for 25-30 min, keeping the temperature of the fastener semi-finished product between 720 ℃ and the upper temperature limit for not less than 15min, and keeping the heating rate of the heating process to be not more than 2 ℃/s; when the temperature is raised to 650 ℃, methanol is introduced into the heating furnace, and the introduction amount is 25-35 ml/min; pre-cooling the heated fastener semi-finished product to ensure that the temperature of the fastener semi-finished product is reduced to 760-780 ℃, then carrying out water cooling, controlling the temperature of the fastener semi-finished product to 70-80 ℃ after the water cooling is finished, and then carrying out tempering treatment.

Further, the surface coating treatment process of the high-strength fastener comprises the following tempering treatment steps:

transferring the quenched semi-finished product of the fastener into a tempering furnace, heating the tempering furnace to 540-560 ℃, preserving heat for 50-60 min, naturally cooling the semi-finished product of the fastener to 220-240 ℃ along with the furnace after heat preservation, taking out the semi-finished product of the fastener, and naturally cooling the semi-finished product of the fastener in the air to room temperature; and cooling to 65 ℃ in air cooling, performing primary high-temperature tempering, heating to 600-650 ℃ at a heating speed of 300-400 ℃/h, keeping the temperature for 40min, and cooling in air after discharging.

Further, in the surface coating treatment process of the high-strength fastener, the passivation solution in the step S9 is:

lithium carbonate: 5-20 g/L, fluoride salt: 1-10 g/L, meta-aluminate: 2-15 g/L, and casein: 2-15 g/L, silicate: 5-15 g/L.

Further, in the surface plating treatment process of the high-strength fastener, the activation solution in the step S7 is:

H₃PO₄：5.0～14g/L、CaH₂PO₄：5.4～10.2g/L、ZnH₂PO₄：0.8～3.8 g/L、NaNO₃：1～3g/L、NaNO₂：2～6g/L。

further, in the surface plating treatment process of the high-strength fastener, in the step S1, the weight ratio of the high-strength steel is selected as follows:

c: 0.08 to 0.12, Si: 0.6-0.8, P is less than or equal to 0.015, S is less than or equal to 0.015, Ni: 15-20, Cr: 15-18, V: 0.15 to 0.55, Mo: 1.4-1.8, Ti: 3-4.5, Mn: 0.12 to 0.25, W: 0.01 to 0.03, Nb: 0.05-0.10 wt% and Fe for the rest.

Further, in the surface plating treatment process of the high-strength fastener, the PTFE anticorrosive coating in the step S11 includes the following components in parts by mass:

12 parts of phenolic resin, 4 parts of polyethylene, 4 parts of organic silicon resin, 8 parts of aluminum powder, 5 parts of anticorrosive filler, 2 parts of lubricant, 5 parts of thixotropic agent, 2 parts of plasticizer, 2 parts of dispersant and 8 parts of solvent.

The technical scheme shows that the invention has the following beneficial effects: the surface coating treatment process for the high-strength fastener disclosed by the invention is used for developing the high-strength fastener, and can solve the problem that the automobile fastener loosens and falls off after being used for a long time.

Detailed Description