阅读说明：本技术 一种大扁头螺丝及其加工方法 (Big flat-head screw and processing method thereof ) 是由 林乾来 曹江华 金志顺 祝建华 于 2020-11-27 设计创作，主要内容包括：本申请涉及螺丝加工技术领域,具体公开了一种大扁头螺丝及其加工方法。本申请的大扁头螺丝的加工方法,包括如下步骤：1)将线材进行拉丝、退火处理,然后精拉、打头、夹尾、搓丝得到半成品工件；2)将步骤1)得到的半成品工件进行清洗防腐处理,所述清洗防腐蚀处理包括以下步骤：清洗处理、电镀处理、成膜处理,所述成膜处理是将电镀处理后的半成品工件依次进行第一成膜液浸泡、干燥、第二成膜液浸泡、干燥、喷涂第三成膜液。本申请大扁头螺丝的加工方法能够大幅度提高螺丝的防腐蚀性能,制备出综合性能优良的大扁头螺丝。(The application relates to the technical field of screw machining, and particularly discloses a large flat-head screw and a machining method thereof. The processing method of the large flat-head screw comprises the following steps: 1) carrying out wire drawing and annealing treatment on the wire, and then carrying out fine drawing, heading, tail clamping and thread rolling to obtain a semi-finished workpiece; 2) carrying out cleaning and corrosion prevention treatment on the semi-finished workpiece obtained in the step 1), wherein the cleaning and corrosion prevention treatment comprises the following steps: cleaning, electroplating and film forming, wherein the film forming is to perform first film forming liquid soaking, drying, second film forming liquid soaking, drying and third film forming liquid spraying on the electroplated semi-finished workpiece in sequence. The processing method of the large flat-head screw can greatly improve the corrosion resistance of the screw and prepare the large flat-head screw with excellent comprehensive performance.)

1. A processing method of a large flat head screw is characterized by comprising the following steps:

1) carrying out wire drawing and annealing treatment on a steel wire, and then carrying out fine drawing, heading, tail clamping and thread rolling to obtain a semi-finished workpiece;

2) carrying out cleaning and corrosion prevention treatment on the semi-finished workpiece obtained in the step 1), wherein the cleaning and corrosion prevention treatment comprises the following steps: cleaning, electroplating and film-forming, wherein the film-forming is to perform first film-forming liquid soaking, electroplating and film-forming on the electroplated semi-finished workpiece in sequence,Drying, soaking in the second filming liquid, drying, spraying the third filming liquid, the first filming liquid contains PO₄ ^3-、HPO₄ ^2-、H₂PO₄ ^-At least one of (1) and Mn²⁺(ii) a The second film forming solution contains CrO₄ ^2-、Cr₂O₇ ^2-At least one of; the third film forming liquid is acrylic emulsion or is obtained by mixing acrylic emulsion and water.

2. The processing method of the large flat-head screw according to claim 1, wherein the first film-forming liquid is mainly prepared by mixing the following raw materials in parts by weight: 20-26 parts of manganese acid phosphate, 32-48 parts of phosphoric acid and 1000 parts of water.

3. The processing method of the large flat-head screw according to claim 2, characterized in that the raw materials for preparing the first film-forming liquid further comprise manganese nitrate, sodium pyrophosphate and sodium molybdate, and the mass ratio of the manganese nitrate, the sodium pyrophosphate and the sodium molybdate to the manganese acid phosphate is 8-12:5-10:1-3: 20-26.

4. The processing method of the large flat-head screw according to claim 1, wherein the second film-forming solution is prepared by mixing the following raw materials in parts by weight: chromic anhydride 2.2-3.0 parts, potassium dichromate 4.0-5.8 parts, and water 1000 parts.

5. The processing method of the large flat-head screw according to claim 2, wherein the raw materials for preparing the second film forming solution further comprise lithium fluoride, lead tetrafluoroborate, sulfuric acid, potassium dichromate, lithium fluoride, lead tetrafluoroborate and sulfuric acid in a mass ratio of 4.0-5.8:3.2-4.5:0.5-1.1: 18-25.

6. The method for processing a large flat-head screw according to claim 1, wherein the acrylic emulsion is composed of one or two of styrene-acrylic emulsion and silicone-acrylic emulsion.

7. The processing method of the large flat-head screw according to claim 1, wherein the soaking time of the first film-forming solution is 15-25 min; the soaking time of the second film forming liquid is 5-8 min.

8. The processing method of the large flat-head screw according to claim 1, wherein the drying temperature after the first membrane forming solution is soaked is 120-130 ℃, and the drying time is 20-30 min; the drying temperature of the second film forming liquid after soaking is 140-150 ℃, and the drying time is 30-50 min.

9. The method for processing the large flat-head screw according to claim 1, wherein the step 2) of spraying the third film-forming solution is carried out for 10 to 20 seconds in an atomization environment formed by spraying the third film-forming solution.

10. A large flat-head screw manufactured by the method for processing a large flat-head screw according to claim 1.

Technical Field

The application relates to the technical field of screw machining, in particular to a large flat-head screw and a machining method thereof.

Background

The fastener has wide application in a plurality of industries such as energy, electronics, electrical appliances, machinery, chemical engineering, metallurgy, dies, hydraulic pressure and the like, and is a basic mechanical accessory. The screw is a common fastener, has various types and rich functions, gradually forms a standardized, serialized and generalized product, and becomes a standard component.

The screw is usually made of metal wire through wire drawing, heat treatment, finish drawing, heading, thread rolling and secondary heat treatment, and in order to improve the surface quality of the screw and the corrosion resistance of the screw, the screw is subjected to electroplating treatment after the secondary heat treatment, and an electroplated layer is formed on the surface of the screw.

The Chinese patent with application publication number CN108890223A discloses a production process of an anti-loose double-section screw, which comprises the following steps: s1: drawing: processing the low-carbon steel wire to a required diameter by a wire rod drawing machine; s2: spheroidizing: spheroidizing the drawn low-carbon steel wire by a spheroidizing furnace; s3: blanking: selecting a low-carbon steel wire, and cutting the steel wire into steel wire sections with fixed lengths; s4: heading: adopting a heading machine to process one end of the steel wire section into the shape of the head of the screw by using a die; s5: tail clamping: processing the other end of the steel wire section into a double-section wire shape by adopting a tail clamping machine; s6: thread rolling: machining threads on the periphery of the steel wire section by using a thread rolling machine; s7: and (3) heat treatment: normalizing and quenching the screw sequentially, wherein the normalizing temperature is 600-650 ℃, and the quenching temperature is 760-780 ℃; s8: and (4) galvanizing.

In view of the above-mentioned related technologies, the inventor believes that after the surface of the screw is galvanized, only one layer of zinc plating is used for protection, and after long-term use, the zinc plating on the surface of the screw is easily corroded, so that the corrosion resistance of the plating is reduced.

Disclosure of Invention

In order to improve the corrosion resistance of a protective layer on the surface of the screw, the application provides a large flat-head screw and a processing method thereof.

In a first aspect, the present application provides a method for processing a large flat head screw, which adopts the following technical scheme:

a method for processing a large flat-head screw comprises the following steps:

1) carrying out wire drawing and annealing treatment on a steel wire, and then carrying out fine drawing, heading, tail clamping and thread rolling to obtain a semi-finished workpiece;

2) carrying out cleaning and corrosion prevention treatment on the semi-finished workpiece obtained in the step 1), wherein the cleaning and corrosion prevention treatment comprises the following steps: cleaning, electroplating and film forming, wherein the film forming comprises the steps of sequentially soaking and drying a first film forming solution, soaking and drying a second film forming solution and spraying a third film forming solution on a semi-finished workpiece after electroplating, and the first film forming solution contains PO₄ ^3-、HPO₄ ^2-、H₂PO₄ ^-At least one of (1) and Mn²⁺(ii) a The second film forming solution contains CrO₄ ^2-、Cr₂O₇ ^2-At least one of; the third film forming liquid is acrylic emulsion or is obtained by mixing acrylic emulsion and water.

Through adopting above-mentioned technical scheme, this application carries out film forming process again after carrying out electroplating treatment to the screw work piece, forms the one deck protection film on the cladding material surface of screw, and the protection film forms compound inoxidizing coating with the cladding material, has improved the guard action to the screw greatly, has increased anti-corrosion. The first film-forming solution contains PO₄ ^3-、HPO₄ ^2-、H₂PO₄ ^-At least one of (1) and Mn²⁺The phosphate in the phosphate layer is relatively loose, and a fine microporous structure can be formed in the phosphate layer after drying. After the second film forming solution is immersed, the second film forming solution enters a micropore structure in the phosphate layer, and after the second film forming solution is dried, the chromate is adsorbed in the micropores, fills most of the space in the micropores and forms a composite protective layer with the phosphate. The chromate may also partially shrink after drying, the third film-forming solutionAfter spraying, liquid microdroplets formed by the acrylic emulsion enter the residual space in the micropores to fully block the micropores, and a channel which is in contact with the coating from the outside is closed, so that the corrosion of gas and moisture in the environment to the coating is fully reduced.

Preferably, the first film-forming liquid is prepared by mixing the following raw materials in parts by weight: 20-26 parts of manganese acid phosphate, 32-48 parts of phosphoric acid and 1000 parts of water.

By adopting the technical scheme, the first film-forming solution is compounded by acid manganese phosphate, phosphoric acid and water, so that the concentration of phosphate radicals in the first layer of film-forming solution is increased, more phosphate radicals are combined with manganese ions to generate manganese phosphate and are combined on the surface of a coating, more microporous structures are provided for chromate and acrylic emulsion to enter, and the protection effect of the protective layer is enhanced.

Preferably, the raw materials for preparing the first film-forming liquid also comprise manganese nitrate, sodium pyrophosphate and sodium molybdate, and the mass ratio of the manganese nitrate, the sodium pyrophosphate, the sodium molybdate and the manganese acid phosphate is 8-12:5-10:1-3: 20-26.

By adopting the technical scheme, the manganese nitrate is added into the first film-forming solution to provide more manganese ions, the sodium pyrophosphate and the sodium molybdate can provide pyrophosphate and molybdate to the film-forming solution, and the pyrophosphate and the molybdate can enhance the combination between phosphates, so that a continuous phosphate film is formed on the surface of the screw, and the protection on the surface coating of the screw is more comprehensive.

Preferably, the second film forming solution is prepared by mixing the following raw materials in parts by weight: chromic anhydride 2.2-3.0 parts, potassium dichromate 4.0-5.8 parts, and water 1000 parts.

By adopting the technical scheme, the second film forming solution contains potassium dichromate, and after the potassium dichromate is dissolved in water, a small amount of chromate can be generated in the aqueous solution by the dichromate, so that the second film forming solution contains various chromium-containing acid radical ions, can be well combined with microporous structures with different structures, and is more fully combined with a phosphate layer. The chromic anhydride enters the microporous structure of the phosphate under the drive of the chromate, and has better corrosion resistance after later drying.

Preferably, the raw materials for preparing the second film forming solution further comprise lithium fluoride, lead tetrafluoroborate, sulfuric acid, and the mass ratio of potassium dichromate, lithium fluoride, lead tetrafluoroborate and sulfuric acid is 4.0-5.8:3.2-4.5:0.5-1.1: 18-25.

By adopting the technical scheme, the second film forming solution also contains lithium fluoride and lead tetrafluoroborate, and the lithium fluoride can be dissolved in water under the condition of adding sulfuric acid, and then enters into the microporous structure of phosphate, so that the compactness of the protective layer is improved, and the acid resistance of the protective layer can also be improved. The lead tetrafluoroborate is introduced into the protective layer, so that the acid resistance of the protective layer can be greatly improved, and the comprehensive protective performance of the protective layer is further improved.

Preferably, the acrylic emulsion is composed of one or two of styrene-acrylic emulsion and silicone-acrylic emulsion.

By adopting the technical scheme, the styrene-acrylic emulsion and the silicone-acrylic emulsion have good water resistance, and fine liquid droplets formed by spraying are sprayed on the surface of the screw and enter the phosphate micropores to block the channels in the micropores, so that the protective layer has a very strong water-resisting effect.

Preferably, the soaking time of the first membrane forming liquid is 15-25 min; the soaking time of the second film forming liquid is 5-8 min.

By adopting the technical scheme, the first film forming liquid is soaked for a longer time, so that phosphate can form a phosphate layer with a larger thickness on the surface of the coating of the screw, more chromate and acrylic emulsion can be contained in the phosphate layer, and the second film forming liquid is soaked for a shorter time, so that the deposition amount of chromate on the outer surface of the phosphate layer is reduced.

Preferably, the drying temperature after the first membrane forming liquid is soaked is 120-130 ℃, and the drying time is 20-30 min; the drying temperature of the second film forming liquid after soaking is 140-150 ℃, and the drying time is 30-50 min.

By adopting the technical scheme, because the phosphate forms the phosphate layer on the surface of the electroplated layer, the moisture in the phosphate layer is not easy to discharge, the drying temperature of the first film-forming liquid after soaking is more than 100 ℃, and most of the moisture in the phosphate layer can be discharged. And after the second film forming solution is soaked, micropores in the phosphate are blocked, the drying is carried out at a higher temperature and for a longer drying time, so that the moisture in the chromate in the micropores can be more fully discharged.

Preferably, the third film-forming liquid sprayed in the step 2) is processed for 10 to 20 seconds in an atomization environment formed by spraying the third film-forming liquid.

By adopting the technical scheme, when the third film forming liquid is sprayed, the third film forming liquid is sprayed to form mist-shaped liquid drops, the mist-shaped liquid drops can more easily enter phosphate micropores filled with chromate, the treatment time in the atomizing environment is controlled to be 10-20s, acrylic emulsion liquid drops in the third film forming liquid can be ensured to enter the micropores in the phosphate layer, the deposition of acrylic resin on the surface of the phosphate layer is reduced, and the rigidity of the surface of the screw is further ensured.

In a second aspect, the present application provides a large flat head screw, which adopts the following technical scheme:

a large flat-head screw manufactured by the processing method of the large flat-head screw.

By adopting the technical scheme, the composite protective layer of phosphate, chromate and acrylic resin is formed on the surface of the electroplated layer besides the electroplated layer on the surface of the large flat-head screw prepared by the processing method, and the large flat-head screw has good corrosion resistance.

In summary, the present application has the following beneficial effects:

1. according to the processing method of the large flat-head screw, the composite protective layer is formed on the electroplated layer on the surface of the large flat-head screw in a deposition mode, so that the protection of the electroplated layer is improved, and the corrosion resistance of the screw is greatly improved. After the first film forming liquid is deposited and dried on an electroplated layer of the screw, a formed phosphate layer has a large number of microporous structures, chromate in the subsequent second film forming liquid is deposited and adsorbed in the microporous structures, micropores of phosphate are filled, and finally, the microporous structures are filled with mist-shaped liquid drops of acrylic emulsion, so that the water resistance of the composite protective layer is greatly improved, and the large flat-head screw with excellent comprehensive performance is finally prepared.

2. Lithium fluoride, lead tetrafluoroborate have been added to the second membrane forming liquid in this application to with the sulphuric acid cooperation, improved the compact degree and the acid resistance of compound inoxidizing coating, further improved the comprehensive protection performance of big flat head screw.

Detailed Description

The present application will be described in further detail with reference to examples.

According to the processing method of the large flat-head screw, the first film forming liquid is prepared by adding acid manganese phosphate and other raw materials into water for mixing, or is prepared by adding sodium phosphate, potassium dihydrogen phosphate and manganese nitrate into water for providing phosphate ions, dihydrogen phosphate ions and manganese ions.

When the first film forming solution and the second film forming solution are soaked, the solution is kept still, so that disturbance to the deposition state of a deposition layer on the surface of the screw during stirring is reduced.

The drying after the immersion in the first and second deposition solutions is performed in a vacuum drying furnace. The cooling after drying is furnace cooling in a vacuum drying furnace.

Preferably, the third film forming liquid is prepared by mixing the following raw materials in parts by weight: 200 portions of acrylic emulsion and 300 portions of water.

And (3) placing the workpiece in an atomization environment formed by spraying the third film forming liquid, and standing by using ultrasonic atomization spraying equipment. The power of the ultrasonic atomization spraying equipment is 500W, the atomization amount is 200L/h, and the particle size of atomized liquid drops is about 50 μm.

Standing in an atomization environment formed by spraying the third film-forming liquid, and drying at 70-80 deg.C for 2 h.

The steel wire is subjected to acid pickling pretreatment before cold wire drawing. The pickling pretreatment is carried out by soaking for 8min by using hydrochloric acid with the mass fraction of 10%. And after the acid washing pretreatment, washing, drying and coating a lubricant. The lubricant is aluminum stearate.

And (2) annealing after cold wire drawing, wherein the annealing treatment is to heat up to 450 ℃ at a heating rate of 100 ℃/h, then heat up to 850 ℃ at a heating rate of 45 ℃/h and preserve heat for 2h, then cool down to 550 ℃ at a cooling rate of 50 ℃/h, preserve heat for 2h, then cool down to 300 ℃ at a cooling rate of 35 ℃/h, preserve heat for 4h, and then cool down to room temperature along with the furnace.

The acid washing solution adopted when the steel wire is acid washed after the annealing treatment is hydrochloric acid or mixed acid, and the mixed acid is formed by mixing hydrochloric acid and sulfuric acid. The mass fraction of the hydrochloric acid is 15 percent, and the mass fraction of the sulfuric acid is 10 percent. The volume ratio of the hydrochloric acid to the sulfuric acid is 3: 1. The secondary pickling is to soak the steel wire rod in the pickling solution for 2-3 min.

Preferably, the pickling solution adopted in the pickling passivation treatment is prepared by mixing the following raw materials in parts by weight: 20-25 parts of oxalic acid, 12-16 parts of lactic acid and 100 parts of water; preferably, the pickling solution for the pickling passivation treatment is prepared by mixing the following raw materials in parts by weight: 20-25 parts of oxalic acid, 12-16 parts of lactic acid, 6-7 parts of glycolic acid, 2-3 parts of polyaluminium sulfate and 100 parts of water. After acid pickling passivation treatment, phosphating is directly carried out without water washing. The phosphating is carried out by soaking in phosphating solution which is obtained by mixing zinc dihydrogen phosphate and water in a mass ratio of 5-8: 100. And soaking in phosphating solution for 5-8min during phosphating.

The cleaning and antiseptic treatment comprises cleaning treatment and antiseptic treatment. The cleaning treatment is to add the semi-finished workpiece into cleaning solution for stirring treatment or ultrasonic treatment. The stirring time is 10-15 min. The ultrasonic treatment time is 1-2 min. The power of ultrasonic treatment is 1200-1500W. Preferably, the cleaning solution is prepared by mixing sodium hydroxide, sodium bicarbonate, sodium dihydrogen phosphate, potassium sodium tartrate and water in a mass ratio of 2.5-3.5:6-8:7-10:5-6: 100. And (3) soaking the semi-finished workpiece subjected to stirring treatment or ultrasonic treatment in hot water at 70-80 ℃ for 15-20min, and then soaking in cold water at 5-10 ℃ for 20-30 min.

Preferably, Al is contained in the plating liquid used for the plating treatment³⁺、Zn²⁺、Ni²⁺The molar ratio of (A) to (B) is 0.5-1.5:3-8: 1-2. The current density of the electroplating treatment is 2-5A/dm²The time of electroplating treatment is 5-25 min. Zn in plating solution during plating treatment²⁺The concentration of (B) is 0.2-0.5 mol/L. Mn is also included in the plating solution²⁺，Mn²⁺With Zn²⁺The molar ratio of (A) to (B) is 0.3-0.5: 3-8. In is also included In the electroplating solution³⁺。In³⁺With Zn²⁺The molar ratio of (A) to (B) is 0.005-0.02: 3-8.

The electroplating solution is mainly prepared by mixing water-soluble aluminum salt, water-soluble zinc salt, water-soluble nickel salt, water-soluble manganese salt, water-soluble indium salt and water. When water-soluble aluminum salt, water-soluble zinc salt, water-soluble nickel salt, water-soluble manganese salt and water-soluble indium salt are mixed with water, sodium thiosulfate and sodium silicate are also added, and the mass ratio of the sodium thiosulfate to the sodium silicate to the water is 6-8:3-5: 1000. And when the water-soluble aluminum salt, the water-soluble zinc salt, the water-soluble nickel salt, the water-soluble manganese salt and the water-soluble indium salt are mixed with water, a surfactant and a dispersant are also added, wherein the mass ratio of the surfactant to the dispersant to the water is 10-15:6-8: 1000. Preferably, the electroplating solution is prepared by uniformly mixing aluminum nitrate, zinc nitrate, nickel nitrate, manganese chloride, sodium thiosulfate, sodium silicate, indium chloride, nonylphenol polyoxyethylene ether-9, guar gum and water in a mass ratio of 10.5:57:18.5:4:6:5:0.38:10:8: 1000.

The phosphoric acid was contained in an amount of 65% by mass. The mass fraction of the sulfuric acid is 32-40%

The lead tetrafluoroborate in the application is a lead tetrafluoroborate solution with the mass fraction of 28%.

Preferably, when the large flat-head screw is processed, the 17-4PH stainless steel wire is adopted as the steel wire.

During electroplating, the semi-finished workpiece is used as a cathode, and a zinc plate and nickel plate mixed composite plate is used as an anode, or a zinc-nickel alloy is used as an anode. Or a zinc plate, a nickel plate and an aluminum plate mixed composite plate is adopted as the anode, or zinc, nickel and aluminum alloy are adopted as the anode, and the mass ratio of zinc, nickel and aluminum in the alloy is approximately the same as that of zinc, nickel and aluminum in the electroplating solution. Preferably, zinc, nickel, aluminum, manganese, indium alloy is used as the anode.

Examples

Example 1

The processing method of the large flat-head screw comprises the following steps:

1) annealing the wire, pre-treating the wire by pickling, washing the wire by water, drying the wire, and then coating a layer of lubricant on the surface of the wire, wherein the lubricant is aluminum stearate; the pre-treatment of acid washing is to soak the raw materials for 8min by adopting hydrochloric acid with the mass fraction of 10%;

2) carrying out cold wire drawing on the wire rod treated in the step 1), drawing the wire rod to a proper wire diameter, and then carrying out annealing treatment again;

3) pickling the annealed steel wire, wherein the pickling solution adopted in pickling adopts hydrochloric acid with the mass fraction of 15%; the pickling is carried out by soaking for 3min with pickling solution, then washing with three-stage countercurrent water, and drying;

then, carrying out acid pickling passivation treatment on the steel wire, wherein acid pickling solution adopted in the acid pickling passivation treatment is prepared by uniformly mixing oxalic acid and water in a mass ratio of 20: 100; the pickling passivation treatment is to soak the pickling solution for 5 min;

then, directly soaking the steel wire rod in phosphating solution for 5min without water washing, wherein the phosphating solution is prepared by mixing zinc dihydrogen phosphate and water in a mass ratio of 8: 100; then, cleaning by adopting three-stage overflow water;

4) carrying out finish drawing, heading, tail clamping and thread rolling on the steel wire rod treated in the step 3) to obtain a semi-finished workpiece;

5) cleaning and antiseptic treatment is carried out on the semi-finished workpiece obtained in the step 4), wherein the cleaning and antiseptic treatment comprises cleaning treatment and electroplating treatment which are carried out in sequence;

the cleaning treatment is to add the semi-finished workpiece into cleaning liquid to be stirred and cleaned for 10min, wherein the cleaning liquid is prepared by mixing sodium hydroxide, sodium bicarbonate and water according to the mass ratio of 3.5:8: 100; then washing with three-stage countercurrent water;

the electroplating treatment is to add the cleaned semi-finished workpiece into electroplating solution for electroplating, wherein the electroplating solution is obtained by uniformly mixing zinc chloride and nickel chloride in a mass ratio of 41:13: 1000; the current density of electroplating is 3A/dm²The electroplating time is 10 min; then, three-level overflow water is adopted for cleaning and drying;

6) step 5) performing film forming treatment on the workpiece after electroplating treatment, wherein the film forming treatment is to put the workpiece after electroplating treatment in the step 5) into the first film forming liquid to soak for 15min, then take out the workpiece, dry the workpiece for 20min at 120 ℃, cool the workpiece, then put the workpiece into the second film forming liquid to soak for 5min, take out the workpiece to dry the workpiece for 30min at 150 ℃, cool the workpiece, then place the workpiece in an atomization environment formed by spraying of the third film forming liquid to stand for 10s, take out the workpiece and dry the workpiece to obtain the film;

the first film-forming liquid is prepared by uniformly mixing acid manganese phosphate and water in a mass ratio of 20: 1000; the second film forming solution is prepared by uniformly mixing potassium dichromate and water in a mass ratio of 4: 1000; the third film forming liquid is prepared by uniformly mixing styrene-acrylic emulsion and water in a mass ratio of 200:1000, and the solid content of the styrene-acrylic emulsion is 48%.

Example 2

The processing method of the large flat-head screw in the embodiment is different from the processing method in the embodiment 1 in that the first film-forming solution in the step 6) is prepared by uniformly mixing manganese acid phosphate and water in a mass ratio of 26: 1000; the second film forming solution is prepared by uniformly mixing potassium dichromate and water according to the mass ratio of 5.8: 1000; the third film forming liquid is prepared by uniformly mixing styrene-acrylic emulsion and water in a mass ratio of 300:1000, and the solid content of the styrene-acrylic emulsion is 48%.

Example 3

The processing method of the large flat-head screw in the embodiment is different from the processing method in the embodiment 1 in that the first film-forming solution in the step 6) is prepared by uniformly mixing manganese acid phosphate and water in a mass ratio of 22: 1000; the second film forming solution is prepared by uniformly mixing potassium dichromate and water in a mass ratio of 5.2: 1000; the third film forming liquid is prepared by uniformly mixing a styrene-acrylic emulsion and water in a mass ratio of 270:1000, and the solid content of the styrene-acrylic emulsion is 48%.

Example 4

The processing method of the large flat-head screw in the embodiment is different from that in embodiment 3, the workpiece electroplated in step 5) is placed in the first film forming liquid to be soaked for 25min in step 6), then the workpiece is taken out, dried for 30min at 130 ℃, cooled, then the workpiece is placed in the second film forming liquid to be soaked for 8min, taken out, dried for 50min at 140 ℃, cooled, then the workpiece is placed in an atomization environment formed by spraying of the third film forming liquid to be kept stand for 20s, taken out and dried, and the large flat-head screw is obtained.

Example 5

The processing method of the large flat-head screw in the embodiment is different from that in embodiment 4, the workpiece electroplated in step 5) is placed in the first film forming liquid to be soaked for 20min in step 6), then the workpiece is taken out, dried for 25min at 125 ℃, cooled, then placed in the second film forming liquid to be soaked for 6min, taken out, dried for 40min at 145 ℃, directly placed in an atomization environment formed by spraying of the third film forming liquid without cooling, and then taken out and dried to obtain the large flat-head screw.

Example 6

The processing method of the large flat-head screw in the embodiment is different from the processing method in the embodiment 5 in that the first film-forming solution in the step 6) is prepared by uniformly mixing acid manganese phosphate, phosphoric acid and water in a mass ratio of 22:32: 1000; the mass fraction of phosphoric acid is 65 percent; the second film forming solution is prepared by uniformly mixing potassium dichromate, chromic anhydride and water according to the mass ratio of 5.2:2.2: 1000; the third film forming liquid is prepared by uniformly mixing a styrene-acrylic emulsion and water in a mass ratio of 270:1000, and the solid content of the styrene-acrylic emulsion is 48%.

Example 7

The processing method of the large flat-head screw in the embodiment is different from the processing method in the embodiment 6 in that the first film-forming solution in the step 6) is prepared by uniformly mixing acid manganese phosphate, phosphoric acid and water in a mass ratio of 22:48: 1000; the mass fraction of phosphoric acid is 65 percent; the second film forming solution is prepared by uniformly mixing potassium dichromate, chromic anhydride and water according to the mass ratio of 5.2:3: 1000; the third film forming liquid is prepared by uniformly mixing a silicone-acrylic emulsion and water in a mass ratio of 270:1000, and the solid content of the silicone-acrylic emulsion is 48%.

Example 8

The processing method of the large flat-head screw in the embodiment is different from the processing method in the embodiment 7 in that the first film-forming solution in the step 6) is prepared by uniformly mixing manganese acid phosphate, phosphoric acid, manganese nitrate, sodium pyrophosphate, sodium molybdate and water in a mass ratio of 22:48:8:6:1: 1000; the mass fraction of phosphoric acid is 65 percent; the second film forming solution is prepared by uniformly mixing potassium dichromate, chromic anhydride, lithium fluoride, lead tetrafluoroborate, sulfuric acid and water according to the mass ratio of 5.2:3:3.2:0.5:18: 1000; the mass fraction of the sulfuric acid is 40 percent; the third film forming liquid is prepared by uniformly mixing a silicone-acrylic emulsion and water in a mass ratio of 270:1000, and the solid content of the silicone-acrylic emulsion is 48%.

Example 9

The processing method of the large flat-head screw in the embodiment is different from the processing method in the embodiment 8 in that the first film-forming solution in the step 6) is prepared by uniformly mixing manganese acid phosphate, phosphoric acid, manganese nitrate, sodium pyrophosphate, sodium molybdate and water in a mass ratio of 22:48:12:10:3: 1000; the mass fraction of phosphoric acid is 65 percent; the second film forming solution is prepared by uniformly mixing potassium dichromate, chromic anhydride, lithium fluoride, lead tetrafluoroborate, sulfuric acid and water according to the mass ratio of 5.2:3:4.5:1.1:25: 1000; the mass fraction of the sulfuric acid is 40 percent; the third film forming liquid is prepared by uniformly mixing a silicone-acrylic emulsion and water in a mass ratio of 270:1000, and the solid content of the silicone-acrylic emulsion is 48%.

Example 10

The processing method of the large flat-head screw in the embodiment is different from that in the embodiment 9 in that the third film forming liquid is prepared by mixing acrylic emulsion and water in a mass ratio of 270:1000, the acrylic emulsion is obtained by mixing styrene-acrylic emulsion and silicone-acrylic emulsion in a volume ratio of 1:3, and the solid contents of the styrene-acrylic emulsion and the silicone-acrylic emulsion are both 48%.

Example 11

The processing method of the large flat-head screw in the embodiment is different from the embodiment 10 in that the electroplating solution in the step 5) is obtained by uniformly mixing aluminum nitrate, zinc chloride, nickel chloride and water in a mass ratio of 10.5:41:13: 1000; the current density of electroplating is 5A/dm²The time of electroplating is 5 min.

Example 12

The processing method of the large flat-head screw in the embodiment is different from the embodiment 11 in that the electroplating solution in the step 5) is obtained by uniformly mixing aluminum nitrate, zinc chloride, nickel chloride and water in a mass ratio of 25:85:25: 1000; the current density of electroplating is 2A/dm²The plating time was 20 min.

Example 13

The processing method of the large flat-head screw in the embodiment is different from the processing method in the embodiment 12 in that the electroplating solution in the step 5) is obtained by uniformly mixing aluminum nitrate, zinc nitrate, nickel nitrate, manganese chloride, sodium thiosulfate, sodium silicate, indium chloride, nonylphenol polyoxyethylene ether-9, guar gum and water in a mass ratio of 10.5:57:18.5:4:6:5:0.38:10:8: 1000.

Example 14

The processing method of the large flat-head screw in the embodiment is different from the embodiment 13 in that the cleaning solution used in the cleaning treatment in the step 5) is prepared by uniformly mixing sodium hydroxide, sodium bicarbonate, sodium dihydrogen phosphate, sodium potassium tartrate and water in a mass ratio of 3.5:8:7:6: 100.

Example 15

The processing method of the large flat-head screw in the embodiment is different from the embodiment 14 in that the pickling solution used for pickling the annealed steel wire rod in the step 3) is obtained by uniformly mixing hydrochloric acid with a mass fraction of 15% and sulfuric acid with a mass fraction of 20% in a volume ratio of 3: 1; the pickling solution used for pickling and passivation is prepared by uniformly mixing oxalic acid, lactic acid, glycolic acid and water in a mass ratio of 20:16:7: 100.

Comparative example

Comparative example 1

The processing method of the large flat-head screw in the comparative example is different from that of the example 1 in that the film forming treatment in the step 6) is to put the workpiece electroplated in the step 5) into the first film forming liquid to be soaked for 15min and then take out, dry the workpiece at 120 ℃ for 20min and cool the workpiece to obtain the large flat-head screw. The first film-forming liquid is prepared by uniformly mixing acid manganese phosphate and water in a mass ratio of 20: 1000.

Comparative example 2

The difference between the processing method of the large flat-head screw in the comparative example and the processing method of the large flat-head screw in the example 1 is that the film forming treatment in the step 6) is to put the workpiece electroplated in the step 5) into the second film forming liquid to be soaked for 5min, take out and dry the workpiece for 30min at the temperature of 150 ℃, and cool the workpiece to obtain the large flat-head screw. The second film forming solution is prepared by uniformly mixing potassium dichromate and water in a mass ratio of 4: 1000.

Comparative example 3

The difference between the processing method of the large flat-head screw in the comparative example and the processing method of the large flat-head screw in the embodiment 1 is that the film forming treatment in the step 6) is to place the workpiece electroplated in the step 5) in an atomization environment formed by spraying of a third film forming liquid for standing for 10s, take out and dry to obtain the large flat-head screw. The third film forming liquid is prepared by uniformly mixing styrene-acrylic emulsion and water in a mass ratio of 200:1000, and the solid content of the styrene-acrylic emulsion is 48%.

Comparative example 4

The processing method of the large flat-head screw in the comparative example is different from that of the example 1 in that the film forming treatment in the step 6) is to put the workpiece electroplated in the step 5) into the first film forming liquid to be soaked for 15min, then to be taken out, to be dried for 20min at 120 ℃, to be cooled, then to be put into the second film forming liquid to be soaked for 5min, to be taken out, to be dried for 30min at 150 ℃, to be cooled, and then to be the large flat-head screw. The first film-forming liquid is prepared by uniformly mixing acid manganese phosphate and water in a mass ratio of 20: 1000; the second film forming solution is prepared by uniformly mixing potassium dichromate and water in a mass ratio of 4: 1000.

Comparative example 5

The processing method of the large flat-head screw in the comparative example is different from that in the example 1, the film forming treatment in the step 6) is to put the workpiece electroplated in the step 5) into the first film forming liquid to be soaked for 15min, then to be taken out, to be dried for 20min at 120 ℃, to be cooled, then to be placed in an atomization environment formed by spraying of the third film forming liquid to be stood for 10s, to be taken out and to be dried, and then the large flat-head screw is obtained. The first film-forming liquid is prepared by uniformly mixing acid manganese phosphate and water in a mass ratio of 20: 1000; the third film forming liquid is prepared by uniformly mixing styrene-acrylic emulsion and water in a mass ratio of 200:1000, and the solid content of the styrene-acrylic emulsion is 48%.

Performance test

The screw (specification M4) prepared by the processing method of the large flat-head screw in the embodiments 1-15 and the comparative examples 1-5 is tested according to the test method in GB/T3098.1-2010 mechanical performance bolt, screw and stud of the fastener, the salt spray resistance of the screw is tested according to the test method in GB/T10125-.

TABLE 1 comparison of the Performance of the large flat head screws of examples 1-15 and comparative examples 1-5

According to the embodiment 1, the comparative example 1 and the table 1, the salt spray corrosion resistance and the sulfur dioxide corrosion resistance of the large flat-head screw prepared by the processing method of the large flat-head screw are greatly improved, and the wear resistance is also greatly improved.

According to the example 1, the comparative example 2 and the table 1, it can be seen that the salt spray resistance and the sulfur dioxide corrosion resistance of the large flat-head screw prepared by the processing method of the large flat-head screw are improved obviously, and the chromate and the acrylate have an obvious effect on improving the corrosion resistance of the screw.

According to the example 1, the comparative example 3 and the table 1, the wear resistance of the large flat-head screw manufactured by the processing method of the large flat-head screw is good, which is related to the formation of the composite protective layer on the surface of the plating layer of the screw.

According to the example 1, the comparative example 4 and the table 1, the salt spray corrosion resistance and the sulfur dioxide corrosion resistance of the large flat-head screw manufactured by the processing method of the large flat-head screw are relatively balanced, because the micropores in the phosphate layer on the surface of the electroplating layer are fully blocked, and the comprehensive corrosion resistance is excellent.

According to the example 1, the comparative example 5 and the table 1, the salt spray resistance of the large flat-head screw prepared by the processing method of the large flat-head screw is obviously improved, and it can be seen that chromate has a better promotion effect on the salt spray resistance in the protective layer.

In summary, the large flat-head screw prepared by the processing method of the large flat-head screw has good salt mist corrosion resistance and acid gas corrosion resistance, an electroplated layer is not easy to corrode, the comprehensive corrosion resistance is good, and the service life of the screw is long.