The prevalence of ion heat treatment

As early as the early 1970s, Beijing Machine Tool Research Institute successfully developed the first 10A ion nitriding test device in China. Since then, research on ion nitriding technology has sprung up all over the country. The relationship between process parameters, structure and properties of the infiltration layer was systematically studied, and the effects of carbon content and alloying elements in the steel as well as the original structure, temperature, time, pressure, and gas medium composition on the structure of the infiltration layer were explored. The conditions for the formation of γ, ε phase, γ’+ε or ε+Fe3C composite phase compound layer and compound-free layer were identified, and the most suitable structure of steel under various service conditions was determined. These conclusions laid a good foundation for the expanded application of ion nitriding. By the end of 1980, there were thousands of ion nitriding equipment and dozens of ion nitriding equipment manufacturing plants across the country, and there was a climax of popularizing ion nitriding technology. Tension spring

In addition to ion nitriding, many scientific research institutions, universities and colleges have also carried out the research and development of ion carburizing, carbonitriding, ion soft nitriding, sulfur nitrogen and carbonitriding sulfur, ion boronizing and other technologies. Factors such as complex technology, high production costs, environmental protection, safety and sanitation have not been widely used, and ion nitriding is the most widely used in production.

The research and application of ion plating technology is also an example of the progress of heat treatment technology in my country. Taiyuan University of Technology, Beijing Union University and the First Research Institute of the Ministry of Electronics have conducted in-depth research on the ion plating mechanism, optimization of process parameters, the relationship between coating quality and process, and developed multi-layer glow ionizing metal and multi-arc ion Plating technology can not only obtain a dense TiN deposition layer on the surface of metal products, and obtain single element plating layers such as W, Mo, Cr, Ni, but also make W, Cr, Mo, V and other elements at the same time in different combinations and proportions. Infiltrate ordinary steel to obtain a relatively thick plating layer similar to high-speed steel on the surface, thereby replacing expensive high-speed steel.

Popularization of vacuum heat treatment technology

In the 1970s, the oil and gas quenching and cooling cold-wall vacuum heat treatment furnace began to be developed, and it was mass-produced in series in the 1980s. At present, local manufacturing enterprises have been able to provide a series of vacuum heating, oil and gas quenching furnaces, low pressure carburizing furnaces, 1MPa (10bar) high pressure gas quenching furnaces, vacuum sintering furnaces, and brazing furnaces. The maximum temperature of vacuum quenching and high-pressure gas quenching furnace can reach 1350℃, and that of vacuum sintering furnace can reach 1800℃. The output of various furnace types and furnace types is more than 200 sets. In recent years, the development of the aviation industry and the mold industry has put a lot of demand on vacuum heat treatment furnaces, vacuum brazing furnaces, especially vacuum heating and high pressure gas quenching furnaces, which has promoted the prosperity of vacuum equipment manufacturing. The combination of low-pressure carburizing and high-pressure gas quenching technology provides a new way for vehicle gears to extend life, reduce distortion (distortion) and reduce noise. The development of a semi-continuous production line that embodies this advanced technology is a mass production of automotive gears. The technical transformation of heat treatment provides the possibility. At the beginning of the new century, several domestic automobile and diesel gear manufacturers have introduced such equipment and production lines. Stainless steel spring

Due to the high requirements of molds for surface quality and distortion, vacuum high pressure gas quenching has almost become an irreplaceable technology for mold heat treatment. At present, in the coastal areas of South China and East China, large-scale private heat treatment processing enterprises have at least one 0.4MPa vacuum heating and high-pressure gas quenching furnace (the largest number is 6). In the cutting tool industry, the wide application of CNC and machining centers strongly requires tools with high quality and long life, and urban environmental protection also puts forward stricter requirements on heat treatment. Vacuum heating and high pressure gas quenching has therefore become a substitute for high-speed steel tool heat treatment. The preferred process for bath heating and quenching.

Cold formed spring manufacturing process

Cold formed spring manufacturing process
When using materials that do not need to be quenched and tempered to make springs after forming, the process is spiral springs, compression springs: rolling, stress relief annealing, grinding on both ends, (shot blasting), (aligning), ( Stress relief annealing), standing or pressure treatment, inspection, surface anti-corrosion treatment, packaging.

Spiral tension spring: coiling, stress relief annealing, hook and loop production, (tail trimming), stress relief annealing, standing treatment, inspection, surface anticorrosion treatment, packaging.

Spiral torsion spring: coiling, stress relief annealing, torsion arm making, tail trimming, stress relief annealing, standing treatment, inspection, surface anticorrosion treatment, packaging.

The manufacturing processes of the spiral tension and torsion springs described above are all the hook loops or torsion arms at both ends after being wound on the ordinary coil spring. In recent years, many domestic and foreign manufacturers have produced and used computerized forming machines or special forming machines. The shape of the spring body and tail can be completed on the forming machine at one time, eliminating the need for processing hooks or torsion arms.

When using materials that need to be quenched and tempered after forming, the main difference from the above process is that they need to be quenched and tempered after forming. Sometimes the spring end processing needs to be normalized.

The process with brackets is a non-fixed process, and whether it is performed depends on the performance requirements of the spring.

Tips for bright heat treatment of metals in oxidizing atmosphere furnace

Tips for bright heat treatment of metals in oxidizing atmosphere furnace
It is to burn off the oxygen in the airtight container where the workpiece is placed to form a stable solid compound, so that the metal product is heated under oxygen-free and low vacuum conditions.

The specific method is to put the metal spring products (single piece or batch) in an iron (low carbon steel) container, and put a small piece of metal sodium or lithium into the container at the same time, and then cover the lid to weld the seam. . Heat the sealed container in an air oven. When the container is heated to a low temperature, the sodium or lithium burns and the oxygen in the container (accounting for 21% of the container volume) combines to form a stable solid compound. The reaction is as follows:

4Na+O2→2Na2O

4Li+O2→2Li2O.

Further heating is carried out in pure nitrogen below atmospheric pressure, and after heating is maintained, it is cooled in the furnace or taken out of the furnace. That can make the metal achieve the purpose of bright annealing or normalizing. After processing, take out the workpiece with gas cutting method.

The amount of sodium or lithium (XNa, Xli) put in the container can be calculated according to the volume (V. in L) of the container,

XNa=0.86V,g

XLi=0.26V,g.

That is to say, only 0.86gNa or 0.26gLi is required for a 1L container. However, in actual applications, the calculated value should be slightly excessive, such as adding 105%.

Attention should be paid to the application of this method for heat treatment:

1. When welding a closed container, cooling measures should be taken to prevent sodium and lithium from burning in advance.

2. Metal sodium and lithium are easily oxidized in the air, so they must be stored in gasoline, kerosene or inert gas when not in use.

7005 aluminum alloy heat treatment process

7005 aluminum alloy heat treatment process
Through the determination of mechanical properties and stress corrosion resistance, the heat treatment process of 7005 aluminum alloy has been studied. The results show that the ideal heat treatment system for this alloy is 470 ℃ solution treatment followed by water quenching, and the artificial aging system is two-stage aging 100 ℃ ×8 h +120 ℃×24 h. After heat treatment, the room temperature tensile strength of the alloy reaches more than 400 MPa, the corrosion resistance is good, and the precipitates are fine and dispersed, which has a good strengthening effect on the alloy.

Spring copper plated

Preparation of electroless copper plating bath

(1) Dissolve the required sodium cyanide with cold water.

Add the required cuprous cyanide slowly to the sodium cyanide water to dissolve. This process is an exothermic reaction and cannot be overheated.

(2) Add other additives, stir evenly, take samples for analysis.

(3) According to the analysis results, supplement and correct each component.

(4) Weak electrolysis to remove impurities at low current density for several hours.

4.4.9 Defects of electroless copper plating and their causes

1. The coating is dark red, black, and hydrogen and oxygen are violently precipitated. The reasons are:

Current density is too high bath temperature is too low

Too little copper salt, too much arsenic cyanide

2. The coating is uneven, and some are not plated. The reasons are:

Improper installation, too low current

Too much cyanide

3. The coating blisters, peels, and has poor adhesion due to:

Incomplete surface pretreatment, oil film, oxide film bath temperature is too low

Too much current

4. The plating layer has a white film layer, blue crystals appear, and the plating solution turns blue. The reasons are:

Small anode area, insufficient potassium and sodium tartrate

Insufficient sodium cyanide

4.4.10 Formula for copper plating

(1)  Sodium cyanide NaCN 65~89g/l

Cuprous cyanide CuCN 45~60g/l

Sodium carbonate Na2CO3? 15g/l

Sodium hydroxide NaOH 7.5~22.5g/l

Potassium Sodium Tartrate (rochelle salt) 45g/l

Free sodium cyanide 15~22.5g/l

Bath temperature 60~70℃

(2) Full potassium bath

Potassium cyanide KCN 80~110g/l

Cuprous cyanide CuCN 45~60g/l

Potassium carbonate K2CO3? 15g/l

Potassium hydroxide KOH 7.5~22.5g/l

Rochelle salt 45g/l

Free sodium cyanide 12~22.5g/l

Bath temperature 60~70℃

4.4.11 Gloss cyanide copper plating

1. Add gloss agent:

(1) Lead: use lead carbonate or lead acetate to dissolve in water 0.015~0.03g/l

(2) Sodium thiosulfate: Dissolve in water with Haibo 1.9~2g/l

(3) Sulfur: Use sulfur to dissolve in water 0.1~0.5g/l

(4) Arsenic: Dissolve in NaOH 0.05~0.1g/l with arsenous acid

(5) Selenium: Dissolve in NaOH 1~1.5g/l with selenite

(6) Potassium thiocyanide: Potassium thiocyanide is soluble in water 3~10g/l

2. Use current waveform

(1) PR current:

a. Smoothing: 35 seconds for the cathode and 15 seconds for the anode.

b. Glossing: 15 seconds for cathode and 5 seconds for anode.

(2) AC and DC combined use:

a. Smoothing: DC 25 seconds, AC 10 seconds.

b. Glossing: DC 20 seconds, AC 6 seconds, the cycle of AC is 1.25-10 cycle.

(3) DC interruption: interrupt the current instantly and then resume the current.

4.5 Copper Pyrophosphate Plating Bath

It needs more control and maintenance, but the solution is less toxic than the copper cyanide bath. It is mainly used in printed circuit plastic plating and electroforming. Steel and zinc castings will produce replacement coatings and poor adhesion. You must first strike with a cyanide copper plating bath or a 10:1 P2O7Cu low pyrophosphate copper plating bath.

4.5.1 Copper pyrophosphate base plating bath formula (Strike Bath)

Copper pyrophosphate Cu2P2O7‧3H2O 25~30g/l

Potassium pyrophosphate K2P2O7 95.7~176g/l

Potassium acetate potassium nitrate 1.5~3g/l

Ammonium Hydroxide ?1/2~1ml/l

pH value 8~8.5

Bath temperature 22~30℃

Current density 0.6~1.5A/d㎡

Stirring machine or air

Filter continuous

Copper content 9~10.7g/l

Pyrophosphate 63~107g/l

P2O7/Cu ratio 7~10.1

4.5.2 Maintenance and control of copper pyrophosphate plating bath

1. Ingredients:

(1) Ammonia (ammonia) can help dissolve the anode and make the crystallization fine, and the evaporation loss needs to be supplemented every day.

(2) Acetate (nitrate), increase the current density operating range and remove the cathodic polarization.

(3) The pH value is adjusted and controlled by pyrophosphate or potassium hydroxide.

2. Temperature: Temperature over 60°C will hydrolyze pyrophosphate into ortho phosphate.

3. Stirring: Adequate stirring is required. Air stirring or mechanical stirring is generally used. Ultrasonic wave and solution spraying methods can also be used.

4. Impurities: It is very sensitive to organic impurities such as the decomposition products of oil and organic additives, which will make the coating dark and uneven, and the operating range will be smaller. Cyanide and lead impurities will also make the coating uneven and the operating range smaller. Organic impurities are treated with activated carbon. Add hydrogen peroxide or potassium permanganate before treatment to remove cyanide. Lead can be removed by weak electrolysis.

5. Phosphate: Too high temperature and too low pH will increase phosphate rapidly. Back to list

4.6 Copper Fluoborate Bath

Since the copper borofluoride salt is soluble in water in a large amount and has a large solubility, a higher current density can be used to increase the plating speed. Its disadvantage is corrosiveness, and the use of materials is limited to hard rubber, polypropylene and PVC plastic or carbon.

4.6.1   borofluorate copper plating bath formula

Copper pyrophosphate Cu2P2O7‧3H2O 57.8~73.3g/l

Potassium pyrophosphate K2P2O7? 231~316.5g/l

Potassium acetate 8.2~15.8g/l

Ammonium hydroxide 2.7~7.5m1/1

Additives (improve the ductility and uniformity of the coating) as indicated

pH value 8~8.4

Bath temperature 49~54

Current density 2.5~6A/d㎡

Stirring mechanical or air

Organic impurities will affect the appearance, uniformity and mechanical properties of the coating, especially ductility.

This plating bath requires continuous activated carbon filtration.

Additives usually do not use organics. Molasses will harden the coating and reduce edge effects. Some copper sulfate bath additives can be used.

4.6.2   Advantages of borofluoride copper plating bath

Allows high current density, smooth coating, good appearance

The coating is soft and easy to grind, additives can be used to increase the hardness and strength of the coating

Cathodic current efficiency is nearly 100%, low anodic polarization

No crystallization in the tank, easy to equip with plating bath

Stable plating bath, easy to control, high-speed plating permit

General copper plating process:

Steam degreasing

Inspection before plating (R) Solvent washing (R) Mounting (R) Chemical degreasing (R) Hot water washing (R) Cold water washing (R) Acid leaching (R)

Electrolytic degreasing

Cold water washing (R) Electrolytic degreasing (R) Hot water washing (R) Activation (R) Neutralization (R) Cold water washing (R) Cyanide coating (R) Cold water washing (R) Acid copper plating (R) Cold water washing (R) ) Light emitting (R) Cold water washing (R) Drying (R) Unloading (R) Drying (R) Inspection

4.7 Stainless steel copper plating process

4.8 Stripping of copper plating

(1) Chemical method:

Chromium CrO3? 200~300g/l

Ammonium sulfate (NH4)2SO4? 80~100g/l

Bath temperature room temperature

(2) Electrolysis method:

Sodium nitrate NaNO3? 800~100g/l

Current density 2~4A/d㎡

Bath temperature room temperature

Spring copper plated

Low-concentration copper bath formula (base plating bath formula)

Coprous cyanide CuCN 20g/l

Sodium cyanide (sodium cyanide) NaCN 30g/l

Sodium carbonate (sodium carbonate) Na2CO3? 15g/l

pH 11.5

Temperature 40℃

Current efficiency 30~60%

Current density 0.5~1A/cm2

4.4.2 The formula of the concentration bath in copper

Coprous cyanide CuCN 60g/l

Sodium cyanide (sodium cyanide) NaCN 70g/l

Sodium hydroxide (sodium hydroxide) NaOH 10~20g/l

Free cyanide 5~15g/l

pH 12.4

Temperature 60~70℃

Current density 1~2A/dm2

Current efficiency 80~90%

4.4.3 Copper cyanide high concentration bath formula

Cuprous cyanide CuCN 120g/l

Sodium cyanide NaCN 135g/l

Caustic soda NaOH 42g/l

Brightener 15g/l

Free sodium cyanide) 3.75~ 11.25g/l

pH 12.4~12.6

Temperature 78~85℃

Current density 1.2~11A/dm2

Current efficiency 90~99%

4.4.4 Cyanide copper plating full potassium bath formula

Cuprous cyanide CuCN 60g/l

Potassium cyanide KCN 94g/l

Potassium carbonate 15g/l

Potassium hydroxide KOH 40g/l

Free potassium cyanide 5~15g/l

pH value <13

Bath temperature 78~85℃

Current density 3~7A/dm2

Current efficiency 95%

4.4.5 Advantages and disadvantages of electroless copper plating full potassium bath

High current density can also get gloss, coating, high conductivity

Wide gloss range brings out less loss

Good gloss, more expensive medicine

Good smoothing effect

4.4.6 Potassium sodium tartrate cyanide copper plating bath formula (Rochelle cyanide Buths)

Cuprous cyanide CuCN 26g/l

Sodium cyanide NaCN 35g/l

Sodium carbonate Na2CO3? 30g/l

Sodium potassium tartrate NaKC4H4O6‧6H2O 45g/l

Free sodium cyanide 5~10g/l

pH 12.4~12.8

Bath temperature 60~70℃

Current density 1.5~6A/d㎡

Current efficiency 50~70%

4.4.7 The role and influence of the components of the electroless copper plating bath

1. Main salt: NaCu(CN)2 and Na2Cu(CN)3 exist in two forms, and its functions are:

CuCN+NaCN=NaCu(CN)2? CuCN+2NaCN=Na2Cu(CN)3? Na2Cu(CN)3? 2Na + (aq) +Cu(CN)3-(aq) Na2Cu(CN)3? 2Na+ (aq ) +Cu(CN)3-(aq) Cu(CN)3-? Cu++3CN- Cu(CN)2-? Cu++2CN-

Because the ionization constants of copper complex ions Cu(CN)2- and Cu(CN)3- are very small, the cathode has a great polarization effect, making it difficult for copper to be replaced and precipitated. Therefore, copper can be plated directly on steel. The current efficiency is reduced, hydrogen is generated, and the plating output is reduced. The main salt has a great influence on the cathode polarization, and the increase of the main salt concentration can reduce the cathode polarization, help the anode dissolve, and prevent the formation of anode passivation.

2. Free cyanide, NaCN, KCN, help anode dissolve, prevent wrong salt precipitation, stabilize the plating bath. Too much content will deepen the polarization and produce a large amount of hydrogen and reduce the current efficiency.

3. Sodium carbonate prevents sodium cyanide from being hydrolyzed, reduces anode polarization and helps anode dissolution.

4. Caustic soda, reduce hydrogen ion concentration, increase conductivity, improve current efficiency and use of electricity

Flow density.

Spring copper plated

Maintenance and Control of Acid Copper Plating Bath (Maintenance and Control)

Composition: Copper sulfate is the source of copper ions in the solution. Since the current efficiency of the cathode and anode is normally close to 100%, the copper ions supplemented by the anode copper is quite stable. Sulfuric acid improves the conductivity of the solution and reduces the polarization of the anode and cathode, prevents salt precipitation and improves throwing power. The ratio of copper to sulfuric acid in the high uniformity plating bath should be maintained at 1:10. When the sulfuric acid content exceeds 11 vol%, the current efficiency decreases. Chloride ions can reduce polarization and eliminate striated deposits with high current density in the high uniformity and gloss plating bath. Phosphor bronze spring

# Temperature: Too part of the plating bath is operated at room temperature. If the temperature is too low, the current efficiency and plating range will be reduced. If gloss is not required, the bath temperature can be increased to 50°C to increase the electroplating range, which can be used in electroforming, printed circuits or printed boards.

# Stirring: It can be stirred by air, mechanical, solution jet or moving plating. The better the stirring, the greater the allowable current density.

# Impurities: Organic impurities are the most common in acid plating baths, and their sources are the decomposition products of brighteners. The tank lining and anode bag are not filtered to the substances, electroplating stopoffs, rust prevention substances and Impurities of acid and salt. The green of the plating bath indicates a considerable amount of organic pollution. Activated carbon must be used to remove organic impurities. Sometimes hydrogen peroxide and potassium permanganate can help activated carbon to remove organic impurities, but cellulose filters cannot used.

Metal impurities and their effects are as follows:

Antimony (antimony): 10-80 g/l, rough and embrittled coating, adding glue (gelatin) or monocitrate (tannin) can inhibit antimony co-precipitation (codeposition).

Arsenic 20-100 ppm: same as antimony.

Bismuth: Same as antimony.

Cadmium>500ppm: It will cause immersion deposit and anodic polarization, which can be controlled by chlorine.

Nickel>1000 ppm: same as iron.

Iron>1000 ppm: reduce uniformity and conductivity.

Tin 500-1500ppm: same as cadmium.

Zinc>500ppm: same as cadmium.

4.3.4 Failures and causes of acid copper plating bath

1. Burn in high current density area:

Too little copper, organic pollution

The temperature is too low and there are too few chloride ions

Not enough stirring

2. Loss of luster:

Too little gloss agent, too high temperature

Organic pollution, too little copper

Low chloride ion concentration

3. Rough coating:

Solid particle pollution Poor quality of anode copper

Broken anode bag, insufficient chloride ion content

4. Pinhole:

Organic matter pollution Too little chloride ion

Anode bag rot

5. The current is too low:

Organic pollution too much chlorine

The sulfuric acid content is not enough, the current density is too small

Insufficient additive temperature too high

6. Anode polarization:

Tin and gold pollution, too much chlorine

Temperature is too low too much sulfuric acid

Anode copper quality is not good enough copper sulfate content is insufficient

4.3.5 Additives for acid copper plating bath

There are many additives such as glue, dextrin, sulfur, interface active agent, dye, urea, etc. The main purposes are:

Smooth coating, reduce dendrites

Increase current density and gloss

Hardness change prevents pinholes

4.4 Copper Cyanide Baths

Cyanide copper plating brings human health hazards and waste disposal problems. The use of thick plating has been reduced, but it is still widely used in primer plating. Cyanide copper plating The most important chemical composition of the plating bath is the free cyanide and total cyanide content. The calculation equation is as follows:

K2Cu(CN)3 total potassium cyanide amount = cuprous cyanide required amount × 1.45 + free potassium cyanide required amount

K2Cu(CN)3 Total sodium cyanide amount = cuprous cyanide required amount × 1.1 + free sodium cyanide required amount

Example: The plating bath requires 2.0g/l copper cyanide and 0.5g/l free potassium cyanide. How much potassium cyanide is required?

The amount of potassium cyanide needed for solution=2.0×1.45+0.5=3.4g/l

The anode copper whisker is pure copper without oxides. It can be packed in a steel basket with copper plates or copper blocks and wrapped in anode bags. The steel anode plate is used to adjust the copper content. The area ratio of cathode to anode should be 1:1 and 1:2.

Spring copper plated

Spring copper plated
4.1 Properties of copper

4.2 Types of copper plating solution formula

4.3 Copper Sulfate Baths

4.4 Copper Cyanide Baths

4.5 Copper Pyrophosphate Plating Bath

4.6 Copper Fluoborate Bath

4.7 Stainless steel copper plating process

4.8 Stripping of copper plating

4.9 Copper Plating Patent Literature (US Patent)

4.10 Journal papers related to copper plating

4.1 Properties of copper

Color: rose red Atomic weight: 63.54

Atomic number: 29 Specific gravity: 8.94 Melting point: 1083°C

Boiling point: 2582℃ Brinell hardness 43-103

Resistance: 1.673 l W -cm, 20 ℃ Tensile strength: 220~420MPa

Standard potential: Cu++e- →Cu is +0.52V; Cu++ +2e-→Cu is +0.34V.

Soft and tough, good ductility, easy plastic processing, excellent electrical and thermal conductivity

Good polishing and optical rotation, easy to oxidize, especially when heated, it cannot be used as protective coating

It will react with sulfur in the air to form brown copper sulfide. It will react with carbon dioxide in the air to form a copper record.

Will form copper chloride powder with chlorine in the air

The copper plating layer has good uniformity, compactness, adhesion and polishing rotation, so it can be used as the bottom plating layer of other electroplating metals.

The plating layer can be used to prevent carburizing and copper nitride. The only practical application for the electroplating of zinc castings.

The source of copper is sufficient. Copper is easily electroplated and easy to control

The amount of copper plating is second only to nickel

4.2 Types of copper plating solution formula

Can be divided into two categories:

1. Acid copper electroplating solution:

The advantages are:

Simple ingredients, low toxicity, easy to dispose of waste liquid

Stable plating bath without heating, high current efficiency

Low price, low equipment cost, high current density, high production rate

The disadvantages are:

Coating crystals are coarse and cannot be directly plated on steel

Poor uniformity

2. Formula of copper cyanide electroplating solution:

The advantages are:

Fine coating, good uniformity

Can be plated directly on steel

The disadvantages are:

Strong toxicity, troublesome waste disposal, low current efficiency

High price, high equipment cost, low current density, low production efficiency

The plating solution is unstable and needs to be heated

With the advantages of the above two formulas, P.S generally uses cyanide copper plating solution for primer, and then uses acid copper plating solution for copper plating, especially for plating parts with thicker plating thickness.

4.3 Copper Sulfate Baths

The preparation, operation and waste treatment of copper sulfate plating bath are very economical, and can be applied to printed circuits, electronics, photogravure, electroforming, and decoration (decorative) and plastic plating (plating on plastics). Its chemical composition is simple, containing copper sulfate and sulfuric acid. The plating solution has good conductivity and poor uniformity, but there are special formulas and additives that can be improved. Steel plated parts must be primed with a copper cyanide bath or strike with nickel to avoid the formation of replacement diposits and low adhesion. Copper-plated spring

Zinc castings and other acid-sensitive metals must be fully primed to prevent corrosion by sulfuric acid. The plating bath is operated at room temperature. The anode must be high-purity rolled copper, free of oxides and phosphating (0.02 to 0.08wt%P), and copper anode nuggets can be used in titanium baskets. The anode must be added with an anode bag, the area ratio of the anode to the cathode should be 2:1, the current efficiency of the anode and the cathode can reach 100%, and the anode copper should be taken out when it is not electroplated.

4.3.1 Standard acid copper plating

(1) General formulation:

Copper sulfate 195-248 g/l

Sulfuric acid 30-75 g/l

Chloride 50-120 ppm

Current density 20-100 ASF

(2) Semibright plating: Clifton-Phillips formula

Copper Sulfate 248 g/l

Sulfuric acid 11 g/l

Chloride 50-120 ppm

Thiourea 0.00075 g/l

Wetting agent 0.2 g/l

(3) Bright plating: beaver formula

Copper sulfate 210 g/l

Sulfuric 60 g/l

Chloride 50-120 ppm

Thiourea 0.1 g/l

Dextrin 0.01 g/l

(4) Bright plating: Clifton-Phillips formula

Copper sulfate 199 g/l

Sulfuric acid 30 g/l

Chloride 50-120 ppm

Thiourea 0.375 g/l

Wolasses 0.75 g/l

4.3.2 High uniformity acid copper plating bath formula (High Throw Bath)

Used for printed circuits, drum plating and other plating applications that require high uniformity.

Copper sulfate 60-90 g/l

Sulfuric acid 172-217 g/l

Chloride 50-100 ppm

Proprietary additive   as indicated

Heat treatment of steel-soft nitriding

In order to shorten the nitriding cycle and make the nitriding process not restricted by the steel type, two new nitriding processes have been developed on the basis of the original nitriding process in the past one to twenty years.
Soft nitriding is essentially a low-temperature carbonitriding based on nitriding. At the same time as the nitrogen atomization of steel, there is also a small amount of carbon atom infiltration. Compared with the aforementioned general gas nitrogen, the hardness of the nitrided layer is higher. It is low and brittle, so it is called soft nitriding.

1. Soft nitriding method, soft nitriding method is divided into gas soft nitriding and liquid soft nitriding. At present, the most widely used in domestic production is gas nitrocarburizing. <,br>Gas nitrocarburizing is a low-temperature carbon and nitrocarburizing in an atmosphere containing activated carbon and nitrogen atoms. Commonly used co-permeating media are urea, formamide and triethanolamine, which generate heat at the nitrocarburizing temperature. The decomposition reaction produces activated carbon and nitrogen atoms.

The activated carbon and nitrogen atoms are absorbed by the surface of the workpiece and penetrate into the surface of the workpiece through diffusion, thereby obtaining a nitrogen-based carbonitriding layer.

The gas nitrocarburizing temperature is usually 560-570℃, because the hardness of the nitrided layer is the highest at this temperature. The nitriding time is usually 2-3 hours, because more than 2.5 hours, the depth of the nitriding layer increases slowly with time.

2. The structure and characteristics of nitrocarburizing layer: After the steel is nitrocarburized, the outermost layer of the surface can obtain a white layer of several microns to tens of microns, which is composed of ε phase, γ`phase and nitrogen-containing Carbon body is composed of Fe3 (C, N), and the sublayer is a 0.3-0. 4 mm diffusion layer, which is mainly composed of γ`phase and ε phase.

Soft nitriding has the following characteristics:

(1) The processing temperature is low, the time is short, and the deformation of the workpiece is small.

(2) Not limited by steel type, carbon steel, low alloy steel, tool and die steel, stainless steel, cast iron and iron-based powder metallurgical materials can all be soft-nitrided. The surface hardness of the workpiece after nitrocarburizing is related to the nitriding process and material.

3. It can significantly improve the fatigue limit, wear resistance and corrosion resistance of the workpiece. It also has anti-abrasion and anti-seize properties under dry friction conditions.

4. Since there is no brittle ξ phase in the soft nitrided layer, the nitrided layer is hard and has certain toughness and is not easy to peel off.

Therefore, nitrocarburizing has been widely used in the treatment of wear-resistant workpieces such as molds, measuring tools, high-speed steel tools, crankshafts, gears, and cylinder liners.

It should be noted that the current problem of gas nitrocarburizing is that the thickness of the iron-nitrogen compound layer in the surface layer is relatively thin (0.01-0.02mm), and the hardness gradient of the nitride layer is steep, so it is not suitable to work under heavy load conditions. In addition, during the nitriding process, toxic gases such as HCN will be generated in the furnace. Therefore, attention must be paid to the sealing of the equipment during production to prevent the furnace gas from leaking out and polluting the environment.