Nitriding method of stainless steel and high-speed steel

Nitriding method of stainless steel
The key to the nitriding of stainless steel is to remove its passive film, which is the reason why stainless steel is rust-proof and cannot be nitrided. Therefore, the key to nitriding stainless steel is to remove the passive film on the surface. The purpose of nitriding stainless steel is to increase its hardness, improve its wear resistance and corrosion resistance. There are chemical and mechanical methods to remove the passivation film.

(1) Sandblasting. Before nitriding, the workpiece is sandblasted with fine sand at a pressure of 0.15%26mdash; 0.25MPa until the surface is dark gray, and the surface dust is cleared and immediately enter the furnace.

(2) Phosphating. Phosphating treatment on the workpiece before nitriding can destroy the oxide film on the metal surface and form a porous and loose phosphating layer, which is conducive to the infiltration of nitrogen atoms.

(3) Chloride bubble. The blasting or finishing work piece is bubbled or coated with chloride, which can effectively remove the oxide film. Commonly used chlorides are TiCl2 and TiCl3.

The ferritic, martensitic and austenitic stainless steels and heat-resistant steels that are usually nitrided.

The chemical method is to soak the workpiece in 50% (volume) hydrochloric acid (temperature 70 degrees), and then clean it with water;

Nitriding of high speed steel

Generally, the nitriding of high-speed steel should not have three phases, otherwise the infiltrated layer will become brittle. According to the above rules, high-speed steel should be nitrided at low temperature and short time. Because the thickness of the infiltration layer increases slowly at a lower temperature, it is easy to control, and the nitrogen concentration on the surface of the infiltration layer is lower. The short-term low-temperature nitriding concentration is lower and the toughness is better. High-speed steel (w18cr4v) generally uses 510% 26 mdash; 520 degrees Celsius) with a diameter of 15 mm, 15% 26 mdash; 20 minutes, larger ones use 25% 26 mdash; 32 minutes, and large ones use 60 minutes.

Standard for heat treatment quenching oil

Performance characteristics and application range of heat treatment oil:

1. Ordinary quenching oil: strong cooling performance, good oxidation stability, suitable for the quenching of bearing steel, tool die steel, alloy steel and carburizing steel in salt bath furnace or protective atmosphere. The best use temperature is 50 -80 ℃.

2. Quick quenching oil: fast cooling speed, good oxidation stability, medium brightness, suitable for quenching of high cooling speed quenching and tempering, carburizing and other parts and large forgings, large gears and quenching presses. The use temperature is 20 -80 ℃.

3. Fast bright quenching oil: fast cooling speed, good oxidation stability, good brightness, suitable for quenching bearing steel, tool steel and other structural steel under protective atmosphere. The use temperature is 20 -80 ℃.

4. Ultra-speed quenching oil: faster cooling speed, good oxidation stability, suitable for heating quenching, carburizing or carbonitriding quenching of large parts in the automobile, bearing, mining machinery, metallurgical machinery and mold industries, and also suitable for medium Quenching of carbon steel and other types of alloy steel. The operating temperature is 20 -60 ℃.

5. Vacuum quenching oil: low saturated steam pressure, good cooling performance, and good brightness. It is suitable for vacuum quenching of bearing steel, tool steel, large and medium-sized aviation structural steel and other materials. The air in the oil should be removed under vacuum during initial use. The use temperature is 20 -80 ℃.

6. Isothermal graded quenching oil: good cooling performance, small deformation of parts, suitable for quenching of bearing steel, carburized steel bearing inner and outer circles, precision parts, automobile gears, semi-shafts and other workpieces and easily deformable parts. The operating temperature is 120 ℃ for No. 1 and 150 ℃ for No. 2.

7. Tempering oil: high viscosity, high flash point, low volatilization, good thermal oxidation stability, suitable for tempering the workpiece after quenching, the temperature of No. 1 is 150 ℃, and the temperature of No. 2 is 200 ℃.

Heat treatment oil products

It is mainly used for heat treatment oil for rapid cooling in quenching processing. It is used for a long time on-site performance to improve the stability and stability of the oil.

1. Features:

Although it is in a non-oxidizing atmosphere, it can also exert excellent brilliance in a continuous furnace.

Because of the cooling characteristics, the burning depth is increased through the cooling of the vapor film stage, and the cooling energy of the slow convection stage is

Maintain high hardness and minimize deformation.

Reduce costs by extending tool life.

Because of its excellent oxidation stability to open-type oil grains, it minimizes the change in cooling performance caused by increased dirt in the short term.

In use, the viscosity change is minimized to reduce the product quality dispersion caused by the change of cooling energy.

2. Physical and chemical properties:

HSQ-270\New oil management\Properties and appearance (original solution)

-Specific gravity (15/4 ℃)

-Viscosity (40 ℃, mm /s) below 26 \ flash point (℃) \ over 170 \ total acid value (m KOH)

-Moisture (ppm) below 500 \ Cooling characteristics

Characteristic temperature:

800~400( ℃ ){ second}

800 ~ 300( ℃ ){ second}

580 or less

615 and above

4.0 or less

2.8 or less

No regulations


3. Cooling performance test results:

4. Usage:

Applicable equipment: continuous furnace, PIT furnace and other open furnace firing and high-frequency wave firing.

Applicable column of processed products

Continuous furnace firing of small or thick bearing steel.

Continuous furnace soaking of low-alloy steel for large-scale products, grease burning in.

PIT furnace firing of large carbon tool steel and alloy tool steel.

The immersion screw is fired in a continuous furnace.

The deep hardness of large fittings used in PIT furnaces increases.

5. How to use:

Because the viscosity of the burned oil will change with the temperature of use, and the oil temperature will also cause changes in the cooling characteristics under the same stirring conditions, so an appropriate temperature is required, and the use temperature range of HSQ-270 is 60 ℃ ~ 80 ℃ is the most suitable.

The oil temperature of 60 ℃ ~ 70 ℃ is more appropriate.

Do not increase the temperature of the burned oil grains above 20 ℃.

6. Matters needing attention:

Please refer to the MSDS (material health and safety information) provided by our company.

7. Product validity period:

The shelf life is half a year from the date of manufacture.

International classification of heat treatment oil

The TC28 subcommittee of the International Organization for Standardization (ISO) proposed in 1993 the classification of ISO/DIS 6743/14 lubricants, industrial lubricants and related products (class L)-Part 14: Group U (heat treatment). my country has proposed the classification standard of SH0564-93 heat treatment oil with reference to the JIS-K2242-80 standard. The following is the international standard classification method:

1. Oil for heat treatment: some kinds of oil are easily washed away by water, because demulsifiers are added to the oil formula. These oils can be called “soluble oils”. The manufacturer can determine this oil according to user requirements. Stainless steel spring

(1) Cold quenching (<80 ℃): A rapid quenching oil, UHA; B ordinary (normal) quenching oil, UHB.

(2) Semi-thermal quenching (30 ℃-130 ℃): A rapid quenching oil, UHC; B ordinary (normal) quenching oil UHD.

(3) Thermal quenching (130 ℃-180 ℃): A rapid quenching oil, UHE; B ordinary (normal) quenching oil, UHF.

(4) High temperature quenching (> 180 ℃): A rapid quenching oil, UHG; B ordinary (normal) quenching oil, UHH.

(5) Vacuum quenching, UHV.

(6) Others, UHK.

2. Heat treatment water:

(1) Surface quenching: A water, UAA; B water-containing liquid for rapid quenching, UAB; C water-containing liquid for slow quenching, UAC.

(2) Overall quenching: A water, UAA; B water-containing liquid for rapid quenching, UAD; C water-containing liquid for slow quenching, UAE;

(3) Others: UAK.

3. Molten salt for processing:

(1) 150 ℃-500 ℃: molten salt (150 ℃-500 ℃), USA;

(2) 500 ℃-700 ℃: molten salt (500 ℃-700 ℃), USB;

(3) Others: USK.

4. Gas for heat treatment: A air, UGA; B neutral gas, UGB; C reducing gas, UGC; D oxidizing gas, UGD.

5. Fluidized bed: UF.

6. Other: UK.

Domestic classification of heat treatment oil

Type I cold quenching oil:

A. Ordinary quenching oil, used for quenching small size materials with good hardenability.

B. Quick quenching oil, used for quenching large and medium-sized materials.

C. Ultra-speed quenching oil, used for the quenching of large and poor hardenability materials.

D. Bright quenching oil, used for quenching of medium and small section bearing steel, tool and die steel, measuring tool steel and instrument parts under protective atmosphere.

E. Fast bright quenching oil, used for medium-sized and poor hardenability materials for quenching in a controlled atmosphere.

F, No. 1 vacuum quenching oil, used for quenching medium-sized materials under vacuum.

G, No. 2 vacuum quenching oil is used for quenching materials with good hardenability under vacuum.

Type II hot quenching oil:

A, No. 1 isothermal, graded quenching oil, used for hot oil quenching at around 120 ℃.

B, No. 2 isothermal, graded quenching oil, used for hot oil quenching at about 160 ℃.

Type III tempering oil:

A. No. 1 tempering oil, used for tempering at around 150 ℃.

B. No. 2 tempering oil, used for tempering at about 200 ℃

Quenching process, quenching medium and cooling method

The quenching process is a heat treatment process in which the steel is heated to a temperature above AC3 or AC1 for a certain period of time, and then cooled at an appropriate speed to obtain martensite and (or) bainite structure.
The purpose of quenching is to improve the hardness, strength and wear resistance to meet the performance of the parts. Quenching process is the most widely used, such as tools, measuring tools, molds, bearings, springs and automobiles, tractors, diesel engines, cutting machine tools, pneumatic tools, drilling machinery, agricultural machinery, petroleum machinery, chemical machinery, textile machinery, aircraft and other parts. Use quenching process.

(1) Quenching heating temperature

The quenching heating temperature is determined according to the composition, structure and different performance requirements of the steel. Hypoeutectoid steel is AC3 (30-50°C); eutectoid steel and hypereutectoid steel are AC1 (30-50°C).

If the quenching heating temperature of hypoeutectoid steel is lower than AC3, the steel has not been completely austenitized at this time, and there is some untransformed ferrite. After quenching, the ferrite still remains in the quenched structure. The hardness of ferrite is low, so that the hardness after quenching is not up to the requirement, and it also affects other mechanical properties. If the hypoeutectoid steel is heated to a temperature much higher than AC3 for quenching, the austenite grains will be significantly coarsened, which will damage the properties after quenching. Therefore, the quenching heating temperature of hypoeutectoid steel is AC3 (30-50℃), which not only guarantees sufficient austenitization, but also keeps the austenite grains fine.

The quenching heating temperature of hypereutectoid steel is generally recommended as AC1 (30~50℃). In actual production, the temperature should be appropriately increased by about 20°C according to the situation. Heating in this temperature range, its structure is fine-grained austenite and some fine and uniformly distributed undissolved carbides. After quenching, except for a small amount of retained austenite, its structure is uniformly distributed fine carbonized material points on the flaky martensite matrix. Such a structure has high hardness, wear resistance, and relatively less brittleness.

The quenching heating temperature of hypereutectoid steel cannot be lower than AC1, because the steel has not yet been austenitized at this time. If heated to a temperature slightly higher than AC1, the pearlite completely transforms into austenite, and a small amount of cementite is dissolved into the austenite. At this time, the austenite grains are fine, and the carbon mass fraction is slightly higher than the eutectoid composition. If the temperature continues to increase, the secondary cementite will continue to dissolve into the austenite, causing the austenite grains to grow and the carbon concentration to increase, which will increase the tendency of quenching deformation and increase the microcracks of the quenched structure And brittleness increases. At the same time, due to the high carbon content of austenite, the amount of retained austenite after quenching increases, which reduces the hardness and wear resistance of the workpiece. Therefore, it is inappropriate for the quenching heating temperature of hypereutectoid steel to be too much higher than AC1, and it is even more inappropriate to heat to a temperature of ACm or above which is fully austenitized.

When selecting the quenching heating temperature of the workpiece in production practice, in addition to complying with the above general principles, the chemical composition, technical requirements, size and shape, original structure of the workpiece, heating equipment, cooling medium and many other factors should also be considered. Make appropriate adjustments. For alloy steel parts, the upper limit is usually taken, and the lower limit is taken for parts with complex shapes.

The quenching heating temperature selected for the new strengthening and toughening process is different from the commonly used quenching temperature. For example, sub-temperature quenching is the quenching of hypoeutectoid steel after austenitization at a temperature slightly lower than AC3, which can improve toughness, reduce brittleness transition temperature, and eliminate temper brittleness. For workpieces made of materials such as 45, 40Cr, 60Si2, the heating temperature for sub-temperature quenching is AC3-(5~10℃).

High temperature quenching can obtain more lath martensite or increase the strength and toughness of all lath martensite. For example, 16Mn steel is quenched at 940°C, 5CrMnMo steel is quenched at 890°C, and 20CrMnMo steel is quenched at 920°C. The effect is better.

High-carbon steel is quenched by low-temperature, rapid and short-time heating, and the quenching heating temperature of high-carbon steel is appropriately reduced, or the method of rapid heating and shortening the holding time can reduce the carbon content of austenite and improve the toughness of steel.

(2) Holding time

In order to make the internal and external parts of the workpiece complete the structure transformation, carbide dissolution and austenite composition, it is necessary to keep the quenching heating temperature for a certain time, that is, the holding time.

(3) Quenching medium

The medium used for quenching and cooling of the workpiece is called the quenching cooling medium (or quenching medium). The ideal quenching medium should have the condition that the workpiece can be quenched into martensite without causing too much quenching stress. This requires slow cooling at the temperature above the “nose” of the C curve to reduce the thermal stress caused by rapid cooling; the cooling rate at the “nose” should be greater than the critical cooling rate to ensure that non-Martensite supercooled austenite does not occur Body transformation; under the “nose”, especially when Ms is at the same temperature, the cooling rate should be as small as possible to reduce the stress of tissue transformation.

Safety operation rules for spring coiling machine

Applicable models: 3P28, Z52-1.6 (A520), Z53-3, 4850A, A522A, A524, Z53-14, A541, A451A, Z56-2.5.
1. Conscientiously implement the relevant provisions of the “General Operating Regulations for Forging Equipment”.
2. Conscientiously implement the following relevant supplementary regulations:
(1) Before the idling vehicle, the equipment should be manually turned to check whether the actions of the various agencies are coordinated, and after confirming that it is normal, start the equipment test run.
(2) Seriously at work:
, the burrs of the steel material used for cold coiling should be ground off. In the case of pan material, pay attention to the working condition of the pan material rack, and stop the machine immediately if there is any confusion. When the coil is almost finished, the tail should be taken out of the tray.
. The steel used for hot coiling should be heated in accordance with the process regulations. It is forbidden to put unheated or insufficiently heated steel on the equipment for coiling.
, when it is necessary to change speed, it should be carried out after stopping. The shift lever must be moved to the correct position.

What is heat treatment and why should the workpiece be heat treated

The process of changing the internal structure of metal parts through certain heating, heat preservation and cooling processes (or at the same time changing the chemical composition of the surface layer) to obtain the required performance is called heat treatment.

Many machine parts and engineering components are subject to various heat treatments. The main purposes are:

1) Make the workpiece obtain good craftsmanship, so that various processing can be carried out smoothly.

2) Give the workpiece the mechanical properties (or physical or chemical properties) required by the design to make it work normally, increase the service life, reduce costs, and obtain good economic effects.

The influence of wire rod cooling process on the performance of steel wire

The influence of wire rod cooling process on the performance of steel wire

Defects in mechanical properties of steel wire can be eliminated or improved by controlling cooling. In order to study the influence of the structure and mechanical properties of the wire rod on the finished steel wire, Canadian scientists and technicians adjusted the process parameters of the wire rod cooling process to improve the performance of the wire. These process parameters include:

Enough cooling capacity;

Able to maintain the high temperature during the wire rod rolling process;

Long cooling distance and flexible conveyor speed.

There are four main factors affecting the cooling of wire rod on the Steyrmore production line:

Spinning temperature;

Cooling efficiency;

Fan power;


Spinning temperature affects both the composition and thickness of the scale. At about 650 degrees Celsius, FeO and Fe3O4 begin to form. FeO accounts for about 65%, Fe3O4 accounts for about 35%; at 800 to 900 degrees Celsius, FeO accounts for about 95%, Fe3O4 accounts for about 5%. After 900 degrees Celsius, as the temperature increases, the FeO content gradually decreases, and the Fe3O4 content gradually increases. At about 920 degrees Celsius, Fe2O3 begins to form. As the temperature increases, the Fe2O3 content gradually increases.

The speed of the conveyor belt determines the spacing of the coils. The speed is fast, the spacing is large, the cooling is fast, and the tensile strength is high. Cooling efficiency, fan power, and covering on the conveyor belt also have an important influence on the cooling of the wire rod.

Through the different combinations of 4 factors, two solutions of fast cooling and slow cooling can be obtained. Fast cooling is achieved by turning on all fans, the conveyor belt is fast and the cover is opened; slow cooling is achieved by stopping the fans, the conveying speed is slow, and the cover is closed.

With the introduction of electric arc furnaces, the increase of residual elements (Cu, Ni, Cr, Mo) has a significant impact on the production of high-quality products, especially for low-carbon steel, higher residual element content increases the solid solution strengthening of steel Significantly.

In order to prove that slow cooling can reduce the tensile strength of the final product, the low carbon steel with different residual element content is subjected to different cooling treatments and drawn to the same specification. The strength of the wire rod at the normal cooling speed increases by 9Ksi (1Ksi = 6.89 N/mm2).

After hot-rolled wire rods obtained with different cooling speeds are drawn to steel wires of the same diameter and spheroidizing annealing, the tensile strength of slow-cooling wire rods is 5% lower than that of fast-cooling wire rods.

For steel wires that require low tensile strength and good rust removal performance, moderate cooling can achieve a better combination of the two properties. The tensile strength of moderate cooling is 7% lower than that of rapid cooling.

The application of rapid cooling is where more uniform tensile strength is required. The application of rapid cooling to medium carbon steel may also obtain similar tensile strength of lead-quenched wire rod. The tensile strength fluctuation of the carbon steel wire rod in a circle was measured, and the results showed that the slow cooling fluctuation was 5.4%; the rapid cooling fluctuation was 1.3%; the lead quenching fluctuation was 1.9%.

Specification for austempering of common spring steel

Specification for austempering of common spring steel

Steel number Heating temperature Austempering temperature Isothermal holding time Hardness HRC

T10A 800+-10 250-360 10-30 40-53

65 820+-10 320-340 15-30 46-48

65Mn 820+-10 270 / 320-340 15-30 52-54 / 46-48

50CrVA 850+-10 300 30-45 52

60Si2MnA 87+-10 280 30-45 52

Heat treatment of copper alloy material spring

1. Heat treatment of tin bronze Tin bronze cannot be strengthened by heat treatment, but must be cooled and deformed to improve its strength and elastic properties.

The main methods are:

(1) Fully annealed, used in the intermediate softening process to ensure the plastic deformation performance of large deformation processing in the subsequent process.

(2) Incomplete annealing is used to obtain plasticity consistent with the subsequent process before the elastic element is formed, so as to ensure a certain amount of forming deformation in the subsequent process and make the spring reach the performance.

(3) Stable annealing, used for the final heat treatment after the spring is formed, to eliminate cold working stress, and stabilize the shape and elastic properties of the spring.

Specification for heat treatment of tin bronze spring material

Material grade

Fully annealed

Incomplete annealing*

Stabilized tempering



































Note: *The specification of incomplete annealing can be adjusted according to the subsequent forming deformation of the spring.

2. Heat treatment of beryllium bronze

The heat treatment of beryllium bronze can be divided into annealing treatment, solution treatment and aging treatment after solution treatment.

The return (return) fire treatment is divided into:

(1) Intermediate softening annealing can be used as a softening procedure in the middle of processing.

(2) Stabilized tempering is used to eliminate the processing stress generated by the precision spring and calibration, and stabilize the external dimensions.

(3) Stress relief tempering is used to eliminate machining stress generated during machining and calibration.

Specification for heat treatment of beryllium bronze spring material

Material grade

Intermediate softening annealing

Stabilized tempering

Stress relief



































Specification for solution treatment and time efficiency treatment of beryllium bronze spring material



Solution treatment

Processing purpose and scope of use

Aging treatment

Temperature ℃

Thickness/time (min)*

Temperature ℃

Time h








The grains are easy to grow, suitable for thicker and coarser materials






Y state: 1~2

Y2 state: 2

C state: 2~3

780±10 1.0~5.0 /12~30

Good comprehensive performance, used for softening treatment and tissue preparation before aging

760±10 5.0~10 /25~30

Obtain a fine grain structure, which is beneficial to improve the fatigue strength of the spring

Note: The holding time of solution treatment has a great influence on the grain size of the material and the performance after precipitation hardening. It should be determined by the diameter and thickness of the material and through experiments. The aging treatment can be cooled in the air after the holding time is over.

3. Heat treatment of silicon bronze wire

Silicon bronze is a Cu-si-Mn ternary alloy. It has good strength, hardness, elasticity, plasticity and wear resistance, and its hot and cold processing performance is also better. It cannot be strengthened by heat treatment and can only be used in annealed and processed hard conditions. After the spring is formed, only 200~280℃ stress relief tempering treatment is required. Note: Some of the materials in this series have been summarized by referring to the “Aeronautical Manufacturing Engineering Manual”, and after practice, they have been revised, supplemented, and improved.

Rebound force testing machine for spring detection

When testing springs, some equipment is often used, because springs need to detect many functional details. Here is an introduction to the working state and working range of the spring resilience testing machine.
Spring rebound force testing machine

This machine is a test instrument specially designed for sofa spring frames and spring bags. It can meet the following three test requirements

(1) Durability test

Repeated pressing test can be performed according to the preset pressure conditions, the cycle can be preset, and it will stop automatically when the number is reached.

(2) Detection of the relationship between compression range and pressure

Press down according to the preset stroke and stop in place. Read the spring force of the stroke on the pressure gauge, and display the stroke value on the display.

(3) Detection of spring compression under specific pressure

After the pressure plate is pressed down to the set pressure, it stops, and the compression stroke length of the pressure value is displayed on the display.

(Spring package test)

Note: a) The maximum pressure of the machine = 50 kg, and the maximum pressing stroke is 150 mm.

b) Pressure sensor accuracy: 0.3% FS

c) Stroke accuracy: ±0.2 mm

Power supply: 220 volts, power = 300 watts

Spring machinery-CNC equipment

1. GH-CNC428 computer four-axis compression spring machine
Application range: debugging various compression springs, oil seal springs, battery springs, conical springs, double conical springs, safety springs, magazine springs and various simple wire forming.

product manual:

(1) The GH-428 machine is a four-axis computer-type compression spring machine, which is divided into four axes: wire feeding, outer diameter, spacing, and cutter; the four axes can act separately or simultaneously.

(2) The upper and lower sliding blocks adopt two independent motors, which can be used as spacing and cutter axes respectively; the two axes can be interchanged.

(3) The spacing adopts two methods of cam plate direct push, inclined plane spacing knife type and spacing rod push type, and the spacing adjustment is convenient and flexible.

(4) The outer diameter axis is independent, and the outer diameter can be easily adjusted through the setting program.

2.GH-CNC 320 Computerized Disc Torsion Spring Machine

Application range: PC control, servo power, simple mechanical adjustment, multiple motion stations, can make all kinds of torsion springs with complex shapes. The upper control system adopts the domestic top CNC controller.

product manual:

CNC3-320 three-axis computer torsion spring machine can process steel wire with a maximum diameter of φ1.0mm and copper wire with a maximum diameter of φ2.0mm. Special-shaped torsion spring equipment. The minimum accuracy of this machine’s computerized winding is 0.1 degree, and the minimum accuracy of Z-axis up and down movement is 0.5 wire. The Z-axis of the machine moves smoothly and conveniently up and down, and the positioning is accurate. Its advantages are more reflected when winding dense coils. And easy to operate, use the hand wheel, input positioning coordinates, angle, easy to complete the program control. The machine is equipped with ten stations with different forming directions such as inclined up, inclined down, up, down, and horizontal.

3.YLSK-35 computer universal spring machine

Application: mechanical equipment for producing springs

product manual:

Camshaft, thread feeding shaft, rotating mandrel, auxiliary shaft (optional accessory), four shafts can be transported together. The mechanical part has eight sets of sliding seats, cranks and cam shafts. The cam is fixed on the revolving wheel shaft, which can be screwed to adjust the front and back, and is used to push the movement of the sliding seat. There are three ways of mechanical action: extrusion, stamping and forming. Program data is easy to set and change on the keyboard, and debugging is very convenient and quick.