Stainless steel terms

Generally speaking, stainless steel is not easy to rust steel, in fact, some stainless steel, both stainless steel and acid resistance (corrosion resistance). The rust resistance and corrosion resistance of stainless steel are due to the formation of chromium rich oxide film (passive film) on the surface of stainless steel. This rust resistance and corrosion resistance are relative. The results show that the corrosion resistance of steel increases with the increase of chromium water content in the weak medium such as atmosphere, water and nitric acid. When the chromium content reaches a certain percentage, the corrosion resistance of steel changes suddenly, that is, from easy to rust to not easy to rust, from non corrosion to corrosion resistance.

 

There are many ways to classify stainless steel. According to the structure classification at room temperature, there are martensite, austenite, ferrite and duplex stainless steel; according to the main chemical composition, it can be divided into two systems: chromium stainless steel and chromium nickel stainless steel; It can be divided into pitting corrosion resistant stainless steel, stress corrosion resistant stainless steel, intergranular corrosion resistant stainless steel, etc. according to the functional characteristics, it can also be divided into non-magnetic stainless steel, free cutting stainless steel, low-temperature stainless steel, high-strength stainless steel, etc. Because of its excellent corrosion resistance, formability, compatibility and toughness in a wide temperature range, stainless steel has been widely used in heavy industry, light industry, daily necessities industry and building decoration industry.

Austenitic stainless steel: stainless steel with austenite structure at room temperature. When the content of Cr is about 18%, Ni is 8% ~ 10%, C is about 0.1%, the austenite structure is stable. Austenitic Cr Ni stainless steel includes famous 18Cr-8Ni steel and high Cr Ni series steel developed by adding CR and Ni contents and adding Mo, Cu, Si, Nb, Ti and other elements. Austenitic stainless steel is non-magnetic and has high toughness and plasticity, but its strength is low. It can not be strengthened by phase transformation, but can only be strengthened by cold working. If s, CA, Se, TE and other elements are added, it has good machinability. This kind of steel can resist the corrosion of sulfuric acid, phosphoric acid, formic acid, acetic acid, urea, etc. The intergranular corrosion resistance of this kind of steel can be significantly improved if the carbon content in the steel is less than 0.03% or contains Ti and Ni. High silicon austenitic stainless steel with concentrated nitric acid has good corrosion resistance. Because of its comprehensive and good comprehensive properties, austenitic stainless steel has been widely used in all walks of life.

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Ferritic stainless steel: stainless steel with ferrite structure as the main structure in service state. The content of chromium is in the range of 11% ~ 30%, and it has a BCC crystal structure. This kind of steel generally does not contain nickel, and sometimes contains a small amount of Mo, Ti, Nb and other elements. This kind of steel has the characteristics of large thermal conductivity, small expansion coefficient, good oxidation resistance and excellent stress corrosion resistance. It is mainly used for manufacturing parts resistant to atmospheric, steam, water and oxidizing acid corrosion. This kind of steel has some disadvantages, such as poor plasticity, obvious reduction of plasticity and corrosion resistance after welding, which limits its application. The application of secondary refining technology (AOD or VOD) can greatly reduce the interstitial elements such as carbon and nitrogen, so this kind of steel is widely used.

Austenite ferrite duplex stainless steel: it is a stainless steel with austenite and ferrite structure accounting for about half. In the case of low C content, Cr content is 18% ~ 28%, Ni content is 3% ~ 10%. Some steels also contain Mo, Cu, Si, Nb, Ti, N and other alloy elements. This kind of steel has the characteristics of both austenitic and ferritic stainless steel. Compared with ferrite, this kind of steel has higher plasticity and toughness, no room temperature brittleness, significantly improved intergranular corrosion resistance and welding performance. At the same time, it also maintains the brittleness of ferritic stainless steel at 475 ℃, high thermal conductivity and superplasticity. Compared with austenitic stainless steel, it has higher strength, intergranular corrosion resistance and chloride stress corrosion resistance. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel saving stainless steel.
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Martensitic stainless steel: stainless steel whose mechanical properties can be adjusted by heat treatment. Generally speaking, it is a kind of hardenable stainless steel. The typical brand is Cr13, such as 2Cr13, 3Cr13, 4Cr13, etc. It is mainly used for steam turbine blades, tableware and surgical instruments. According to the difference of chemical composition, martensitic stainless steel can be divided into martensitic chromium steel and martensitic chromium nickel steel. According to the different structure and strengthening mechanism, it can be divided into martensitic stainless steel, martensitic and semi austenitic (or semi martensitic) precipitation hardening stainless steel and maraging stainless steel.Two phases (austenite ferrite),
④ Stainless steel, precipitation hardening stainless steel and high alloy with iron content less than 50% are usually named by patent name or trademark.
4) . classification and classification of standards
4-1 classification:
① National standard GB
② Industry standard Yb
③ Local standards
④ Enterprise standard Q / CB
4-2 classification:
① Product standards
② Packaging standard
③ Method standard
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④ Basic standards
4-3 standard level (divided into three levels)
Y level: international advanced level
Level I: international general level
Class H: domestic advanced level
4-4 national standards
GB1220-84 stainless steel bar (grade I)
Gb4241-84 stainless welded disc (grade H)
Gb4356-84 stainless welded disc (grade I)
GB 1270-80 stainless steel pipe (grade I)
GB 12771-91 stainless steel

Main function of steel tempering

Main function of steel tempering
1. Reduce brittleness, eliminate or reduce internal stress. There are great internal stress and brittleness in steel parts after quenching. If the steel parts are not tempered in time, the steel parts will deform or even crack.
2. Obtain the mechanical properties required by the workpiece. After quenching, the workpiece has high hardness and high brittleness. In order to meet the requirements of different properties of various workpieces, the hardness can be adjusted by proper tempering to reduce brittleness, and the required toughness and plasticity can be obtained.
3. Stabilize the workpiece size
4. For some alloy steels which are difficult to soften after annealing, high temperature tempering is often used after quenching (or normalizing) to make carbides in steel gather properly and reduce hardness, so as to facilitate cutting.

Spring material national standard and other standards

Spring material national standard and other standards
Executive standard: GB / T14975-2002, GB / T14976-2002, GB / t13296-91
American Standard: ASTM A312 / a312m, ASTM A213 / 213a, ASTM A269 / 269M
German standard: din2462
Japanese standard: JIS g3463
Material: 301 (1cr17ni7), 304 (0Cr18Ni9), SS304, TP304
304L(00Cr19Ni10)、SS304L、TP304L
316(0Cr17Ni12Mo2)、SS316、TP316
316L(0Cr17Ni14Mo2)、SS316L、TP316L
321(1Cr18Ni9Ti)、SS321、TP321
310S(0Cr25N20)、SS310S、TP310S
Specification: outer diameter: Φ 6 — 830mm, wall thickness: 0.5 — 40mm

Application of oil quenched spring steel wire

1、 Brief review of the development history of quenched tempered spring steel wire
Oil quenching tempering spring steel wire production technology originated in Europe, and its representative enterprise is Swedish gaffeten company. And Bekaert, Belgium. Soon the technology spread to Japan, and its representative enterprises are Kobe, Sumitomo, Gao Zhoubo, etc. In the early 1970s, China began to study its own oil quenching tempering spring steel wire production technology.

In the process of research on the production technology of oil quenched tempered spring steel wire in China, the engineering and technical personnel in the wire drawing workshop of the former Beijing special steel works and the teachers and students of the former Beijing Institute of iron and steel (Beijing University of science and Technology) have made outstanding contributions. In October 1974, the technology was successfully put into mass production in the wire drawing workshop of the former Beijing special steel plant, which opened a new chapter in the production of oil quenched tempered spring steel wire in China, and maintained the situation that the plant has been in the domestic market for nearly 20 years.

During this period, under the system of planned economy, some iron and steel enterprises have put this technology into trial production, but it has not been realized due to the problems of mechanism and technology. After the reform and opening up, especially in recent years, with the rapid development of automobile industry, motorcycle industry, diesel engine industry and machinery industry, China has gradually become the development trend of world processing base. And interest temptation makes all kinds of capital compete to enter the industry. More than a dozen oil quenched tempered spring steel wire manufacturers have emerged, such as Zhengzhou metal products research institute, pilot plant No.2, Henan Hebi, Zhengzhou Xinya, Tianjin Dihua, Tianjin Xinhao, Jiangsu Shenwang, Shanghai Sanlian, Hunan sipuling, Nanjing Dongwu, Zhejiang Haina, etc. And there are still domestic and foreign capital invested in the industry.

2、 Brief review of the development history of oil quenching tempering spring steel wire technology
In the research of oil quenching tempering spring steel wire production technology in China, the technical standards and process ideas of Sweden and Japan are mainly referred to. But in the early stage of research and development, due to the problems of technology, equipment, production efficiency and product cost, it took a detour. It was not until the late 1980s and early 1990s that the production process of oil quenched tempered spring steel wire in China was basically stable. According to the commonly used materials in China, the product stability is as follows: 50CrVA, 60Si2MnA, 65Mn, 70#, 82B, 55CrSi, sup12, sae9254, 55crsiv.

3、 A brief review of quality development history of oil quenched tempered spring steel wire in China
The quality of oil quenched tempered spring steel wire in China is not stable to basically meet the requirements of middle and low end spring products, and many quality problems are encountered. Some problems have been solved, and some problems still need to be further studied.
The problems that have been basically solved are as follows:
1. Brittle fracture of steel wire (natural fracture and wound spring fracture)
2. Problems caused by poor decarburization process
3. Crack problem (raw material problem, poor process)
4. Uneven size problem (poor processing)
5. Sickle bending problem (poor processing)
6. Dimensional accuracy

Although the above single problems have been basically solved in China. However, these problems still affect the comprehensive properties of oil quenched tempered spring steel wire. The specific performance is that the performance of steel wire strip is unstable, which leads to the increase of spring instability, especially the fatigue life of valve spring can not meet the specified requirements.
In order to narrow the quality gap between China’s oil quenched tempered spring steel wire and foreign products, it is necessary to further improve the cognitive level of this kind of product and increase the investment in research and development, technology and equipment. At the same time, strengthen the cooperation with raw material manufacturers. Ensure the product quality to a new level, otherwise we can only hover in the field of low-end spring products.

4、 Characteristics of oil quenched tempered spring steel wire
1. The ratio of yield to strength is high and the residual deformation of spring is small.
2. The performance of the strip is stable: the same disc difference is less than 75mpa, which is beneficial to coil spring and improve the fatigue life of spring.
3. Compared with the traditional spring production method, some procedures after winding the spring can be omitted.
4. The coil spring has high yield and can reduce the cost.

5、 Application scope of oil quenched tempered spring steel wire
Oil quenched tempered spring steel wire can not completely replace cold drawn spring steel wire. Especially the small size spring steel wire. Oil quenched tempered spring steel wire is developed for the anti fatigue performance of valve spring and suspension spring. In order to achieve the best effect, shot peening should be combined after the spring winding. Spring manufacturers should pay attention to the aging effect when storing this kind of steel wire. After winding the spring with this kind of steel wire, the following treatment should be carried out in time.

Avoid loss due to improper use. In recent years, with the improvement of the cognitive level of this kind of product, this kind of product is gradually applied to clutch spring and automobile rigging and other products. Whether the oil quenched tempered spring steel wire can fully meet the requirements of tension spring, torsion spring, special-shaped spring and the spring that needs coating needs to be further discussed.

6、 Brief analysis on market situation of oil quenched tempered spring steel wire
China will become the world’s processing base and the largest market in the world. Because of this, the market competition of oil quenched tempered spring steel wire will be more heated. Although some large spring factories use imported steel wire at present, there are some limitations due to delivery time, price and other issues, and most spring enterprises still choose to use steel wire from domestic enterprises. However, with the increase of domestic production enterprises, competition is bound to intensify, especially in May this year, the “giant Mac” factory jointly invested and built by a domestic enterprise and two Japanese enterprises in Shanghai was put into operation

Analysis and prevention of fatigue failure of wave spring

1、 Introduction
Although spring industry is a small industry in the whole machinery manufacturing industry, its role can not be underestimated. With the deepening of the opening degree, the imported industrial equipment such as machinery manufacturing, automobile, petrochemical and electric power has been widely used in China. Accordingly, we also know that some new components with superior performance, multi-layer wave spring is a relatively new elastic element.
Ordinary single-layer wave spring is an elastic element with several peaks and valleys on a metal ring. It seems that the multi-layer wave spring is composed of several common single-layer wave spring. The difference is that it is not simply superimposed, but processed by a special continuous winding process.

 

2、 Classification and working principle
Wave spring is usually divided into: A, single-layer wave spring
Single layer closed wave spring with “O” shape
The single-layer open-ended type is “C” shape wave spring;
b. Multi layer peak to peak (Series) wave spring;
c. The multi-layer stacked peak type is also called nested type (parallel type);
Single layer wave spring: suitable for working conditions of short displacement and low elastic force, with good reliability and high working principle: wave spring has the accuracy of double working principle of cylindrical spring and disc spring.
Multi layer wave spring opposite peak type (series type): the elastic force value is inversely compared with the number of coils. It is mainly used in large displacement, medium and low elastic requirements, and is the substitute of cylindrical spring. Nested type (parallel type): the force value of the spring is proportional to the number of turns. It can maintain all the accurate characteristics of the wave spring while generating huge elastic force. In many cases, the nested (parallel) wave spring can be used instead of the disc spring.

 

3、 Effect of material and temperature on fatigue failure
For the same material, the material with fine grain structure has higher yield strength and fatigue elasticity than that with coarse grain structure; the fatigue life of surface strengthened material is much higher than that without strengthening treatment; the smaller the surface roughness is, the smaller the stress concentration is, the higher the fatigue strength is; The fatigue life of the material with metallurgical defects will be greatly reduced, which makes the spring fatigue failure in advance.
The wave spring made of common spring steel has good elasticity, strong conductivity and wear resistance. The fatigue failure of the spring is within the normal range at normal temperature (at? 200?). However, with the increase of temperature, the spring elasticity will gradually decrease and the failure phenomenon will increase obviously.
The wave spring made of stainless steel has high fatigue life and good relaxation resistance. At the same time, stainless steel also has high corrosion resistance and non-magnetic properties. Generally, stainless steel will fail when the temperature is higher than 400?. special stainless steel has extremely high corrosion resistance, non magnetism and other characteristics. When the working temperature of special stainless steel reaches 650?, it also has high relaxation resistance and fatigue resistance, which is an irreplaceable material in special working conditions.

 

4、 Prevention of fatigue failure of wave spring
The following is the wave spring load, stress calculation formula, we can use the formula to design the wave spring stress in the low stress state, the waveform spring fatigue failure is not obvious.
(1) Calculation formula of single-layer wave spring: F = pkdm / ebt3n4 * ID / OD
S=3IIPDm/4bt2N2 ;
(2) Calculation formula of multi-layer series or peak to peak wave spring;
f=PKDm3Z/Ebt3N4*ID/OD ; S=3IIPDm/4bt2N2 ;
(3) The calculation formula of multi-layer stacked peak spring is also called nested or parallel wave spring;
F=PKDm3/Ebt3N4Z*IDOD ; S=3IIPDm/4bt2N2Z ;
Where: F = displacement; P = load; k = multi turn coefficient; DM = average diameter;
Z = number of turns; E = modulus of elasticity; b = width of material; t = thickness of material;
N = wave number; id = inner diameter; OD = outer diameter; s = bending stress;
Through the fatigue test of the wave spring, we get that the fatigue life of the wave spring is far more than 500000 times, and the normal life is more than 1 million times. The outer diameter d = 137mm, inner diameter d = 125mm, thickness t = 0.8mm, wave crest height h = 6mm, working force value f = 1225n when working displacement is 3.5mm. After more than three years of use in a petrochemical enterprise, the service life of this type of wave spring has reached 1.8 million times, and some of them are even longer.
Therefore, we should select reasonable wave crest height and material thickness according to load and displacement, effectively control the stress of wave spring, and use adjustable wave number to control the fatigue failure of wave spring more effectively.

What is torsion bar spring

Torsion bar spring is a kind of rod spring with one end fixed and the other end connected with working parts. Its main function is to absorb vibration energy by torsion force
Application: the torsion bar spring is used for automobile frame and wheel, one end of which is fixed on the frame and the other end is connected with the wheel. When the wheel jumps up and down, the torsion bar produces torsion deformation and absorbs the vibration energy by torsional elastic force; the torsion bar spring is used as the damping component of automobile frame and wheel, with simple structure and small structure, which is suitable for small cars.

Small spring big effect

Spring is a kind of mechanical part that uses elasticity to work. It is usually made of spring steel. Although the spring is small, as a general basic part, it has a large quantity and a wide range of varieties. It is used to control the movement of machine parts, mitigate the impact or vibration, store energy and measure the size of force. It is widely used in machines and instruments, and its application fields involve almost all fields of national economy.

 

In recent years, the rapid development of China’s national economy has also promoted the rapid growth of China’s spring industry. Experts predict that this growth trend will continue, and the sales volume of the whole industry will exceed 4 billion yuan in 2010. According to the analysis, there are five major markets for spring products: transportation, daily hardware, instruments and electronic appliances, industrial and mining accessories, and overseas export markets.

Common sense of leaf spring

After 1000 km driving, the tightening torque of U-bolt and nut for clamping leaf spring should be checked to keep the tightening torque value when leaving the factory, so as to avoid the central fracture fault of leaf spring.
When the optional leaf spring is one end lug and one end sliding plate structure, when the vehicle is unloaded, do not pass through the convex and concave sections at a higher speed, which can avoid the fracture of the bending end of the plate spring due to impact load.

After driving a certain mileage, the leaf spring ear hole and the ear hole pin should be checked and lubricated in time. If the rolling ear bushing is found to be seriously worn, a new bushing should be replaced in time to avoid the loud noise from the connecting part of the rolling ear and the ear hole pin. At the same time, it can also prevent the distortion of leaf spring caused by the uneven wear of bushing, and avoid the deviation of vehicle during driving.

When the vehicle needs to replace the leaf spring assembly after driving for a period of time, the left and right leaf springs should be replaced at the same time, so as to avoid the possibility of vehicle tilting caused by only replacing one leaf spring and the possibility of vehicle overturning during rapid turning.

gas spring

The special nitrogen spring for die and mould (referred to as die nitrogen spring or nitrogen spring or nitrogen cylinder or nitrogen cylinder for short) is a new type of elastic component with high pressure nitrogen as working medium. It has small volume, large elasticity, long stroke, stable operation, precise manufacturing, long service life (one million times), gentle elastic curve, and no need of pre tightening, etc The performance of the elastic component can make up for its deficiency, and replace the conventional elastic component to complete the work difficult to be completed by the conventional elastic component, simplify the mold design and manufacturing, facilitate the mold installation and adjustment, extend the service life of the mold, and ensure the stability of product quality. It can be installed in the mold as an independent component, and can also be designed as a nitrogen spring system. As a part of the mold, it can easily realize the elastic pressure constant and delay action in the system. It is a new generation of most ideal elastic components with flexible performance.

Nitrogen spring has been widely used in foreign mold manufacturing industry. The use of nitrogen spring in the mold can reduce the mold volume, shorten the manufacturing time, reduce the number of mold test and improve the success rate, prolong the mold life, greatly improve the product quality and yield, and has high economic benefits.

Compared with foreign countries, the application of nitrogen spring in domestic mold manufacturing industry is still very backward. Because the manufacturing of nitrogen spring is the process of comprehensive application of various new technologies, the technical quality index is high, so it is difficult to manufacture. At present, there are few domestic professional production enterprises, so most of them can only rely on import. However, the high price of imported nitrogen spring has affected the widespread use of die and mold industry in China.

Spring steel wire and elastic alloy wire

Elastic material is widely used in machinery and instrument manufacturing industry to make various parts and components. Its main functions in all kinds of machinery and instruments are as follows: absorbing vibration and impact energy through deformation, easing vibration and impact of machinery or parts; controlling the movement of machinery or parts by using the energy stored in its own deformation; and; Realize the functions of medium isolation, sealing and flexible shaft connection. The physical properties of elastic materials, such as elasticity, corrosion resistance, magnetic conductivity and conductivity, can also be used to make instruments and instrument components. The physical quantities such as pressure, tension and temperature can be converted into displacement so as to measure or control these physical quantities.
Classification of elastic materials

1.1 classification by chemical composition
Elastic materials can be divided into: carbon spring steel, alloy spring steel, stainless spring steel, iron-based elastic alloy, nickel based elastic alloy, cobalt based elastic alloy, etc.
1.2 classification by use characteristics
According to the service characteristics of elastic materials, they can be classified as follows:
1.2.1 general spring steel
(1) Deformation strengthening spring steel: carbon spring steel wire.
(2) Martensite strengthened spring steel: Oil quenched and tempered steel wire.
(3) Comprehensive strengthening spring steel: precipitation hardening stainless steel wire
1.2.2 elastic alloy
(1) Corrosion resistant high elastic alloy
(2) High temperature and high elasticity alloy
(3) Constant elastic alloy
(4) Elastic alloy with special mechanical and physical properties

2. Main performance indexes of spring steel and elastic alloy
2.1 elastic modulus
When the tension does not exceed a certain value, the deformation is directly proportional to the external force, which is usually called Hooke’s law. The formula is as follows:
ε=σ/E
Where ε – strain (deformation size)
σ – stress (external force)
E-tensile modulus of elasticity
The tensile modulus of elasticity (also known as young’s modulus of elasticity or elastic modulus) is an index to measure the degree of elastic deformation of metal materials. Different grades of elastic modulus are different, and the elastic modulus of the same brand is basically a constant.
In engineering, in addition to the elastic modulus (E) which represents the tensile deformation resistance of metals, the shear modulus of elasticity (g) is often used to express the shear deformation resistance of metals.