Heat treatment springs and springs. Spring steel Mark.

In the production of spring steel, material is obtained with a large yield strength. Thanks to this property, all products manufactured from this material are able to take the original shape even after twisting or significant bending. It is for the production of elastic products that do not have residual deformation, and these materials are intended.

Use of use

Spring steel produces a wide range of products and parts used in vehicleah, aggregates and factory equipment. Torsions and springs that can be found in car suspensions and armored vehicles are made of steel grades 55c2, 60c2a and 70c3a. Recently, steel of the brand 50HF began for the same goals. From it is usually made valve for springs.

Details for vehicles are not the only sphere in which spring steel is applied. Materials from this category are used for the manufacture of launders, springs for friction discs, as well as for of different kind mechanisms, including production. For certain articles and springs, steel of certain brands is suitable. Between them there are great differences in terms of important performance:

• 50 Chgfa. - apply to create time springs;
• 55C2. - springs and springs used in vehicle suspension;
• 60g, 65. - for the manufacture of wear-resistant and vibration resistant springs, stubborn washers;
• KT-2. - for rolled cold rolled wire.

There are other numerous brands, and many of them are able to intermitted each other. For example, steel grade 68 can be applied instead of 65g, and steel grade 70 (g) perfectly replaces 60g. In GOST, you can find the tables in which all existing brands with their processing modes and properties are presented.

Composition and production

For the assembly of springs and mechanisms based on them, steel is used, which includes from 0.5% to 0.75% of carbon. In the event that the content of this element exceeds the mark of 0.7%, the material is called tool steel. It is a solid and high-strength material for manufacture different tools. And also it is used to create springs, maximum resistant to mechanical effects.

Carbon is not the only element affecting the important characteristics of steel for springs. In the production of metal in its composition, alloying components are intentionally introduced in the following concentrations:

• nickel - up to 1.7%;
• tungsten - up to 1.2%;
• chrome - up to 1.2%;
• vanadium - up to 0.25%;
• manganese - up to 1.25%;
• silicon - up to 2.8%.

The most important stage manufacturing process is grinding grain. As a result, the resistance of the finished metal with small plastic deformations increases significantly. This has a positive effect on the relaxation resistance of the springs, which are made of high-alloy steels.

Modern methods for manufacturing alloys for creating springs allow materials with any design, any surface and diameter if we are talking About spring wire. Strictly observed both domestic and international Standardsdefining performance features become. In addition, careful quality control is carried out behind each stage of creating spring alloys.

Marking

The steel marking for the production of spring products is quite simple, but at the same time informative. According to the designation, it is possible to understand the composition of the material that all its operational properties are determined. Marking is deciphered in the direction from left to right. It includes the following positions:

• first position Of the two digits, it expresses a lot of carbon in the hundredths of percent;
• second position From one or more letters indicates the name of the alloying element;
• third position Shows the fraction of the alloying element rounded to the whole value.

If the share of the alloying element in the metal is less than 1.5%, it does not specify in the marking. According to the designation, it is easy to understand what metal belongs to. For example, spring steel grades 65, 70, 75, 80 and 85 refers to the category of carbon. Materials, in the marking of which there are at least two positions are classified as doped, since there are a high concentration of alloying elements.

Characteristics

The main properties of materials for the manufacture of steel brake ribbons, springs and other products are high fluidity and elasticity. A significant increase in elasticity is achieved by hardening the alloy in oil at high temperatures in the range from +820 ° C to +870 ° C. After hardening, a vacation is required in the temperature range from +400 ° C to +480 ° C. If there is a need to increase such properties of metal as durability, viscosity and plasticity, production is resorted to isothermal hardening.

Based on the characteristics of the material to create springs, the following metals groups are distinguished:

• by chemical composition - ordinary, stainless, alloyed metal;
• by processing method - Calibrated, hot-rolled, forged rental, with special trim.

Metals going on the manufacture of springs are necessarily checked and normalized by chemical composition. In this case, the rental is classified by category. There are 14 categories in total, which are marked from 1 to 4b inclusive. For some characteristics, the rationing is not performed. For example, the metals of categories 1, 1a, 1b are not normalized for the presence of a decarbered layer and calcination.

Primary requirements

Key characteristics of spring rolled products are subject to strict requirements of GOST. Basic list technical requirements GOST 14959-79 is regulated. It contains a list of both carbon and alloyed steel grades. There are also described requirements for marking, packaging, the rules for transportation, storing and applying rolled products from spring steels.

List of some requirements:

• maximum mass fraction copper - 0.2%, the residual nickel content is not more than 0.25%;
• steel of the 51HFA brand can be used exclusively for the manufacture of elastic wire;
• the maximum mass fraction of sulfur and phosphorus in steel brands 60c2g is not more than 0.06%.

Some requirements for spring steel may not be observed. For example, the aforementioned GOST allows a change in the concentration of manganese as part of the alloy at the request of the customer. However, this action is permissible only for those spring alloys, which contains such alloying elements as nickel and chrome. And it is also not recommended to deviate greatly from the tables in which the permissible concentrations of the elements are indicated.

Features Steel

Spring steel - a number of brands, in the process of creating a plastic cold deformation method. For the implementation of this method, shot blasting and hydroabrasive technologies can be used. Specific methods used in the production of spring metals emphasize not only positive, but also negative qualities. By cons of such materials include:

• difficulty cut - This process is possible, however, the processing of finished products is difficult;
• bad weldability - Metals for the production of springs are not at all designed for welding.

Separately, it is necessary to allocate such a type of metals as a corrosion-resistant steel. This is Mark. special purpose, its main feature is high resistance to corrosion destruction. In order to endow the material with such characteristics, alloying elements - nickel and chrome are added to its composition. Nickel content varies from 9 to 12%, and chromium - from 13 to 27%, depending on the necessary properties.

In general, the spring metal enjoys high demand, even despite some disadvantages. The use of such materials is not limited to springs, friction discs and springs. Steel is used in piano strings, for rolled wire and other purposes.

Kazan State Technical University them. A. N. Tupolev

Institute of Aviation, Terrestrial Transport and Energy

Department: "Materials science and structure of forming technologies"

Discipline: "Materials science C.2"

Course work

Topic: "Spring Steel"

Made:

Checked:

Elabuga, 2009

Plan:

1. Description

2. Application

3. Marking and main characteristics

4. Feature of rolling spring steel

5. Basic requirements imposed on spring-spring steel

6. Characteristics of material 68a

7. Literature

Description:

Spring steel - steel intended for the manufacture of elastic elements (springs, spring, etc.)

The work of the springs, the springs and the like details is characterized by the fact that they use only the elastic properties of steel. The large total magnitude of the elastic deformation of the spring (springs, etc.) is determined by its design - the number and diameter of the turns, the spring length. Since the occurrence of plastic deformation in springs is not allowed, then the material of similar products does not require high shock viscosity and high plasticity. The main requirement is that the steel has a high limit of elasticity (fluidity). This is achieved by quenching with the subsequent release at a temperature in the region of 300-400 ° C. With this vacation temperature, the limit of elasticity (fluidity) gets the highest value, and the fact that this temperature lies in the range of development interval of the selling fragility I of the genus, by virtue of the circumstance marked above It does not matter much.

Springs, springs and similar parts made from structural steels with an increased carbon content (but, as a rule, it is still lower than that of instrumental steels) - approximately 0.5-0.7% C, often with the additives of manganese and Silicon. For specially responsible springs, steel 50khf containing chrome and vanadium and the highest elastic properties have the highest elastic properties. Thermal processing of springs and springs from alloyed steels lies in quenching from 800-850 ° C (depending on the steel grade) in oil or water, followed by leave around 400-500 ° C on HRC hardness 35-45. This corresponds to ST B \u003d 1304-1600 kgf / mm 2.

Sometimes such heat treatment is subject to details of large-length structures and with thin walls, which should have high spring properties. In this case, steel SOGS is used; After quenching and leave at 250 ° C, it will have the strength (A B) of 160 kgf / mm 2, but the viscosity (A D) is only 5 kgf / cm 2, and the plasticity (b) is 7% and (f.) 40%. Often, the springs are made of grinding cold-made wire (so-called silver). Low (Nagarovka) from the cold broach creates high hardness and elasticity. After the appeal (or other method of manufacture), the spring should be released at 250-350 ° C to remove the internal stresses, which will increase the limit of elasticity. For the manufacture of silver, ordinary carbonaceous instrumental steel U7, U8, U9, U10 is used.

On the quality and performance of the spring, the condition of the surface has a great influence. In the presence of cracks, the captivity and other surface defects are unstable in operation and are destroyed, due to the development of fatigue phenomena in places of stress concentration around these defects. In addition to conventional spring materials, there are also special, operating in specific conditions (elevated temperatures, aggressive media, etc.).

General characteristics: Steel spring-spring, lowly sensitive to fluke-forming, prone to the vacation fragility when the content of Mn≥1% is not used for welded structures. Density at 20 ° C - 7,81x10³Kg / m³. Module of normal elasticity at 20 ° C - 215 GPa. Specific heat at 20-100 ° C - 490 J / (kg · ° C)

They operate in the field of elastic deformation of the metal under the influence of cyclic loads. Therefore, they must have a high value of the limit of elasticity, fluidity, endurance, if necessary, plasticity and high resistance to fragile destruction.

Spring steel contain C \u003d 0.5 - 0.75%, Si to 2.8%, Mn to 1.2%, CR to 1.2%, V to 0.25%, BE to 1.2%, Ni up to 1.7%. In this case, the grinding of grain, which contributes to an increase in resistance has become small plastic deformations, and consequently, its relaxation resistance. Widespread use on transport found siliceous steel 55С2, 60С2A, 70С3A. However, they may be shut-off, graphitization, sharply reduce the characteristics of the elasticity and endurance of the material. The elimination of these defects, as well as the increase in the calcination and braking inhibition of grain growth, is achieved by an additional introduction to chromium, vanadium, tungsten and nickel. For the manufacture of springs, a cold-trailed wire (or tape) from high carbon steels 65, 65g, 70, U8, U10, and more are also used. Special purpose springs from martensitic steels 30x13a, martensite-aging 03x12N10D2T, austenate-martensitic 09x15n8 and other steels and other steels are also used. Alloys. Steel hardened from temperatures 830 - 880 ° C and release to cane (380 - 550 ° C).

Have a high yield strength. The ratio of the yield strength to the strength limit of 0.8-0.9. For leafy springs and springs of suspension, siliceous and manganese steel 50HG, 50G2, 05G, 55С2, etc., 45HNMF, G0C2A, 70Cza are used for torsion shafts.

To increase the fatigue strength of parts operating at high vibrational loads, it is necessary to ensure the creation of residual compressive stresses in the surface layer. To this end, it is used sprouting springs, pincers and chasing of torsion shafts, rollers, plastic sediment and shot blasting of leaf springs. The alloyed spring-spring steel, heat-treated to HRC 45-50 hardness, has a limit of fatigue with 190 MPa torsion. After shot blasting, the fatigue limit increases to 350 MPa (3500 kgf / cm2).

Application:

Springs, springs, stubborn washers, brake ribbons, friction discs, gears, flanges, bearings, clamping and feeding collet and other parts to which the requirements of high wear resistance are presented, and parts operating without impact loads.

Types of products supplied: in hot-rolled state (without heat treatment) with hardness no more than HV285; in high-fold state - no more than HB241

Marking and main characteristics:

Spring Steel Stamps:

Maintenance mechanical properties Spring steel after special heat treatment.

steel grade	Recommended thermal processing mode			Mechanical properties
				ΣT, kgf / mm2	ΣВ, kgf / mm2	Δ5,%	φ , %
	Download temperature, ° С	Hardening medium	Leaves
				No less
65	840	Butter	480	80	100	10	35
70	830	»	480	85	105	9	30
75	820	»	480	90	110	9	30
85	820	»	480	100	115	8	30
60g	840	»	480	80	100	8	30
65g	830	Butter	480	80	100	8	30
70g	830	»	480	85	105	7	25
55gs	820	»	480	80	100	8	30
50c2	870	Oil or water	460	110	120	6	30
55С2.	870	Also	460	120	130	6	30
55С2A.	870	» »	460	120	130	6	30
60c2	870	Butter	460	120	130	6	25
60C2A.	870	»	420	140	160	6	20
70С3А.	860	»	460	160	180	6	25
50Hg.	840	»	440	110	130	7	35
50khga	840	»	440	120	130	7	35
55Hgr	830	»	450	125	140	5	30
50hf.	850	»	520	110	130	8	35
50 Chgfa.	850	»	520	120	130	6	35
60s2 chops	850	»	410	170	190	5	20
50xsa	850	»	520	120	135	6	30
65С2VA	850	»	420	170	190	5	20
60C2N2A.	880	»	420	160	175	6	20
60s2ha	870	»	420	160	180	5	20
60SGA	860	»	460	140	160	6	25

Spring steel rolling feature:

A feature consists in a sequence of heat treatment of such steels. So, when unscrewing the springs, the rod is in an annealed state, which ensures the simplicity of the operation. Then the spring is hardened. The last stage is a low vacation (130 ... 150 degrees), it is also called spring.

Basic requirements for spring-spring steel:

The overall requirement for spring-spring steel is to ensure high resistance to small plastic deformations (the limit of elasticity) and relaxation resistance (stress relaxation resistance). These characteristics provide accuracy and reliability of springs and constancy in the time of such operational properties such as torque, power parameters. Spring steel in the form of wires and ribbons are strengthened with cold plastic deformation and quenching on martensite with subsequent release. Finished springs are subjected to a stabilizing vacation.

Elastic properties of spring suspension are evaluated by silets characteristics and a stiffness coefficient or flexibility coefficient (flexibility). In addition, springs and springs are characterized by geometric dimensions. The main dimensions (Fig. 1) include: the height of the springs or springs in the free state without cargo n and height under the load H gr, the spring length, the diameter of the spring, the diameter of the bar, the number of work turns of the spring. The difference between H and H Gy is called spribb Springs (springs)f.. The deflection received from calmly lying on the spring of the cargo is called static. In leafy springs, for a more convenient measurement, the deflection is determined by the dimensions of H and G G G C near the clamp. Flexible properties Spring (springs) Defined by one of two quantities:

• flexibility coefficient (or just flexibility);
• rigidity coefficient (or just rigidity).

Fig. 1 - Main sizes Spring and springs

Spribe springs (springs) under the action of force equal to one, is called flexibility F 0:

where r - external forceoperating on the resor, n;

f - deflection of springs, m.

An important characteristic of the springs is its rigidity. j.which is numerically equal to the power of deflection, equal to one. In this way,

j. \u003d P / f.

For the springs, whose deflection is proportional to the load, equality is valid

P \u003d. j.f.

Rigidity - The value, inverse flexibility. Flexibility and rigidity Spring (springs) depend on their basic sizes. With an increase in the length of the springs or with a decrease in the number and cross section of the sheets, it increases, and the rigidity decreases. Springs with an increase in the average diameter of turns and their number and with a decrease in the cross section of the rod, flexibility increases, and the rigidity decreases.

The magnitude of the stiffness and deflection of the spring or springs is determined by the linear relationship between its deflection and the elasticity of the elasticity P \u003d j.f, presented graphically on (Fig. 2). The diagram of the operation of a cylindrical spring that does not have friction (Fig. 2, a) is depicted by one straight line 0a, corresponding to both the loading of the spring (increasing P) and its unloading (decrease in P). Stiffness In this case, the value is constant:

j. \u003d P / F ∙ TG α.

The springs of the stiffness variable (aperiodic) without friction have a diagram in the form of line 0AV (Fig. 2, b).

Fig. 2 - Spring Spring Charts (A, B) and Springs (B)

For work sheet springs There is friction between her sheets, which contributes to the attenuation of the oscillations of the priestly crew and creates a calmer movement. At the same time, too much friction, increasing the rigidity of the springs, worsens the quality of hanging. The nature of the change in the strength of the elasticity of springs during static loading is depicted on (Fig. 2, B). This dependence is a closed curve of the line, the upper branch of which 0a 1 shows the relationship between the load and the spury of the springs during its loading, and the lower a 1 A 2 0 - when unloading. The difference between branches, characterizing the change in the forces of elasticity of springs during its loading and unloading, is due to friction forces. The area bounded by branches is equal to the work spent on overcoming the friction forces between the springs. When the friction force is load, it seems to resist the increase in the deflection, and during unloading prevent the rectification of the springs. In the carriage springs, the friction force increases in proportion to the deflection, since accordingly the forces of the pressed sheets are increasing to each other. The magnitude of friction in the spring is usually estimated by the so-called relative friction coefficient φ, equal to the ratio of the friction force R Tr to the power of P, creating an elastic deformation of the springs:

The magnitude of the friction force is associated with the deflection f and the rigidity of the springs j.due to its elastic properties, addiction

The structural carbon or high carbon is believed steel spring - spring. To give it the narrow-controlled properties, it is dumping in small quantities of 2-3 elements, in the total amount to 2.5%. But the use of these stamps is not limited to the manufacture of springs. Call this group so because of the fact that the name is most strongly reflecting them main feature - Elasticity.

Spring Steel Characteristics

Spring steel are characterized by an increased yield strength (Δ c) and elasticity. it the most important characteristic Metal - withstand mechanical loads without changes in its original form. Those. Metal exposed to stretching or vice versa compression (elastic deformation), after removing it existing forcesmust remain in the initial form (without residual deformation).

Stamps and scope of spring steel

According to the presence of additional properties, the spring steel is divided into doped (stainless) and carbon. The basis of alloyed steel is taken carbon with content from 65-85% and is doped with 4 main elements, all or selectively, each of which makes its features:

1. chromium;
2. manganese;
3. silicon;
4. tungsten.

Chrome - at a concentration of more than 13%, it works for the provision of corrosion resistance of the metal. At a chromium concentration of about 30%, the product can operate in aggressive media: acid (except for sulfuric acid), alkaline, water. Corrosion spring steel is always doped by the second concomitant element - tungsten and / or manganese. Working T to 250 ° C.

Tungsten - refractory substance. If it enters its powder into the melt, forms numerous crystallization centers, shredding grain, which leads to an increase in plasticity without loss of strength. This brings its advantages: the quality of such a structure remains very high when heated and intensive abrasion of the surface. In thermal processing, this element retains a fine-grained structure, eliminates the softening of steel when heated (during operation) and dislocation. During hardening increases the calcination, as a result of which the structure receives homogeneity on great depththat in turn increases the operational period of the product.

Manganese and silicon - usually participate in doping mutually, and the ratio always increases in favor of manganese, about 1.5 times. That is, if the silicon content is 1%, then the manganese is added in the amount of 1.1-1.5%.

Helicing silicon is not a carbido-forming element. If it gets into the melt, one of the first takes part in crystallization, thusing carbon carbides to the grain boundaries, which corresponds to the hardening of the metal.

Manganese can be called a stabilizer of the structure. At the same time distorting the metal lattice and hardening it, the manganese eliminates the excessive strength of silicon.

In some stamps of steels (when working in high temperature conditions, at T above 300 ºC) Nickel is seated into steel. It eliminates the formation of chromium carbides on grain boundaries, which lead to the destruction of the matrix.

Vanadium can also be a alloying element, its function is similar to the action of tungsten.

In spring stamps, such an element is stipulated as copper, its content should not exceed 0.15%. T. K. Being a low-melting substance, copper concentrates at the grains boundaries, reducing strength.

Spring stamps include: 50Hg, 3k-7, 65g, 65g, 50xgf, 50hf, 51xf, 50xs, 55С2, 55С2A, 55С2GF, 55HGG, 60G, 60C2, 60С2A, 605, 70, 70G, 75, 80, 85, 60С2х , 60s2 chops, 65С2va, 68a, 68g, 70g2, 70s2h, 70c3a, 70xgf, SH, SL, SM, DM, DN, KT-2.

The brands of such steel are used for the manufacture of not only springs and springs, although these are their main purpose, which characterizes the main property. They are used everywhere where there is a need to betray the product, both plasticity and durability are simultaneously. All parts that are manufactured from these brands are subject to: stretching and compression. Many of them are experiencing loads, periodically replacing each other, and with a huge cyclic frequency. It:

• bearing housings that are tested at each point compression and tensile with high frequency;
• friction discs experiencing dynamic loads and compression;
• stubborn washers, the main time they experience the load on compression, but they can be added to them and a sharp change in stretching;
• brake tapes for which one of most important tasks It is elasticity with repeated stretching. With such a dynamics with enhanced aging and wear, more durable steel (with less elasticity) is susceptible to rapid aging and sudden destruction.

Also concerns the gear, flanges, pucks, colangu, etc.

Marking

Spring-spring steel can be grouped by positions:

• illegated with a carbon content of 65-85% - inexpensive overall use steel;
• manganese-Silicon - the cheapest with high physico-chemical indicators;
• chromo-manganese - stainless steel, works in aggressive media at T -250 +250 C;
• additionally alloyed and / or tungsten, vanadium, boron - are steel with an increased resource of the work due to a homogeneous structure, an excellent strength ratio and plasticity due to chopped grain and withstands high mechanical loads. Used on such objects as railway transport.

Spring steel marking is carried out as follows. We will analyze in the example of 60s2 chops:

• 60 - the percentage of carbon in tenths (carbon is not indicated in the letter);
• C2 - letter notation silicon with index 2, denotes an increased standard content (1-1.5%) by 2 times;
• X - the presence of chromium up to 0.9-1%;
• F - tungsten content up to 1%;
• A - added letter index A at the end of the marking indicates minimal content harmful impurities phosphorus and sulfur, no more than 0.015%.

Production

Depending on the further processing and the final type of detail, the steel is supplied in sheets, wire, hexagon, squares. High performance quality products are provided by 2 components:

1. the structure of the metal that is determined chemical composition and subsequent processing;
2. the presence in the structure of non-metallic inclusions, more precisely minimum quantity and dimensions, which is eliminated at the stage of smelting and casting;
3. the form of the part (spiral, arc) and its dimensions, which is determined by the calculated method.

When stretching the spring, the inner and outer side of the turns are experiencing various degrees of load: external less susceptible to stretching, while the internal experiences the greatest degree of deformation. Also concerns the ends of the spring: they serve as a fastening point, which increases the load in these and bordering places. Therefore, steel grades are developed, which are preferably used on compression or stretching.

Thermomechanical processing

Everyone without exception, spring steel is rotated thermomechanical processing. After it, the strength and wear resistance can increase by 2 times. The form of the product is given in an annealed state when steel has the highest possible softness, after which heated to 830-870 C and cooled in oil or aquatic environment (only for brand 60 CA). The resulting martensite is released at 480 ºC.