Features of heat treatment of metals - CityTolyatti
Thermal treatment of metal-containing materials can be characterized as an effective technological method of influencing their condition using different temperature regimes (heating and cooling).
Along with heat treatment, thermal bluing of metal is also used today. Regular heating and cooling implies the frequency and speed of the processes.
Heat treatment modes are selected in accordance with the phase and structural transformations of the material base to obtain certain properties.
Heat treatment in metallurgy
Heat treatment of metals today is the basis of the metalworking industry, with the help of which this industry has the opportunity to create unique alloys with different structures.
The heat treatment method is a process of thermal influence on the structure of alloys and metals to give them specified qualities. Heat treatment of metals can be divided into: chemical-thermal, thermomechanical.
Thermal processing processes change the internal structure of metals, and cooling sets the desired mechanical and physical properties. Heat treatment is essentially hardening.
Heat Treatment Capabilities
Non-ferrous metals, steel of any category, alloys can be subjected to heat treatment in accordance with the type of heat treatment, the specified heating mode, and cooling temperature. Heating and cooling at different speeds under certain conditions are set separately, depending on the structure and properties of the metal. This type of processing can be final or preliminary.
Preliminary heat treatment is used to prepare the structure and material for further technological procedures. Heat treatment is used at the production stage of products. The main types of heat treatment include: annealing, hardening, recrystallization, polygonization, tempering, aging, normalization. The maximum approach to equilibrium is realized using diffusion processes.
Heat treatment is the optimal method in industry today.
Source: https://tlt.volga.news/527068/article/osobennosti-termicheskoj-obrabotki-metallov.html
Basic methods of metal processing
Holding a metal product in your hands, you don’t think about how long the material has traveled before becoming a finished product.
The extraction of metal from ore alone is a multi-stage operation that involves thousands of people. However, obtaining a product from a metal ingot is no less labor-intensive task.
For these purposes, metalworking of various types is carried out, which allows you to change the internal structure, chemical properties and shape of a strong and durable material.
Chemical treatment
Although steel has high strength, it is susceptible to corrosion, which reduces the attractiveness and durability of products. To protect the metal from oxidation, it is chemically treated. In particular, using electrochemical galvanic treatment, a protective layer is applied to the surface, which protects the metal from corrosion and makes the product more attractive.
Electroplating is the final stage, but chemical treatment can also be used as a preliminary stage. For example, a controlled chemical reaction allows the metal surface to be cleaned before welding.
Mechanical restoration
This is one of the most common metalworking methods, which allows you to change the shape and size of a product due to mechanical impact on it with a harder object. There are many methods of mechanical metalworking:
- Turning - a cylindrical workpiece is installed in a rotating machine tool, after which a cutter is brought to it, which removes layer by layer from the workpiece;
- Drilling - an operation is performed to make holes; for this, the workpiece remains stationary and a rotating drill enters it;
- Milling - unlike a drill, a milling cutter has a working surface not only on the front, but also on the side;
- Grinding - this operation is performed to change the roughness of the product (giving it a smoother structure).
In addition to these, other metalworking methods can be used.
Thermal metalworking
To change the structure of a metal, transforming a face-centered cubic crystal lattice into a stronger body-centered cubic crystal lattice, you will need to heat and cool the metal to certain temperatures at a given speed. There are several types of heat treatment:
- Normalization;
- Hardening;
- Vacation;
- Annealing.
The choice of a particular method depends on the ratio of hardness and toughness to be obtained. In addition to chemical, thermal and mechanical processing, the manufacture of metal products uses pressure processing, welding and artistic processing.
Source: http://kfaktiv.ru/osnovnye-sposoby-obrabotki-metalla.html
Heat treatment of steels and metals, what is it - the main types of heat treatment of alloys
14Nov
articles
Varieties of metallic substances have varying degrees of strength, susceptibility to corrosion and other chemical reactions. Using heating, you can achieve the required properties from the workpiece, improve wear resistance, and prepare it for further procedures during metalworking. In this article we will talk about heat treatment of steel parts - what it is, what are the main types of heat treatment of metals.
Purpose of the technological process
You can work with both blanks and finished products. For the former, internal stress is relieved after various types of casting and stamping, the material becomes more plastic, and it is much easier to work with, especially cutting it. If a whole part is processed, then the following goals are pursued:
- increased strength;
- protection against premature rusting;
- increased resistance to temperature changes, the upper and lower temperature thresholds at which the item can be used become larger;
- extension of potential service life.
Features of heat treatment
The process affects not only external physical characteristics, but also changes the chemical structure from the inside. The shape of the crystal lattice changes during the secondary crystallization of the alloy, that is, under the influence of high heat, melting occurs, and then cooling and solidification again, but with different properties. The iron heats up and the discharge changes from the “alpha” category to the “gamma” category, while previously scattered particles combine into plates.
Benefits of technology
This process is used universally in many enterprises - every second production of metal products requires thermal exposure. This is due to the advantages:
- You can work with steel, non-ferrous metals and alloys - a wide range.
- Increased product shelf life.
- Reduced level of abrasive wear.
- The percentage of defects in production shops is becoming much lower.
- Cost savings, since it is easier to carry out a number of manipulations with a heat-treated workpiece.
Processing principles
The main rule is that the time spent on one part is equal to the duration of heating of the material, depending on its maximum temperature, holding period and cooling. The total count allows you to calculate the total time value. Each of these points depends on:
- workpiece dimensions;
- type of metal subjected to heat treatment;
- oven power.
All this determines how quickly the transformations will take place.
Classification
All varieties are used for different purposes, with different materials. For this, the technology remains the same - heating, holding, cooling, but the time of each stage changes. Features are presented in the video:
Vacation
During primary processing, for example, during casting, all metals receive internal stress - this is a special, close type of contact of molecules. Tension leads to increased fragility. The procedure allows to achieve impact resistance and reduce rigidity. There are three subspecies.
Short
The main task is to increase viscosity at the same hardness. This is achieved by giving the internal microstructure a needle or plate type. Often used for heat treatment of cutting parts and medical instruments. The workpiece is heated within 150-250 degrees. Leave for at least one and a half hours, and then cool with air or oil.
Average
Here, martensite (the type of structure described above) is transformed into trustite, which is characteristic of cast iron. Feature – high dispersion. At the same high viscosity, the hardness also increases. This is very important for elements that will be subject to large elastic loads. Temperature limits – from 340 to 500, air cooling.
High
Crystallization occurs with the appearance of sorbitol. Thanks to it, the stress inside the alloy is completely eliminated. This method is used for structures that are very important - in aircraft construction, in the construction of space objects. Heating temperature – from 450 to 650 degrees.
Annealing
The operation is carried out to obtain the required equilibrium structure with minimal hardness, for the purpose of further metal processing of the resulting products by cutting. The video will introduce you to the features:
General definition and types
During casting or other primary processing processes, in addition to stress, defects appear. You can remove these changes and achieve a homogeneous structure of the crystal lattice using the following algorithm of actions:
- heating - it is necessary to slightly exceed the critical level for this type of steel;
- a certain period is required to maintain a stable temperature;
- The workpiece should be cooled slowly along with the oven.
Annealing has the following varieties.
Homogenization
Refers to the first kind, when changes are considered minor. The purpose of such manipulation is to remove the heterogeneity of the structure and bring it to uniformity. In this case, the product should be heated at a temperature range of 1000 to 1150 degrees, then held for about 8-15 hours and gradually reduced heating, cooling the workpiece with oxygen.
Recrystallization
Also a type of annealing phase 1. The purpose of the procedure is to bring all the crystals into a single form, as well as relieve the internal stress of the metal. There are two subspecies:
- softening - usually used as a final treatment, implies an improvement in plastic characteristics;
- strengthening – increases elasticity, especially important for hardening springs.
The temperature is selected depending on the alloy, usually 100-200 degrees higher than the recrystallization point. It is necessary to maintain the temperature for an hour or two, then allow it to cool slowly.
Isothermal annealing
The goal is to achieve high-temperature face-centered modification of iron (decomposition of austenite) to soften it. This results in a more uniform structure of the product. More often, this type of metalworking is used for small stampings, because they can be subjected to rapid cooling without problems. Process:
- heating is 20-30 degrees more than the material limit;
- short aging;
- rapid cooling is an advantage over other subspecies.
To eliminate stress
This is an operation of removing, removing the negative internal state of excessive hardness, due to which the metal becomes brittle and short-lived. It quickly deforms from external physical influences. The process involves temperatures from 700 to 750, then a slight cooling to 600 and holding for up to 20 hours, then slowly cooling under the influence of air.
Complete annealing
Used to create a plastic, uniform fine-grained structure. The most typical method of intermediate impact on rolled metal is after casting, forging, stamping and before cutting by any method. Stages:
- heating is 30-50 more than the steel limit;
- holding;
- very slow cooling with the oven - no more than 50-150 degrees in 60 minutes.
Incomplete
There are no significant transformations at the level of the crystal lattice, but hardness is imparted to previously plastic materials. This is especially necessary for structures formed by welded joints, as well as tools that require special strength. The method involves a temperature of about 700, and after 20 hours gradual cooling.
Hardening as the main type of heat treatment of steel
A very common method of heat treatment, as it allows you to make the product less susceptible to compression, shear, and also give it strength and durability, immunity to external physical influences. This occurs by imparting a needle-like structure to the metal. The substance hardens with “needles” due to a lack of alloying materials.
The workpiece is heated up strongly, and then cooled as quickly as possible, using external sources - water, oil, a solution with added salt. Due to the speed, diffusion processes do not have time to occur in the semi-molten alloy. It is cheapest to create water baths, but cracks may appear on the surface; an oil medium is the most preferable.
Normalization
The goals are to eliminate coarse grain, steel tension, and improve qualities for further processing. The tasks and process are reminiscent of complete annealing, there is one difference - cooling does not take place in an oven with the ability to control the temperature, but in ordinary air conditions.
Cryogenic heat treatment
Another thermal method of exposure, but without heating. The product is placed in a refrigeration unit, sometimes an entire workshop is used for large-sized structures. Low temperatures and subsequent warming reduces the risk of corrosion, extends service life, increasing strength.
Chemical-thermal treatment
The second name is cementation or CTO. Only the outer layer is processed by applying chemicals to it at a certain temperature. The medium can be different - gas, powders, liquids. The most commonly used are carbon or nitrogen.
Thermo-mechanical effect
TMO was used by blacksmiths in ancient times. These are any plastic deformations (impacts, compressions) produced by heating the entire product or element. It is usually combined with hardening, that is, after deformation it is quickly cooled.
Hardenability and hardenability of steel
These indicators determine the results of all of the above procedures. The first term is hardness, which is directly related to the amount of carbon, and the second is the depth of hardening, that is, which top layer has been subjected to changes.
Cooling methods
There are several environments in which temperature can be taken:
- air;
- liquid;
- molten salt;
- oil;
- brine;
- a combination of the above substances.
Selected depending on the type of heat treatment.
Conclusion
This is one of the most common metalworking methods in production; without it, hot stamping and cutting are often not started. We have listed all the main types of heat treatment of metals and alloys, their features, and to complete the article, watch a few videos:
To clarify the information you are interested in, contact our managers by phone 8 (908) 135-59-82; (473) 239-65-79; 8 (800) 707-53-38. They will answer all your questions.
Source: http://rocta.ru/info/termicheskaya-obrabotka-stali-metallov-chto-ehto-takoe-osnovnye-vidy-i-opisanie/
Types of heat treatment
Heat treatment (heat treatment) of steel, non-ferrous metals is the process of changing the structure of steel, non-ferrous metals, alloys during heating and subsequent cooling at a certain speed.
Heat treatment (heat treatment) leads to significant changes in the properties of steel, non-ferrous metals, and alloys. The chemical composition of the metal does not change.
Annealing is a thermal treatment (heat treatment) of a metal that involves heating the metal and then slowly cooling it. This heat treatment (i.e. annealing) comes in different types (the type of annealing depends on the heating temperature and the cooling rate of the metal).
Hardening
Hardening is a heat treatment (heat treatment) of steel and alloys, based on the recrystallization of steel (alloys) when heated to a temperature above critical; After sufficient exposure to the critical temperature to complete the heat treatment, rapid cooling follows. Hardened steel (alloy) has a nonequilibrium structure, so another type of heat treatment is applicable - tempering.
Oysters: benefits, harm, chemical composition, how many calories, rules of consumption
Oysters have been known for many years. In ancient times, this product was popular among the poor due to the high cost of animal meat. With its spread, the population of mollusks gradually declined. This led to an increase in the cost of seafood, which began to be considered a delicacy. The benefits of oysters for the body are associated with the presence of valuable substances.
Protein source recommended for consumption by men and women
Chemical composition of oysters
Seafood belongs to the family of mollusks (bivalves). A comfortable habitat is warm water bodies where both oyster colonies and solitary settlements are found.
The bivalve shell of mollusks is asymmetrical. Its size, shape and color vary significantly. Oysters live at depths of up to 70 m and have more than 50 varieties. Deep mollusks vary in size up to 50 cm, and flat mollusks - up to 5 cm.
Harvesting seafood is often seasonal. Their cultivation is possible in an artificial environment. Low temperatures are essential for adequate life activity.
Attention! It is necessary to differentiate between oysters and mussels. Seafood differs in shell appearance, structure and taste; the cost of mussels is significantly lower than oysters.
A substance is synthesized in the shell that helps increase size. Oyster shell composition:
- calcium carbonate;
- phosphate admixture;
- magnesium carbonate.
The product includes the following beneficial substances:
- tocopherol;
- retinol;
- ascorbic acid;
- vitamins belonging to group B;
- calcium;
- magnesium;
- potassium;
- phosphorus;
- iron.
Nutritional value:
- fats – 2.5 g;
- proteins – 8.7 g;
- carbohydrates – 4 g;
- water – 83 g.
The amount of dietary fiber is 1.1 g.
The delicacy is low in calories
Health Benefits of Oysters
The benefits of the product can be expected when consumed raw. Heat treatment leads to the loss of important components and taste.
The following useful properties are called:
- strengthening bone tissue;
- normalization of the functioning of the thyroid gland;
- lowering blood pressure and cholesterol levels;
- improvement of psycho-emotional state;
- reducing the risk of developing malignant tumors;
- restoration of visual acuity;
- increase in hemoglobin level.
Important! Including seafood in the diet has a positive effect on the condition of the skin.
What are the benefits of oysters for women?
Eating this delicacy helps prolong youth. Therefore, the product is recommended for women. The beneficial effect is due to the presence of arginine in the composition. The amino acid improves the condition of the skin, eliminating fine wrinkles. Hair becomes healthier and grows faster.
Source: https://poleznii-site.ru/pitanie/prochie-produkty/ustritsy-poleznye-svoystva-sostav-i-protivopokazaniya.html
