Nowadays, it is quite difficult to overestimate the importance of metallurgy products that are widely used in industry, construction, the manufacture of household utensils, household goods. But alloy steels deserve special attention, without which a large number of industries (engineering, petrochemical, energy, food, manufacturing of special structures, the main purpose of which is work in aggressive conditions) could not fulfill their main functions.
A logical question arises: what is alloy steel and its alloys? What is the classification of alloying elements? What are the main characteristics and properties of high alloy steel? We will try to answer these and some other questions in the most detailed manner in our article.
What is alloy steel?
Let's first find out what this metal is. Alloy steel is an alloy of iron with carbon, which incorporates special elements that affect the main mechanical or physical properties of the final products of the metallurgical industry. Elements that are added to the basic composition of the alloy are called alloying. Chrome, nickel, vanadium, manganese, copper - their main group.
Types of steel
There is a classification of alloying elements, which is based on their percentage in the alloy:
- High alloy steel - 10-50%.
- Medium - doped - 2.5-10%.
- Low alloyed up to 2.5%.
Types: high alloy steels, alloys
Consider another interesting point. High alloy steel and its alloys are also classified. Each of the following types is used in certain conditions:
- Heat resistant or heat resistant steels.
- Corrosion resistant.
Based on the percentage of the alloying element, the following types are distinguished:
- Chrome Manganese Steel.
- Nickel Chromium.
- Chrome
The use of high alloy steels
Where is such metal used? High alloy steels and their alloys are integral components in the production of various products. The following industries cannot do without using them:
- Chemical.
- Oil industry.
- Engineering.
- Construction.
- Production of structures, the main purpose of which is to work in aggressive conditions (high temperature, extremes).
Adding alloying elements allows you to achieve certain mechanical properties. Therefore, high alloy steel is used as a cold resistant component. This metal is especially common in mechanical engineering. The most popular are high alloyed austenitic steels, in which the alloyed component accounts for about 55%, and the rest is iron, chromium (about 18%), nickel (8%). Alloying components of a similar composition determine the further purpose of the manufactured products.
The use of corrosion resistant steels
Corrosion resistant high alloy steels are used in a gaseous environment or alkaline acid. Their characteristic difference is a low carbon content of approximately 0.12%. Further alloying and heat treatment make it possible to obtain a special alloy that can withstand the aggressive conditions of a gas or liquid metal environment.
The use of steels containing tungsten or molybdenum at the level of 7% and boron allows working at temperatures up to 1100 degrees. Tungsten and molybdenum are elements that belong to hardeners. To increase the scale resistance of the manufactured products, silicon or aluminum is added as alloying elements. Such designs can be used as heating elements or furnaces.
The main characteristics of the metal
High alloy steel has properties and characteristics that allow more widespread use of manufactured products. Such steels have the following characteristics:
- Strength (achieved through heat treatment).
- Corrosion Resistance
- Resistance to deformation processes.
- Plasticity (in comparison with carbon steel, plasticity is many times greater).
- Non-magnetic (steel used in mechanical engineering).
- Elasticity.
- Hardenedness.
- Weldability.
Due to the fact that the alloy formula is different, various properties are obtained. The structure is easily changed due to heat treatment and alloying components. Thus, you can get the properties that are required by the terms of the project. For example, high-alloyed 18% chromium steel may contain nickel, which makes it possible to obtain corrosion resistance and cold brittleness.
Welding high alloy steels allows you to get products that can be used in any climatic conditions. So, the stamp welding method allows you to use the final product at critically low temperatures - up to minus 253 degrees Celsius. Special processing with silicon allows to obtain ferrosilides that can work in strong acids (nitric, phosphoric and others).
High alloy steel is characterized by hardness and high abrasion resistance. So, acid-resistant materials are C15 and C17, and chromium, vanadium and manganese increase the wear resistance of the alloy.
Types of high alloy steels by thermal properties
Based on thermal characteristics, there is the following classification:
- Platinum (EN42) - is used to produce electrodes that are used in incandescent lamps. This is because the expansion coefficient is the same as that of glass.
- Elinvar (X8H36) - ideal for watch springs and measuring instruments. This is because the elastic modulus is constant and does not collapse at temperatures from -50 to +100 degrees Celsius.
- Invar (I36) - is used for the production of standards, calibration elements, since the expansion coefficient is zero.
An interesting property of corrosion steel (only high alloy stainless steel) is its magnetism. Therefore, non-magnetic and magnetic types of such metals are distinguished. The former are divided into soft and magnetically hard subspecies, and the latter are composed of cobalt and chromium.
GOST: high alloy steels
The requirements for such strong metals and heat-resistant alloys are regulated by special standards, namely GOST 5632-72.
High alloy steels
The following steel grades are most demanded and known:
- Ferritic: 1528, 1217, 08181, 1525, 0818, 1013.
- Martensitic: 1511, 4092, 1811, 40102, 9518, 25132, 20172, 131122, 4013, 2013, 20172, 131432.
- Austenitic-martensitic: 07166, 081753, 08176, 091771.
- Austenitic-ferritic: 08Kh21N6M2T, 08Kh22N6T, 08Kh20N14S2, 20Kh23N13, 12Kh21N5T, 03Kh22N6M2.
- Martensitic-ferritic: 1213, 1812, 14172, 1512.
- Austenitic: 05X18H10T, 45X22H4M3, 45X14HMB2M, 10X14G14H4T, 03X18H10T, 08X16H13M2B, 12X18H12T, 03X18H12, 03X16H15M3B, 10X11H23T3MR, 20X23H18, 10X9HNX20X20X20X20X20H20.
The use of alloying steel grades:
- 4013, 3013 - used for carburetor needles, springs for vehicles, surgical instruments.
- 12X17 is a high-alloy steel grade used for the manufacture of kitchen utensils or household items.
- 20X13, 12X13, 08X13 - used for the manufacture of elements of hydraulic units, structures that work in slightly aggressive conditions.
- 95X18 - used for the production of high hardness ball bearings.