The steels can be divided in the following way:
General construction steels
According to DIN 17,100 these are the kind of steels that have not predicted heat treatment for them. The most important characteristic of these
steels is the mechanical properties (for example, tensile strength, tensile stress and extended relative length), the qualitative group and their characteristic for shaping.
Minimum tensile strength of 310 N / mm2 for steel St 33 to 690 N / mm2 is for Steel St 70-2. Tensile strength depends on the thickness of the product. For example, in St 50-2 steel with a thickness of 16 mm, the tensile strength of 295 N / mm2 and in the thickness of 60-80 mm is only 265 N / mm2.
The increase in relative length decreases with increasing strength, that is, the steel become brittle. Steel St 37-2 and St 70-2 have a relative length of 25% and 10%, respectively.
The qualitative group 2 and 3, having the same mechanical properties, divide the steel in terms of fragility and welding characteristics. The quality group steel, having the same mechanical properties, divides steel in terms of fragility and welding properties. The qualitative group 3 steel is of high quality in terms of low phosphorus, sulfur and nitrogen content it has.
The assignment of capability to shape is given by another character in the standard attribute (Table 1)
General construction steels are used for parts that are not under abrasion and need no hardening, such as template sequence, buttress, blocks, and so on.
Sheets and straps are made of soft and non-alloy steel and are often produced by cold rolling. In thicknesses of 0.5-3 mm (which is called a delicate sheet) is used to form (for example, deep stretch). Depending on the application, the delicate sheet is classified in terms of surface type and appearance and qualitative group (Table 2).
The delicate sheet and the white sheet (DIN 1616) has less than 0.5 mm thickness. These sheets are delivered with varying degrees of hardness and thickness.
Characteristic example: DIN 1616-0.30-T52 Very weak sheet
the thickness = 0.30 mm, the degree of hardness = T52 and the maximum hardness according to HR 30 Tm is 56.
automatic steels are non-alloy or low-alloy quality steels that have high level of sulfur and phosphorus, or -manganese, or lead. These steels are mainly used for serialization fragments (mass production) on automatic milling machines. Alloys, sulfur or lead cause crushing the filings, which results in increased chipping speed.
Example: 9 S 20; 9 SMnPb 28. Automatic carburetor steel10 S 20, upgradeable automatic steel 60 S 20.
Carburetor steel (or cementitious steel)
Carburetor steels are used for components that are more resistant to abrasion and bending, for this reason, it should have a tough, abrasion resistance surface, soft and tough brain with high strength. Carbureted steels are divided into two groups of non-alloy carbureted steels with a carbon content of less than 0.2% (for example, Ck 15 and Ck 10), and alloy carbureted steel, alloyed with manganese, chromium, molybdenum or nickel (eg 16 MnCr 5, 20 CrMo 4, 22 CrMoS 3 5). Carburetor alloyed steel have high tensile strength. For example, 16 MnCr 5 steel has a tensile strength of 1080-780 N / mm2, while this value in non-alloy steel C 10 is 490-630 N / mm2.
Refined steels are used for components that are subjected to heavy-tensile loading, bending, and a torsion of sudden loads. With special heat treatment, these steels have high tensile strength and increased toughness (energy absorption).
Non-alloyed refining steel is used for low strength components and small cross-sections (for example, C 60 and Ck 45 and C 35) and alloyed refining steels with chromium, molybdenum, nickel or vanadium alloys are used for high-bulk material loading components with large cross-sections (for example 34 CrNiMo 6 and 42 CrMo 4 and 38 Cr 2). The tensile strength can be increased to about 1,300 N / mm2, if the extension of relative length is 9%.
In a revamped state with letter V,
In the normalized annealing with the letter N,
In softened annealing with letters G and
In the heat treatment condition, for better machining, it is specified with the letter B.
Nitrified steels are used for components that are particularly subject to high and variable abrasion, and also are used due to the fact that they are not subject to change and twisted in terms of dimensionality under heat treatment. With the penetration of nitrogen to the surface of the work piece, a special anti-abrasion layer of iron nitride is produced.
Nitrified steels are low-alloy steels with nitride-forming elements of aluminum, chromium and vanadium (e.g. 31 CrMo 12 G or 34 CrAlMo 5 V). Of course, carbureted steel and low-alloy refining steel, gray cast-iron, sheet graphite-, and-spherical graphite, as well as hot-work steels, and-cold- work steel can be nitrified.
These steels include spring steel (e.g., C 75, 66 Si 7), high temperature resistant steels (eg X 4 NiCrTi 25 15), refractory steels (e.g. X 15 CrNiSi 25 20), stainless steels (e.g. X 5 CrNi 18 8) and non-magnetic steels (e.g. X 40 MnCr 18).
Non-alloy tool steels:
Non-alloy tool steels are used to make tools that are not subject to high thermal stress. These steels do not have a deep surface and lose their hardness above 200 ° C.
Heavy loads are tolerated by his stiff brain. The carbon content of these steels is 5% and 0.5-1. The higher the amount of carbon, the higher the hardness becomes. Non-alloy tools are produced in three groups of qualities. The W1 qualitative group has the highest degree of purity in terms of sulfur and phosphorus content.
Alloy tool steels:
In instrumentation and moulding, the work piece temperature during deformation has a decisive influence on the choice of steel. The used tools which their surface heat up to 200 ° C when working, are made of cold work steels. The Cr, W, Mn, Mo and Ni alloys make these steels are hardened even in large sections and not get severe twists.
Cold work steel:
The cold work steels must have a high abrasion resistance, as well as high compressive strength and toughness. In annealed state, it has good machining ability and in heat treatment it has less dimensional change and twisting.
Hot work steels:
The strength, hardness and abrasion resistance of the hot work steels even at very high temperatures will only change very little. These characteristics, as well as increased thermal stability, – thermal toughness, – return resistance, and – the resistance of temperature fluctuations are due to the alloying elements of chromium, vanadium, tungsten, nickel and molybdenum.