Castings

Abrasion resistant steel and Cr-cast iron

Conversion table of produced steels. We prefer to supply final product according to Chomutov marking. On special customer´s request is possible to supply castings according to other standard.

ČSN 42 2920 (Austenitic Mn Steel)

Chemical composition in percents

The castings are delivered as austenitized (+AT).

Mechanical properties and values

ČSN 42 2921 (Austenitic Mn Steel)

Chemical composition in percents

The castings are delivered as austenitized (+AT).

Mechanical properties and values

ČSN 42 2920 (Z) (Austenitic Mn Steel with narrower range of chemical composition)

Chemical composition in percents

The castings are delivered as austenitized (+AT).

42 2922 (Z) (Austenitic Mn Steel with narrower range of chemical composition)

Chemical composition in percents

The castings are delivered as austenitized (+AT).

42 2924 (Z) (Austenitic Mn Steel with narrower range of chemical composition)

Chemical composition in percents

The castings are delivered as austenitized (+AT).

42 2920 (Zr) (Austenitic Mn Steel with fine grained structure including Zr)

Chemical composition in percents

The castings are delivered as austenitized (+AT).

42 2921 (Zr) (Austenitic Mn Steel with fine grained structure including Zr)

Chemical composition in percents

The castings are delivered as austenitized (+AT).

It is typical of the austenitic manganese steels that at slow cooling the carbon carbide Fe3C, and/or chrome carbide is generated,and deposited on the austenitic grain edges.
The heat treatment will prevent the generation of carbides as much as possible, and make austenitic structure as fine as possible as well.
By application of narrower range of chemical composition and/or by addition of zircon (Zr) at the production of austenitic manganese steel, the microstructure will show significantly finer austenitic grain, and therefore the steel castings made of these steels have better mechanical properties.

Steels ( ČSN 42 2920, ČSN 42 2921, ČSN 42 2920 (Z), ČSN 42 2921 (Z), 42 2922 (Z), 42 2924 (Z), 42 2920 (Zr), 42 2921 (Zr) ) are designed for the most drastic stress conditions by strong dynamic impacts and pressure. Through these characteristic stresses, a strengthened layer develops on the working surface of the parts with a thickness of several millimetres. The core of the parts maintain a high toughness so that they will not tend to break. If the parts are not subjected to such stresses, but only to abrasion, the strengthened and hardened surface layer cannot develop. These steels in their resistance to abrasion begin to behave similar to carbon steel with a high C-content of about 0.80%. By a C-content greater than 1,30%, the plasticity characteristics R_e, A, Z, KC and K decrease. The result of this is then an increase in hardness. At a C-content near to the lowest limit of the range, a lower thickness of the strengthened and hardened layer occurs and, in the same time, the hardness – abrasion resistance decrease.

Weldability

Difficult. These steels are not suitable for welding. They have no use for local heating. In unavoidable cases, preheating to 350°C is required. Only short weld beads are to be done with offset to Ievel the temperatures around the weld. The weld metal normally never achieves the characteristics of welded steels. After welding, heat treatment is required again. For weld deposits of the worn parts, the same principles apply. It depends on the type of weld metal whether or not heat treatment is necessary. In general, neither welding nor weld deposits are recommended.

Machinability

Very difficult. Tool develops great pressure in the places of cut which results in high hardening and strengthening of the surface appears. To grind the surfaces is more suitable However this develops local heating and creates micro-cracks. Grinding must be done with small reductions and cooling. It is recommended to use the parts directly without any machining.

Application

Changeable parts of machines subjected to abrasion by strong shocks and pressures, where no machining is require, mainly for machines doing earth work. Crusher and granulators jaws, conical and centrifugal crushers in quarries, plates of fan mills, hammers and beaters in rotary crushers and grate bars, bandage of the sand mill wheels, teeth of excavators, blades of bulldozers, etc. The steels are not suitable for environments of classical abrasion, e.g. in wet preparation of ores, preparation of ceramic raw material, etc. For high stress hammers of crushers at scrap yards (e.g. preparation of wreck a cars), is used the modified steel, that is delivered under mark HSMo.

EXTRA L-1

Mechanical properties and values

R_m = F_m x L₀cm / 4(S₀cm² x L₀cm)

For short:

R_m = F_m / 4 x S₀cm²

where:
(S₀ cm² x L₀ cm) = section modulus
4 = constant of section modulus

Weldability

Welding or welding up of hard metals on the surface is prohibited!

Machinability

Only grinding. The castings are designed for direct applications.

Application

The alloy is designed exclusively for wear resistant parts where only wear actuates without dynamic impacts and higher pressures. Suitable for the mineral, ceramic and brick industries, etc. for mixing, kneading and wet and dry grinding of fine fractions. For lining of rotating sand blasters, suspension plates, lining of concrete mixtures mixing vessels, lining of mixing blades, etc. They can also be used for lining of the second chambers of cement mills. By larger thickness in the thermal axes of the castings, segregation and liquation occur displaying itself in these places as inhomogeneity, which mayor may not shown itself as defect according to how the steel is used. For mentioned typical manifestation, it is more advantageous to use derived material EXTRA L-1A with a lower carbon content and with almost the same mechanical properties. The alloys are markedly brittle and difficult to manipulate as well as transport. They are to be used in temperatures up to 250°C.
Material EXTRA L-1A is suitable for crushing rotary bars into machines for preparation of demolition material.

EXTRA L-5

Mechanical properties and values

R_m = F_m x L₀cm / 4(S₀cm² x L₀cm)

For short:

R_m = F_m / 4 x S₀cm²

where:
(S₀ cm² x L₀ cm) = section modulus
4 = constant of section modulus

Weldability

Welding and welding hard metals on the surface is prohibited!

Machinability

Only grinding. The casting are designed for direct usage.

Použití

The castings from this alloy are designated for abrasive stress resulting from dynamic impacts and pressures of medium intensity. They are suitable and required mainly for cladding of the first chamber in cement mills as well as for their casing and front walls. They are especially suitable for grinding of dry materials where the working surface of the jacket cladding has been hardened by at least 5 HRC to a long-term surface hardness 51-54 HRC into a depth of 0.03 – 0.08 mm under the impact of the strokes of grinding balls. It is also suitable for casting of larger grinding balls to be used in first chambers. Not suitable for classical abrasion where surface hardening cannot occur. Not suitable also for dry or wet grinding of very hard and abrasive mineral raw materials based on SiO₂ AI₂O₃ x SiO₂ and the like. Applicable for operating temperatures up to 250°C.