RU2415194C1 - Steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: steel contains carbon, manganese, silicon, aluminium, niobium, chromium, nitrogen, iron and impurities at following ratio of components, wt %: carbon 0.36 - 0.44, manganese 1.10 - 1.60, silicon 0.90 - 1.50, aluminium 0.005 - 0.025, niobium 0.010 - 0.030, chromium 0.80 - 1.20, nitrogen 0.008 - 0.020, iron and impurities - the rest. As impurities steel contains sulphur not more, than 0.030 %, phosphorus not more, than 0.030 % and copper not more, than 0.40 %.

EFFECT: reduced cleavability of balls at quenching in water, increased operational resistance due to increased hardenability and raised hardness on surface and through cross section.

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Description

The invention relates to ferrous metallurgy, in particular to high hardenability steel used for the production of grinding balls of particularly high hardness with a diameter of 80 to 100 mm

Known steel [1] used for the manufacture of grinding balls, containing (in wt.%):

carbon 0.45-0.65 manganese 0.60-1.00 silicon 0.60-1.20 aluminum 0.01-0.06 boron 0.0025-0.0040 copper 0.06-0.36 titanium 0.02-0.06 iron rest

A significant disadvantage of this steel is the insufficiently high wear resistance of balls with a diameter of 80 to 100 mm made of this steel, due to the low hardness on the surface and in cross section.

Also known steel [2], selected as a prototype, containing (in wt.%):

carbon 0.50-0.85 manganese 0.70-1.50 silicon 0.80-1.50 aluminum 0.002-0.06 one of the elements group containing niobium and cerium 0.0002-0.05 iron rest

The disadvantages of this steel are increased cracking when quenching in water, as well as insufficiently high operational resistance of balls with a diameter of 80 to 100 mm made of this steel.

The desired technical results of the invention are: a decrease in cracking during quenching in water, as well as an increase in the operational resistance of grinding balls with a diameter of 80 to 100 mm by increasing hardenability and increasing hardness on the surface and cross section.

To achieve this, steel containing carbon, manganese, silicon, aluminum, niobium and iron additionally contains chromium and nitrogen in the following ratio of components (in wt.%):

carbon 0.36-0.44 manganese 1.10-1.60 silicon 0.90-1.50 aluminum 0.005-0.025 niobium 0.010-0.030 chromium 0.80-1.20 nitrogen 0.008-0.020 iron rest

while the impurities are contained in the following amounts: sulfur - not more than 0.030%, phosphorus - not more than 0.030% and copper - not more than 0.40%.

The inventive chemical composition of the steel is selected based on the following premises.

The carbon content of 0.36-0.44% was chosen based on the fact that at a given carbon concentration, rack martensite is formed, which is less brittle than brittle plate martensite, which is formed at a carbon concentration of more than 0.44%.

The ratio of manganese is selected based on the fact that when the manganese content is up to 1.60%, an increase in hardness, hardenability and resistance to cracking is provided. The lower limit is chosen based on the fact that manganese with a content of less than 1.10% does not have the desired effect on hardness and hardenability.

Silicon up to 1.5% increases hardenability and increases the wear resistance of balls. With a decrease in silicon concentration of less than 0.90%, these characteristics significantly decrease.

With an increase in the chromium content to 1.20%, the hardness and hardenability of the steel increases and a finely dispersed structure is obtained, which in turn leads to an increase in the wear resistance of grinding balls. When the chromium content is less than 0.80%, a decrease in the hardenability of steel and, consequently, the wear resistance of the balls is observed.

The aluminum content (0.005-0.025%) was selected based on, on the one hand, the production of fine real grains, and on the other, the exclusion of unacceptable alumina non-metallic inclusions, which increase the tendency of the balls to crack during impact loads.

Nitrogen promotes the formation of aluminum nitrides in steel. A nitrogen concentration of less than 0.008% does not lead to the formation of nitrides, which ensures the grinding of the actual grain and, as a result, reduces the tendency of the balls to crack under shock loads. With an increase in nitrogen of more than 0.020%, there may be cases of spotted segregation and bubble formation in steel as a result of "nitrogen boiling".

When the niobium content is in the amount of 0.010%, complex alloyed carbides are formed, which positively affect the grinding of austenitic grains and cleanse their boundaries of harmful impurities, as well as increase impact strength and hardenability. An increase in the niobium content in excess of 0.030% is economically disadvantageous and impractical due to its negative effect on the fluidity of steel and on the surface quality of the balls, as well as their cracking.

The limitation of the content of sulfur, phosphorus and copper is selected based on the surface quality of the finished grinding balls.

A series of experimental swimming trunks with the claimed chemical composition was smelted in arc furnaces DSP-1 00N10. The chemical composition is shown in table 1. After casting the steel at the continuous casting machine, the balls were rolled and heat treated from the rolling mill using the two-stage cooling technology with self-tempering. The test results are shown in table 2. Thus, the claimed chemical composition provides increased hardness and operational stability of the balls.

Information sources

1. A.S. USSR No. 1446189, C22C 38/16.

2. A.S. USSR No. 1733495, C22C 38/12.

Table 1 The chemical composition of steel Structure C Mn Si Al Nb Cr N P S Fe one 0.35 1.46 1.29 0.014 0.012 0.88 0.013 0,021 0.014 rest 2 0.40 1,60 1.30 0.011 0.01 1.20 0.014 0.016 0.012 rest 3 0.43 1.48 1.42 0.016 0.02 1,11 0.012 0,023 0.016 rest four 0.44 1,58 1.24 0.012 0.015 1.15 0.011 0.015 0.013 rest 5 0.42 1.25 1.36 0.013 0.017 1.14 0.015 0.024 0.018 rest 6 0.48 1,52 1.48 0.014 0,022 1.10 0.013 0,021 0,023 rest prototype 0.50-0.85 0.70-1.50 0.80-1.50 0.002-0.06 0.0002-0.05 - - 0.022-0.032 0.018-0.024 rest

table 2 Mechanical properties of steel Structure Hardness, MPa Wear, g Ball cleavage,% The magnitude of the martensitic and semi-martensitic zones, mm on the surface at a depth of 1/2 R (25 mm) one 495 415 0.31 0 38 2 514 477 0.23 0.5 fifty 3 555 514 0.20 2.5 fifty four 534 495 0.22 2.1 fifty 5 555 495 0.23 2.7 fifty 6 578 534 0.18 3.0 fifty prototype 496-524 - 0.19-0.41 2.2-3.7 19-28

Claims (1)

Steel for the production of grinding balls with a diameter of 80 to 100 mm, containing carbon, manganese, silicon, aluminum, niobium, iron and impurities, characterized in that it additionally contains chromium and nitrogen in the following ratio, wt.%:
carbon 0.36-0.44 manganese 1.10-1.60 silicon 0.90-1.50 aluminum 0.005-0.025 niobium 0.010-0.030 chromium 0.80-1.20 nitrogen 0.008-0.020 iron and impurities rest,
while as impurities, sulfur is contained - not more than 0.030, phosphorus - not more than 0.030 and copper - not more than 0.40.