RU2425169C2 - Steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: steel contains carbon, silicon, manganese, aluminium, nitrogen, chromium, nickel, calcium, iron and impurities at following ratio of components, wt %: carbon 0.65 - 0.80, manganese 0.70 - 0.90, silicon 0.20 - 0.40, aluminium 0.005 - 0.020, nitrogen from more, than 0.01 to 0.025, chromium 0.30 - 0.60, nickel 0.01 - 0.30, calcium 0.0005 - 0.0040, iron and impurities - the rest. As impurities steel contains sulphur - not over 0.030 %, phosphorus not over 0.030 % and copper - not over 0.30 %.

EFFECT: raised wear resistance and hardness on surface and in cross section of balls.

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Description

The invention relates to ferrous metallurgy, in particular to steel used for the production of grinding balls with a diameter of 40-100 mm

Known steel [1], 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 - the rest

A significant drawback of this steel is the increased fragility of the balls due to the formation of a boride eutectic in the microstructure of the metal.

Also known steel [2], containing (in wt.%):

carbon 0.95-1.10 manganese 0.15-1.25 silicon 0.10-0.70 chromium 1.30-1.65 iron - the rest

A significant disadvantage of this steel is the high tendency of the balls to crack during quenching in water.

Known steel [3] having abrasion resistance, containing (in wt.%):

carbon 0.35-0.80 aluminum 0-2.00 manganese 0-2,50 nickel 0-5.00 chromium 0-5.00 molybdenum 0-0.50 tungsten 0-1.00 boron 0-0.02 titanium 0-2.00 zirconium 0-4.00 sulfur 0-0.15 nitrogen less than 0.03

if necessary, copper 0-1.50

if necessary, at least one element selected from the group: niobium, tantalum and vanadium,

provided: Nb / 2 + Ta / 4 + V≤0.5

if necessary, at least one element selected from the group: selenium, tellurium, calcium, bismuth, lead with a content of less than or equal to 0.1%.

the rest is iron and inevitable impurities, under the following conditions:

0.35≤Si + Al≤2.00

0.1≤Mo + W / 2≤0.5

0.05 <Ti + Zr / 2≤2.00

Subject to the following ratios:

0.1≤C-Ti / 4-Zr / 8 + 7 × N / 8≤0.55

Ti + Zr / 2-7 × N / 2≥0.05;

1.05 × Mn = 0.5 if B≥0.0005 and K = 0 if B <0.0005.

Significant disadvantages of this steel are the wide concentration boundaries of chemical elements, leading on the one hand to low hardness and wear resistance of balls, on the other hand, increasing their tendency to crack during quenching in water and operation.

Known selected as a prototype steel [4], containing (in wt.%):

carbon 0.30-0.70 manganese 0.50-2.00 silicon 0.01-0.50 aluminum ≤0.07 nitrogen ≤0.01 chromium 0.05-0.50 nickel ≤0.30 calcium 0.0005-0.0060 sulfur 0.003-0.05 phosphorus ≤0.03 copper ≤ 0.50 iron - the rest

The disadvantage of this steel is the poor performance of the balls, due to unstable hardness on the surface and the cross section of the balls.

The desired technical results of the invention are: increased wear resistance and hardness on the surface and in the cross section of the balls.

To achieve this, steel for the production of grinding balls with a diameter of 40-100 mm, containing carbon, manganese, silicon, aluminum, nitrogen, chromium, nickel, calcium, iron and impurities, characterized in that it contains components in the following ratio (in wt.% )

carbon 0.65-0.80 manganese 0.70-0.90 silicon 0.20-0.35 aluminum 0.005-0.020 nitrogen from more than 0.01 to 0.025 chromium 0.30-0.60 nickel 0.01-0.30 calcium 0.0005-0.0040 iron and impurities rest,

while it contains sulfur as impurities - not more than 0.030%, phosphorus - not more than 0.030% and copper - not more than 0.30%.

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

Carbon content in the range indicated is selected based on the provision of high hardness on the surface and at _^half the radius of the ball diameter of 40-100 mm. When its concentration in steel is less than 0.65%, the hardness of the balls decreases, and with an increase in carbon concentration of more than 0.80%, their tendency to crack formation increases.

The ratio of manganese is selected based on the fact that when the manganese content is up to 0.90%, 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 0.70% does not affect hardenability.

Silicon within the claimed limits eliminates the split balls during shock loads. At a silicon concentration of less than 0.20%, the tendency of the balls to crack during impact loads significantly increases. In the manufacture of steel balls above the upper declared limit of the silicon content of more than 0.40%, the tendency of the balls to crack during hardening increases.

With an increase in the chromium content to 0.60%, the hardness and hardenability of steel increases, which in turn leads to an increase in the wear resistance of grinding balls. When the chromium content is less than 0.30%, there is a decrease in the hardenability of steel, and, consequently, the hardness and wear resistance of the balls.

The established limit of nickel concentration from 0.01 to 0.30% has a positive effect on reducing the tendency of balls to crack during impact loads and increases the hardenability of steel. When the nickel content is less than the specified limit, the required hardenability of the steel is not provided. Nickel content of more than 0, 30% is not economically feasible.

The content of aluminum from 0.005 to 0.020% and calcium from 0.0005-0.0040% is selected based on, on the one hand, obtaining fine real grain, and on the other, obtaining a favorable form of non-metallic inclusions, as well as the exclusion of unacceptable alumina non-metallic inclusions that increase the tendency of balls cracking under shock loads.

A nitrogen concentration of less than 0.01% does not lead to the formation of nitrides, which ensure the grinding of the actual grain, and as a result, reduce the tendency of the balls to crack during impact loads. With an increase in nitrogen of more than 0.025%, there may be cases of spotted segregation and the formation of bubbles in the steel as a result of "nitrogen boiling".

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 melts with the claimed chemical composition was smelted in DSP-100N 10 arc furnaces. 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 crack resistance and hardness of the balls.

Information sources

1. A.C. USSR No. 1446189 C22C 38/16.

2. GOST 7524-89 "Steel grinding balls for ball mills."

3. RU 2327802 C2, C22C 38/54, 06/27/2008.

4. JP 08-337843 F, C22C 38/18, 24/12/1996.

Table 1 The chemical composition of steel Structure FROM Si Mn Cr AI Ca N Ni S P Cu Fe one 0.65 0.20 0.70 0.30 0.005 0,0005 0.005 0.01 0.008 0.019 0.09 rest 2 0.70 0.28 0.82 0.40 0.009 0.0010 0.008 0,03 0.009 0,020 0.06 rest 3 0.80 0.24 0.75 0.42 0.018 0.0030 0.010 0.10 0.012 0,029 0,07 rest four 0.68 0.33 0.79 0.45 0.016 0.0037 0.013 0.28 0.005 0,028 0.14 rest 5 0.70 0.26 0.79 0.60 0,020 0.0040 0,022 0.25 0,020 0,023 0.25 rest 6 0.75 0.35 0.80 0.50 0,025 0.0020 0,025 0.30 0,030 0,030 0.30 prototype 0.95-1.10 0.10-0.70 0.15-1.25 1.30-1.65 - - - - - - 0.06-0.36 rest

table 2 Mechanical properties of steel Structure Hardness, MPa Wear, g The number of balls with cracks After heat treatment After a 10-fold drop one 490 0.44 0 0 2 575 0.31 1,6 4.0 3 595 0.19 2.1 4.8 four 517 0.37 2.9 4.3 5 524 0.33 2.0 3.9 6 575 0.30 1,5 4.6 prototype 440-560 0.31-0.45 3.2-7.0 5.8-10.0

Claims (1)

Steel for the production of grinding balls with a diameter of 40-100 mm, containing carbon, manganese, silicon, aluminum, nitrogen, chromium, nickel, calcium, iron and impurities, characterized in that it contains components in the following ratio, wt.%:
carbon 0.65-0.80 manganese 0.70-0.90 silicon 0.20-0.40 aluminum 0.005-0.020 nitrogen from more than 0.01 to 0.025 chromium 0.30-0.60 nickel 0.01-0.30 calcium 0.0005-0.0040 iron and impurities rest,
while it contains sulfur as impurities - not more than 0.030%, phosphorus - not more than 0.030% and copper - not more than 0.30%.