Method of manufacture high carbon content steel

Details Method of manufacture high carbon content steel Method of manufacture high carbon content steel

1997-03-27

1999-01-05

Yee, Deborah

Metal treatment

Process of modifying or maintaining internal physical...

With casting or solidifying from melt

148548, C21D 936

Patent

active

058557016

DESCRIPTION:

BRIEF SUMMARY
OBJECT OF THE INVENTION

The present invention relates to steel alloys with high carbon content, particularly for use in making wearing parts, more particularly for grinding media such as grinding balls.


STATE OF THE ART

In the mining industry, it is necessary to release valuable minerals from the rock in which they are embedded taking into account their concentration and extraction.
For such release, the mineral must be finely ground and crushed.
Considering only the grinding stage, it is estimated that 750,000 to 1 million tons of grinding media are annually used worldwide, in the form of spherical balls or truncated cone-shaped or cylindrical cylpebs. Grinding media commonly used: 1%) formed by rolling or by forging followed by heat-treatment to obtain a surface hardness of 60-65 Rc. chrome) formed by casting and heat-treatment to obtain a hardness of 60-68 Rc in all sections. than 2%), untreated and with a hardness of 45-55 Rc obtained by casting.
All of the present solutions have their own disadvantages: forging or rolling machines and the heat-treatment apparatus which raises energy consumption. linked with the alloy elements (mainly the chrome) and the heat-treatment. are generally fairly low but their wear-resistance properties are not as good as the other solutions. Further, usually only grinding media of less than 60 mm are industrially produced.
Overall, in the case of minerals where the rock is very abrasive (e.g. gold, copper, . . . ), the present solutions do not completely satisfy the users as the costs of the products and materials subject to wear (grinding balls and other castings), still contributes greatly towards the cost of production of the valuable metals.


AIM OF THE INVENTION

The object of the invention is to provide steels having improved properties and, particularly, to overcome the problems and disadvantages of the state of the art solutions for wear parts (particularly grinding media). The composition, casting and cooling conditions after casting of the invention allow wear resistance, especially in very abrasive conditions, which is comparable to forged steels and chrome cast-irons but with less cost and superior to pearlitic cast-irons (but with a comparable cost).
Other objects and disadvantages of the present invention will become apparent from reading the following description of the characteristics of the invention and preferred embodiments thereof.


BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1 and 2 are micrographs showing structures of the steels obtained according to the invention.


CHARACTERISTIC ELEMENTS OF THE INVENTION

The invention provides an alloy steel of high carbon content and the process of production of grinding media made of the alloyed steel characterized in that their composition complies with the following composition expressed in % weight:


______________________________________ carbon from 1.1 to 2.0% manganese from 0.5 to 3.5% chromium from 1.0 to 4.0% silicon from 0.6 to 1.2% ______________________________________
The remainder being made up of iron with the usual impurity content, such that they provide a metallographic structure mainly comprising non-equilibrium fine pearlite, with a hardness of between 47 Rc and 54 Rc.
Preferably, for grinding media, particularly grinding balls, the carbon content is between 1.2 and 2.0% preferably between 1.3 and 1.7% to achieve an optimal wear resistance while maintaining shock resistance.
In practice, it is advisable to select the manganese content as a function of the diameter of the grinding ball and the rate of cooling to obtain the fine pearlite structure.
The following compositions are interesting with regard to the resistance to wear for grinding media, particularly grinding balls of 100 mm diameter.


______________________________________ carbon in the order of 1.5% manganese in the order of 1.5 to 3.0% chromium in the order of 3.0% silicon in the order of 0.8% ______________________________________
For grinding balls, of 70 mm diameter, an alloy composition of:


_________________________

REFERENCES:
Patent Abstracts of Japan, vol. 6, No. 78, May 15, 1982, JP57-13150.
Patent Abstracts of Japan, vol. 14, No. 77, Feb. 14, 1990, JP1294821.
Derwent Publications Ltd., Database WPI, Week 7814, Feb. 23, 1978, JP53019916.

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