CS208163B2 - Ferrochromecarbon alloy - Google Patents

Abstract

1362648 Ball mills BOHLER & CO Gebr 23 March 1973 [23 March 1972] 14226/73 Heading B2A [Also in Division C7] A ball-mill lining comprises plates having grinding surfaces formed with grooves which have in cross-section the shape of a segment of a circle and substantially the same radius as the largest grinding balls used in the mill, the plates being castings of an iron-chromiumcarbon alloy which contains 0.05 to 0.5% nitrogen, percentage being by weight. The balls may be of an iron-chromium-carbon alloy with a chromium content exceeding 12% hardened to a Rockwell C hardness about 60. The chromium content exceeds that of the plates. An alloy composition for the plates is set forth (see Division C7).

Description

(54) Geochromochulous alloy

The invention relates to the use of an iron-carbon-carbon alloy.

It is customary to produce grooved plates as well as grinding balls for ball mills from iron-carbon-alloy alloy, taking into account in particular that the residual austenite content of these tools when installed is small, for example less than 5%. Impact loads turn the residual austenite into martensite, which creates a risk of embrittlement and flaking and hence device failure. This is the reason ^{1 * * * 5} , however, the residual austenite must be contained in as little as possible; amount.

The abovementioned drawbacks are overcome by the use of an iron-carbon-carbon alloy containing, by weight, 0.5 to 3% of carbon, 5 to 30% of chromium, 0.5 to 2% of silicon, 0.5 to 5%, preferably 0.8 to 1.2 v _/ manganese 0.05 to 0.5%, advantageously 0.1 to 0.3 ° / o nitrogen and optionally a trace to 5%, suitably 0.5 to 1.5% molybdenum, from traces up to 5% tungsten, steppes up to 1% vanadium, traces up to o / o nickel and traces up to 0.5% aluminum, zirconium and titanium, singly or at once, the rest of iron and non-removable impurities as a material for lining the ball mills.

Although it has been found to date that large residuals of austenite are essentially harmful, attempts have shown that, under comparable loads, the service life of the flute plates can be increased by at least 20% when cast from a conventional iron-carbon-carbon alloy but with nitrogen addition. The possible amount of this additive is dependent on the amount of nitride-forming elements, in particular the amount of manganese, chromium and molybdenum and, if appropriate, aluminum, zirconium and titanium, in the usual alloy melts, and can range from 0.05 to 0.5% by weight. . In particular, the weight of the content of the pulp is between 0.1 and 0.3%.

Accordingly, the invention is based on the discovery of a novel feature of the above-mentioned alloy, that in using it as a material for the internal lining of ball mills, the above-mentioned failures do not occur. At present, however, it is not clearly established whether the nitrogen and wear improvements are due to an increased proportion of residual auístenite or nitride forming elements, or both interact. Experiments have all shown that the nitrogen additions according to the invention are particularly advantageous in particular in the region of the highest stresses in the mill, i.e. coarse grinding.

For ball mills provided with such flute plates as; The grinding balls are expediently used with an overwhelming content greater than that of chromium (grinding plates, the chromium content of the balls being less than 12% by weight).

The flute plates can be used in uncured, cured and tempered. or · compensating _; state as usual iud ^ else ^ ik without grooves. The grinding balls are usually hardened to a hardness of over 60 HRC if they contain 12% by weight or more of chrolir.

Addition of nitrogen to. grinding ball alloys have not generally yielded any detectable results. However, if alloys containing, in small amounts by weight, aluminum, zirconium or titanium up to a maximum of · 0.5% for each additive are used for the grinding balls, the wear by nitrogen additive is reduced somewhat by up to 0.5 ° / o.

Claims (1)

SUBJECT Use of an iron-carbon alloy containing, by weight, 0.5 to 3% carbon, 5 to 30% chromium, 0.5 to 2% silicon, 0.5 to 5%, suitably 0.8 to 1.2% w / w manganese 0.05 to 0.5%, advantageously 0.1 to 0.3% nitrogen, and, optionally, traces to 5 o / _0, suitably 0.5 to 1.5% molybdenum, from traces to the invention 5% tungsten, traces up to 1% vanadium, traces up to 5 o / ₀ nickel and traces up to 0.5% aluminum, zirconium and titanium, individually or at the same time, the remainder iron and non-removable impurities as material for lining the ball mills.