JPS62146238A - Novel production of steel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Background of the invention The present invention relates to a new steel.

Wear is one of the most commonly encountered problems with equipment used in mining operations. There is a growing trend towards mechanical systems in mining. Their success depends in large part on overcoming the problems of severe abrasive wear, which in South Africa is tied to the mining and handling of very hard abrasive quartzite ores. To justify the expense of creating such a system, these σ)
Parts must have as long a wear life as possible.

In mining environments, wear occurs due to abrasion effects and also due to corrosion by mineral waters. Therefore, regular stainless steel will last considerably longer than mild steel in a mining environment, absent abnormal abrasion, due to stainless steel's corrosion resistance.

It is an object of the present invention to provide a new steel that has greater corrosion and abrasion resistance than commercially available steels.

SUMMARY OF THE INVENTION The steel of the present invention, excluding iron and incidental impurities, has a
It consists of from 0.27% carbon, from ZO to 8.5% chromium and from 2.8% to 3.2% nickel (all percentages by weight). Chromium should aim for a nominal 8%.

Furthermore, according to the invention, σ) If incidental impurities are present, they must not exceed the following percentages:

Sulfur 0 mouths 08. Phosphorus 0.02, copper
0.2 Tin 0.05, Titanium 0.00
1. In the as-rolled condition, this steel exhibits a fairly high Vickers hardness after 7 baths, but
Charpy measurements show relatively low toughness. To improve toughness, steel is heated to a temperature of around 1100℃,
Must be quenched in oil. Tempering at temperatures between 200° and 25°C further improves the M properties. Further heat treatment does not improve toughness, but a small increase in hardness can be obtained at the expense of some toughness.

DESCRIPTION OF EMBODIMENTS In an embodiment of the present invention, a steel containing the following elements in addition to iron in weight percentages was prepared.

CO,24, Cr 7.08, Ni 3.2
, S O,007°P O,012, Si O,02
A 5 Kv ingot of 7, Mn 0.02 and Mo 01 O1 54 mm square was rolled into 12 flat bars in approximately 7 passes. At the beginning of each bath the temperature was 'r''zl100'c. The finishing temperature was not measured.

Samples of finished bars were cut and polished. The Pinkers hardness and toughness of one rolled sample and four samples subjected to different heat treatments were measured. The results are shown in the table below.

*OQ = The skull structure of the oil quench heat-treated product was a microstructure of low carbon martensite with retained austenite.

4 tons of the above steel was made by local steel mills,
Test parts were made. The part was heat treated as sample A5. The parts were bath-welded together before heat treatment.

The parts were characterized by high strength and good ductility.

The steel also exhibited high hardness with good toughness. Usually hardness and toughness are mutually exclusive.

As shown in Figure 1, the limits for many impurities are quite high, so standard steelmaking operations and equipment can be used.

It has been found that no special machining operations are required as the steel can be easily cut and bath welded.

Due to its hardness and toughness, the pot has only 40% machinability compared to steel En9.

The product was also well served due to the synergistic effect of corrosion and abrasion. Although commercial stainless steels are more corrosion resistant, they have higher coefficients of friction making them unsuitable for use in applications involving sliding wear such as vibratory conveyors.

Claims (1)

Claims: (1) 0.22 to 0.27% carbon, 7.0 to 8.5% chromium and 2.8 to 3.2%, excluding iron and incidental impurities. 1. A method for manufacturing steel, which comprises making a molten metal of nickel (all expressed in weight percent) and casting the molten metal to form an ingot. (2) Claim No. 1 characterized in that when the following impurities are present in the molten metal, they do not exceed the following percentage:
). Sulfur 0.008, Phosphorus 0.02, Copper 0.2 Tin
0.03, titanium 0.001, manganese 0.5, molybdenum 0.06 and aluminum 0.05 (3) characterized by a process involving rolling an ingot in multiple baths to form a steel product. A method according to any one of claims 1 to 2 above. (4) The method according to claim (3), characterized in that the steel product is heated to a temperature of about 1100° C. and then quenched in oil. (5) A method according to claim (4), characterized in that the hardened product is tempered at a temperature between 200° and 250°C. (6) Furthermore, heat the product to a temperature of about 1100°C,
Quench in oil and then heat to 200° to 250°C
A method according to claim 5, characterized in that it is accompanied by a heat treatment of tempering at a temperature between.