Product produced from continuous coating lines requires levelling or flattening as the final processing stage. This is generally carried out by skin-pass rolls and a tension levelling unit but which, in the past, was only moderately effective on high strength product as used in much roofing and walling. A new theory of leveller operation was developed in the research department and incorporated in new in-line equipment for No. 3 galvanizing line. The new equipment, commissioned in 1985, led to paintline rejections for lack of flatness dropping by a factor of 10. The innovation, which is covered by patents, recently won a prestigious engineering award.

BHP's Coated Products Division also won a marketing innovation award for design and development of a completely 'knock-down' laundry cabinet. Judges said that the concept of marketing a flat-pack laundry cabinet for do-it-yourself assembly was an imaginative way for BHP CPD to market Colorband steel to secondary processors manufacturing steel furniture. The cabinet has a reduced number of components that slide together using mating joints, thus eliminating the need for welds or other fasteners.

Advances in rail technology

With the opening in 1982 of the Whyalla Rail Plant of BHP Steel International Long Products Division, BHP moved into modern rail technology, supported by the BHP Melbourne Research Laboratories where research and development in this field had been in progress for nearly fourteen years. The Long Products Division is one of the few companies in the world producing rails by the Universal Method, which uses two horizontal driven rolls and two vertical idling rolls, so that the rail is rolled on four sides simultaneously. The advantages of universal rolling include the fact that the important surfaces of the rail, that is the top of the head and the rail base, receive direct rolling pressure in the later stages of rolling and the rolling geometry, symmetrical about the centre line of the rail section, leads to much lower internal stress in the finished piece.

The combination of the Universal Rolling Mill and a modern cold finishing plant enables BHP to produce rails for all rail traffic conditions. Even at the bloom stage, before rail rolling, a controlled cooling operation is conducted to reduce hydrogen content, and spot scarfing is used to remove any existing surface blemish. After final rolling, roller-straightening of each rail ensures production of a uniformly straight rail that can be supplied in length up to 27.4 metres.

A recent innovation has been the introduction of Head Hardened Rails which are particularly suitable for railway conditions involving heavy wear, such as curved track, restricted access locations, or where there are heavy axle loadings. These head hardened rails are produced to a restricted chemical composition and the head of the rail is heat treated by a two-stage induction heating process followed by a high pressure air quench. This controlled process results in the formation of a fine pearlitic micro-structure. Such rails have been used and thoroughly tested by Mt. Newman Mining Co. Pty. Ltd. on the 430 km Newman to Port Hedland railway, where axle loading is a mean of 32.5 tonnes. The line carries about 50 million gross tonnes each year and the rails have been in service for four years. Head-hardened rails are now also used in other heavy duty areas around Australia.

Australian Academy of Technological Sciences and Engineering