Steel Plays a Vital Role in All Modern Building Construction

Otago Daily Times, Issue 26841, 4 August 1948, Page 6

Steel Plays a Vital Role in All Modern Building Construction

In these days when modern buildings for industrial or commercial purposes are erected in concrete suitably reinforced with steel, the question of maintaining an adequate and regular supply of materials Is one of paramount importance. Dunedin is fortunate in that in the iron and steel rolling mills at Green Island it has a source of supply, but even this meets only a small proportion of the country's requirements

The Green Island industry, which commenced operations over 61 years ago, is the only one of its kind in New Zealand. Three other processing mills have operated at various periods, two in the North Island and one other In Christchurch, the latter for only a very short period. During the war, when the threat of Invasion by the Japanese arose, the Government erected a complete duplicate mill at Green Island next to the present one. It covers a very large area and stands to-day complete with all the necessary machinery, after having been used for only six months. It has been idle for four years

now and machinery and buildings which cost £150,000 are rapidly

deteriorating. During its period of activity, this rolling mill operated in conjunction with its prototype next door, both using steel billets imported from Australia and the United States.

When the threat of invasion passed, the Government rolling mill closed down, but even since the war the company itself, which has been operating over so many years, has had to cease operations for a total of eight months in a period of two years because of inability to secure steel billets from Australia.

The Broken Hill mills, the largest in the British Empire, with a capacity output of 1,000,000 tons a year, are now restricted to a production of 600,000 tons because of coal shortages. New Zealand relies almost wholly upon the Australian output for both the finished steel materials used for building purposes or for the steel billets which are finally rolled out to the required dimensions at the mill at Green Island. Of the output from this local mill, the New Zealand Railways take a large proportion, leaving the remainder for distribution where it is urgently required. Steel of three ranges of tensile strength is secured in billets for processing. These billets range in length up to 40ft and in. sizes from 3m to 6in square and are rectangular in shape. / They are cut into required lengths, brought to a white-hot temperature, and then passed backwards and forwards through the mills, the rollers of which gradually reduce the metal to the required shape , and thickness. Rounds, squares, flat, angles, T’s and various other shapes are thus produced. Where earthquakes are a possibility the tendency has been to concentrate more and more on the shock-proof building. Into their construction go many miles —and tons —of steel. In a normal double-storeyed building covering a ground space area of 120 ft by 50ft, the quantity of steel used would be anything up to 60 or 70 tons. Placed end to end, such reinforcing material would extend for about 50 miles. In bigger buildings, where heavy reinforced foundations are necessary, and where a number of floors are erected and heavy girders used, the steel so absorbed may amount to as much as 1000 tons or more.