| 摘要 |
1342582 Rail steel BRITISH STEEL CORP and BRITISH RAILWAYS BOARD 19 April 1971 [20 March 1970] 13487/70 Heading C7A A steel rail section contains by weight:- at least one of the following hardening elements in the stated amounts: - provided that a total hardening element content of 5% is not exceeded; at least one of the following grain refining elements in the stated amounts:- together with nitrogen in an amount between 0À003 and 0À030% and in a substantially stoichiometric proportion to the amount of grain refining elements, the balance being iron and incidental impurities; the steel rail section having been subjected either to a normalising process wherein the steel is reheated to above its upper critical point of e.g. about 850‹ C and then air-cooled or to a controlled rolling process wherein the steel is rolled down to temperatures in the range 700‹ C to 900‹ C, to produce a ferrite grain structure finer than ASTM 8. The steel has an ultimate tensile strength greater than 69 kg/mm<SP>2</SP>. |
