Modern day “quenched and tempered” steel plate evolved out of military armour. Following World War II, steel producers sought to modify expensive, heavily alloyed, high-hardness (360-500 BHN) armour steel plate for use in structural applications. This re-engineering required a standard. To meet this need, the American Society for Testing and Materials (ASTM) wrote the engineering standard specification ASTM A514. This standard detailed engineering criteria and acceptable steel mill parameters governing the production of quenched and tempered 100,000 psi (pounds per square inch) (690 MPa) yield strength steel with a hardness of approximately 235-293 BHN.
Some 40 years ago, the Canadian Standards Association (CSA) essentially renamed the ASTM A514 specification for engineering in Canada, calling it CSA G40.21 100QT. Although there have been minor changes within the specifications, reflecting changing steel mill practices in both Canada and the United States, the specifications have remained virtually unchanged since the original writing of ASTM A514 almost 70 years ago.
Although the evolution of quenched and tempered steel plate for structural applications proceeded in a standardized manner, the evolution of steel plate for wear applications did not. No independent testing authority in the United States or Canada, like the ASTM or CSA, formulated a standard specification for wear applications. As a result, today we have an engineering standard for many structural applications, but no engineering standard for wear applications. Moreover, the structural standards we do have tend to focus on historical steel mill production criteria and often do not address contemporary fabrication concerns or developments in practice.
In an effort to fill this void, steel mills around the world have written their own trade name specifications. In addition to creating a brand name for their steels, these specifications have allowed producers to offer engineering design criteria and fabrication practices for both structural and wear applications. As a result, steel buyers must grapple with trade names substituting for standards and with standards that often sit uncomfortably with contemporary realities. To add to this confusion, the ongoing development of steel making and heat-treating technology has further blurred the lines between structural and wear applications, with new products having 130,000 and 160,000 psi (890 and 1100 MPa) yield strengths and hardnesses surpassing 600 BHN. Is it any wonder the marketplace still struggles with limited standards and confusing trade names?