Study on Nodular Graphite Steel Rolls

Abstract

In order to improve the resistance to fire cracking and wear of steel rolls for primary hot-rolling mills, such as blooming, slabbing and roughing mills, without reduction of their strength and toughness, some characteristics of cast iron must be accompanied with the properties of steel rolls.
It was, therefore, undertaken to apply nodular graphite steel to rolls for primary mills to realize the above idea. One of the authors has recently developed nodular graphite steel, with use of a special Fe-Ca alloy, this steel having free nodular graphite even in as-cast state.
The characteristics of nodular graphite steel were first investigated mainly from the metallurgical point of view, and its promising applicability to rolls was clarified.
The trial manufacture of actual rolls with nodular graphite steel was next performed for several millsThe results of service performance of these rolls were, as expected, superior to that of rolls, which hitherto had been used, with special reference to the following points:
(1) Nodular graphite steel roll has a considerable strength and toughness. It has, therefore, almost no tendency to breakage in service which has been often experienced in cast iron rolls.
(2) Nodular graphite steel roll has a great resistance to fire cracking. It has, therefore, further less occasions to be shortened its life by surface cracking than usual steel rolls.
(3) Nodular graphite steel roll has a great resistance to wear. Combining with the resistance to fire cracking, it can give more rolling tonnage and finer rolled products with dimensions of higher precision than usual steel rolls.