Two-step production process cuts cost for premium steel.

A NEW STEEL, that meets premium bearing quality at two-thirds less cost, has been developed by SKF Steel, Inc.

The new MR-PBQ steel is designed to replace vacuum arc and electroslag remelted steels used in high stress transmission and bearing parts, offering manufacturers a means to decrease overhead costs without decreasing product quality.

The company says the steel's production process is divided into two stages. Melting occurs in a twinshell water-cooled electric arc furnace, in which carbon and phosphorus contents are reduced to stipulated levels.

Then the steel is refined in a second ASEA-SKF ladle furnace.

The separate ladle refining principle is said to give greater control and flexibility than can be obtained in other steel-making processes. Critical refining and alloying stages take place in a controlled deoxidizing environment under constant inductive stirring while alloying elements are added under computer control.

When specific alloy and machineability characteristics have been developed for a customer, the computer-controlled system can assure repeatability of future batches. SFK notes that this consistency is particularly important for automated machining operations.

SKF says the MR process produces very clean steel with good fatigue strength characteristics, but this cleanliness leads to long chips during machining, a potentially undesirable characteristic.

To counter this, sulfide micro-inclusions are available in percentages that adjust the level sufficiently to act as a "chip breaker" while having minimum effect on other characteristics of the steel. Additives other than sulfur can be used, depending on machining requirements, but all with the net effect of increasing tool life or possibly increasing cutting speeds.