85% of the world' s steel shot production is martensitic quality; whereas the remaining 15% consists of bainitic, chilled iron and stainless steel shots. Martensitic quality is the latest technology and the widest production type.
High carbon (martensitic) steel shots are made by melting steel sheets, pipes and other steel scraps called "extra", plus additives such as silicium, manganese and carbon in an induction furnace reaching 1600 - 1650 C. After atomisation of melted steel by water jets, the material is cooled down in water. Following the primary sieving, the shots are tempered in special furnaces and the martensitic microstructure is reached. At the end of this process, the hardness of the shots is approximately 63 HRC. In the next steps, with additional heat treatment and tempering, the hardness is lowered to 40 HRC.
The main point in shot blasting or any surface treatment is that the hardness of the steel shot or grit has to be 3-4 HRC higher than the surface so that the desired cleanliness and roughness can be reached within a short period of time with less energy consumption. The use of softer (for example, bainitic quality) blasting media will not perform as well as martensitic quality steel shots and will take more time and energy to reach a similar result, which is the main reason of the high energy consumption and high labor cost. In the whole blast cleaning process, the cost of the steel shot/ grit is between 12-15 %. The remaining 85-88% is energy and labor cost. Therefore the choice of right size and correct hardness is vital for the process in total. Martensitic quality allows us to produce material betwen 40-63 HRC, which minimizes blasting time, i.e. energy and labor costs.
With its customer-oriented philosophy, BÜNSA A.Ş. is proud to be the only Turkish company which produces martensitic quality, special hardness surface treatment materials.