High Carbon Steels
CSM researchers have raised a remarkable experience about the metallurgical aspects of microstructures affecting the mechanical properties and geometrical features of High Carbon Steels flat products as, for example, they are derived from the cooling patterns of hot rolling mill Run-out-Tables. This skillfullness is supported by home-made models relating the microstructural parameters (i.e., austenite grain size, interlamellar pearlite spacing, etc.) with the alloy mechanical features (i.e., strength, ductility, toughness, ecc.).
Those models are also used to direct the line manager to the optimal setting-up of UFC (Ultra Fast Cooling) banks, well fitted for thermal and phase transformation needs, and in tune with enforced geometrical constraints (e.g., ovalisation due to recoalescence of grains).
Microalloyed and Low-Alloyed Steels
In terms of microalloyed steels, CSM knowledge has been gained while supporting the italian steel industry in the development of advanced metallurgical products for large diameter UOE welded and seamless pipes. This cooperation lasts for longer than 40 years and has allowed the development of the metallurgy for all the steel grades up to X145.
This expertise allows CSM metallurgists to design microstructures (i.e., packet size, cell size, fine ppts) in order to govern the desired strength-toughness properties, Y/T ratios, the strain-ageing alloy susceptibility and the stress-corrosion cracking, measuring also the effects after multiple plastic straining cycles (reeling) or welding cycles, so becoming today the supplier of several worldwide industrial groups.
This knowledge also concerns the effects of chemical composition and Q&T practice on microstructure and steel strength-toughness balance, taking into consideration the following factors: - the austenite grain growth in reheating (inhibition due to ppt);
- the alloy hardenability (CCT diagram data base);
- the alloy response to tempering treatment of martensite and mixed martensite/bainite microstructures (recovery, recrystallization, grain growth)
- the evolution of type and size of ppts (dissolution, coarsening, spheroidisation);
- the microstructural parameters which control both strength and toughness (packet size, cell size, fine ppts).
This capability is rooted on a whole set of models integrating thermal aspects, CCT data base, ANN aiming at relating microalloyed steels mechanical and corrosion properties to their microstructures and fabrication practices (i.e., TMCP – Thermo-mechanical control practice).
Therefore, today whatever steel or end-user industry is interested in expanding its own products set to microalloyed steels, or in improving the yield and quality of its own production line, may find at CSM the right skill, and the practical and theoretical instruments for the task.