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Steel Metallurgy

Steel Metallurgy historically constitutes the technological core of the company and is still one of its main market targets. CSM competencies are focused on the following topics:

Carbon Steels

Carbon Steel Metallurgy has been, since foundation in 1968, one of the most outstanding objects and interests of Centro Sviluppo Materiali S.p.A. The knowledge and expertise expressed by its researches has allowed a very active design of solutions for steel customers well-fitted with the market needs. That was true yesterday at a national level, it is even more true today and will be in the future within a global operational scenario where the company personnel is increasingly qualified to support most needs of worldwide steel actors and manufacturing companies.

 

Ultra-Low and Low Carbon Steels
CSM is active in the field of hot and cold rolled, pickled, and annealed steel products targeting the optimization and improvement of the mechanical properties (i.e., grain size, yield point elongation, strain ageing, and so on) according to market needs.

This is obtained through the balance of a number of process factors, such as:

  • the manipulation of alloy chemical elements;
  • the adoption of the optimal:
    • thermo-mechanical treatment practices;
    • cold rolling reductions;
    • annealing cycles in the hot-dip zinc coating line;
    • repartition of pre-deformation between skinpass and stretch levelling;
    • response to the pickling problem. 

The Ultra-Low and Low-Carbon Steels manufacturers, moreover, may receive a profitable support in finding new perspectives in the market through the development of new products and low cost processes (i.e., ferritic hot milling), and understanding and removal of the causes of product non-conformity, possibly with the help of microstructural models for process automation, control and monitoring.

High Strength Low Alloy Steels (HSLA)

In respect to High Strength Low Alloy Steels (HSLA) for automotive applications (i.e., seats, suspensions, steering wheels, cross beam, etc.) the expertise gained by the CaSM metallurgists is aimed at creating the microstructures that are best suitable to forming and guaranteeing the needed performance for the product. In this field proper, being involved in microstructures means, for CSM metallurgists, not only optimised new compositions, but also activities oriented to match the following criteria:

  • to raise the quality standards of consolidated products;
  • to introduce more efficient models for the control of both the austenite and the precipitates during the strip cooling;
  • to revise chemical and process parameters in order to impose narrow manufacturing allowances for various mill & ROT configurations, and reduce both the number of the steel quality codes and the scattering of their features.

HR (ferrite-bainite), Dual Phase (ferrite-martensite), TRIP (bainite-retained austenite) and TWIP (high Mn, austenitic) steels

In the field of HR (ferrite-bainite), Dual Phase (ferrite-martensite), TRIP (bainite-retained austenite) and TWIP (high Mn, austenitic) steels metallurgy the technical offer of CSM mainly encompasses such alloy design capabilities as:

  • Investigation of recrystallization and phase transformation by quench-deformation dilatometry devices, hot deformation simulators and pilot mills;
  • Modelling of both austenite recrystallization during hot rolling and phase transformation on the ROT when using step cooling patterns;
  • Identification of relationships between microstructural parameters and mechanical properties (YS, UTS, Y/T, El, uniform strain, work-hardening, etc.);
  • Modelling of the effect of volume fraction, morphology and size of microstructural constituents on stress-strain curves.

This offer is also integrated by the process setting capability for several steel grade products (HR45 – HR60 and DP600 – DP 800) manufactured by means of both conventional and thin-medium slab routes, with either standard laminar cooling (LC) or combined with Ultra Fast Cooling (UFC + LC).


CSM metallurgists succeeded in developing a very lean chemical composition and the related thermo-mechanical treatment practice capable of maximizing the quality of the thin hot-rolled
DP600 grade steel (1.5, 2.5 mm) and also in obtaining hot rolled DP600 1.2 mm thick strips, by means of an intercritical treatment carried out during the hot dip galvanizing phase of the process.

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.

Alloyed, Low-Alloyed and Microalloyed Steels

Today, the CSM metallurgists are at the frontier in the development of Low-Alloyed steels metallurgy for such applications as rails, hangers, cables, wires, bars and rods.

In that respect, their expertise allows CSM to provide clients with answers on a wide spectrum of topics like the following:
  • how to use the chemical composition or hot rolling practice leverage for fine pearlite microstructures;
  • which is the better correlation amongst bainitic microstructures, transformation characteristics and mechanical properties;
  • how to establish the right practices in order to low the bainitic content and have steel characterised by high strength values (UTS> 1400 MPa), good ductility (total elongation > 10%), adequate toughness, slide and rolling wear resistance;
  • how to improve the weldability of low alloyed steels or optmise their hardness;
  • which are the better guidelines for the thermomechanical treatment (TMT) - inclusive of austenite conditioning through hot rolling and cooling strategies- with reference to the alloy chemistry (i.e.: Si, Cr,V, Nb, etc.) to adopt in order to shorten the whole cycle, dispensing of the need of such final heat treatments as “annealing”;
  • how to meet novel steel design criteria and innovative process approaches to match strength & toughness with fatigue through the reduction/refinement/elimination of pearlite, introduction of non-traditional microstructures containing acicular ferrite, carbide-free bainite, retained austenite and so on;
  • how to maximise the control of segregation, decarburizing and non-metallic inclusions.

Stainless Steels

The CSM metallurgical offer on stainless steels covers the whole spectrum of expertises. It is aimed at designing better performing stainless steels through the choice of chemical compositions, fabrication and transformation practices in accordance with the microstructures (i.e., austenitic, ferritic, austeno-ferritic, martensitic, PH, etc.) able to satisfy the demanded applications.

 


So, the CSM metallurgists have gained, through a more than fourty years' experience, a remarkable capability in this field, being able to accomplish the better balance between bulk and surface properties, by governing the microstructures and surfaces throughout the whole process, or by developing new production concepts (i.e., thin slab casting, strip-casting, integrated cold rolling, pickling and finishing treatments, etc.) able to fullfill the customer requirements.

 


Well-appreciated by customers not only for research and support activities focused on improving the quality of the more consolidated productions, the CSM metallurgists are also capable to deal with any border-edge topic concerning stainless steels technology.

 


In this regard, they are constantely challenging themselves in such fields as the setting-up of profitable microstructures for automotive (i.e., ferritic steels), structural (i.e., low Nickel high mechanical strength stainless steels), chemical and processing (i.e. High alloyed stainless steels), buildings and architecture (i.e., special austenitic and duplex grades) applications, an so on.

Electrical Steels

Four decades ago, when the CSM metallurgists were asked by the company managers to draw a development strategy on Electrical Steels, they really got surprised in hearing a paradigm sounding quite different from that of common steels.

 

Today, it is safe to affirm that what seemed to be a simple cultural discussion about a steel which was a non-steel material because of its extremely low carbon content, its silicium-induced high brittleness and , lastely, the positive effect of hydrogenum on the fabrication process, is turned into a consolidated and well-satisfactory reality at CSM whose limits have been successively extended to magnetic amorphous and ferrite materials.

 

In fact, this capability of Centro Sviluppo Materiali S.p.A. does not only cover all topics related to the design, fabrication and characterisation of electrical steels, but it is also concerned with both the technology of ferrites and magnetic glassy materials for all aspects related to their design, synthesis, mixing, pre-consolidation, near-net-shape geometries final sintering and magnetic characterisation.

 

It is supported and empowered by the rich availability of physical models guaranteeing a theoretical predictive approach, such as those developed for the hydrogen-induced decarburation and recristallisation kintetics for not- and oriented grained steels, and laboratory, pilot-plant scale equipments for the simulation of processes, and the microstructural (EM, TEM,OIM, Xrays, …) and functional magnetic measuraments (B-H curves, Losses, magnetostriction, etc.).

© 2014 - Centro Sviluppo Materiali S.p.A. Via di Castel Romano, 100 - 00128 - Rome - ITALY
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