Predicting the ferrite grain size in low-alloy steel

Mathematical models are proposed for calculating the onset temperature of ferrite transformation and the ferrite grain size as a function of the cooling conditions and the initial austenite grain size. The models are calibrated on the basis of experimental data for steels with ferrite-pearlite microstructure. The models are integrated in HSMM software, with considerable gain in computational power when considering the mechanical properties of steel rolled on the 2000 mill at OAO Severstal??.     

Influence of steps in the manufacture of large-diameter pipe on its final properties

An approach has been developed for simulating multistep plastic deformation—for example, rolling on a thick-sheet mill—by the tension-compression method. By means of the Pocket Jaw module in the Gleeble system, controlled strip rolling and pipe manufacture (including pipe fabrication, expansion, and thermocyclic polymer-coating application) may be reproduced on a single sample. At each moment in simulating rolling or pipe manufacture, the structure and properties of the steel may be investigated, and therefore the contribution of each operation to the pipe’s final properties may be determined. The results show that the straightening temperature of the metal after controlled rolling makes a marked contribution to the final properties of the pipe.     

Surface-crack formation in the two-phase region when rolling thick microalloyed-steel sheet

The formation of a surface defect (a lobed scab) in the final stage of large-diameter pipe production is analyzed. Surface microcracks are assumed to form in the rolling of thick sheet on account of problems in the two-phase region on rolling, with localization of the plastic strain, as well as the action of tensile stress in the surface layer and the attainment of limiting stress values. Physical modeling in the Gleeble system permits determination of the limiting stress (rupture strength) in rolling in the two-phase region, which depends on the temperature and is structure-sensitive. The limiting stress is determined by ferritic and bainitic transformation in the steel.     

Hot plasticity of microalloyed pipe steel in continuous casting and hot rolling

The influence of continuous casting and hot rolling (on a broad-strip 2000 mill) on the hot plasticity of microalloyed pipe steel (strength category X42) is investigated. A Gleeble 3800 system is used for physical modeling of the hot plastic deformation. The temperature intervals corresponding to loss of plasticity are determined in different conditions of slab cooling during continuous casting. In subsequent rolling, the loss of plasticity typical of cooling in the continuous-casting machine is not seen, and the steel is highly plastic.     

The condensation of steam from steam-water mixture on water jets at high pressure

A physical model for condensation of steam in water flow at high pressure is developed, and analytical dependences for calculating heat transfer are obtained, in particular as applied to the operation of a direct-contact feedwater heater for a new-generation reactor plant with lead coolant.     

Kinetics of Structure Formation in the Heating of Cold-Rolled Automotive Steel Sheet

The softening kinetics associated with recovery and recrystallization is investigated, along with the kinetics of phase transformation (austenitization) on heating cold-rolled autompotive steel sheet. The kinetics of softening in isothermal holding is studied using the Gleeble 3800 system for 12 steels, and the phase transformation in continuous heating at constantrate is studied for 6 steels of different strength class, with different chemical composition. Considerable slowing of the steel’s recovery and recrystallization is observed with increase in the Mn and Ti content in the ferrite solid solution. The grain size of the recrystallized ferrite hardly depends on the annealing temperature. The results may be used in developing a quantitative integral model to describe the complex microstructural evolution of cold-rolled steel sheet on annealing in industrial production.     

Influence of dynamic austenite decomposition on the microstructure and mechanical properties of pipe steel

The influence of deformation-induced ferrite transformation on the microstructure of microalloyed pipe steel is investigated by means of a Gleeble 3800 test system. The results show that such dynamic transformation permits considerable reduction in ferrite grain size and improves the mechanical properties of the steel.     

Structural evolution of high-strength dual-phase steel in hot rolling

The influence of the hot-rolling parameters used in 2000 continuous broad-strip mills on the structure of high-strength dual-phase steel is investigated. The structure formation and mechanical properties of the steel are simulated by means of Hot Strip Mill Model (HSMM), ThermoCalc, AusEvol+, and AusTran software. A Gleeble-3800 thermomechanical simulator is used for physical modeling of the metal treatment. By adjusting the treatment parameters, dual-phase ferrite-martensite, ferrite-bainite, or ferrite-martensite-bainite steel may be produced.     

Studies of a direct-contact feedwater heater at a fragment of the secondary coolant circuit of a new-generation reactor plant

Results obtained from experimental investigations of a direct-contact heater at an experimental installation simulating a fragment of a power unit’s secondary coolant circuit are presented, and a heat-transfer calculation model obtained on an experimental setup equipped with a small-scale model of a direct-contact heater is subjected to a comprehensive check.