A Secondary Cooling Pattern for Preventing Surface Cracks of Continuous Casting Slab

Abstract

In order to redllce the occurrellce oj suiftlCe difects oj a cOlltillUOUS castillg slab, the most suitable secolldary coolillg pattern was de filled all the basis oj the results oj a theoretical calCillalioll allri a laboratory scale ex-Ilerimellt all the thermal hysteresis similar to those oj cOlltilluous castillg slabs. M oreover, i t has been considered ill this study that the trallsverse corner cracks could be relaled to the p resellce oj precipitates appeared ill the austenite grain boundaries. (1) T rallsverse corner cracks are formed by the precipitates oj AI N ap/leared all the grain boundary in the austenite region at the temperatures in the rallge oj 700 0 to 950°C. Especially, the AIN Jormatioll is accelerated by reheatillg it at th e temperature above 700 0 e Jrom Ihp. lower temperature. (2) From tlIP experimelltal results all the roles oj secondary coolillg pattern and oj temperature nt th e unbending roll in slnbs continuously cnst, it is nscertained that the occurrence oj transverse corner crack is SllC-cessflll~l' prevellted ~y the secolldary cooling pattern , that is, a suitable coolillg rate is less thall 83 e lm ill the upper part oj continuolls casting machille. (3) T he lI<w~)'-dev leoped slnay coolillg I,nttern is also eflective Jar th e redllctioll oj 10llgitudillal slIr/ace cracks.

Uneven Solidification during Wide-thick Slab Continuous Casting Process and its Influence on Soft Reduction Zone

“…Based on some simplified assumptions, 11) the mathematical heat transfer model of quarter slab transverse section was developed to predict the temperature field of wide-thick slab. A two-dimensional transient heat conduction equation was employed to describe the heat transfer behavior as follow:…”

“…12,15) The fundamental equations were described in detail by Ueshima et al 12) Figure 4(a) shows the phase fraction evolution of peritectic steel during its solidification, and (b), (c), and (d) show its conductivity, density and enthalpy, respectively, which were calculated by weighted phase fraction equations that were described in detail by Li and Thomas. 16) It should be noted that the thermal conductivity of liquid steel is usually increased compared to its solid state conductivity due to its flow and convection 11,17) in the calculations.…”

“….......................... (12) Where, N R i is the roller number of i th cooling zone; R i L is the contact length between roller and slab in i th cooling zone, m; Z i L is the length of the i th cooling zone, m. According to the previous research, 17,20,21) h c i is set as 0.4-1.4 Kw/(m 2 ·°C), and R i L is equal to 0.02 m. According to the experimental results of F. Ramstorfer et al 6) and Nozaki et al, 11) the h i w is the function of the water flux distribution, and it could be expressed as:…”

On the optimal cooling strategy for variable‐speed continuous casting

“…Reference [4]), which is a port of the well-known Livermore Solver for Ordinary Di erential Equations (Adaptive) (cf. Reference [5]) to C++, in which the required modiÿcations have been carried out to allow the seamless use of automatic di erentiation (AD, cf. References [7; 8]) techniques.…”

Research on the On‐Line Simulation of a Three‐Dimensional Temperature Field Model of Slab Continuous Casting

“…Because it cannot meet the requirements of on‐line control in terms of calculation efficiency and cannot be used on‐line to distinguish the differences in cooling conditions in the width direction of the slab continuous casting in the secondary cooling zones, at present, the mostly simulation model of on‐line heat transfer and solidification for providing real‐time temperature field data to the slab continuous casting secondary cooling dynamic water model and dynamic soft‐reduction model is only used for determining the cooling difference in the direction of the casting, ignoring the direction of the slab width . As a result, it is impossible to adjust the amount of cooling water according to the temperature in the width direction of the slab continuous casting, resulting in an increase in the thermal stress of the slab and easily leading to poor quality . An irregular shape of the solidification end is not conducive to the implementation of soft‐reduction …”