DFG Project PF 394/7–1

Simulation of the velocity and temperature distribution in tundishes with electric arc heating

The flow in a con­ti­nuous cas­ting dis­tri­bu­tor with a capa­ci­ty of 69 t steel melt was inves­ti­ga­ted. Sin­ce inves­ti­ga­ti­ons of the real melt flow in the steel­works are not fea­si­ble due to the extre­me boun­da­ry con­di­ti­ons and the lack of opti­cal acces­si­bi­li­ty, the­se inves­ti­ga­ti­ons were car­ri­ed out in com­pli­ance with the cha­rac­te­ristic simi­la­ri­ties on a redu­ced water model dis­tri­bu­tor on a sca­le of 1:3. Par­tic­le image velo­ci­me­try was used as the mea­su­ring method. The nume­ri­cal cal­cu­la­ti­ons were per­for­med with the com­mer­cial flow sol­ver FLUENT based on the RANS equa­tions. The nume­ri­cal and phy­si­cal simu­la­ti­on of the sta­tio­na­ry cas­ting show­ed that very hete­ro­ge­neous are­as with strong vor­ti­ces are pre­sent in the dis­tri­bu­tor. The domi­nant flows are depen­dent on ther­mal boun­da­ry con­di­ti­ons. The tran­si­ent cas­ting is inves­ti­ga­ted over the enti­re cas­ting peri­od (cas­ting of the first lad­le, sta­tio­na­ry cas­ting pha­se and lad­le chan­ge). The results show that the ther­mal con­di­ti­ons in the two strand dis­tri­bu­tor are influen­ced by the cas­ting con­di­ti­ons and the cas­ting dura­ti­on. This results in chan­ging flows over the cas­ting time which have a signi­fi­cant influence on the dis­tri­bu­ti­on cha­rac­te­ristics. Addi­tio­nal mea­su­res to increase the melt tem­pe­ra­tu­re by means of elec­tric arcs also lead to a signi­fi­cant ther­mal stra­ti­fi­ca­ti­on, which leads to a sharp increase in the tem­pe­ra­tu­re of a part of the melt. The heat sup­pli­ed is main­ly trans­por­ted via heat con­duc­tion. Only in the inlet area does the shadow tube jet lead to mixing and thus to a more homo­ge­neous tem­pe­ra­tu­re dis­tri­bu­ti­on. This method repres­ents a pos­si­bi­li­ty to increase the tem­pe­ra­tu­re of the melt flowing out of the dis­tri­bu­tor. Howe­ver, due to the slow heat con­duc­tion phe­no­me­na com­pared to con­vec­tion, this sys­tem has a long reac­tion time. The com­pa­ri­son bet­ween the expe­ri­men­tal and nume­ri­cal inves­ti­ga­ti­ons car­ri­ed out for both sta­tio­na­ry and tran­si­ent cas­ting shows that with FLUENT it is pos­si­ble to cor­rect­ly repro­du­ce the flow in the con­ti­nuous cas­ting dis­tri­bu­tor. Howe­ver, it is important to use rea­li­stic boun­da­ry con­di­ti­ons. In tran­si­ent cas­ting, this means that self-pro­grammed boun­da­ry con­di­ti­ons are inte­gra­ted into the model. The­se include, among other things, the heat los­ses via the sur­face and walls as well as the ther­mal ener­gy sup­pli­ed by means of arcs.

Logo DFGThe pro­ject was fun­ded by the Deut­sche For­schungs­ge­mein­schaft (DFG) under the refe­rence num­ber PF 394/7–1.