B Eghbali
,
M Shaban
钢铁研究学报(英文版)
Hot torsion testing was performed on a low carbon Nb-Ti microalloyed steel to study the effects of hot torsion parameters, strain and strain rate, on ultrafine ferrite grains production through dynamic strain-induced transformation, at a deformation temperature just above Ar3. The initiation and evolution of ultrafine ferrite grains were studied. The results show that the amount of strain and strain rate has conversely effect on the volume fraction and grain size of ultrafine ferrite grains. With increasing strain, the interior of austenite grains become activated as nucleation sites for fine ferrite grains. As a result, ferrite grains continuously nucleate not only at the former austenite grain boundaries but also inside the austenite grains which leads to a rapid increase in volume fraction of ultrafine grains. Increasing of strain rate reduces the tendency of ferrite grains coarsening so that ultrafine ferrite grains are achieved, while the volume fraction of ultrafine grains decreases at the same strain level.
关键词:
dynamic strain induced transformation
,
grain refinement
,
ferrite
,
hot torsion
,
steel
V Soleymani
,
B Eghbali
钢铁研究学报(英文版)
Grain refinement is one of the successful and low-cost methods to develop metals having excellent combination of strength and ductility. Low carbon steel was deformed by using multidirectional forging (MDF) technique at room temperature. The influence of strain amount and annealing process on the microstructure and mechanical properties of investigated steel was studied. The grain refinement mechanism was studied by the microstructure observation. The results showed that the grain refinement was attained by multidirectional forging technique. The initial coarser grains of average 38 μm size fragmented into very fine ferrite with grain sizes of about 1.2 μm. After MDF, the strength properties improved significantly, although uniform elongation and elongation decreased with increasing strain.
关键词:
multidirectional forging
,
grain refinement
,
annealing
,
steel
,
recrystallization
吴迪，李壮，吕伟
钢铁
通过实验室热轧机组的控轧控冷试验，研究了控轧控冷参数对超高强铁素体/贝氏体双相钢组织性能的影响。结果表明，采用不同温度终轧，轧后不同方式冷却，抗拉强度几乎都在1000MPa以上，屈强比在0.54～0.62之间，伸长率在13%～17%之间。铁素体晶粒随终轧温度降低和冷却速度加快而细化；终冷温度降低，贝氏体量增多。经800℃终轧后层流冷却至560℃左右空冷，由于铁素体晶粒细化，组织中大量的粒状贝氏体、无碳化物贝氏体、少量的孪晶马氏体以及残余奥氏体的存在使抗拉强度达1130MPa，伸长率达16%，强塑积达到18080MPa·%的最高值。控轧控冷获得以铁素体/贝氏体双相组织为主并含有少量残余奥氏体+马氏体的复相组织，使试验钢具有了优异的力学性能。
关键词:
铁素体/贝氏体双相钢
,
controlled rolling and cooling
,
grain refinement
,
mechanical property
