AISTech - WAI Joint Session: Metallurgy of Wire Rod
TUESDAY, MAY 6, 2014
10:00 a.m. - 10:30 a.m.
Recent Applications of a Heater Cover in a Stelmor Cooling System
Siwon Yoon, Gwansik Min, Seongkyu See, and Sanghyun Oh, POSCO, South Korea
From the advent of the Stelmor cooling system, it has been a major part of wire rod manufacturing. To overcome the drawbacks of the process, however, the application of a slow cooling cover with a resistance heater has been considered. Experiments with pilot-scale equipment were conducted to investigate the effect of the heater setting temperature, the number of heaters turned on and the diameter of wire rods. The results show that the wire rod diameter and the applied heater power are inversely proportional to the cooling velocity.
10:30 a.m. - 11:00 a.m.
Influence of Drafting Schedule in High-Speed Drawing of Carbon Steel Wires on Their Structure and Mechanical Properties
Jan Krnac, ZDB Bohumin, Czech Republic; Jana Kavulokova, VSB Ostrava, Czech Republic; and Jan W.Pilarczyk, Czestochowa University of Technology, Poland
The influence of four different drafting drawing schedules for 1.5-mm-dia. high-carbon steel wires on their structure and mechanical properties is elaborated. The initial material for the wire drawing was a 5.5-mm-dia. Stelmor wire rod of steel C78D which has been drawn on the multistage KOCH drawing machine with total reduction of 92.6% in 13 passes and a drawing speed in the last draw of 15 m/s. After each draw, tensile strength (Rm), the number of bends (Nb) and the number of twists (Nt) of the drawn wires, according to the four different drafting schedules, were determined. After a total reduction of approx. 40, 70 and 90%, longitudinal and cross-sections of wires were examined with scanning electron microscope, and the effect of the applied drafting schedule on deformation and fracture of the cementite lamellae was determined.
11:00 a.m. - 11:30 a.m.
Effect of Cryogenic Uniform-Deformation on Strengthening of High-Carbon Steel Wire
Tadakuni Hori, Motohiro Nakano, and Atsushi Sasaki, Shinko Wire Co. Ltd.; and Hiroshi Utsunomiya, Osaka University, Japan
Recently interests increases on global environment. Demand on structural components and lightweight parts increases. It is necessary to increase the strength of the high-carbon steel wire further. The strain aging and non-uniform deformation are focused. The authors studies the suppression of ductility decrease by means of cryogenic temperature wiredrawing and by uniform deformation wiredrawing. The latter was realized by an optimum combination of the die geometry and reduction in area.
11:30 a.m. - 12:00 p.m.
The Influence of Oxygen-Enriched Burner Systems on the Scale Formation of Steel Alloys During Heating Processes
Christina Viktoria Sobotka and Helmut Antrekowitsch, University of Leoben, Austria
The influence of oxygen enrichment on the scale formation of steel alloys in burner-fired furnaces is investigated. Oxygen-enriched combustion leads to a higher amount of oxidizing agents (CO2 and H2O) in the atmosphere which react with the steel surface during the heating process and affect the high-temperature oxidation. Therefore, experiments with various steel grades are carried out using thermogravimetric analyses and compared with real forging and reheating furnaces using oxygen-enriched burners. The results imply that there is a change in the kinetic model of the oxidation reaction at a temperature above 1,000°C.
2:00 p.m. - 2:30 p.m.
MicroNiobium® Steelmaking Alloy Approach in 1080 Wire Rod
Steven Jansto, CBMM North America Inc., USA
The MicroNiobium® alloy approach is applied in higher-carbon steels exceeding 0.20% carbon. This study evaluates different Nb and Nb-V compositions from 0.020 to 0.120%Nb in AISI 1080 steels for wire rod applications. Although the Nb solubility is limited in high-carbon steels compared to low-carbon steels, the optimized Nb content is defined based on experimental results. The optimized Nb content leads to improved mechanical properties due to the finer interlamellar pearlite spacing. Seven different eutectoid steel developmental chemistries were evaluated to determine the effectiveness of Nb, V or Nb-V concentrations on the pearlite interlameller spacing, mechanical properties and drawability consistency.
2:30 p.m. - 3:00 p.m.
Interplay Between Grain Size and Austenite Stability on the Deformation Behavior of High-Strength, High-Combination Austenitic Stainless Steels
Venkata Sai Challa and Devesh Misra, University of Louisiana at Lafayette, USA; and Mahesh Somani and Pentti Karjalainen, University of Oulu, Finland
Currently there are no reports that show a systematic grain size effect on the deformation mechanisms in a relatively large grain size spectrum from ultrafine-grained (UFG) to coarse-grained (CG) regime in a single material, processed using a single set of identical parameters. Utilizing the concept of severe deformation-annealing sequence involving phase reversion, together with nanoscale deformation experiments, the authors elucidate the dependence of grain size on deformation mechanisms. It is illustrated that there is a clear distinction and fundamental transition in the deformation behavior of UFG austenitic stainless steel such that deformation twinning contributed to the excellent ductility of high-strength UFG steel, while in low-strength CG steel, ductility was also good but because of strain-induced martensitic transformation.
3:00 p.m. - 3:30 p.m.
The Study of the Microstructural Evolution of a Pearlitic Steel During Cold Drawing and Static Strain Aging
Aude Lamontagne, Xavier Kleber, and Véronique Massardier, INSA de Lyon, France; and Daniele Mari, Swiss Federal Institute of Technology (EPFL), Switzerland
Microstructural changes in a pearlitic steel during cold drawing and during isothermal aging have been investigated using thermoelectric power (TEP), internal friction (IF) and differential scanning calorimetry (DSC). The TEP and the IF evolutions versus strain were compared. These techniques mainly highlight the increase in the amount of carbon atoms dissolved in ferrite due to the strain-induced decomposition of cementite during cold drawing. This phenomenon is likely to underlie the post-drawing aging. Then, the aging kinetics are monitored by TEP and exhibit three aging mechanisms occurring even at 20°C. DSC confirms the occurrence of these three mechanisms.
Schedule subject to change.