Materials Sciences and Applications, 2013, 4, 70-76 http://dx.doi.org/10.4236/msa.2013.41009 Published Online January 2013 (http://www.scirp.org/journal/msa) Influence of Hot Band Annealing and Cold Rolling on Texture and Ridging of 430 Stainless Steel Containing Aluminum Sudipta Patra, Lokesh Kumar Singhal Jindal Stainless Limited, Hisar, India. Email: psudiptapatra@gmail.com Received October 7 th , 2012; revised November 4 th , 2012; accepted December 2 nd , 2012 ABSTRACT An approach to optimize the processing parameters to get superior ridging resistance and mechanical properties in commercial production of 430 ferritic stainless steel has been studied. Attention was also paid to improve productivity and energy saving without hampering the surface and mechanical property aspects of the material. Hot rolled coils an- nealed by slow cooling under insulated cover exhibit better ridging resistance than bell annealing treatment with a mi- nor decrease in ductility. Soaking temperature prior to hot rolling has a significant effect on ridging resistance. Keywords: Ridging; Hood Annealing; Bell Annealing; Microstructure; Texture; 430 Stainless Steel 1. Introduction Ferritic stainless steel 430 grade is extensively used in various applications like kitchen wares, electrical app- liances, automobile parts and white goods on account of its good corrosion resistance, high thermal conductivity and beautiful surface gloss as a low cost alternative to nickel containing austenitic stainless steel. Occurrence of ridging after cold forming operation can hamper the sur- face finish of the material necessitating considerable ef- fort in polishing of the surface. Wright [1] has pointed out that ridging is associated with anisotropic plasticity of bands of contrasting textures. Shin et al. [2] estab- lished that differences in the deformation behavior of {001} <110> and {111} <110> grain colonies arises due to difference in their plastic strain ratio during cold forming operation thereby causing ridging. Extensive efforts have been made to minimize ridging. Kim et al. [3] suggested refinement of solidification structure by using EMS to avoid columnar grains with <001>//ND orientation is utilized for improving ridging resistance. This entails significant capital cost. Kimura et al. [4] advocated high interpass time during roughing in con- junction with high reduction per pass to facilitate recrys- tallization in the colony structures. High interpass time during rough rolling can adversely affect the productivity of the hot mill. Since 430 stainless steel has two phase α + γ structure during hot rolling, some martensite forms on cooling of the hot coils. Such coils are generally sub- jected to bell annealing to transform the martensite to ferrite to facilitate cold rolling. Jha et al. [5] concluded that continuously hot band annealed material exhibits superior roping characteristic. In this study, they also noticed that more than 25% martensite in the micro- structure can cause breakage of the coil during cold roll- ing. Huh et al. [6] observed pronounced through thick- ness texture gradient in hot bands of this grade which had an impact on appearance of ridging in the final recrystal- lised sheet. Huh and Engler [7] suggested that introduce- tion of intermediate anneal during cold rolling weaken the texture gradients and minimize the extent of ridging compared to single stage cold rolled product. Avila & Zapata [8] annealed the hot bands of 430 grade in 2 phase region and followed by controlled cooling to ob- tain dual phase structure. These authors noted that grain refinement due to martensite dispersion during cold roll- ing resulted in significant improvement in ridging. Mola et al. [9] found that samples without hot band annealing when subjected to cold rolling and subsequent bell an- nealing exhibited superior ridging resistance compared to conventional bell annealed product which was continu- ously annealed after cold reduction. Batch annealing is an energy intensive operation which increases cost of the finished product. The present paper highlights the bene- ficial use of the intrinsic heat of the hot rolled coil under an insulated hood to enable the coil to cool slowly and thereby facilitate transformation of austenite to ferrite and reduce the hardness of martensite to permit extensive cold reduction. In this manner 430 grade with superior Copyright © 2013 SciRes. MSA