Three Generations Micro-Allying Steel Processing: Thirty Years of Successive Work at CMRDI

Abstract

The present article presents cumulative works, which were carried out in the field of micro-alloying steel processing at Central Metallurgical R&D Institute (CMRDI) and/or full scale trials in collaboration with the Egyptian steel industry.It was agreed upon defining three main generations of processing micro-alloying steel. The 1stgeneration starts officially on 1975 and continues up to 1995, where it deals with using Ti and V as micro-alloying elements for steel long products. On the year 1985, Central Metallurgical R&D Institute (CMRDI) succeeded to implement of HSLA V-micro-alloyed rebar steel grades at Delta steel mills instead of conventional rebar grades.The 2nd generation was starting on late 1995 and continued to 2005. It was dealing mainly with low carbon content steel (0.04-0.08 %) for flat products (plate and sheet). The most successfully used micro-alloying element was Nb. Beside its precipitate forming effect, Nb is working as substitution solid solution strengthener. Moreover, it raises the recrystallization temperature (Tr). Mainly, micro-alloyed flat steels were developed to fulfill the requirements of the American Petroleum Institute (API) specifications 5L- Product Specification Levels (PSL1) and (PSL2) for manufacturing oil and natural gas pipelines. Meanwhile, a newly born Compact Slab Processing (CSP)-hot strip direct rolling technology was created. On years 2002, the metal forming department in CMRDI succeeded to implement controlled rolling of hot strip Nb-steel sheet at the Compact Slab Process (CSP) Machine in Alexandria National Iron and Steel (ANSDK) Company. Controlled hot rolling schedules were used and followed by early and late cooling at the run out table (ROT). Both contracts were fruitfully succeeded to introduce the API X52 grade at ANSDK Company, followed by X60, and X70 steel grades at Ezz Flat Steel (EFS) Company. The essential mechanical properties of the processed API steel sheets were matched with the API 5L-PSL2 specifications.The 3rd generation was initially developed after 2005 and continued up to day. It deals with micro-alloying with special functional elements like Boron (B). Boron was favored as a micro-alloying element for bilateral effects. Boron carbide (B4C) precipitates are the hardest after diamond, which would be reflected on raising the mechanical properties of the steel. Moreover, Boron was favorably used because it delays the temper embrittlement phenomena. On year 2014, the National for Military Industrialization authority requested from CMRDI to collaborate with Military Factory 100 to develop a technology package for processing armor steel plates. Trials were started with a 3rd generation B-micro-alloyed steel alloy. Many other alloying elements were used beside Boron to develop extra high strength 6.0 mm thickness plates. Finish hot rolled plates were then subjected to a subsequent water quenching from 900 °C and followed by tempering at 250 °C for 20 min. Representation 50X50 cm2 steel plates were successfully passed after 3 bullets in front and 3 bullets rear shooting.