Steels get rusty over the time, to remove these rustyparticles, or contaminants, it is dipped into pickle bath that containsHydrochloric Acid. This strong acid will remove the impurities and result in shinysteel again. The used hydrochloric acid, or any other acids, are now known asspent acid, or can be said as used acid, waste acid, spent pickle liquor orpickling sludge.
Pickling sludge is a hazardous waste based on EnvironmentalProtection Agency, it cannot simply be released to the landfill, and thereforeit is usually neutralized with lime and then disposed in a landfill. Thischapter will be an introduction to several materials that will be involved inthis project and also explains in detail about spent acid, how cold rollingindustry works, how steel making process is, what are iron hydroxide, inorganiccolor pigment and iron oxide as red color pigment are. The differences between hot working and cold working dependson processing temperature with respect to the material recrystallizationtemperature 1. If the processing temperature of mechanical deformation ofsteel is above recrystallization temperature, then it is hot working, else, itis cold working. Hot rolled steel are cheaper than cold roll steel because itis often manufactured without delays in the process, therefore the reheating ofthe steel is not required 2 . The differences in terms of appearance for bothhot roll and cold roll are, hot roll are scaly, has blue-gray finish and isrough to touch whereas for cold roll, it is glossy, has gray finish and smoothto touch.
It is a mill process that involves rolling of steel at hightemperature (normally over 927?C), which is above the steel’s recrystallizationtemperature. When steel is above recrystallization temperature, it can beformed and shaped easily, large deformation can be successively repeated,because the metal remains soft and ductile. Hot rolled products like steel barsare used in welding and constructions to make railroad tracks and I-beams 2,also used as agriculture equipment because of its high strength level andformability.
It is essentially further processing of hot rolled steel, itis processed further in cold reduction mills, where the material is cooled atroom temperature and follow by annealing or tempers rolling. This process willproduce steel with closer dimensional tolerances. When referring to barproducts, ‘cold finishing’ term is used, it helps result in higher yield pointsthat has 4 advantages, they are, cold drawing (increases yield and tensilestrengths), turning (gets rid of imperfect surface), grinding (narrows originalsize tolerance range) and polishing (improves surface finish) There are two facilities that are used in producing steel,first would be basic oxygen furnace (BOF) and second would be electric arcfurnace (EAF).
25 to 35% old scrap steel are used in making new steel for BOFprocess whereas EAF process uses 100% old scrap steel to make new steel. Theraw materials involved in steel making process would be scrap, Direct ReducedIron (DRI), Hot Briquette Iron (HBI) and Fluxing Agent (Lime)