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Steel knowledge
Basic Knowledge on Steel
This information is created by G Steel PCL. to facilitate better understanding for the interested people or public with simple and straightforward content. So, this page is not suitable to be officially referenced to. G Steel PCL. reserves the right irresponsible for misinterpretation or any mistakes appearing in the content.
Iron & Steel?
Iron and steel seem similar to each other, but actuallly are different. Anyway, both iron and steel have been very important basic materials in developments of human society and living since the past until a long run. Iron, chemical symbol Fe, is a kind of metal element that exists in the nature, found in reddish-brown color the form of ore and combined with stone or other metals mostly in high land and mountain areas. To use iron, we have to refine iron ore by "smelting" process (to burn ore with very high temperature to make solid ore become liquid of white color while getting rid of other unwanted materials). In addition, iron is an essential nutrient for life as it is used to build hemoglobin in red blood cells. If a person lacks iron will easily get an anemia (deficiency in red blood cells). Steel is a major kind of alloy metal that usually refers to "carbon steel", which is simply composed of iron (Fe) and carbon (C), and a little content of manganese (Mn), silicon (Si) and some other elements. Steel is a metal that does not exist in the nature but made by human (and machines) using the basics of improving the quality of iron/Fe to achieve better properties, such as better formability or drawability, stronger, more flexible, tougher against crashing, able to load heavier weight, harder to be broken or torn off, etc., for suitability in different applications in real human life, however at low cost and affordable for people in general. And these are major advantanges of steel over other materials.
Carbon steel is a very basic material used in human living. The proportion of carbon steel use may be estimated around 80% of total steel use (every kinds of steel) in the world. Alloy steel is another kind of steel that has several subcategories: stainless steel, electrical steel, tool steel, and specialty steel. Because iron and steel are fully (100%) recyclable, at present, modernized steel production, like the one our "G Steel" mill has been doing since the startup till now, applies the process of taking unused steel scraps to recycle by melting in hi-tech "electric arc furnace (EAF)" to get liquid steel ready for properties improvement according to the customers' requirements. This production process conserves energy and environment better than the traditional smelter like a blast furnace that electric furnace is cleaner because blast furnace emits more carbon and other green-house gases to the Mother Earth's atmosphere, and the scrap reclying in electric furnace helps reduce wastes to the Mother Earth as well. The raw water consumed in our "G Steel" mill is circulated in a closed system, therefore puts no effect to the cummunity at all.
"Iron" vs "Steel"
Iron and steel seem to be similar, but are actually different from each other in several aspects that:
  • Steel is made of iron with carbon reduction to below 2% (by weight) so that it contains purity with iron content of higher than 94% and little portion of some other elements.
  • Steel is more flexible, durable, can be shaped into several different shapes and used in more various applications than iron as steel goes through quality improvement in steel-making (melting) process.
  • Iron is harder than steel, but iron is less strong than steel.
  • We can change the shape of Iron by manually hit and form it such as making a sword, or melt iron to be liquid iron and cast it into a mold or a die (this method is called "casting") such as casting a car engine; while we can change the shape of steel by rolling (with "rollers" equipment), folding, welding, forming, pressing, stamping, punching, drawing, etc., that vary according to the need of different applications, for examples, folding steel sheet to make a C-channel or folding and welding it to be a tube, pressing and drawing it to be an automotive part.
  • There are so many grades of steel under different countries' standards and also under the customers' specifications, while there are much less grades of iron, hence limited applications and market base than steel.
"Steel Sheets" vs "Steel Bars"
Steel sheets are defenitely different from steel bars that:
  • Almost 100% of steel bars are mainly used in construction, but steel sheets are used in various applications, for examples, construction, structures, manufacturing of automobiles, motorcycles, ships, other vehicles, packaging, water irrigation, public utilities, furniture, signs and posts.
  • The production of steel bars requires different machines other than the production of steel sheets, so a steel mill typically produces either steel bars, or steel sheets. If a mill wants to produce both, a huge investment in both distinguished production lines will be needed.
  • Basically, the content and surface of steel sheets are required to be purer, cleaner and smoother than those of steel bars according to the above-mentioned purposes of use.
  • Steel sheets need to be made from raw materials of higher quality than what steel bars need as quality of steel sheets is typically higher. Producing steel bars merely needs steel "scraps" as a main raw material, but that's not enough for producing steel sheets due to such unqualified purity of steel content, so it needs "pig iron" to be mixed with "scraps" by ratio of around 20:80 up to 30:70.
Hot-rolled Steel Sheet/Coil
Hot-rolled steel sheet is a kind of steel with flat shape made by hot-rolling process (with big rollers or rolling machines) that reduce the thickness of a "slab", semi-finished product, from typically 100 mm (as defined by G Steel) to be a thinner sheet of thickness range between 1.00 to 13.00 mm as ordered by the customer. Hot-rolled steel sheet is finished in a shape of coil called "hot-rolled coil" or "black coil" for the purpose of efficiency in storage, movement and transportation. Anyway, in case a customer wants the hot-rolled steel in smaller sheet shape, our mill can cut (shear) the coil into sheets as per width and length specified.
Hot-rolled coils/sheets are widely and regularly used in human's everyday living, mainly (more than 80%) are as per the following application groups:
  • Cold-rolling: to make cold-rolled coils for further processing into various downstream products.
  • Pickling and oiling: to make pickled and oiled hot-rolled coils/sheets further processing into various downstream products.
  • Forming into steel shapes: to make structural steel shapes, such as tubes or pipes (cylinder shape), angle (similar to L-shape), U-channel, C-channel, for use in construction, civil engineering and structures.
  • Cutting to sheets: to be retail products for use in industrial manufacturing, construction; general structures, mechanics and industrial uses.
  • Making gas cylinders (LPG, GNC/NGV), compressor cylinders (of cooling systems) and pressure vessels : for vehicles, gas stations, home uses, industrial uses and in hospitals.
  • Making gas line pipes, oil and petrochemical line pipes: mainly for industrial uses.
  • Others.
Steel uses in real life. (Location: Narathiwat Rachanakarin Road, Bangkok)
Click here.. to view example pictures of steel uses in real life!

Value-Added Products on Hot-Rolled Coil (HRC)
Hot-rolled coil is an upstream steel product that is widely processed further to add more values to downstream products and increasing marketing and trade opportunities, as well as profit margins.
  • Hot-rolled sheet
  • Hot-rolled strip (narrow width)
  • Skinpassed HRC
  • Pickled and oiled HRC
  • Galvanized hot-rolled coil/sheet
  • Cold-rolled coil
    • Cold-rolled sheet
    • Cold-rolled strip (narrow width)
    • Galvanized cold-rolled coil/sheet
    • Tin plate, tin-free (steel sheet)
    • Prepainted cold-rolled coil/sheet
    • Other coated coil/sheet