Frequently Asked Question (FAQ)

Frequently Asked Question (FAQ)

Hot Rolled Coil steel grade HR1 is used for general forming application according to Thailand Industrial Standard TIS 528-2548 regulated for domestic market.Hot Rolled Coil steel
grade SPHC is also used for general forming application according to Japanese Industrial Standard JIS G3131-2005.
Both grades of Hot Rolled Coil steel are similar in terms of mechanical properties and chemical composition. More details are shown as below:
Hot Rolled Coil steel grade HR1 (TIS 528-2548)
Chemical composition (wt %)
C = 0.15 max.
Mn = 0.60 max.
P = 0.05 max.
S = 0.05 max.

Mechanical property
Tensile strength = Not specified

Hot Rolled Coil steel grade SPHC (JIS G3131)
Chemical composition (wt %)
P = 0.050 max.
S = 0.050 max.

Mechanical property
Tensile strength = 270 N/ (min.)

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Hot Rolled Steel grade SS400 is used for general construction application. This steel can be supplied as Hot Rolled Coil, Slitted Coil, Plate and Cut Sheet according to TIS 1479-2541 and JIS G3101-2004 standard specification. Mechanical properties and chemical composition are shown as table below.

TIS 1479-2541 and JIS G3101-2004

Mechanical Property
GradeY.S. (Mpa)T.S. (Mpa)%EL
 THK ≤ 16 mm16 mm < THK ≤ 40 mmTHK > 40 mm THK (mm)%EL (min)
SS400245 min.235 min.215 min.400 – 510≤ 5
5 < THK ≤ 16
16 < THK ≤ 50 > 50
Chemical Composition


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Hot rolled steel grade S20C is used for machinery structure according to TIS 1501- 2552 and JIS G4051-2005 standard specification.
Chemical composition are shown as table below (wt%)




Steel grade S20C is suitable used in machinery component and engine such as gearwheel or chain etc., which required suitable hardness for use.

Hot rolled steel is steel that produced by hot rolling process at high temperature. Its thickness range can be 0.9 mm and more. Hot rolled steel surface is generally gray black surface because of the iron oxide formed at high temperatures. Hot rolled steel can be supplied in coils or sheets and can be used for many applications that do not require such a high surface quality.

  •  C-Channel
  • Pipe and tube
  • Spiral pipe
  • Gas Cylinder
  • Container
  • Shipbuilding
  • Automotive Structural parts
  • Raw materials for cold rolled steels

Cold rolled steel is steel that produced by cold rolling process and used hot rolled steel as raw material. Hot rolled steel are put into the cold rolling process and thickness will be reduced at room temperature. Typically, cold rolled steel thickness is ranging from 0.14 mm to 3 mm, shiny surface suitable for application that requires a higher surface quality and thin gauge steel.

In general, cold rolled steel higher residual stress with high hardness, low elongation and inconsistent mechanical properties, so that, it is not suitable for forming application. In order to improve the properties of cold rolled steel, annealing process should be applied to cold rolled steel to relieve the residual stress in the steel which is no effect on thickness. Surface quality is also improved and elimination of yield point elongation can improve formability. Application of cold rolled steel are following:

  • Automotive parts
  • Electronics and home appliance
  • Continuous product
  • Using for galvanize steel or coated steel

Hot Rolled Coil
Hot rolled coil is produced by slab as raw materials. Slab thickness range is about 200 to 250 mm. Slab are heated in furnace and then hot rolled at the temperature range about 1,000 to 1,250 C to final thickness about 0.9 mm to 20 mm according to customer requirement. Then, strip is cooled down by water coolant before entering the coil box as hot rolled coil. Hot rolled coil surface is dull black and wounded in a roll (coil) called “hot rolled coils” for convinient to be stored, transported and feasible to be processed for end product.

Hot Rolled Coil Pickled and Oiled
Hot rolled coil pickled and oiled is produced through a pickling process to remove out iron oxide on the steel surface and then coated with rust preventive oil. The surface of hot rolled steel pickled and oiled is dull gray, suitable for automotive part and home/electrical appliance. It can be used instead of cold rolled steel with a thickness greater than 1.2 mm.