World of Steel® - POSCO Manufacturing Process

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Home> WOS Recommends > Posco for High Carbon Steel > Manufacturing Process

MANUFACTURING PROCESS:-

A) Production Process (at the customer) :-

Production processes differ according to the intended use of the parts. In addition, the heat treatment of the completed parts will determine the quality of the metal.

Usage Type	Parts Production Processes	Applications(Specifications)	Remarks
Structural	Hot rolling ->pickling ->Shearing ->Forming ->	Farm tools, chains (S45C)	Mainly for low grade uses
Structural	heat treatment (quenching and tempering)	Shanks (SCM435)	Mainly for low grade uses
Re-rolling	Hot rolling ->pickling ->skelp ->annealing (BAF) ->cold rolling ->	Needles,	Mainly for high greade uses
Re-rolling	Annealing (BAF) ->forming ->heat treatment (quenching and tempering)	Measuring tape (SK85)	Mainly for high greade uses
Working	Hot rolling ->shearing ->hot press & mold quenching	Impact beams	Some processes omitted
Pipe	Hot rolling ->skelp ->ERW pipe ->heat treatment	Automobile door impact beams (AUTOBEAM)	Replacement for round bar

*AUTOBEAM: POSCO standard (high-carbon boron steel)

Quenching & Tempering Heat Treatment:-
Heat treatment increases hardness and is consisted of two processes: Quenching (which brings high hardness along with great brittleness) is performed by heating the steel to a high temperature and then cooling it rapidly. Tempering (which lowers hardness while raising stiffness) is a re-heating process to a proper temperature. The degree of hardness after quenching as well as the hardness and heat treatment depth after tempering must be determined before heat treatment begins. Carbon content, degree of heat treatment, alloy content, and spherodized structure are all factors used in determining hardness.

B) Quality Requirement for Each Process (Quality Control Points):-

POSCO	Re-rolling Mill (Service Center)			Parts Maker
Steelmaking-Rolling	Pickling	Cold rolling	Annealing	Parts production	Q & T Heat Treatment
Chemical compostion	Pickling effectiveness	Cold roling efficiency -Strip breakage -Loss ratio	Surface decarbonization	Blanking efficiency -Fine blanking -Burrs -Cracks	Heat treatability -Hardenability
Inclusions,segregation	Sup-pression of ash defects	CR thickness tolerance	Spheroidization rate	Consistent structure and properties	Post heat treatment properties -TS, EL, hardness
Surface scale			Hardness after annealing		Final product performance -Fatigue resistance -Wear resistance -Durability
Crown
Property deviations along the longitudinal direction (hardness)
Microstructure control
Decarbonization

Low sulfur content is controlled to prevent internal quality degradation (1/4t, 1/2t lamination) from high-carbon segregation.
Cr is added to increase wear resistance, prevent surface decarbonization, and improve quenching effectiveness by suppressing pearlite transformation.
Low soluble aluminum content is maintained to improve quenching effectiveness through austenite growth.

PRODUCTION SPECIFICATIONS

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