Posco 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
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Hot rolling ->pickling ->Shearing ->Forming -> | Farm tools, chains (S45C) | Mainly for low grade uses |
heat treatment (quenching and tempering) | Shanks (SCM435) | ||
Re-rolling
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Hot rolling ->pickling ->skelp ->annealing (BAF) ->cold rolling -> | Needles | Mainly for high greade uses |
Annealing (BAF) ->forming ->heat treatment (quenching and tempering) | Measuring tape (SK85) | ||
Working
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Hot rolling ->shearing ->hot press & mold quenching | Impact beams | Some processes omitted |
Pipe
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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 Productions | Q & T Heat Treatment |
Chemical Composition
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Pickling effectiveness | Cold roling efficiency -Strip breakage -Loss ratio |
Surface decarbonization | Blanking efficiency -Fine blanking -Burrs -Cracks |
Heat treatability -Hardenability |
Inclusions,segregation
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Sup-pression of ash defects | CR thickness tolerance | Spheroidization rate | Consistent structure and properties |
Post heat treatment properties
-TS, EL, hardness |
Surface scale
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Hardness after annealing | Final product performance -Fatigue resistance -Wear resistance -Durability |
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Crown
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Property deviations along the longitudinal direction (hardness)
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Microstructure control
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Decarbonization
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- 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.