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QUALITY

CLEAN STEEL / QUALITY IMPROVEMENT PROGRAM


Objectives
The development of an effective clean steel practice that demands an active involvement of all aspects of the steelmaking operations. The Clean Steel Process is not a single program or technology. It involves:

  • Melting - charge mix design, refractory selection, slag chemistry
  • Tapping – temperature management
  • Ladle Management – temperature, carryover slag , chemistry and operational control
  • Ladle Metallurgy Processes – Argon Stir control, vacuum treatment, slag management
  • ontinuous casting – SEN design, tundish slag covers, spraying and drying practices, nozzle clogging and castability issues
  • Cast product inspection and testing – steel and slag sampling
  • Quality control and Scheduling – visual and precision testing equipment and identifications


Methodology
The complete Clean Steel Practice assessment and implementation program is as follows. The full implementation is carried out by a team of seven (7) specialists over a period of 8 to 12 months with 55 man weeks on site; 26 man weeks offsite. The program will involve high-tech tools such as:

  • Tundish water modelling
  • Mold water modelling
  • Special testing equipment
  • On line dynamic models

Secondly, several training sessions will be conducted for 10 – 20 technical and operating personell over a 6 week period to look at the following items:
Clean steel practice in the furnace and ladle

  • Slags and slag management
  • Deoxidation and the role of carbon and deoxidizers
  • Ladle management, cleanliness and temperature control
  • The role of slags and refractories in Clean Steel

In the development of a clean steel Practice one of the key issues is the implementation of a dynamic cast product inspection and test program. Fast and effective cast product sampling and testing systems are required to provide:

  • Sulphur prints
  • Hot macro etch
  • Electrolytic etch

 

                                                          Figure # 1. Technical Assistance Activities

SPECIAL BAR QUALITSPECIAL BAR QUALITY (SBQ) - A QUALITY IMPROVEMENT PROGRAM

                                                                        Figure # 2. SBQ Mini-Mill


Objetives

  • Clean steel is a prerequisite for the steelmaking process to obtain special bar quality
  • SBQ products are HSBQ products are Hot Rolled Steel in a variety of shapes (round, flat, hex, etc.) for the production of specific finished products through a defined processing route typically classified as quality criteria.

Real String Flats:

  • 5160 and 5160H gradend edge flats

Automotive suspension forging steels:

  • 1045, 1050, 4100, 8600 series steels – 1” to 1 ½” range

Engine component Forging (Connecting Rod)

  • 1140 and 1141 grade (re-sulphurized)

Cold Drawn Cylinder Shafting (for Chrome Plating)

  • 1045 Rounds
  • SBQ section set tolerances on the rolled section to ½ of the standard AISI/SAE tolerances for merchant bar.
  • Chemical specifications that have many restrictions for residual elements, most notably Cu, Cr, Mo, Ni, Sn, P and S.
  • SBQ physical properties include specific tensile, bend, fatigue, hardenability and machinability.
  • Surface quality must be Y2 AISI/SAE tolerances or better.

Metallurgical issues:

  • SBQ products require set tolerances
  • Chemical specifications
  • SBQ physical properties
  • Surface Quality

Methodology

Initial Assessment - Phase 1

Cooling bed issues - There are two significant issues related to the cooling bed design and maintenance:

  • Bed Flatness
  • Capability to pack bars

                                                                Figure #3. Dimensional Tolerances.

Real Rolling Advantages:

  • Roll a range of bar thickness from a single set of edge rolls. This will reduce mill changes and roll inventory requirement.
  • Tagging products for automotive application requires tagging in compliance with AIAG (Automotive Industry Action Group) specifications. Review visual eddy current and ultra sonic inspection system.

Initial Phase

  • Two or three specialists on site for four to six weeks.
  • Developement of Implementation Plan.

Implementation Plan
Same specialists for six to 12 weeks working with clients team to implement the plan.