CLEAN STEEL / QUALITY IMPROVEMENT PROGRAM
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
- Ladle Metallurgy Processes – Argon Stir control, vacuum treatment, slag
- 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
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
- 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.
- SBQ products require set tolerances
- Chemical specifications
- SBQ physical properties
- Surface Quality
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.
- Two or three specialists on site for four to six weeks.
- Developement of Implementation Plan.
Same specialists for six to 12 weeks working with clients team to implement the plan.