Tim nhl hockey jerseys -
Jamie Hansen, Melt Shop Manager
Tom Curry, Melt Shop General Supervisor
NSS St. Paul, Minnesota, U.S.A.
Fernando Martinez, Vice President
Cesar Gamez, Specialist
AMI-GE, Monterrey, Mexico
Abstract
With the Smart Arc EAF arc regulation software, AMI-GE has already applied this fuzzy logic to numerous AC EAF installations with Tim nhl hockey jerseys great success. The Tim nhl hockey jerseys natural extension of this technology is the development of this system for the DC EAF. North Star Steel (NSS), with its policy in continuous enhancements programs for reducing conversion costs, was approached by AMI-GE with an optimization project for the EAF, using systems and expertise obtained from their installations on several AC EAF'ss, to be used for the first time on a DC electric arc furnace. A system was jointly developed at North Star Steel's Minnesota division to regulate the DC electric arc in a way, which yielded significant savings in electrical energy and graphite electrode consumption. Additional
improvements have been realized in the area of DC bottom electrode life, cold startup practices, and peak EAF power demand.
Introduction
AMI-GE supplies automation software to numerous metals industries worldwide, with special emphasis on electric furnace steelmaking. They hold majority market-share in AC EAF arc regulators in North America, and hence their knowledge base in this area is very strong. A recent innovation has been the development of "Smart Arc" addition to their regulator that utilizes fuzzy logic to optimize the arc to user-defined parameters. The system is flexible to receive input (and work in combination) from multiple inputs ? i.e. off gas, scrap, chemical energy systems, etc.
North Star Steel's Minnesota division is a diverse producer of long bar products. They produce a wide variety of steel grades comprising about rebar, structural, high C grinding media, and special bar quality. The melt shop is equipped with a 95 short ton VAI/Fuchs DC EAF, a ladle furnace, and a 4-strand continuous billet caster. Typical melt shop production is 500,000 short billet tons per year.
NSS St. Paul Melt Shop Data:
Furnace:
VAI/Fuchs DC EAF Commissioned May 1994.
19' Diameter EBT Shell
28" Diameter Electrode
Tamini 80 MVA total (2 x 40MVA) Transformer
GE rectifiers rated at 120 KA Max
In line Reactor Coils 25 micro Henries
Slag Door Oxy Lance with oxy-fuel burner/carbon lance (no other burners)
Bottom Electrode (Anode) design uses a "fin" type design where an array of thin sheets of steel are embedded in a monolithic magnesia refractory ramming mass.
Ladle Furnace:
Commissioned 1992 by VAI (from decommissioned EAF)
33 MVA transformer
Porous plug stirring
Bulk alloy, carbon injection, and wire feed capability
Caster:
Four Strand with various equipment manufacturers
26' radius
JME Dual Coil Mold EMS
Concast short lever arm oscillators
Stel Tek Dual point unbending withdrawals
14-ton tundish with alumina lining and metered nozzle practice
Bellows gas shrouding for tundish to mold stream protection
All grades cast with Oil Lubrication practice in the mold
6 section sizes:
120mm square
5 ? inch square
6 ? inch square
6 x 7 inch
6 x 8 inch
6 x 9 ? inch
Project Motivation
Before the AMI-GE partnership, the Minnesota Melt Tim nhl hockey jerseys Shop team had already put significant effort into tuning their existing power profiles. They tried to adjust the power profiles to the way they layered scrap in the bucket. These efforts yielded significant improvement and helped them understand their process and its limitations, but it helped them realize that their power profiles were a "one size fits most" profile which was unable to account for changing EAF conditions. This was most noted with changes in scrap density, which varied significantly with the higher quantities of obsolete scrap in the blend. Even when they adopted a strict "scrap layering" practice, the variation in the composition of the obsolete scrap was too great for a "one size fits most" power profile.
They also realized that the arc needed to have reaction characteristics (gains) tailored not only to the power program, but to the phase of the melt- namely bore in, melt in, and refine.
Scrap melting by definition has significant variability in its physical composition and a more flexible tool was needed to react to the constantly changing conditions in the EAF. NSS St. Paul realized that an improved tool was needed to further enhance their EAF improvements. Specifically, they needed a power program with more than simple discrete set points for current and voltage as a function of KWH. NSS needed a power program that would modulate set points within a defined range based on conditions in the EAF . AMI-GE wanted to develop such a tool for the DC furnace based on their similar expertise on AC furnaces. The partnership was a good match from the start, as both parties had common goals and a common vision of how it would be achieved.