Advanced Process Control Program

In April 1993, the American Iron and Steel Institute (AISI)--with 70% funding support from the U. S. Department of Energy -- launched an ambitious, five-year collaborative research program aimed at keeping North American steel makers on the leading edge of world steelmaking technology.

The joint project, called the Advanced Process Control Program, or APC, has already made substantial progress toward meeting it's goal of providing continuous, online measurements of critical product properties.

The APC microstructure engineering project has continued under a TRP project and gone into commercialization and for more information, please go to the website of our commercial partner, INTEG process group, inc. at the following link:

http://www.integpg.com/hsmm/optimization_models.aspx

By leveraging the resources and research capabilities of 15 AISI member steel companies with world-class scientific skill from academia and government...and from our suppliers and customers; APC is helping move the steel industry towards realizing their vision of the steel plant of the future -- one where a collection of tightly controlled energy efficient processes yields superior product quality on a near inventory free basis.

The program initially had six separate research projects dealing with the making, rolling and coating of steel. Today five of those projects remain active and are progressing well. One product is being used by APC participants, is commercially available, and two more are nearly complete and ready for commercial marketing.

Let's look at the progress that's been made.

One important project - Microstructure Engineering in Hot Strip Mills, is aimed at improving hot rolling, perhaps the most complex process in steelmaking. Researchers at the National Institute of Standards and Technology, The University of British Columbia and U. S. Steel are developing computer models that quantitatively link mechanical properties to the process parameters of the mill.

The first stage of this five-year project was the development of a predictive model for A-36 carbon steel. The model was delivered in May 1995 to participating steel makers for use in their mills. This model was the first product in the program to go into actual use in the industry. The model is user-friendly so participants can evaluate it quickly, then tailor it to the configuration of their hot strip mills in a matter of minutes. Continuous user feedback has been extremely valuable for demonstrating how well the model predicts mechanical properties on line and in identifying improvements for upgrading future releases.

Currently, the model has been expanded to include DQSK, HSLA-V and HSLA-Nb grade steels. The latest version was released to participating steel makers in October 1997. Enhancements to this version include the addition of bottom sprays to the run out table model and an improved Steckel mill model. For the remainder of the program, efforts will focus on tailoring the model to include micro-alloy grades such as titanium and niobium-bearing steels. Also, we'll have added interstitial-free steels for critical automotive applications. At that time, we'll have a commercially marketable product for these grades.

The Microstructure Engineering project will allow steel companies to optimize their hot rolling practices, specifically those regarding cooling and coiling. And equally important, it will reduce the time and expense of developing new grades of steel by permitting much of the experimentation to be done off-line.

The second and third projects both relate to galvannealed steel, a product that's popular with the auto industry because of its outstanding forming, painting and corrosion resistance qualities.

In the galvanneal process, steel is coated with a mixture of zinc, the steel strip is first dipped into a zinc bath, then passed through a Galvannealing furnace. The furnace extends the time in which the steel is in contact with the molten zinc and enhances migration of the iron from the steel into the zinc coating. During this stage of the process, temperature variations and the distribution of the iron/zinc phases in the Galvanneal steel strip surface directly affects the quality of the end product.

The first Galvanneal project -- Temperature Measurement of Galvanneal Steel uses thermographic phosphor technology to assure accurate online temperature control of the Galvannealing furnace. The two year project is being conducted by Oak Ridge National Laboratory, with National Steel Corporation as the sponsoring company.

Despite lengthy contract negotiations which delayed the initial project start date by 12 months, early successful Laboratory demonstrations bolstered a one-year acceleration of the project schedule. The research and development phase of the project successfully completed in August 1996 - one year ahead of schedule and on budget.

Plant trials were conducted during 1996 at National Steel's Midwest plant, in Portage Indiana, during these trials, the sensor provided accurate online temperature measurements, independent of surface emissivity, within + or - 5 degrees Fahrenheit.

Bailey Engineers, Canonsburg, PA has been selected to commercialize this technology. Commercial Galvanneal temperature Measurement sensors should be available in late 1998 - early 1999.

The second galvanneal project -- Phase Measurement of Galvanneal Steel successfully completed its research effort last year. Researchers from Data Measurement Corporation (now Measurex - DMC), working with industry sponsors, Inland Steel and Stelco, have developed an online instrument to determine the microstructural distribution of iron and zinc phases present in the galvanneal coating. Because the final product properties for Galvanneal depend on the phase distribution in the coating, this instrument will allow producers to make this measurement online in order to produce galvanneal having the required properties with minimum rejection. Recently we contracted Measurex - DMC to manufacture, market and sell this technology.

The fourth advanced process control project -- Online Non - Destructive Mechanical Properties Measurement deals with the consistent production of large quantities of steel with well-controlled and uniform mechanical properties. An essential step in meeting this challenge is the development of reliable sensors to non-destructively monitor the mechanical properties of cold rolled steel--yield and tensile strength, elongation and strain hardening value online. Current determinations of mechanical property measurements are done off line in time consuming and costly destructive tests.

This project is developing a sensor which uses a laser to direct ultrasonic waves at the strip. The strength of the waves is reduced by irregularities in the microstructure, such as porosity and grain size. Changes are detected by a second laser, which translates the pulses into a digital signal for the computer.

Early work on this part of the project has improved the state of the art of laser ultrasonics. Early results indicate that the laser energy doesn't damage the surface of the strip. Prototype design and development began in December 1995. Initial prototype trials are scheduled for 1998.

The fifth---and perhaps most extensive---of the APC projects is the development of Optical Sensors and Controls for Improved Basic Oxygen Furnace (BOF) Operation it builds on initial research by Sandia national laboratory, Bethlehem steel and Insitec Measurement Systems.

One objective of the project is to develop laser-based sensors to measure the temperature and composition of off-gases, which provides an early and direct indicator of when the steelmaking process is complete.

The process uses an infrared laser beam fired across the mouth of the vessel to a spectrometer that detects molecular interference with the beam. The instantaneous analysis of CO, CO2 and H20 in the gases indicate the carbon level of the bath with a high degree of accuracy.

Another part of the project involves the use of an optical sensor, mounted in the tip of the oxygen lance, to measure the temperature of the hot spot zone where oxygen ignites as it contacts the steel. Since the hot zone temperature drops off rapidly when all the carbon is burned off, it also provides a rapid indication of when the heat is done. When the surface of the steel bath is exposed, the bulk bath temperature can be directly measured.

A prototype was installed in an existing BOF oxygen lance at sparrows point in May 1995. The lance based sensor survived nine heats with no adverse effects from immersion in the bath...And oxygen delivery through the lance was not impaired. Additional trials conducted in October 1995, though limited in duration, helped identify sensor design deficiencies, and what was needed to improve the sensor's mill hardiness to move towards a viable commercial product. Long term trials, six months in duration, have been in progress since June 1997, Four sensors, two on each furnace carriage, allow continuous data collection providing, Bath height measurement using a triangulation technique, the ability to see into the bath, endpoint carbon prediction before the end of blow, and bulk bath temperature measurements from slag temperatures.

Following successful completion of these trials, we will commercialize this technology for BOF's. This project has also been expanded to include the development of two other laser-based sensor applications. These sensors will be able to measure the height of the bath in the furnace...And contour the inner surface of a hot BOF furnace in a matter of minutes. These readings can be used for post-combustion control and will let operators know almost immediately when the refractory is wearing out or slag is building up. Recent results in the development of these sensors are very encouraging.

In summary, the Advanced Process Control Program is helping to lay the foundation for our industry to promote steel's continued role as a key national resource in the years ahead.

Its five ongoing projects have already begun to pay significant dividends. The APC program will elevate our ability to determine product properties online to a new plateau. By helping to establish the critical link between process and product, it will significantly narrow the gap between today's technology and the steel industry of the future.