L-TEC Steel Industry Products is a pioneer and world leader in Scarfing Machines, and the scarfing process. Determined to keep an edge on the growing demands of the steel industry, in both production volume, and quality, L-TEC is continuously making advances in research and development. The Electronic Process Control (EPC) System is one of the newest advances in scarfing development. A combination of gauges, valves, regulators and transducers continuously monitor, regulate, and inform the operator, of the flow of gases to the scarfing machine.

The figure at right illustrates, in simplified form, the process controller system. The pressure at the scarfing unit is the important variable. A pressure tap at the unit senses the pressure, which is conveyed via a signal hose to the P/E unit on the scarfing machine. The P/E unit converts the pneumatic pressure to an analog electrical signal, which is input into the PLC controller. An analog signal is then output by the PLC to an E/P unit. This E/P unit converts the electrical signal to a relative pressure level. This output pressure is input to a P/P unit, which boosts the pressure signal, by a preset ratio factor. The increased pressure signal is of a sufficient pressure and capacity to provide the necessary pilot pressure to the gas regulator. This regulator provides the process supply to the scarfing units.

The PLC control logic provides several functions, two of which are important in the EPC system operation. The first function is logical in that the desired pressure operation is selected for specific time periods of the various operation sequences (e.g. Scarf cycle, pre-heat, etc.). The second function is as an EPC loop controller, whereby the resulting pressure at the unit is obtained and maintained in the required fashion. In the PLC program, the feedback (P/E measurement) is compared against the working pressure requirement, and correction to the analog output control is made. As a closed loop system, any changes in the steady state pressure by various disturbances can be corrected instantaneously.

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L-TEC Steel Industry Products is a pioneer and world leader in the Scarfing Machines, and the scarfing process. Determined to keep an edge on the growing demands of the steel industry, in both production volume, and quality, L-TEC is continuously making advances in research and development. The Smooth Surface Preheat Block (patent no. 6.174.491) is one of the newest advances in scarfing development. Scarfing oxygen exiting from the slot formed by the upper and lower preheat blocks must be uniform across its width and shielded against the aspiration of air into the stream to provide an efficient, uniform, and smooth metal removal. The fuel gas, which exits from the upper and lower preheat blocks, performs this shielding function. The lower preheat block (LPB) fuel gas is the most critical to surface quality since it is the last gas to pass over the molten surface of the steel as scarfing progresses. Any discontinuities in the fuel gas stream from the LPB will cause a disruption in the oxygen stream, which in turn will cause ridges or irregularities on the scarfed surface.

In the standard LPB design, fuel gas exits from the end of the block. The gas from each port is immediately drawn against the oxygen stream exiting the slot, providing the shield that prevents the aspiration of air into the reaction. For a continuous uninterrupted gas shield it is critical that each port remains open throughout the scarfing cycle. If ports become plugged by slag there is a disruption in the shield gas, and therefore in the oxygen stream, which in turn will produce irregularities on the surface of the steel. In the Smooth Surface Lower Preheat Block (SS-LPB) design, the physical end of the block is actually some distance beyond the exit point of the fuel gas ports. This extended baffle creates a "chamber" between it and the slot oxygen stream. As fuel gas is drawn from this chamber towards the steel surface, the oxygen compresses it against the end of the baffle. The result is a gas shield uniformly distributed across the width of the block. This design minimizes the effect of plugged gas ports on the surface quality, because uniform distribution of the gas is less dependent on flow from individual ports.

• Very smooth surface finish
• Allows adjacent fuel gas ports, in the preheat block to be plugged without detrimental effect on the scarfed surface. Should not postpone regular cleaning of scarfing units (generally performed after every shift).
• Smooth Surface Preheat Block can be retrofitted to fit any existing scarfing unit. If purchased as a retrofit, it is advisable that all of the lower blocks are exchanged en masse, otherwise a mixed steel surface smoothness will result.

L-TEC Steel Industry Products manufactures custom mechanized scarfing systems tailored to customer requirements. Our customers that scarf slabs sell to customers that make hi-quality sheet product used for cosmetic and thin-walled product which requires superior surface finish and is virtually without voids or inclusions. Applications include automotive (interstitial-free) sheet, appliance grade sheet, pipelines, ship plate, and thin-drawn steel cans.

L-TEC Steel Industry Products manufactures custom mechanized scarfing systems tailored to customer requirements. Our customers that scarf billets and blooms make Special Bar Quality (SBQ) steel. End-use applications include engineered steel products such as crankshafts, gears, steering rack bars, hubs, and connecting rods.

Specialty steel is used for safety-related parts in power trains and chassis. Quality, therefore, is critically important

Other End-User Applications Are Thin-Drawn Wire And Tubes