The Quad R-factor System has paid for itself in months through significant yield improvements. and sustainable production practices. Cobble rates have been cut in half with reported yield increases of up to 2% and shift utilization increased by 3%.
These results have been achieved using a holistic approach to rolling mill operations. The Quad R-factor System (QRFS) clearly shows the operators on the mill floor how the mill is set up and running, compared to the setup sheet. Roll gap (and other mill adjustments) can be made to bring the product into spec at each mill stand, then monitored for timely roll pass wear adjustments. This helps maintain the bar size throughout the entire rolling, greatly reducing cobbles and off spec bars, which delivers the yield improvements.
The QRFS monitors and shows if there is any crew-to-crew or rolling-to-rolling variation, with the ability to see the variation and allow the operators to make the required mill adjustments to get the product back on spec, as defined by the setup sheet. Keeping all the stands set to the correct bar size throughout the rolling allows for optimum guide operation, resulting in fewer guide related cobbles.
During the first few months of operation, the QRFS allows the mill to identify any setup sheet errors by visually comparing the setup sheet plan to the actual roll settings. It is normal to make numerous setup sheet changes based on seeing how the mill crews actually prefer to roll each product. Once the setup sheets are trusted & proven, and crew variation is eliminated, the mill practices become standardized, reliable and repeatable. Improvements to many key indicators have been observed including startup/achieve section time, cobble rate, out of spec bars (at startup and after a pass change), yield and throughput rate.
Products that continue to show excessive variation indicate that there may be something wrong with the pass design. Quad can conduct a pass design review to determine what passes and/or gap settings are causing issues that require the operators to continually make gap adjustments to “fix” the pass design problem. Modifying the pass design to address the initial design flaw can result in significant improvement to the product specific yield and utilization. Yield improvements of up to 6%, with utilization increases over 20% have been observed.
In order to develop standard methods on how to setup, adjust and maintain section, Quad has a portable Lab Training mill that can be brought to the Rolling Mill site for hands-on operator training. Shapes such as rounds, rod, slit rebar, flats and angles can be rolled on the training mill. Classes use actual mill setup sheets as a guide to allow the operators to “see for themselves”. This training method lets the operators see the bar rolled up close and to study the bar after each pass, something that cannot be safely done in the rolling mill environment.
Background:
A steel mill provides a harsh and dangerous environment where it is very difficult and time consuming to measure the hot bar size accurately. In order for the rolling mill process to work properly, the Operator must know how the stand mill stand gaps are actually set. Traditionally this information is obtained by having the operator measure the hot moving bar with a set of calipers. This places the Operator beside the equipment while in operation, putting the Operator into the direct “line of fire” of the hot moving bar.
The electrical speed control system uses a speed matching algorithm along with operator input to set up a tension free condition in the bar between the continuous mill stands. Based on the speed control algorithm, it is possible to use this information, presented in a form the operator can utilize, to estimate the work done on the bar at each pass. This makes it possible for the operator to monitor changes in the bar size (work done) at each stand and determine when the mill stands should be adjusted to compensate for roll pass wear.
The Quad R-factor System automates this data gathering process and presents the results to the operator in a timely, easy to read graph that shows how the mill is currently set up. The results for each bar rolled are stored in the QMOS database, allowing long term trends to be analyzed.