Temper rolling mill is used to suppress yield point elongation in low carbon steels, by providing elongation to the material beyond its elastic region. Coils are passed through Batch Annealing Furnace (BAF) to reduce the internal stress on the coils, and are then fed to the temper rolling mill where a combination of tension (achieved by pay off reel) and roll force helps in suppressing yield point elongation.
There are two setups at temper rolling mill which are Single Reduced (SR) to achieve 1.5% to 2% coil elongation), and Double Reduced (DR) to achieve 15% to 30% coil elongation. Coils of thickness 0.17mm to 0.60mm are fed into SR setup and 0.17mm to 0.35mm are fed into DR setup. The width varies from 600mm to 1200 mm for SR, and 600mm to 1050mm for DR. The minimum coil diameter is 762 mm and maximum is 2075mm for both setups. The coils are passed through the rolling mill at a maximum speed of 1830 mpm for SR and 1400mpm for DR. The rolled-out coil sheets are inspected to check attributes like - surface condition, shape, hardness and strip roughness which is done manually.
Currently, these attributes are measured/inspected by manual intervention as explained below –
Surface Inspection - Post temper rolling, the coil is taken to designated place for sampling. After removing 3 to 5 wraps from the outer diameter, inspection of both (top & bottom) the surfaces are carried out visually as shown in figure 1. Various defects include Luider Band, Dent, Pitted Surface, rough spots, scratches, fluty marks etc.
Shape - A sample of approximately 800mm X 800 mm is cut after removing 3 to 5 wraps from the coil. One edge of the sheet, across the rolling direction is stuck to the magnet on the board of measuring fixture and the other edge is allowed to hang freely. The lift (when the sheet curls up) from the board is measured through a measuring scale as shown in figure 2. This helps in measurement of curling of a sample 800 mm X 800 mm either across or along the rolling direction.
Hardness - A sample of approximately 1 sq. inch is cut after removing 3 to 5 wraps from 3 locations (both edges & middle) across the rolling direction of the coil. The sample is measured on Rockwell superficial scale as shown in figure 3.
Roughness - A sample of approximately 6 inches in width is cut across the rolling direction. A roughness tester is used to measure the strip at 6 locations of the sample (3 locations on the top and 3 on bottom surfaces) to measure the overall roughness as shown in figure 4.
We are looking for
Online measurement of all the attributes with recording facilities is desired. Ideally, all the attributes should be measured by an integrated setup, but different units will also work if the space becomes a constraint.