Interview Questions steel industry

What is the main difference between Hot Rolled Steel and Cold Rolled steel?

Cold Rolled steel will have closed thickness profile and good surface texture & flatness compared with Hot Rolled Steel. Hot Rolled Steel is rolled above Recrystallization Temperature and Cold Rolled steel is of below Recrystallization Temperature. Hot Rolled coils are available above 1.60 mm to 10.00 mm thickness & Cold rolled sheets are available up to 0.10 mm to 4.00 mm Worldwide.

What is hot rolled slitting? Why it is done?

Hot Rolled Slitting is removal of uneven edges & Saw edge of the Hot rolled Coil for smoothening cold rolling operation.

What is Pickling? Why it is being done? Which Acid is used in Pickling process?

Pickling is the process of Acid cleaning of the sheet which removes Scale (Fe2O3) from the surface of the strip. These Oxide layers are to be essentially removed for smooth cold rolling operation & better surface quality. Hydro Chloric Acid is generally used in Pickling process.

What is the advantage of 6HI Hitachi over other rolling mills?

Auto gauge control(AGC), Auto Shape control, X-Ray gauge, Universal crown & IMR Shifting to have better thickness tolerances, good shape in comparison to other Rolling mills.

What is Electrolytic Cleaning process& how it is different from other cleaning process of steel?

Electrolytic cleaning process is capable of removing micro fines of Iron & Dirt and other unwanted foreign particles from cold rolled steel strip surface. This cannot be obtained from conventional cleaning processes.

What type of Alkali used in ECL?

Silicate Alkali with other additives like surfactants etc. is used to achieve required level of cleanliness.

What is Annealing? What are the types of Annealing? What are the benefits of a closed Annealing?

Annealing is the process of Heat Treatment in which internal stresses of highly cold worked material are relieved. Steps of annealing include stress reliving, recrystallization and grain growth. Batch type annealing and Continuous Annealing are two types of Annealing.

What are the advantages of H2 annealing?

Inert atmosphere of H2 gas has good conductivity than N2 gas. This provides good surface appearance of the strip and Consistency of property .

What is Skin pass process? Why it is done over Steel? What is its advantage?

Skin pass is the process of removing Yield Point Elongation of Annealed sheet. This is done for improving Surface finish & Flatness of the Strip. During this stage texture of steel is defined with application of rust preventive oil and also shape control of the required gauge by stress leveller.

What is Corrugation?

The process of forming or ribbing a flat sheet of material into a consistent, symmetrical profile to increase that material’s strength to weight ratio up to 30% over the conventional material. The forming of sheet metal into a series of straight, parallel alternate ridges and grooves with a rolling mill equipped with matched roller dies or a press brake equipped with specially shaped punch and die.

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