Method and apparatus for manufacturing cold-rolled steel strip

A method of removing mill scale from the surface of hot-rolled strip coil in the manufacture of cold-rolled steel strip using an apparatus comprising an uncoiler linked to a scale removing unit by a first looper, a tandem cold-reduction mill linked to the scale removing unit by a second looper and a continuous annealing unit linked to the tandem cold-reduction mill by a third looper, comprising the steps of:

• breaking the mill scale on the surface of the hot-rolled strip coil by elongating the running hot-rolled strip coil to a predetermined percent elongation;
• removing the broken mill scale from the hot-rolled strip coil;
• detecting the condition of the mill scale downstream of at least one of the scale breaking and the scale removing steps adjacent the exit side thereof;
• and
• controlling the predetermined percent elongation as a function of the detected condition of the mill scale so that the top, bottom and middle of the hot-rolled strip coil can be pickled at substantially the same speed.

A method of removing mill scale from the surface of hot-rolled strip coil in the manufacture of cold-rolled steel strip using an apparatus comprising an uncoiler linked to a scale removing unit by a first looper, a tandem cold-reduction mill linked to the scale removing unit by a second looper and a continuous annealing unit linked to the tandem cold-reduction mill by a third looper, comprising the steps of:

• breaking the mill scale on the surface of the hot-rolled strip coil by elongating the running hot-rolled strip coil to a predetermined elongation, controlling the predetermined percent elongation as a function of at least one of the manufacturing conditions of the hot-rolled strip coil and the properties and quantity of the mill scale on the hot-rolled strip coil so that the top, bottom and middle thereof can be pickled at substantially the same speed;
• removing the broken mill scale from the hot-rolled strip coil;
• detecting the condition of the mill scale downstream of at least one of the scale breaking and the scale removing steps adjacent the exit side thereof;
• and
• further controlling the predetermined percent elongation as a function of the detected condition of the mill scale.

A cold-rolled steel strip manufacturing apparatus which comprises:

• an uncoiler linked to a scale removing unit by a first looper, a tandem cold-reduction mill linked to the scale removing unit by a second looper and a continuous annealing unit linked to the tandem cold-reduction mill by a third looper;
• the scale removing unit comprising a tension-leveller-type scalebreaker means for causing hot-rolled strip coil to elongate by 2 percent to 7 percent so that the top, bottom and middle thereof can be pickled at substantially the same speed, a brush unit to scrub off mill scale from the surface of the elongated hot-rolled strip coil and at least one pickling tank disposed such that the hot-rolled strip passes therethrough in series;
• and
• the scale removing unit being adapted to pass the entire length of the hot-rolled strip coil at a substantially constant speed through the tandem cold-reduction mill.