Work rolls crossing type mill, rolling system and rolling method

A rolling method for use in a mill comprising a pair of work rolls and a pair of back-up rolls for respectively supporting said pair of work rolls, comprising the steps of:

• spraying a coolant onto said pair of work rolls from an exit or entrance side of said mill for cooling said pair of work rolls;
• controlling inclinations of said pair of work rolls in horizontal planes so that axes of said pair of work rolls are crossed with respect to axes of said pair of back-up rolls, respectively, and those axes of said pair of work rolls are also crossed with respect to each other, thereby controlling the strip crown of a strip to be rolled;
• and
• simultaneously spraying a lubricant onto a surface of said back-up rolls at locations spaced from contact positions between said pair of work rolls and said pair of back-up rolls without being impeded by coolant gathering in the contact positions to lubricate between said work rolls and said back-up rolls thereby to reduce thrust forces exerted on the back-up rolls and work rolls due to rotation thereof while the axes of said work rolls are crossed with respect to each other.

A work rolls crossing type mill comprising a pair of work rolls and a pair of back-up rolls for respectively supporting said pair of work rolls, said pair of work rolls being inclined in horizontal planes and arranged such that axes of said pair of work rolls are crossed to axes of said pair of back-up rolls, respectively, and those axes of said pair of work rolls are also crossed with respect to each other, said mill further comprising:

• thrust force reducing means for reducing thrust forces exerted on said pair of back-up rolls and pair of work rolls due to rotation thereof while the axes of said work rolls are crossed with respect to each other, said thrust force reducing means including lubricant supply units for supplying a lubricant to between said pair of work rolls and said pair of back-up rolls on an exit side of the mill, said lubricant containing raw lubricant oil meeting the following requirements:
• (a) the coefficient of friction between said work rolls and said back-up rolls is in the range of 0.04 to 0.1;
• (b) the viscosity is not larger than 80 centi-Stokes at 40.degree. C.;
• (c) mineral oil and synthetic ester not less than 5% are included as base oil;
• (d) a fatty acid in the range of 0.03 to 0.5% is included as an oiliness enhancer;
• and
• (e) an extreme pressure additive not less than 0.1% is included.

A work rolls crossing type mill comprising a pair of work rolls and a pair of back-up rolls for respectively supporting said pair of work rolls, said pair of work rolls being inclined in horizontal planes and arranged such that axes of said pair of work rolls are crossed with respect to axes of said pair of back-up rolls, respectively, and those axes of said pair of work rolls are also crossed with respect to each other, said pair of work rolls being further able to shift in respective roll axial directions, said mill further comprising:

• thrust force reducing means for reducing thrust forces exerted on said pair of back-up rolls and pair of work rolls due to rotation thereof while the axes of said work rolls are crossed with respect to each other, said thrust force reducing means including lubricant supply units for supplying a lubricant to between said pair of work rolls and said pair of back-up rolls on the exit side of the mill, said lubricant containing raw lubricant oil meeting the following requirements:
• (a) the coefficient of friction between said work rolls and said back-up rolls is in the range of 0.04 to 0.1;
• (b) the viscosity is not larger than 80 centi-Stokes at 40.degree. C.;
• (c) mineral oil and synthetic ester not less than 5% are included as base oil;
• (d) a fatty acid in the range of 0.03 to 0.5% is included as an oiliness enhancer;
• and
• (e) an extreme pressure additive not less than 0.1% is included.

A rolling method for use in a mill comprising a pair of work rolls and a pair of back-up rolls for respectively supporting said pair of work rolls, comprising the steps of:

• spraying a coolant onto said pair of work rolls from an exit or entrance side of said mill for cooling said pair of work rolls;
• controlling inclinations of said pair of work rolls in horizontal planes so that axes of said pair of work rolls are crossed with respect to axes of said pair of back-up rolls, respectively, and those axes of said pair of work rolls are also crossed with respect to each other, thereby controlling the strip crown of a strip to be rolled;
• simultaneously spraying a lubricant to between said pair of work rolls and said pair of back-up rolls on the exit side of the mill to lubricate between said work rolls and said back-up rolls thereby to reduce thrust forces exerted on the back-up rolls and work rolls due to rotation thereof while the axes are crossed with respect to each other;
• and
• using, as said lubricant, raw lubricant oil meeting the following requirements or an emulsion of said raw lubricant oil:
• (a) the coefficient of friction between said work rolls and said back-up rolls is in the range of 0.04 to 0.1;
• (b) the viscosity is not larger than 880 centi-Stokes at 40.degree. C.;
• (c) mineral oil and synthetic ester not less than 5% are included as base oil;
• (d) a fatty acid in the range of 0.03 to 0.5% is included as an oiliness enhancer;
• and
• (e) an extreme pressure additive not less than 0.1% is included.

A rolling method for use in a mill comprising a pair of work rolls and a pair of back-up rolls for respectively supporting said pair of work rolls, comprising the steps of:

• spraying a coolant onto said pair of work rolls from an exit or entrance side of said mill for cooling said pair of work rolls;
• controlling inclinations of said pair of work rolls in horizontal planes so that axes of said pair of work rolls are crossed with respect to axes of said pair of back-up rolls, respectively, and those axes of said pair of work rolls are also crossed with respect to each other;
• controlling shift amounts of said pair of work rolls in respective roll axial directions in addition to inclinations of said pair of work rolls, thereby controlling the strip crown of a strip to be rolled,
• simultaneously spraying a lubricant to between said pair of work rolls and said pair of back-up rolls on the exit side of the mill to lubricate between said work rolls and said back-up rolls thereby to reduce thrust forces exerted on the back-up rolls due to rotation thereof while the axes of said work rolls are crossed with respect to each other, and
• using, as said lubricant, raw lubricant oil meeting the following requirements or an emulsion of said raw lubricant oil:
• (a) the coefficient of friction between said work rolls and said back-up rolls is in the range of 0.4 to 0.1;
• (b) the viscosity is not larger than 80 centi-Stokes at 40.degree. C.;
• (c) mineral oil and synthetic ester not less than 5% are included as base oil;
• (d) a fatty acid in the range of 0.03 to 0.5% is included as an oiliness enhancer;
• and
• (e) an extreme pressure additive not less than 0.1% is included.

A work rolls crossing type mill comprising:

• a pair of work rolls;
• a pair of back-up rolls for respectively supporting said pair of work rolls;
• cooling means for spraying a coolant onto said pair of work rolls from an exit or entrance side of said mill for cooling said pair of work rolls;
• said pair of work rolls being inclined in horizontal planes and arranged such that axes of said pair of work rolls are crossed with respect to axes of said pair of back-up rolls, respectively, and those axes of said pair of work rolls are also crossed with respect to each other;
• and
• thrust force reducing means for reducing thrust forces exerted on said pair of back-up rolls and pair of work rolls due to rotation thereof while the axes of said work rolls are crossed with respect to each other;
• said thrust force reducing means including lubricant supply units arranged to respectively face said pair of back-up rolls on the exit side of the mill for spraying a lubricant onto surfaces of said back-up rolls at locations spaced from contact positions between said pair of work rolls and said pair of back-up rolls without being impeded by coolant gathering in the contact positions, thereby maintaining a coefficient of friction between said work rolls and said back-up rolls in the range of 0.04 to 0.1.

A work rolls crossing type mill comprising:

• a pair of work rolls;
• a pair of back-up rolls for respectively supporting said pair of work rolls;
• cooling means for spraying a coolant onto said pair of work rolls from an exit or entrance side of said mill for cooling said pair of work rolls;
• said pair of work rolls being inclined in horizontal planes and arranged such that axes of said pair of work rolls are crossed with respect to axes of said pair of back-up rolls, respectively, and those axes of said pair of work rolls are also crossed with respect to each other;
• and
• thrust force reducing means for reducing thrust forces exerted on said pair of back-up rolls and pair of work rolls due to rotation thereof while the axes are crossed with respect to each other;
• said thrust force reducing means including lubricant supply units arranged to respectively face said pair of back-up rolls on an exit side of the mill for spraying a lubricant consisting of emulsion prepared by diluting with water a raw lubricant oil containing mineral oil and synthetic ester not less than 5% as base oil onto surfaces of said back-up rolls at locations spaced from contact positions between said pair of work rolls and said pair of back-up rolls without being impeded by coolant gathering in the contact positions, thereby maintaining a coefficient of friction between said work rolls and said back-up rolls in the range of 0.04 to 0.1.

A work rolls crossing type mill comprising:

• a pair of work rolls;
• a pair of back-up rolls for respectively supporting said pair of work rolls;
• cooling means for spraying a coolant onto said pair of work rolls from an exit or entrance side of said mill for cooling said pair of work rolls;
• said pair of work rolls being inclined in horizontal planes and arranged such that axes of said pair of work rolls are crossed with respect to axes of said pair of back-up rolls, respectively, and those axes of said pair of work rolls are also crossed with respect to each other;
• and
• thrust force reducing means for reducing thrust forces exerted on said pair of back-up rolls and pair of work rolls due to rotation thereof while the axes of said work rolls are crossed with respect to each other;
• said thrust force reducing means including lubricant supply units arranged to respectively face said pair of back-up rolls on an exit side of the mill for spraying a lubricant prepared by diluting with water a raw lubricant oil containing a fatty acid in the range of 0.03 to 0.5% as an oiliness enhancer for suppressing vibrations of said pair of back-up rolls and pair of work rolls due to rotation thereof while the axes of said work rolls are crossed with respect to each other onto surfaces of said back-up rolls at locations spaced from contact surfaces of said back-up rolls at locations spaced from contact positions between said pair of work rolls and said pair of back-up rolls without being impeded by coolant gathering in the contact positions, thereby maintaining a coefficient of friction between said work rolls and said back-up rolls in the range of 0.04 to 0.1.