Rolling

ROLLING

Rolling is the most rapid method of forming metals into desired shapes by plastic deformation in between rolls.

The forming of  bars, plates , sheets, rails and other steel sections  are produced by rolling.

1.Classification of Rolling mill based on number of  rolls.

1.Two High Rolling Mill.

2.Three high Rolling Mill

3.Four high Rolling Mill

4. Multi Rolling Mill.

5.Universal Rolling Mill

6.Planetary Rolling Mill.

1.Two High Rolling Mill.

2. DEFECTS IN ROLLED PARTS

There are two types of major defects on the rolled products.

(a)  SURFACE DEFECTS

(b) INTERNAL SURFACE DETECTS.

(a)  SURFACE DEFECTS Major surface defects on rolled products are scales, rust, scratches,cracks, and pits. These defects occurs on the rolled products due to the impurities and inclusions present in the original cast materials.,

(b).INTERNAL SURFACE DEFECTS

i. WAVINESS OR WAVY EDGES.

It occurs due to the bending of rolls. The rolls acts as a straight beam. If the material flow is continuous and to maintain this continuity, strains with in the material should adjust with itself. There are compressive strain on the edges and tensile strain at the centre. The edges are restrained from expanding freely in the longitudinal direction because of which wavy edges on the sheet will be produced.

ii. Zipper Cracks

It occurs due to poor material ductility, at the rolling temperatureCamber is provided to avoid this defect., Camber is providing slightly large diameter at the center of rolls than that at the edges.

iii. FOLDS

Folds occur if the reduction per pass is very less.

iv. Alligatoring.

It is the splitting of work piece along the horizontal plane on exit, with top and bottom part following the rotation of their respective rolls.

v. Lamination.

These are small cracks which may develop when reduction in thickness is excessive.