The chattering /)henomelloll often occurrillg ill case oj extremely heav)1 cold rolling up to .94 0 0 total reduction has beell illvestiga ted at a Ihreestalld talldem mill. The resulls obtailled are as Jollows : (1) The chatterillg arises Jrom impaired lubricatioll Jar which illstability oj emulsions alld inadequate st"ength oj oil film are res/)ollsible. (2) Th e fluctuatiolls in strip thickness and lellsioll durillg the chalterillg correspolld to the second mode natural vibration(requellcy oj Ihe Toll aligllments. The chattering takes place when the tellsioll flu clllatioll Jrequenc)1 coinsides with the second mode natural./r•equellcy. (3) A theoretical analysis is made all Ih e basis oj NJalhieu's equatioll to predict the stability criterion oj a roll alignment under givell rolling conditiolls. I II order to make the rollillg stable withoul chattering. the stabili(y criterioll. C;C c > (J k jk)2 jll IIlUSt be Julfilled. w here C alld C c : coifficiellts ~(viscous dmll/)ing and critical dall/ping. J k: variatioll ~r rollillg stifflless, alld k : mill moduills combined with equivalent s/)rillg constant ~(stri/) being rolled. U) One oj the IIIOSt /Jractica ble alld ~ffective measure to meet th e above criterioll is the use oj the lubricallt with good lubrici(y. A lIew lubricant containing orgallo-metallic z inc compounds for extreme j)ressure additive is developed to successfully /Jrevent the chatterillg.

One of the important roles of temper rolling is the control of the surface roughness of a carbon steel sheet. The surface roughness is induced by imprinting a dull roll surface texture onto the rolled steel-sheet surface in the temper rolling process. When work roll-wear occurs, the roughness of the rolled sheet cannot be controlled, and the work roll surface must be reground, which affects the operational efficiency and product cost. Therefore, it is important to reduce the microwear of the work roll.1-5) Lubricants used for temper rolling are expected to reduce roll microwear. However, the effect of lubricants on roll microwear in laboratory-scale temper rolling has rarely been reported for the following reasons: (1) roll microwear can be evaluated only after long rolling, and (2) it is difficult to observe the same point of the roll surface before and after rolling. [6][7][8][9][10] In this study, the effects of lubricants on roll microwear have been evaluated in temper rolling. No lubricant (a dry condition), with a water-soluble lubricant, and with a mineral oil were the lubrication states. [7][8][9][10][11][12][13][14] Electric-discharged dull rolls and shot dull rolls were employed. Temper rolling experiments for as-annealed high-carbon steel strips and asannealed low-carbon steel strips were conducted in the reduction range of 1 to 3 %. The surface textures of the rolls were directly observed with a microscope by identifying the exact locations using markers to acquire three-dimensional microgeometry before and after rolling. The surface textures were described in terms of the arithmetical mean deviation of the assessed profile (Ra), the material ratio (Rmr), and the cross-sectional profile. Experimental Procedure MaterialsBoth as-annealed high-carbon steel strips and as-annealed low-carbon steel strips were employed. The characteristics of the high-carbon steel strip are as follows: carbon content, 0.65 wt%; thickness, 0.62 mm; width, 50 mm; length, 250 m; upper yield point, 454 MPa; lower yield point, 427 MPa; elongation at the yield point, 4 %. The characteristics of the low-carbon steel strip are as follows: carbon content, 0.08 wt%; thickness, 0.61 mm; width, 50 mm; length, 250 m; upper yield point, 328 MPa; lower yield point, 320 MPa; elongation at the yield point, 8 %. The Ra of both strip surfaces is 0.2 mm. The hardness of the high-carbon steel is 158 Hv (10) , which is equivalent to 24 Hs. The hardness of the low-carbon steel is 95 Hv (10) . These strips were utilized in temper rolling after degreasing with an alkaline agent. The surface roughness of a roll is imprinted on a carbon steel sheet by temper rolling. It is important to reduce roll microwear; since the roll surface causes microwear, the roughness of the rolled sheet could not be controlled. In most cases, temper rolling is performed using lubricants or under a dry condition. However, the influence of lubricant on roll microwear has not been clarified. In this study, roll microwear has been evaluated under three lubrication states, us...

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A finite‐element elastic‐plastic deformation analysis is required in order to predict a complete stress and deformation in a material for metal forming. There have been a few attempts for rolling analysis using the elastic‐plastic code, because the boundary conditions between roll and deforming material become complicated. In this study, an elastic‐plastic plane‐strain rolling analysis with friction has been attempted by the updated Lagrange code. Both slipping and sticking were taken into account for boundary conditions between roll and material. The stress and deformation analysis is performed using a nonsymmetric stiffness matrix solution (for curved and frictional boundaries). The elastic‐plastic analysis, coupled with the proposed frictional boundary model, evidently provides a reliable stress and deformation solution in the metal rolling process.