PAPER: PREDICTION OF EFFECT OF ROLLING SPEED ON

COEFFICIENT OF FRICTION IN HOT SHEET ROLLING OF STEEL

USING SLIDING ROLLING TRIBO-SIMULATOR

Authors: Akira Azushima, Yoshifumi Nakata, Takahiro Toriumi

Presenter: Gary HedbergDate: September 11, 2009

Introduction

Need To Solve Problems of Increased Rolling Force, and Friction Pick Up in High Reduction Hot Rolling

Use of Lubricants Has Been Common Since the 1970’s

Measure the Effect of Lubricants on Hot Rolling at Different Rolling Speeds

References1) Azushima, A., Xue, W.D., Aoki, K., 2006. New evaluation method of lubricity of hot

rolling oil. In: 9th International Conferences on Steel Rolling 2006, ATS, CD-ROM,S04-2 P103.

2) Azushima, A., Xue, W.D., Aoki, K., 2007a. Lubricant mechanism in hot rolling by newly developed simulation testing. Annals of the CIRP 56 (1), 297–300.

3) Azushima, A., Xue, W.D., Yoshida, Y., 2007b. Influence of lubricant factors on coefficient of friction and clarification of lubricant mechanism in hot rolling. Tetsu-to-Hagane 93 (11), 27–32 (in Japanese).

4) Azushima, A., Xue, W.D., Yoshida, Y., 2008. Effect of surface roughness of roll on coefficient of friction in hot rolling. Tetsu-to-Hagane 94 (4), 134–140 (in Japanese).

5) Ikeda, J., 1999. Recent trends in hot strip rolling oil. J. Jpn. Soc. Technol. Plast. 40, 1031–1036 (in Japanese).

6) Inoue, T., Yamamoto, H., Watanabe, K., Nishida, K., Sugiura, T., 2003. Lubricity characteristics of particles mixed with organic and inorganic powders and their seizure prevention effect at high temperature. J. Jpn. Soc. Technol. Plast. 44, 266–270 (in Japanese).

7) Kiuchi, M., 2005. Integrated development of metal forming technologies for ultra-fine grained steel, advanced technology of plasticity 2005. In: Proc. 8th ICTP, pp. 55–70.

8) Lenard, J.G., 2000. Tribology in metal rolling. Annals of the CIRP 49 (2), 567–590.9) Mase, T., 1979. Lubricants for hot rolling of strip and the effects by using them. J.

Jpn. Soc. Lubr. 24 (3), 144–149 (in Japanese).10) Nagai, K., 2003. Recent developments for ultrafine-grained steels. Q. Jpn. Weld.

Soc. 21, 142–147 (in Japanese).11) Sato, K., Uesugi, H., Hagihara, H., Nogami, T., 1978. Correlation between chemical

composition and efficacy of hot rolling oils for steel strips. Journal of the JSTP 19 (214), 942–949 (in Japanese).

Models and Design Principles

Simulation Testing Machine (Created by Authors)

Measured: Rolling Force - P Torque of Upper Roll -

G Radius of Upper Roll -

R Calculated:

Coefficient of Friction: μ = G/(PR)

Models and Design Principles

Specification of simulation testing machine for hot rolling.

Velocity of main roll, U ≤207 m/min Ratio of velocity, rv 6.3–24 Velocity of sub roll, V ≤8–32 m/min Rolling load, P ≤200kN Rolling torque, G ≤800Nm Temperature of furnace, Tf ≤1100 ◦C Forward tension, TF ≤3.5kN

Models and Design Principles

Infrared Image Furnace used Three types of upper rollers

used with different surface roughness (Ra= 0.05, 0.2, 0.8 μm)

Rolling reduction of 0.3mm used

Roll speed between 15 & 70 m/min

Colza oil is used in 0.1 & 3% @ 40°C

Statistical process for collection of data is not mentioned in the article

Results

Ra = 0.05 μm

• For Ra = 0.05 μm :– Coefficient of friction is

independent of the rolling speed at 3% emulsion concentration

– Coefficient of friction decreases with increasing rolling speed at 0.1% emulsion concentration

– Scaling and Cracking similar to each other at all speeds for 3% emulsion

– Color is noted as uneven for speeds of 15 & 30 m/min for the 0.1% emulsion

Results

For Ra = 0.2 μm : Coefficient of friction is

independent of the rolling speed at 3% emulsion concentration

Coefficient of friction decreases with increasing rolling speed until around 50 m/min at 0.1% emulsion concentration

Scaling and Cracking similar for all 3% emulsion to that of Ra = 0.05 μm

Plowing tracks are observed on all speeds except 50 m/min for the 0.1% emulsion

Ra = 0.2 μm

Results

For Ra = 0.8 μm : Coefficient of friction is

independent of the rolling speed at 3% emulsion concentration with values larger than those of Ra = 0.05 & 0.2 μm

Coefficient of friction increases with increasing speed and is also larger than those of Ra = 0.05 & 0.2 μm at 0.1% emulsion concentration

Plowing tracks are observed on all speeds for all emulsion concentrations

Failure on the track surface is observed at the 70 m/min and 0.1% emulsion

Ra = 0.8 μm

Results

The Authors Propose the following models For Ra = 0.05 μm &

3% emulsion :

μ= μb

For Ra = 0.8 μm & 3% emulsion :

μ= μb+ μpaWhere subscripts b & p stand for adhesion and

plowing

For 0.1% emulsion:Several complex equations

given for different speeds

Conclusions

Very Limited Industrial Use Presents equations to calculate μ when

using lubricants Equations not yet verified Lubricant greater than 1% shown to lower

coefficient of friction for Hot Rolling Impacts companies looking to develop

ultra-fine grain steels using high reduction