The Study Of DDQ Grade Cold Rolled Steel Plate Surface Quality Control

Because of the DDQ grade cold rolled steel plate’s excellent stamping molding performance,more and more automobile manuf-acturers select it for the use of outside cover parts of automobile,the automobile outer panel requires high surface quality,which is mainly reflected on the high requirements for steel surface cleanliness,surface roughness and peak value.In this paper,the cold rolling process control is introduced,which describes the surface quality control points of cold rolled steel.In the acid pickling line,the acid concentration is improved,the ferrous ion’s content is decreased,the tension leveler elongation and insert value are increased,the oxide scale of hot rolled plate surface is effectively eliminated,the steel plate surface quality is improved.To the characteristics of five stand tandem cold mill,the emulsion concentration of the front tandem cold mill is improved,the emulsion flow opening degree is increased,the emulsion concentration of the end of the tandem cold mill is reduced,the emulsion flow opening degree is reduced,and the use of chrome work rolls and other methods,which can reduce the wear between the roller and steel plate during rolling process,the iron powder production is reduced,thereby the residual oil and residual iron content of the rolled steel surface are reduced,the surface reflectance of the steel plate is improved,and the reasonable control of emulsion flow rate can also reduce air purging burden,and reduce the residual emulsion.According to the characteristics of electrolytic cleaning line,in accordance with the upper limit control of alkali concentratio,the alkali cleaning and electrolytic cleaning ability are improved,reducing the rinsing process conductivity,the steel plate’s surface ion entrainment is reduced.After the detection of emulsion volatilization curve,when the temperature reaches 430℃ the emulsion volatile decomposition rate reaches the maximum,so after the bell type annealing furnace process curve is set reasonable,which can ensure the plate’s emulsion is fully eliminated.Cleaning mill frame regularly,which can ensure the steel plate rolling process is clean.Experimental study found that,because of the chrome work roll’s surface has strong resistance,so it has higher ability to maintain the surface roughness,after the use of chrome work roll,the steel plate surface roughness value is stable,and we can reduce the initial work roll surface roughness,improve the work roll surface peak,which indirectly make the steel plate has a good RPc value after the rolling of the chrome work roll.Through the optimal control of every process,the cold rolling strip surface residual oil amount is decreased by 32 mg/m2,which is reached 217 mg/m2;the residual iron content is reduced 6 mg/m2,which is reached 39.8 mg/m2;the strip reflectivity is increased by 4%,which is reached 96%;the use of chrome plated roll in temper mill,the rollingg cycle is extended 1800 tons,which is up to 2900 tons,the maintain ability of steel plate surface Ra value is good,the RPc value is increased7-8 per/cm.which is up to 50 per/cm,so the quality of products are improved,and they have stronger competitive power in the market.