Research And Development Of High-end Stamping Pickling Plate SPHC For Compressor

The pickling plate is an intermediate product between the hot rolled plate and the cold rolled plate.It is mainly used in automobile,compressor,water heater and hardware machinery industry.As the replacement of cold rolled plate in some applications,it can save costs for the enterprises.The number of compressor for refrigerator and air conditioner that we need to produce in China every year has been over 200 million for 7 consecutive years.More than 1 million tons pickling plates are needed to produce compressor annually,and there is an increasing trend.The compressor shell is usually produced with low carbon aluminum-killed steel SPHC,SPHD and SPHE.The production process of the compressor shell involves stamping,flanging,welding,painting and other process,so pickling plate for compressor should be of excellent stamping performance,high size precision,good surface quality,and the pickling plate is one of the most high-end products in the pickling plates.The current situation of compressor industry(fridge and air conditioner)is analyzed,and the annual demand for hot rolled pickling plate in compressor industry is predicted to be 1～1.2 million tons.Meanwhile,market analysis is carried out in enterprises and sub regions.According to the market analysis,the trial and promotion of the pickling plate SPHC are promoted in six customers,including GREE Lingda,Hitachi Shanghai,Hualin Wuxi,Dongbei Huangshi,Samsung Suzhou,Longxin Zhangjiagang.Based on 1450 Hot Rolling Production Line and the Push-pull Pickling Line of a steel enterprise,the paper study the effect of chemical composition on mechanical property of pickling plate.Comparing microstructure and component of pickling plate from the steel enterprise with other similar enterprises,the results show that the main reason of high yield strength,high yield and strength ratio in SPHC pickling plate is high carbon content with obvious solid solution strengthening effect in the plate from the steel enterprise,and the quasi polygonal ferrite microstructure which is harder than polygonal ferrite high strength.The research and test show that when the content of C decreased from 0.05%to 0.02%,yield strength,yield and strength ratio decrease,the yield strength is below 260MPa,the yield ratio is less than 0.75,and the elongation is good,the quasi polygonal ferrite microstructure turns into the polygonal ferrite microstructure with the same rolling process(final rolling temperature 870℃,coiling temperature 600℃)in SPHC pickling plate.Meanwhile,the content of P and S is strictly controlled to avoid the formation of P segregation and MnS inclusion in steel which will reduce the cold forming performance and low temperature impact toughness of steel plate.The upper limit of P is 0.015%and the upper limit of S is 0.010%.The effect of temperature technology on the microstructure and properties of pickling plate is studied in this paper.The microstructures after four kinds of cooling mode described in this paper are all polygonal ferrite,common quasi polygonal ferrite in SPHC plate is not found.So coiling temperature of SPHC pickling plate is improved from 600℃ to 660℃ to obtain polygonal ferrite,avoid the quasi polygonal ferrite and reduce the strength of steel plate.The plate with low yield,low yield and strength ratio,high elongation rate,the yield strength lesser than 250MPa,yield ratio 0.71,the elongation rate more than 49%can be obtained after the two stage cooling mode.At the same time,the influence of the final rolling temperature on the mixed crystal microstructure was determined by the analysis of the mixed crystal microstructure affecting the stamping and cracking of the pickling plate.The finial rolling temperature is improved from 880 ± 20℃ to 900±20℃ in the thick gauge plate(thickness more than 3.0mm),the finial rolling temperature is improved from 880±20℃ to 890±20℃ in the thin gauge plate(thickness lesser than 3.0mm),then the surface mixed crystal microstructure is controlled in plate side about 40mm effectively to solve the problem of uneven deformation and cracking in the stamping process of the pickling plate.In order to solve the quality problem of the cross print,the yield performance of the pickling plate was analyzed.The pickling plate SPHC belongs to low carbon aluminum killed steel.Its tensile curve has obvious yield platform,and there are obvious upper and lower yield points.The yield platform will produce transverse printing in the pickling process,which will affect the product quality.Flat rolling can eliminate the yield platform of pickling mother plate after hot rolling,but the process can significantly change the mechanical properties of the pickling mother plate.In order to eliminate yield platform with the least affect on the formability of the plate,flat rolling force should be not more than 180 tons in the steel enterprise.After solving the above problems,we start mass production of the pickling compressor plate.From January 2016 to June 2017,the total production of the pickling plate for compressor is more than 30 thousand tons,and profit is 50 yuan per ton more than ordinary SPHC.