Study On Brazing Technology Of Aluminum-steel Composite Plate For Oil Cooler

With the development of automotive and engineering equipment field,higher requirements had been put forward for the performance of oil cooler in engine system,such as lightweight,corrosion resistance and heat transfer performance.At present,the commonly used stainless steel oil cooler on the market had high brazing temperature and low production efficiency which could not meet the need of lightweight;Due to its low strength,aluminum oil coolers would suffer erosion failure during service,causing greater losses.In view of the current problems of stainless steel and aluminum oil coolers,this article proposed the use of brazing filler metal/aluminum/steel/aluminum/brazing filler metal five-layer aluminum-steel rolled composite plate for gas shielded brazing connection of oil coolers in order to improve production efficiency and the overall performance of the oil cooler.First,a preliminary brazing experiment was carried out on the aluminum-steel composite plate oil cooler products.It was found that due to the particularity of the aluminum-steel composite plate,the main problems that occurred when it was applied to the oil cooler were poor gap control,uneven brazing quality,and Interface reaction.Among them,the interface reaction had a great influence on the aluminum steel composite oil cooler,and the excessive thickness of the interface reaction layer would seriously weaken the bonding strength of the oil cooler,and it was easy to fracture under the thermal stress caused by uneven heating,making the oil cooler ineffective.When the brazing temperature was higher than the critical temperature,the solder melted directly into the aluminum steel interface due to the corrosion of the protective layer,resulting in a violent interfacial reaction.The structure of the compound layer was?₅+transition layer+?.Aluminum covered the existence of an important role in inhibition of interface reaction.If other conditions unchanged,improve the protective layer thickness could significantly reduce the formation of intermetallic compounds.The existence of the thicker intermetallic compound could not only reduce carbon steel parts of the loaded area,also produced micro cracks caused brittle fracture,had bigger influence on the performance.Based on the above analysis,the material and structure of the aluminum-steel composite oil cooler were fully optimized.Firstly,the thickness of the protective aluminum layer of the base metal was increased,the Si content of the aluminum layer was reduced,and the diffusion of the melt filler metal to the base metal was slowed down effectively,so as to increase the critical temperature of the aluminum-steel composite plate during brazing.Secondly,the optimum brazing process parameters were furnace temperature of 625?and mesh belt speed of310-340mm/min,and the brazing quality was the highest.Finally,the structure of the oil cooler was optimized,and the more compact integral structure of the oil cooler was used,so that different parts of the oil cooler could have similar heating curves.At the same time,the stamping degree of aluminum steel composite plate was reduced,the design of the boss was cancelled,and the stamping part was avoided to bear the load,so as to avoid the failure of the oil cooler caused by the interface reaction.The brazing quality of aluminum steel composite oil cooler produced by comprehensive optimization was good and could meet the demand of use.