Study On Casting Technology Of 4G94 Engine Cylinder

4G94 engine is one kind of products which are made by Mitsubishi company. It is the original power supplier for a small SUV,Mitsubishi Pajero IO. It performs prettty well at power, torque, smooth operation, the little noise at high speed and etc. 4G94 engine has some advantages, such as working Smoothly at low-speed torque, powerfully at high-speed torque, low fuel consumption and low emissions which fully meets the EuropeⅢemission regulations and may reach the level of EuropeⅣ. Fuel consumption meets the national fuel consumption regulations (GB19578-2004) Phase II requirements. And the actual fuel consumption is also much lower than the domestic equal displacement engines.Casting process design for casting plays a big role on quality, productivity and production costs .Therefore we did a lot of work on the design of cylinder body's casting process during the development of cylinder. "Good Design" is the biggest savings while "poorly designed" is the biggest waste. For example, when we provided Beijing Jeep BJ2021 with cylinder head castings, due to the original process design deficiencies which have not been overcome, the qualified cylinder head casting was about 70% on average. Therefore, to successfully achieve the development and trial production of 4G94 cylinder body, the following problems need to be solved.Reasonable process not only has to match the existing workshop equipment, but also to meet quality requirements. The problems of coating technology need to be solved, to make sure the cylinder has smooth surface finish, and eliminate waste cylinder holes. Resolve cold and hot core box process technical problems. Determine the melt composition,and parameters of sand prepareing process.Based on the rough cylinder 4G94 technical requirements and existing equipment of the Company,this paper aims to determine the casting process and the process parameters. After the study, combined with existing production, the method of one casting in one mold, the use of closed - open-pouring system, and making cores in cold and hot core boxes at the same time are applied. Requirements of the core making technological parameters are as follows : shooting pressure of water jacket sand core, 0.25MPa-0.45Mpa; curing time, 90s- 125s; the shooting pressure of main core,0.25MPa-0.5Mpa; curing time, 45s-65s; the shooting pressure of the rest cold-box,0.2MPa-0.5Mpa; curing time, 25s-85s. Molding process parameters require 2.9% -3.3% water, compressive strength above 0.09Mpa; compaction rate of 37% -47%;broken index,70% -82%; effective clay content, 8% -10%; and total clay content,10% -13%. The best composition of the alloy: C 3.25% -3.4%;Si 1.80% -2.00%; Mn 0.75% -0.8%;P≤0.15%;. The performance of the casting :σb≥274 Mpa; hardness, HB 190 ~ 269,1-2mm from the top of the cross section,and HB≥190,33 ~ 43mm from the top section. Microstructure of the casting : the main graphite morphology is type-A ,while the total content of type-B and type-D≤20%; feldspar,4-6 grade ;the content of free ferrite≤3%; the content of free ferrite cementite≤3%.In the aspacts of mold design, 7 sets of tooling are designed, including 5 sets of core boxes, 2 sets of shaping plate. 5-box sets include 2 sets of vertical type hot-box,making 4 main cores with KC600 Vertical core shooting machine; 2sets of end-core and covercore boxes, making end-core and cover core with horizontal-type shoot core machine SHAR-25L/CF; a set of horizontal type hot-box making water jacket core of 4G94 cylinder body with KA-1000-type core shooting machine. Core assembly and core jig are taken on core setter. The upper and lower plate are used in the APS-H4 type static pressure molding line.Melting and pouring process are strictly controlled. Put the pig iron,scrap steel materials into the furnace for melting, when the liquid metal reaches to 1510℃, remove the slag, and add additional silicon ferrosilicon. Add ferromanganese into the funace till ferrosilicon in the molten iron has been dispersed evenly . 3000kW power are supplied to medium frequency furnace to heat the molten iron to 1540℃-1560℃and then make it in the state of still for 10min. Spectrum samples are taken for composition testing. And when hot metal chemical composition is qualified, it is allowed to pourthe molten iron to the mold. Add inoculants into the laddle for breeding. After that,the molten metal can be puring to cast the test pieces 4G94 block while the pouring temperature is 1390℃-1410℃.Based on the testing of microstructure and mechanical properties of gray cast iron,we analysed the effect of element of alloy such as copper, tin, chromium on the cast iron properties. When the C,Si,Mn and other elements remain unchanged, we determined the prefered ratio alloy compostion : Cu 0.40%, Sn 0.07%; Cr 0.10% which can control the hardness of the casting. Through quantities of researches and tests, 4G94 cylinder body casting can be successfully produced batchly with the qualified rate of the internal castings to 95%, while the external machining to 97% or more. Casting performance is able to meet the requirements given by the user. 4G94 gasoline engine is an advanced engine today , requirs high technology of the cylinder body and very high levels of the process of casting . Right now only the Toyota Production in Kunshan is able to produce it . It will enhance our company's popularity and be a good chance and foundation for my company's castings to the world if we are able to produce the 4G94 cylinder body.