For the production of a corrosion-resistant surface in the region of the surfaces in contact with hot gas of a heating boiler of cast iron, the corresponding parts of the casting mould are treated with a black wash which contains an alloying element, preferably 40-50% ferrosilicon, which converts the edge zone of the not yet solidified cast iron into a corrosion-resistant casting skin
The need for control of raw materials is critical to the success of iron casting production from greensand systems. The base silica sand is often overlooked with the main focus on bentonite additions. Carbonaceous additives can be considered a “necessary evil” to ensure a good surface finish and reduction in sand related surface defects. Other additives are used when systems get out of balance and these in turn add further to the complex nature of greensand systems. For castings requiring cores this becomes a bigger issue as many differing resin systems are employed for core production and these must be taken into consideration when controlling both the carbonaceous levels and the overall grading of the sand system.
The twin effects on additional carbon and loss-on-ignition and overall sand grading need careful understanding and control. Various control methods are examined including traditional methods such as volatiles and loss-on-ignition along with bentonite determination methods and grading methods. Newer control methods such as total carbon are reviewed along with the overall package of testing and control methods.
Various predictive methods are looked at as a control feature as well. The quality of additives and their role and more importantly their interaction is highlighted, as this is an area often neglected as foundry men battle for success in consistent quality castings. Suggested in-coming control tests are discussed allied to additions at the mixer.
Also reviewed is the interpretation of results and the action required to ensure control and more importantly consistent quality castings from greensand systems with the emphasis on the understanding and control of carbonaceous additive on casting performance
Post time: Nov-20-2020