TUPY S.A. manufacturing process of cast iron parts
The process of casting consists in the selection and melting of raw material (scrap steel, pig iron, alloys etc.) followed by the pouring of molten metal into sand molds. Following the solidification, the metal part undergoes a process of cooling inside the mold, demolding and finishing prior to becoming an end product. In addition and in some cases (by customers demand), the product may be subject to machining.
The melting process consists in the transformation of raw material - scrap metal, pig iron and alloys - into cast iron with specific chemical properties adequate to each different application. The raw material is inserted into cupola furnaces (powered by coke), induction furnaces and electric arc furnaces (powered by electricity) where it becomes molten metal at temperatures above 1500ºC (2730ºF).
Tupy woks with diverse kinds of cast iron alloys, such as gray iron, ductile iron and compact graphite iron (CGI). The latter in particular is a material with high mechanical resistance, allowing the construction of more compact, higher power blocks, thus being an important technology for next-generation engines. In the first half of 2013 approximately 16% of revenue from blocks and heads (B&H) were derived from CGI products, and the company estimates that this amount will reach approximately a quarter of revenues of B&H in 2017. Click here for more information on CGI (SinterCast website).
Consist in the making of the sand mold (silica, bentonite, coal dust, water) through its compression against a matrix ("tool") resulting in the negative that will be responsible for giving shape to the outer parts of the cast piece accordingly to dimensional tolerances specified by the customer.
The core making is the process of obtaining sand and resin agglomerates ("cores") which work as internal molds, giving shape to the internal cavities and recesses of the cast piece, ensuring the geometry and internal tolerances specific to each product. Following this process, core (s) and sand mold are assembled together in order to form a single set which will receive the molten metal in the step of the production process: the pouring.
After obtaining the molten iron and assembling core and sand mold together, the process of pouring starts. The molten metal alloy is poured into the core-mold set in which it will fill all cavities within the set, taking a shape similar to the "tool". Following the necessary cooling down period, the item is demolded. Whilst a great portion of the sand utilized in the earlier stages of the process are sent through to regeneration and reuse, the iron part is forwarded to the third stage of the production process: the finishing.
At this stage, the cast piece undergoes internal and external cleaning by jets of steel shots and grits, in order to remove the remaining sand adhered to the piece as well as metal shavings originated from the process. The remaining larger burrs are removed by metal or ceramic abrasives (grinding). Afterwards the product’s quality is tested accordingly to costumer’s requirements and/or specifications, through, amongst others, tightness testing, dimensional inspection, x-ray, ultrasound, acoustic resonance, hardness. Following its approval, some pieces are shipped directly to the customer, while others are given surface protection against oxidation (layer of oil or paint).
The machining phase occurs after the finishing and consists in giving final dimensions and geometry to the piece, making it possible to interface and assemble to other parts. This stage may be done by the customer or by Tupy by customers request.
Tupy’s sales volume of machined products recorded an increasing trend in recent periods. In the first half of 2013 the company machined approximately about 13% of the total sales volume, higher than, for example, 2006, year which the machining volume was approximately 7%.