PIPE CAST IRON
In general Cast Iron (Cast Iron) is Iron which has Carbon content 2.5% - 4%. Therefore Cast Iron with a carbon content of 2.5% - 4% will have a low WELDABILITY. Carbon in Cast Iron can be cementite (Fe3C) or commonly called Free Carbon (graphite). It is also important to know the content of FOSFOR and SULPHUR from this material is very high compared to Steel.
There are several types of Cast Iron, namely:
WHITE CHILDREN IRON (WHITE CAST IRON). Where this Cast Iron all the carbon is in the form of semitite so that it has very hard and brittle properties. The microstructure consists of carbides which cause white.
ABOUT IRON IRON (MALLEABLE CAST IRON). This type of Cast Iron is made from White Cast Iron by re-heat treatment, the purpose of which is to decompose all clumps of graphite (Fe3C) to decompose into Ferrite, Pearlite and Martensite matrices. Has properties similar to Steel.
KELABU IRON (GRAY CAST IRON). This type of Cast Iron is often found (around 70% cast iron is gray). Has graphite in the form of FLAKE. The properties of this Cast Iron are not very high tensile strength and very low tenacity (Nile Ductility).
NODULAR CAST IRON NODULAR CAST IRON IRON is a blend of FIBER OIL IRON. The characteristic of cast iron is the form of FLAKE graphite where the FLAKE ends are TAKIK-AN shaped which have an effect on KELANGGU, KEULET & STRENGTH because to be BETTER, graphite is BALL (SPHEROID) by adding a little INOCULATING AGENT, such as Magnesium or calcium silicide. Because Cast Iron has HIGH EXTENSION, this cast iron is categorized as DUCTILE CAST IRON.
WHAT FACTORS AFFECT WELDABILITY IN THIS MATERIAL ???
Tension during cooling. In theory welding (welding) welding material (weld metal / weld metal) will contract during cooling. Because of the fragility of cast iron, the contraction of cast iron has a lower ability than Steel.
Irregular shape. Generally Cast Iron is made in a form that does not mean or can I say artistic. With the complicated shape of the cast iron, it has more or less uniform thickness, this will affect the stress contractions that occur in the material and cracks easily and keep in mind the background of this is its very low flexural strength.
HAZ is hard. AHZ on Cast Iron adjacent to Metal Weld will have a HARD nature. This hardening is caused by the presence of HAZ parts which do not participate in melting.
Binding of Carbon from Base Metal. Consequences of Welding Cast iron mixed with Base Metal will cause the binding of CARBON on WELD METAL resulting in an increase in the content of SULFUR and PHOSPOR in the WELD METAL.
Oil Absorption on Cast Iron. Because of the characteristic form of this material the porous average is the possibility of oil impregnation in graphite which causes porosity in the weld metal. Usually it is often experienced by fellow practitioners of welding, repair during maintenance.
Why is Cast Iron when Las Often cracked? Before we discuss only cracks in Cast Iron, it is better if we first understand what is called Crack in metals, what causes cracks in metals, what is the effect of Chemical Composition on the ease of cracking of metals, What are diagrams of CCT and CCCT, etc. So we are not wrong in drawing conclusions in understanding the occurrence of cracks on Cast Iron welding ...
Cracks in the Cast Iron welding process, there are several factors that support each other to support the ease of Crack.