casting failure

tom2005

Castings
Several factors effect the quality of metal castings. Some of these factors are listed below:

  Coefficients of thermal conductivity
  Thermal expansion and contraction,
  Chemistry
  Precision of molds and dies
  Shrinkage allowances
  Dryness of molds
  Casting design
  Method of pouring liquid metal
  Design of gates and risers


Imperfections in castings may not be of concern for many types of service.  They are commonly referred to as casting defects since castings are not perfect. This is unfortunate as imperfections beyond engineering design specifications should be considered defects, while imperfections within engineering design specifications should not be considered defects.  

Some casting imperfections may have no effect on the function or service life of castings.  Many imperfections are easily corrected by blast cleaning or grinding.  Other imperfections may be acceptable in some locations.  

It is not uncommon for engineers to zone a casting drawing.  Depending on the criticality of the location or zone the same imperfection would be judged acceptable in one location while unacceptable in another location.  
Casting Discontinuities
Some common casting deficiencies are:

  Inclusions

  Porosity  (blow holes, pinholes)

  Cold Cracking

  Hot Cracking

  Cold Shuts

  Surface irregularities

  Distortion

  Improper composition

Casting failures can be due to various causes.  Some castings fail due to design deficiencies, while other castings fail due to casting deficiencies.



Casting Failure Analysis
Casting failures can be due to various causes.  Improper loading or environment may contribute  to the cause of failure.  Casting imperfections may or may not contribute to the cause of failure.  Some imperfections may be commonly occurring discontinuities or anomalies that are normally expected to be present in castings.  Other imperfections are casting defects that result in failure of the casting.  Failure analysis can determine the cause of the casting failure and determine if a casting imperfections was the primary or contributing cause of failure.


Casting Concerns
Casting issues AMC can evaluate for your organization are listed below:

  Mold designs
  Mold types
  Sand casting
  Investment Casting
  Ceramic mold casting
  Plaster mold casting
  Shell mold casting
  Permanent Mold Casting
  Gating systems
  Cores
  Solidification of metals
  Cast structures
  Fluidity of molten metals
  Heat transfer
  Shrinkage
  Casting defects
   Die casting types
  Centrifugal casting
  Turbine blade casting
  Heat Treatment
  Ferrous alloys
  Non-ferrous alloys
  Heat treatment processes
  Cleaning/finishing methods
  Inspection
  Testing
  Casting quality assurance
  Process Capability
  Allowance and tolerance
  Process capability
  Process variation
  Cast alloys