Manufacturing Processes Effects on Materials

Study Notes

Work hardening or strain hardening: Increases strength and hardness due to increased dislocations in the metal, but reduces ductility and toughness.
Normalizing: Improves grain structure, leading to increased strength, hardness, ductility, and toughness.
Martensitic transformation: Increases hardness and strength.
Fine grain structure: Improves strength, hardness, ductility, and toughness.
Sand Casting: Lower thermal conductivity and poorer mechanical properties.
Die Casting: Finer grain structure and better mechanical properties due to higher thermal conductivity.
Pure metals: Soft and ductile.
Casting properties: Affected by soundness and microstructural features, with cellular structures offering good strength but low ductility, and equiaxed structures offering a good combination of mechanical properties.
Bulk deformation processes (rolling, extrusion, forging, wire drawing): Improve the strength to weight ratio of the product.
Machining: Removes material in the form of chips, leaving a thin layer of material at the surface and potentially leading to softening or hardening due to heat-related effects.

Components can be simple or complex shapes.
Resistance heating furnaces: Used for melting low melting point metals like magnesium, zinc, and aluminum.
Arc furnaces: Used for melting high temperature metals like steel and cast iron.
Coal fired furnaces: Used for melting cast irons, which have a low melting point of 1050-1150°C.
High specific heat metals: Result in increased fluidity.
High thermal conductivity: Can lead to misruns (incomplete filling of the mold cavity) which affect fluidity and solidification time. This also affects riser and gating system design.
Tensile residual stresses: Can be caused by differences in thermal expansion coefficients between the casting and core. This can lead to distortion (warping) and hot tearing.
Hot die casting: Suitable for low melting point metals like zinc, lead, and tin.
Cold die casting: Suitable for high temperature metals like aluminum, copper, and cast iron.
Impurity formation: Metals have affinity to atmospheric gases which can lead to impurities. Filtration is required to remove these impurities, which affects pouring and gating system design.