MECHANICAL AND CHEMICAL PROPERTIES OF METALS

MECHANICAL AND CHEMICAL PROPERTIES OF METALS

Ñ Review documentation related to the actual properties of base and filler metal

Ñ Compare specification values with actual numbers to judge compliance

Ñ He can predict problems which may accur during welding

Mechanical Properties of Metal :

a. Strength

b. Ductility

c. Hardness

d. Toughness

e. Fatigue strength

a. STRENGHT is defined as the capacity of a material to withstand some applied load.

Ñ Tensile strength

Ñ Compressive strength

Ñ Shear strength

Ñ Torsional strength

Ñ Impact strength

Ñ Fatigue strength

Ñ Tensile strength is described as ability of metal to resist failure when subjected to a tensile, or pulling load.

Ñ Tensile strength expressed into two defferent ways i.e Ultimate tensile strength (tensile strength) and Yield strength.

Ñ Ultimate tensile strength (tensile strength) relates to the maximum load carrying capasity of metal, or failure occurs.

Ñ Yield strength is meant when a metal behaves elastically.

Ñ Behavior changes from elastic to plastic is referred to as its yield point.

Ñ Determined by conducting a tensile test, it is also possible to make indirect measurement of strength using hardness test. If hardness increases, tensile strength increase.

Ñ As temperature increases, the strength of a metal will decreases.

Ñ As temperature increases, the ductility increases as well and vice versa.

b. Ductility

Ñ The ability of a material to deform, or stretch (menegang), without failing

Ñ More ductile the more it will stretch.

Ñ Determines whether the metal fails gradually (high ductility) or suddenly (low ductility) when loaded.

Ñ Low ductility is reffered to as being brittle (no deformation before fracture)

Ñ The ductility can be expressed in one of two ways, either as percent elongation or percent reduction area.

Ñ The strength and ductility of a rolled metal is greatest in the direction of rolling.

c. Hardness

Ñ It is defined as the ability of a material to resist identification.

d. Toughness

Ñ The ability of material to absorb energy

Ñ The low toughness value difines brittle behaviour while a high value of toughness is related to a ductile failure.

Ñ The temperature is reduced, the toughness of metal decrease as well.

e. Fatigue strength

Ñ Defined as that strength to resist failure under repeated load applications

Ñ The majorrity of metal failures are the result of fatigue.

Ñ Related to the number of cycles required to cause a failure

Ñ Determined though fatigue testing.

Ñ The S-N curve is simply a graphic description of how many fatigue cycles are necessary (perlu) to produce a failure at various stress level.

Ñ A surface discontinuities, will more quickly lead to fatigue failure.

Chemical Properties of Metals

Ñ Drastic changes will also occur if the chemical composition is change