MaterialsMaterials

MaterialsMaterials

Aim

To gain a basic initial understanding of various materials that are used in the manufacture of lifting equipment.

The following slides and your course handouts will provide adequate information of this subject.

MaterialsMaterials

Materials that are used in the manufacture of lifting equipment must have the

following characteristics: -

They must be strong

Capable of resisting shock loads

Be ductile and tough

Need to be hard to resist wear

Materials must be easily worked by one of the normal processes such as: -

Forging

Casting

Machining

The materials must also be weldable and the finished product must be able to resist

corrosion as far as is possible.

MaterialsMaterials

Ductility: Metal can be reduced in cross sectional area without fracture

Brittleness: Little resistance to failure once the elastic limit has been reached

Elasticity: Return to its original dimensions after the removal of the stress

Plasticity: Retain its new dimensions after the removal of the stress

Toughness: Rapidly distribute within itself stress and strain caused by a suddenly applied load

Hardness: Resist cutting, abrasion or indentation

Corrosion Resistance: Resist oxide formation (rust)

MaterialsMaterials

Cast Iron

Limited use as it is brittle.

The material has very little shock resistance.

Cast iron is however very strong in compression.

Steel

Steel is an alloy of iron and carbon.

May contain other materials:

Impurities which the manufacturing process has been unable to remove

Elements added to the manufacturing process

MaterialsMaterials

Oxides in finished steel can produce a form of brittleness known as strain age

embrittlement

Increases tensile strength

Significantly reduces ductility and toughness

May become brittle if steel is over-strained

Silicon or aluminium can be added which attract oxygen

De-oxidises the steel and produce a steel known as killed steel

Not subject to strain age embrittlement

When steel sections are manufactured by casting and rolling defects are possible.

Cracks, laminations and slag inclusions and are caused by faulty casting,

rolling, or by rolling at the wrong temperature

MaterialsMaterials

Carbon Steel

Low carbon steels (Mild Steels)

Medium carbon steels (Higher Tensile Steels)

High carbon steels (High Tensile Steels)

The quantity of carbon present affects the tensile strength, the form and distribution

of the carbon affecting the mechanical properties.

Mild steel is considered unsuitable for lifting gear ie chain and fittings etc.

Higher tensile steel used to manufacture chain and fittings is 1/3 stronger than mild

steel and can be recognised by a grade mark, 4, 04 or M

Limited use in lifting equipment

Hard wearing properties make them suitable as drive shafts and sheave pins.

MaterialsMaterials

Alloy Steels

Varying carbon content, they obtain their properties from the addition of other

alloying elements

In addition to carbon, silicon and manganese, three additional elements, nickel,

chromium and molybdenum are added

Responds well to heat treatment

Produces chain and fittings one third stronger than higher tensile steel

Hard wearing with good resistance to corrosion

MaterialsMaterials

Non Ferrous Metals

Contain no iron, or, in some cases minute amounts either as an alloying

element or as an impurity.

Most non ferrous metals used are in fact alloys and the most common of

theses being copper alloys.

Copper and its Alloys

Limited use in lifting equipment.

Brass and Bronze are the main copper alloys.

Brass is essentially an alloy of copper and zinc.

Bronze is essentially an alloy of copper and tin.

MaterialsMaterials

Brasss and bronzes are largely used for bearings.

Where spark proof or explosion proof equipment is necessary it is not uncommon to use

these materials as hooks, shackles and trolley wheels.

They may also be found where resistance to corrosion is a consideration, eg load chain

pocket wheels and special equipment in chemical plants.

A small amount of phosphorous (1%) added to cast tin bronzes produces a material

termed phosphorus bronze.

Adding phosphorus increases tensile strength and corrosion resistance.

MaterialsMaterials

Aluminium

Silvery white in colour. Very light, malleable, and ductile with high heat and electrical

conductivity.

1/3 the weight of steel with good corrosion resistance against some chemicals and

acids but weak against other elements such as sea water.

Uses include jacks, tirfor frames, chain block frames, flat sling eyes and ferrules.

Polymers (Plastic)

Man-made chemical based materials.

Good toughness, very light and can be easily fabricated or cast.

Extremely corrosion resistant with selective resistance to chemicals.

Polymers used in lifting equipment are polyamide, polypropylene and polyester.

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