PERFORM WELDING INSPECTION
MATERIAL
ALLOYING ADDITIVES
1. The term ‘steel’ is used to describe many different metals.
2. They are all alloys based on iron.
3. The alloying additions, such as carbon, manganese, silicon, chromium, etc., singly
or in combination produce a range of metals with widely differing physical and
mechanical properties as well as quite different weldibility.
4. Istilah 'keluli' digunakan untuk menggambarkan banyak logam yang berbeza.
5. Kesemuanya adalah aloi berdasarkan kadar besi.
6. Tambahan alloy lain seperti karbon, mangan, silikon, kromium, dan lain-lain, secara
tunggal atau gabungan menghasilkan sebilangan logam dengan sifat fizikal dan
mekanikal yang sangat berbeza serta pengelasan yang sangat berbeza.
MATERIAL SYMBOL FUNCTION
IRON Fe the basic constituent.
CARBON C gives hardness and strength.
MANGANESE gives toughness and strength. Neutralises sulphur.
SILICON Mn a deoxident - oxide reducer. Usually added through filler
wire.
ALUMINIUM Al an oxide reducer, grain refiner and adds toughness. (In
killed steel the oxygen is removed by aluminium.)
CHROMIUM Cr gives corrosion resistance, high temperature strength and
creep resistance. (Grain creep occurs over time at high
temperatures due to gravity.)
MATERIAL SYMBOL FUNCTION
MOLYBDENUM Mo gives high temperature creep resistance.
TITANIUM Ti Ti and Nb are both grain refiners and stabilising agents.
They prevent intergranular corrosion and weld decay.
NIOBIUM Nb Used in austenitic steels.
VANADIUM V gives hardness and strength.
SULPHUR S a contaminant. (Main cause of solidification cracking - ‘hot
shortness')
NICKEL Ni gives low temperature toughness and strength.
COPPER Cu a contaminant - causes loquation cracks. (Though also
used for weathering steel and a possible grain refiner.)
PHOSPHORUS P a contaminant.
MATERIALS INSPECTION
A great variety of materials may require to be inspected with a view to satisfactory
welding. The main topics in material inspection are Size, Type and Condition.
Specification.
It is not, in general, safe for the inspector to identify materials by composition from a
mill sheet, since very small variations or additions to the metal may give rise to
significant changes in properties and weldability.
However limited selectivity is permissible, such as percentage carbon maximum etc.
The procedure is for the mill sheet to be submitted for approval and then the
inspector records and transfers the reference number.
Supplier.
This can be found on the Goods Inwards documents or the receipt documents, or
occasionally on packaging or even marked on the metal.
Quantity.
The quantity being inspected should always be noted as well as the sample size if 100
% inspection is not being employed.
Size.
Sizes must be checked for secondary identification as well as conformance. The
inspector will, as appropriate, be given tolerances on size that are permissible. Check
length, breadth, thickness and diameter.
Distortion.
A check is often required on the degree of distortion, i.e.
Flatness
Squareness
Straightness
Ovality
Consistent wall thickness
Condition.
Rust, paint and grease on the surface of the metal are all harmful to welding and must usually
be removed, at least near to the actual weld.
Guidance is normally given to the inspector regarding acceptable levels or the treatment that is
required. An inspector should be alert to gradual changes, such as increased corrosion.
Carefully maintained specimens showing acceptable conditions are often the best method.
Heat treatment condition, annealed, normalised etc., should all be recorded.
Defects.
In wrought products the most common defects are laps and laminations (Also porosity and
segregation bands.) These will normally be subsurface so, unless NDE is employed, only the
edges of the plate, and particularly cut edges, can be inspected. The lap/lamination will appear
as a narrow black line parallel to the surface.
Storage.
After inspection and approval for use it is essential that the metal is stored in such a way as to
maintain its good condition.
Protect from corrosion and mechanical damage.
MATERIALS INSPECTION CHECK LIST
