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Wilkinson Coutts & Matthews Integrity Training

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WILKINSON COUTTS / MATTHEWS INTEGRITY HUB: an up-to-the-minute information mix designed to help you with your lifework and career development in the asset integrity, inspection and NDE industries.

Matthew Petroleum Notes


 Q1: Material properties

Which of these is not a commonly defined mechanical property of metals used for fabricated pressure equipment?

a) Impact strength
b) Ductility
c) Hardness
d) Malleability

Ans (d) Malleability is the ability to deform under compression (like hitting a lead weight with a hammer) There is no unit of malleability shown on material certificates, and material specifications for weldable steels do not specify it. It may be mentioned for cast components i.e. ‘malleable cast iron’.

Q2: Mechanical properties

Which of these is not a mechanical property of stainless steel?

a) Yield strength under a tensile load
b) % Chromium content to reduce corrosion
c) % Elongation during a tensile test
d) Charpy or Izod impact strength

Ans (b) % Cr is a description of chemical analysis, not a mechanical property.The others are all mechanical properties

Q3: Material tensile tests

Which mechanical property of a metal is quantified by the terms (% E) and (% A) on its material test certificate?

a) Strength
b) Ductility
c) Elasticity
d) All of the above

Ans (b) The parameters % E (elongation) and %A (reduction in area) are a measure of ductility of a material: its ability to deform plastically without cracking. Strength is defined by Yield strength (Y or Re) and Tensile strength (T or Rm).Elasticity is defined by Young’s Modulus E but measured in Ksi or GN/m2, not %.

Q4: Effect of Carbon content on the properties of steel

On balance, medium carbon (0.4% C) steel can be expected to be fairly;

a) Soft
b) Ductile
c) Strong
d) Weldable without PWHT

Ans (c) Strength increases with %C content and 0.4%C is a medium-high carbon tool steel  which has a high Yield and Tensile strength. The high %C content will reduce ductility and increase hardness.

Q5: Material for welded joints

A fillet welded joint on the saddle of a pressure vessel will be subjected to mechanical vibration when in use. The most suitable steel to make it from will be one that has;

a) Tensile strength of 35ksi
b) Yield strength of 350MPa
c) Hardness of 350HB before welding
d) >2% C content

Ans (a) 35ksi tensile steel is a fairly low strength grade (e.g. API 5L) so will be ductile and tough and able to resist fatigue cracking. A yield of 350MPa is high tensile steel, so may be brittle. Hardness of 350HB (before welding or even as-welded) is high hardness and will be brittle. 2% C steel is impractically high (more like cast iron) and will be brittle and unsuitable for welding

If you didn’t get them all correct, have a look through our 5-minute coaching points below


Material mechanical properties

One excellent document covering the properties of steels relevant to the integrity industry is API RP577 Welding and Metallurgy. It forms part of the body of knowledge of most of the API Inspector Certificates. As an integrity inspector/engineer the main mechanical properties you need to know about are yield/tensile strength, ductility (%E, %A), Charpy impact strength and hardness, how they are related, and how they are affected by the %Carbon in the steel.

See our short slide presentation covering this topic 

Welding & Metallurgy

Matthews Masterclass