[
Skip to content
]
Accessibility
|
Text only
Training
|
Careers
|
Find us
|
Site map
|
Register
Log In
Search our Site
Search our site
Home
/
Services
/
Technical Knowledge
/
FAQs
/
Material FAQs
/
FAQ: What is porosity and how can it be prevented?
Share:
Services
Technical Knowledge
FAQs
Material FAQs
FAQ: What are SiAlONs?
FAQ: What is 'galling'
FAQ: Can I bond Teflon?
FAQ: What is Barrikade?
FAQ: What is weld metal?
FAQ: How is Barrikade made?
FAQ: What is Charpy Testing?
FAQ: What is graphitisation?
FAQ: What are electroceramics?
FAQ: Why use ceramic coatings?
FAQ: How do you weld cast iron?
FAQ: What is a carbon nanotube?
FAQ: What is an MCrAlY coating?
FAQ: What is the contact angle?
FAQ: How can I weld naval brass?
FAQ: What are ceramic adhesives?
FAQ: What is 'chevron' cracking?
FAQ: Where can Barrikade be used?
FAQ: What is a sandwich structure?
FAQ: What are engineering ceramics?
FAQ: What is "matching" weld metal?
FAQ: What is a structural adhesive?
FAQ: How does a gel form from a sol?
FAQ: Where do I obtain A-TIG Fluxes?
FAQ: Who supplies recycled plastics?
FAQ: Is it possible to braze diamonds?
FAQ: What are biocompatible adhesives?
FAQ: What are biodegradable adhesives?
FAQ: What are piezoelectric materials?
FAQ: What are carbon-carbon composites?
FAQ: What are superconducting ceramics?
FAQ: Why are some ceramics machineable?
FAQ: How can I easily identify a plastic?
FAQ: What is the Larson-Miller parameter?
FAQ: Can I arc weld free-machining steels?
FAQ: Use of ceramics as bearing materials.
FAQ: What are inorganic ceramic adhesives?
FAQ: Which materials can be laser drilled?
FAQ: What are pressure-sensitive adhesives?
FAQ: What is the Holloman-Jaffe parameter?
FAQ: Do polymers undergo changes in service?
FAQ: How many times can a weld be re-welded?
FAQ: How can I weld aluminium-nickel bronzes?
FAQ: What are liquid crystal polymers (LCPs)?
FAQ: What is a thermal barrier coating (TBC)?
FAQ: Is it possible to weld recycled plastics?
FAQ: What materials can you make with sol-gel?
FAQ: Can I weld mild steel to high yield steel?
FAQ: How can I convert between hardness scales?
FAQ: Where can materials property data be found?
FAQ: How are liquid crystal polymers (LCPs) made?
FAQ: What is a 'fish-eye' and how does it develop?
FAQ: What is creep damage, and how is it detected?
FAQ: What is porosity and how can it be prevented?
FAQ: What types of engineering ceramics are there?
FAQ: Are polymeric adhesives microwave transparent?
FAQ: What are the applications of carbon nanotubes?
FAQ: Can you use organic adhesives to bond ceramics?
FAQ: How can I assess the weldability of a material?
FAQ: What determines the creep strength of an alloy?
FAQ: What is hot cracking (solidification cracking)?
FAQ: Is it easy to weld titanium and titanium alloys?
FAQ: What is meant by wetting and how can it be used?
FAQ: What is the best approach for cleaning ceramics?
FAQ: What P Number is steel to BS (or EN or DIN) xxx?
FAQ: What are wormholes and how can they be prevented?
FAQ: What is type IV cracking, and how is it detected?
FAQ: Which plastics do the recycling symbols refer to?
FAQ: How is microwave energy absorbed into an adhesive?
FAQ: Why are microwave-transparent adhesives important?
FAQ: How are glass, ceramics and glass-ceramics defined?
FAQ: What is meant by post-heating and how is it applied?
FAQ: Can I normalise a welded C-Mn component or structure?
FAQ: What is a sol (in the context of sol-gel technology)?
FAQ: What is an oxide dispersion strengthened (ODS) alloy?
FAQ: What is galvanic corrosion and how can it be avoided?
FAQ: What is meant by the water permeability of a polymer?
FAQ: What is the permissible limit of Cu in Pb-Sn solders?
FAQ: What effect does niobium have on steel HAZ properties?
FAQ: What types of metal powder are used with HVOF spraying?
FAQ: Are HVOF coatings an alternative to hard chrome plating?
FAQ: Are quenched and tempered (Q&T) steels readily weldable?
FAQ: Can ASME IX 'P' Numbers be applied to non-ASME material?
FAQ: Why is the Ca:S ratio specified in steel specifications?
FAQ: Why is the Ti:N ratio specified in steel specifications?
FAQ: What are the implications of welding over existing welds?
FAQ: What is the difference between heat input and arc energy?
FAQ: What types of carbide powder are used with HVOF spraying?
FAQ: Are ferritic stainless steels susceptible to hot cracking?
FAQ: How do you weld grey cast iron using a MMA (SMAW) process?
FAQ: How do you weld malleable cast iron by MMA (SMAW) welding?
FAQ: How reliable are Electrically Conductive Adhesives (ECAs)?
FAQ: What are the residual stresses in a dissimilar metal weld?
FAQ: How do you weld austenitic cast iron by MMA (SMAW) welding?
FAQ: What are the basic physical properties of carbon nanotubes?
FAQ: What is temper embrittlement, and how can it be controlled?
FAQ: Does titanium need gas shielding when it is friction welded?
FAQ: How are oxide dispersion strengthened (ODS) alloys produced?
FAQ: What are the applications of liquid crystal polymers (LCPs)?
FAQ: What stress-strain behaviour can I expect adhesives to have?
FAQ: How can weld porosity be detected and how can it be remedied?
FAQ: How do impurities in an adhesive affect microwave attenuation?
FAQ: What are sheet moulding compounds and bulk moulding compounds?
FAQ: What are the different types of cast iron which can be welded?
FAQ: Are there best practice principles when designing for ceramics?
What is high temperature hydrogen attack (HTHA)/hot hydrogen attack?
FAQ: How do you determine the type of cast iron you are dealing with?
FAQ: what are TMCP (Thermo-mechanically Controlled Processed) steels?
FAQ: Why are my 300 series austenitic stainless steel welds magnetic?
FAQ: What causes porosity in titanium welds and how can it be avoided?
FAQ: Which thermoplastic materials can be RF (Radio Frequency) welded?
FAQ: Which thermoplastics can be joined by hot bar or impulse welding?
FAQ: Is it possible to predict the service life of a plastic component?
FAQ: What sort of adhesives are used for medical/surgical applications?
FAQ: Can friction welding be used to join nickel and cobalt superalloys?
FAQ: What do the markings mean which are stamped on thermoplastic pipes?
FAQ: What solders can be used to overcome gold scavenging on a substrate?
FAQ: What treatments exist for altering the surface energy of a material?
FAQ: Where can I find information regarding porosity in aluminium welds?
FAQ: Do degradable plastics have a place in the medical/healthcare sector?
FAQ: How can I characterise the wear resistance of thermal spray coatings?
FAQ: Is it true that ceramics are not always hard, brittle and insulating?
FAQ: What precautions should I take when welding aluminium and its alloys?
FAQ: How do you weld spheroidal or nodular cast iron by MMA (SMAW) welding?
FAQ: Should steel plate be cold straightened if it is accidentally damaged?
FAQ: What factors affect the choice of adhesive for a specific application?
FAQ: What is meant by postweld heat treatment / stress relief heat treatment?
FAQ: When do I need to use metal coatings as opposed to polymers and paints?
FAQ: How do I measure the diffusible hydrogen level in my ferritic steel weld?
FAQ: What is the relationship between flux moisture content and weld hydrogen?
FAQ: What is the 'surface energy' of a material, and how can it be determined?
FAQ: Is it true that adhesives have more than one function in microelectronics?
FAQ: What are the typical values of surface energy for materials and adhesives?
FAQ: How can cracking be avoided when welding is used to restore tools and dies?
FAQ: How, using simple manual tests, can I identify an unknown plastic material?
FAQ: What is heat-tint and how do I avoid it during welding of stainless steels?
FAQ: Are TMCP (Thermo-Mechanically Contolled Processing) steels readily weldable?
FAQ: Can pickling of stainless steel welds be replaced by other cleaning methods?
FAQ: What are the advantages and disadvantages of liquid crystal polymers (LCPs)?
FAQ: What are the common properties of oxide dispersion strengthened (ODS) alloys?
FAQ: What are the main industrial application areas for sol-gel derived materials?
FAQ: How can I characterise the density and porosity of the thermal spray coatings?
FAQ: In ultrasonic welding, which factors affect the weldability of thermoplastics?
FAQ: What causes crater pipes and what will prevent their formation during welding?
FAQ: Can a welded repair to a pressure vessel be carried out without subsequent PWHT?
FAQ: Do increased preheat and heat input always reduce the risk of hydrogen cracking?
FAQ: What are low alloy steels, and what precautions should I take when welding them?
FAQ: What are the problems with laser cutting of aluminium and how do I overcome them?
FAQ: What is liquid metal embrittlement and what are common embrittling metal couples?
FAQ: What are the functions of the fibres and matrix in glass reinforced plastics (GRP)?
FAQ: What can be done to help achieve a good colour match when welding aluminium alloys?
FAQ: How can I determine the atmospheric corrosion performance of thermal spray coatings?
FAQ: How can I minimise the risk of solidification cracking in Submerged Arc (SAW) welds?
FAQ: What are the equivalent European and American Standards for common stainless steels?
FAQ: What methods of portable hardness testing are available and which is most reliable?
FAQ: What are Electrically Conductive Adhesives, how do they work and where are they used?
FAQ: What checks should be carried out to assess fire damage in a post-fire investigation?
FAQ: What are the causes of and solutions to the preferential weld corrosion in C-Mn steels?
FAQ: What materials issues must be considered when repairing hot section gas turbine blades?
FAQ: What precautions do I need to take to avoid hydrogen cracking when welding C-Mn steels?
FAQ: What is current industry standard practice for welding supermartensitic stainless steels?
FAQ: What is the significance of nickel on sulphide stress cracking in duplex stainless steels?
FAQ: What precautions should I take to avoid cracking when welding creep (heat)-resistant steels?
FAQ: How do I remove heat-tint formed during welding or improper heat treatment of stainless steels?
FAQ: What are the factors involved in the choice of consumables for MMA (SMAW) welding of cast iron?
FAQ: What are the microstructural constituents Austenite, Martensite, Bainite, Pearlite and Ferrite?
FAQ: What are the distinguishing characteristics of steels made using different deoxidation practices?
FAQ: Are duplex and superduplex stainless steels fit-for-purpose under conditions of cathodic protection?
FAQ: Are there any particular points to observe when clinching materials of dissimilar type or thickness?
FAQ: What are the equivalent European and American Standards for common stainless steel filler materials?
FAQ: What is the origin of embrittlement in austenitic stainless steel welds exposed to high temperatures?
FAQ: What is the relationship between hardness, microstructure and toughness in steel heat affected zones?
FAQ: How might the operating temperature limits of austenite-ferrite grades of stainless steel be increased?
FAQ: If a metal or alloy has a high thermal conductivity, does this make it more difficult to friction weld?
FAQ: Is post weld heat treatment normally required when welding chromium-nickel austenitic stainless steels?
FAQ: Why does my steel specification say that the aluminium content must exceed twice the nitrogen content?
FAQ: Has TWI the facilities and skills to carry out reliability tests on polymeric materials and components?
FAQ: Can I weld duplex or superduplex stainless steel to carbon steel and, if so, what consumable should I use?
FAQ: What is the difference between the various carbon equivalent formulae used in relation to hydrogen cracking?
FAQ: What is the effect of moisture or hydrogen in shielding gas on hydrogen content of gas metal arc weld metal?
FAQ: What are the causes of and solutions to preferential weld corrosion in electric resistance welded steel pipe?
FAQ: What is a supermartensitic stainless steel and why is it an attractive alternative to duplex stainless steel?
FAQ: Why are there different types of manganese sulphide (MnS) inclusions, and how can I distinguish between them?
FAQ: I have to weld a non-ferrous metal. What does non-ferrous mean, and what things do I need to be careful about?
FAQ: How do you weld En 5 (subsequently known as 080M30 and 1.1178 C30E), a 0.3% carbon steel, under high restraint?
FAQ: For how long and at what temperature should I heat low hydrogen manual metal arc electrodes when baking is required?
FAQ: My Charpy specification is in J, but my certificate shows J/cm?; how do I compare the results with the specification?
FAQ: What is controlled deposition repair ('cold' repair, without a subsequent post-weld heat treatment), and how is it carried
FAQ: What is the procedure for welding En16 (subsequently known as 605M36), a 0.4%C, 0.25% Mo low alloy steel, under high restra
FAQ: What is the procedure for welding En17 (subsequently known as 608M38), a 0.38% C, 0.5% Mo low alloy steel, under high restr
FAQ: What is the procedure for welding En8 (subsequently known as 080M40 and 1.1186 C40E), a 0.4% carbon steel, under high restr
FAQ: My duplex or superduplex stainless steel WPQ has failed ASTM G48 testing. What can I do about it and what is its relevance
FAQ: What is the procedure for welding En9
FAQ: For duplex stainless steel piping used in sour service environments, are there Standards which provide hardness limits dire
FAQ: What are the requirements of ASME Section IX for retesting and/or retraining of welders (and welding operators) who fail a
FAQ: Why do the proof and tensile strength of Ni-based weld metal (used for welding 9% Ni steels) differ in welds deposited in d
FAQ: Is there a restriction on the heat input that can be used for the welding of TMCP (Thermo-mechanically Controlled Processed
FAQ: What is the procedure for welding En19?
FAQ: What is the procedure for welding En24 (subsequently known as 817M40 and 1.6582 34CrNiMo6), a 0.4% C, 1.25% Cr, 0.3% Mo low
FAQ: I've got to meet Rockwell C hardness limits for duplex stainless steel welds but hardness was measured using the Vickers sy
FAQ: What is the effect on C-Mn and low alloy steels of multiple tempering or stress-relieving heat treatment cycles carried out
FAQ: How can I achieve the specified minimum strength and toughness requirements for thicker section sizes and higher strength g
FAQ: I've got to meet NACE Rockwell C hardness limits for duplex stainless steel welds but hardness was measured using the Vicke
.
What is porosity and how can it be prevented?
TWI Frequently asked questions
Fig. 1. Uniformly distributed porosity
Job Knowledge for Welders 42
.
