Fundamentals of Defects Affecting Carbon Steel

We all rely on carbon steel (CS). Whether in commuter structures, pipelines, wind turbines, oil rigs, or buildings. CS must be strong and s...

We all rely on carbon steel (CS). Whether in commuter structures, pipelines, wind turbines, oil rigs, or buildings. CS must be strong and secure, therefore the need to thoroughly and effectively inspect carbon steel structures for defects is essential.

Carbon Steel is Everywhere
Why? CS is usually easy to weld, doesn’t cost too much, and it’s extremely reliable. Carbon steel can be segmented into four main categories: low carbon steel (sometimes known as mild steel), medium carbon steel, high carbon steel, and ultra-high carbon steel.

Fundamentals of Defects Afflicting Carbon Steel
Low Carbon Steel
Typically, low CS has a carbon range of 0.05–0.25%. This is one of the largest groups of CS. It can take many shapes: from flat sheets to structural beams. Depending on the desired properties of mild steel, other elements can be added or increased in the steel. For example, in drawing-quality low CS, the carbon level is kept low and aluminum is added. This grade of steel is more ductile than commercial-quality CS and it is suited to producing deep-drawn parts or other parts needing severe deformation.

In the case of structural steel, the carbon level is higher and the manganese content increased to improve the hardening depth, strength, and toughness of the steel. This grade of CS is used to make** structural steel shapes** such as I-beams.

Medium Carbon Steel
Typically, medium CS has a carbon range of 0.30–0.60% and a manganese content range of 0.06–1.65%. This grade is stronger than low carbon steel, but it is **more difficult to form, weld, and cut **than mild steel. Medium CS is quite often hardened and tempered using heat treatment. This gradebalances ductility and strength, and offers a good resistance to wear. Medium CS is used for large parts, forging, and automotive components, among others.

High Carbon Steel
Commonly known as carbon tool steel, this grade typically has a carbon range of 0.70–2.50%. High CS is very difficult to cut, bend, and weld, and once heat treated, it becomes extremely hard and brittle. Very strong, it is used for springs, swords, and high-strength wires.

Ultra-High Carbon Steel
This grade of CS has a carbon range of approximately 2.50–3.00%. This grade can be tempered to great hardness and is used for special purposes like non-industrial knives, axles, and punches.

Processes Leading to Defects in Carbon Steel
Of course, carbon steel is not impervious to defects. They are usually the result of one or several of the following processes:


  • Segregation: In metallurgy, this is a process where one component of an alloy or solid solution separates in small regions within the solid or on the solid’s surface. Segregation causes irregularities in the properties of the carbon steel, usually adverse to the quality of the metal, andzones of reduced corrosion resistance in the immediate vicinity of segregation.
  • Porosity: This is defined as void spaces on or in the material. It appears often in castings. In weld metal, it’s usually the result of gas being trapped inside. In castings, Often, porosity is the root cause of coating failures, which manifest themselves as surface pitting, spotting, and corrosion.
  • Shrinkage (or hot cracking): This is the formation of cracks during the solidification of metal. The process is also known as hot shortness, hot fissuring, solidification cracking, and liquation cracking. Hot cracking usually occurs when the available supply of liquid weld metal is insufficient to fill the space available to solidifying metal.
  • Inclusions: These are particles, larger than ~0.5 ┬Ám, generally found in all steels, even the very purest. The most common inclusions in steel are oxides and sulphides, but also include nitrides and silicates, which are all non-metallic. Such inclusions can lead to cause cracks such as sulphide-stress cracking (SSC) and fatigue failures.
  • Residual stresses: Residual stresses are the stresses remaining in a solid material after their original cause is removed. These stresses, if uncontrolled, can lead to the premature failure of critical components.
  • Embrittlement: This process is a loss of material ductility, making it brittle and prone to cracking. The absorption of hydrogen sulfide, leading to SSC, embrittles carbon steel. Similarly, CS absorbing hydrogen leads to hydrogen embrittlement, which can cause the metal to fracture.
  • Fatigue: Progressive and localized structural damage occurring when a material is subjected to cyclic loading. If the loads are above a certain threshold, microscopic cracks begin to appear at stress concentrators such as the surface, persistent slip bands, and grain interfaces. Eventually, cracks reach a critical size, propagating suddenly, resulting in failure.

Carbon steel weld covered with paint
Defects Found in Carbon Steel
Cracking
Cracking is the most prevalent type of defects in in-service carbon steel welds. Cracks come in various shapes and sizes, from surface-breaking cracks to stress-corrosion cracking (SCC). Some of the challenges of inspecting CS surfaces for defects are that they are often rough (hard on surface probes) and very often coated with paint or other types of protective coatings. These often need to be removed to perform surface inspections and then reapplied, which is both costly and time consuming, not to mention harmful to the environment.

Cracking includes:


  • Longitudinal cracks: Breaks in the surface parallel to the weld axis that may be along the centerline of the weld, close to the weld toes, or in the heat-affected zone (HAZ), for example.
  • Transverse cracks: Breaks in the surface perpendicular to the weld axis that may be completely within the weld metal or may extend from the weld metal into the base metal.
  • Crater cracks: Breaks in the surface that occur at the crater of a weld because welding was improperly terminated. Crater cracks are also referred to asstar cracks.
  • Branching cracks: Clusters of connected cracks originating from a common crack.
  • Stress-corrosion cracking: Crack growth leading to the failure of metals under the combined action of corrosion and stress.

Liquid penetrant testing on carbon steel weld
Other Types of Surface Defects
As mentioned above, a number of other types of defects can develop in base metal carbon steel and CS welds:

  • Corrosion: Gradual material destruction by chemical reactions with the
  • surrounding environment
  • Surface porosity: Gas pores that break the carbon steel surface
  • Lack of fusion: Poor adhesion of the weld bead to the base metal
  • Pitting: Form of extremely localized corrosion leading to the creation of
  • small “pits” in the metal
  • Dents: Depressions in surfaces from pressure or blows

Detecting Defects in Carbon Steel
To prevent failures and prolong the life of assets, structures, and equipment, carbon steel must be regularly inspected for defects. There are several standards governing this activity, published by ASTM International, the American Society of Mechanical Engineers (ASME) and the International Standards Organization (ISO). These standards state that ultrasonic testing (UT), eddy current testing (ECT, including eddy current array), magnetic particle testing (MT), and liquid penetrant testing (PT) may be used to inspect for surface-breaking defects, according to specific guidelines.

ASTM E3052-16 covers the use of ECA sensors for the non-destructive testing of carbon steel welds. It includes the detection and sizing of surface-breaking cracks in joints, accommodating for non-magnetic and non-conductive coatings up to 5 mm (0.197 in) thick (typical) between the sensor and the joint. The practice covers a variety of cracking defects, such as fatigue cracks and other types of planar iscontinuities, at various locations in the weld (heat-affected zone, toe area, and weld cap, for example). It covers the length and depth sizing of such surface-breaking discontinuities.

ASME’s *Boiler and Pressure Vessel Code Case 2235-9 *states thatunless UT data analysis confirms defects are not surface connected, said defects are considered surface-breaking, which is unacceptable unless a surface inspection using MT, PT, or eddy current testing (ECT) is performed. The document also mention that all relevant eddy current testing indications open to the surface are unacceptable regardless of their length.

Similarly, in ISO’s BS EN ISO 5817:2007, Welding — Fusion-welded joints in steel, nickel, titanium and their alloys (beam welding excluded) — Quality levels for imperfections, ECT methods are cited as good surface-breaking and near-surface defect inspection methods, mainly in ferritic materials (welds, heat-affected zones, parent materials). The document also sets the minimum size of defects ECT methods should be able to detect in ferritic steel welds (as welded) as 1 mm (0.039 in) deep and 5 mm (0.197 in) long.

As you might expect, these inspection methods have their advantages and disadvantages, making one suited to some applications and others not, but they are all the best way to detect and monitor the progression of defects in assets and an essential part of asset integrity management (AIM).

Wrapping Up
Identifying the type of defect and understanding its root cause are essential in finding and monitoring defects in assets, which we explore in 4 Methods of Detecting Surface Defects in Carbon Steel. Don’t be afraid to leave your questions in the comments!

Branching cracks Carbon steel Corrosion Cracking Crater cracks Defects Dents Eddy current array (ECA) Eddy current testing (ECT) Electromagnetic testing Embrittlement Fatigue Hot cracking Inclusions Information Lack of fusion Longitudinal cracks Oil & Gas Pitting Porosity Processes Residual stress Segregation Shrinkage Stress-corrosion cracking Surface porosity Transverse cracks Ultrasonic thickness measurement (UTM)


Name

• compression couplers,1,• tension couplers,1,1997 UBC,1,56 days Concrete test,1,ADDICRETE,1,additives,1,administer computer networks,1,admixtures,1,Advises Subcontractors,1,alignment of the shafts,1,Allowable Stress Design,1,Anchor Bolts,1,Annual depreciation expense,1,approval of drawings,1,ASCE7,1,ASD,1,Assist in Quantity,1,Assist the Project Manager,1,Authority to Delegate,1,AutoCAD,2,AutoCAD to Etabs,1,bagger,1,bars,1,bars in a bundle,1,BASE ISOLATED DAMAGE,1,base plates,1,basement wall,1,Basic soil properties,1,basic wind speed,1,Beams Inspection Checklist,1,Bearing capacity,1,bell pile bottom,1,bent bars,1,Bitomeneous,1,Bowels,1,breaching spillway,1,BS 8007:1987,1,BS5400,1,BS6399,1,BS8007,1,BS8110-1997,1,building materials,1,buildings height,1,CALCULATION OF CRACK WIDTH,1,Canary Island Dates,1,cantilever footing,1,Carbon Equivalent,1,carbon test,1,cast in-situ,1,cast-in-place anchors,1,cast-in-place concrete pile,1,Cause-and-effect diagram,1,Chairs,1,Check sheets,1,Chemical Admixtures,1,Chute spillway,1,CIRIA,2,CIRIA Report 136,1,civil engineering,1,civil structures,1,Coal ash,1,collars,1,Collision Load,1,columns,3,columns and walls,1,Combination of combinations,1,combinations in Etabs,1,Company's Health,1,Compliant Towers platforms,1,compression test,1,compressive strength,1,concrete,4,concrete block buildings,1,CONCRETE IN HOT WEATHER,1,CONCRETE MOMENT FRAME,1,concrete pile,1,Concrete Rebound Hammer,1,Concrete Shrinkage,1,Concrete Slump Test,1,concrete walls,1,Construction and Stressing,1,Construction companies in Dubai,1,construction drawings,1,construction industry,1,Construction joints,1,Construction Manual,1,continuous external restraint,1,continuous slabs,1,contract planresponsibilities of QA/QC,1,Contracts Manager,1,cooling pipe system,1,Corner reinforcement,1,Cost Plus Award Fee,1,Cost-reimbursable,1,COUPLED SHEAR WALL,1,Couplers,1,couplers in columns,1,CP3,1,CRACK WIDTH,1,Creep,1,CURING,1,day to day work progress,1,Dead load and Self-weight,1,Deck,1,Deflection,1,Deflection discussion,1,Deflection in Prestressed,1,deformed bars,1,Demolition,1,Design Requirements,1,designing a tall building,1,Designs projects,1,detailed review,1,detailing and implementation,1,Development length,1,different codes in one structure,1,Differential elastic shortening,1,dimensions,1,DIRECT TENSION,1,Draftsman responsibilities,1,drawings and specifications,1,Drift Limitations,1,Drop beams,1,dust loads,1,dust on roof,1,Dynamic Pile Head,1,dynamic wind pressure,1,Early age Crackwidth,1,early strength cement,1,Earth pressure,1,Earthquake Design,1,earthquakes,1,EBT adhesive sealant,1,Elastic Shortening,1,electrical and manual,1,elevator requirement,1,Elevators,1,Encasement of pipes,1,end plate connection,1,Energy dissipater,1,engineering design,1,Environmental procedures,1,epoxy compound,1,Epoxy grout,1,equipment performance records,1,Error and warning free model,1,Errors in Etabs,1,establishment of construction,1,Estimating Flow Standard,1,Etabs,2,Etabs Design,1,ETABS to ROBOT,1,excavation,1,Excavation slopes,1,external concrete surfaces,1,Finishing of slip-forms,1,Fire,1,Firm Fixed Price,1,Fixed platforms,1,Fixed Price Incentive Fee,1,Fixed Price with Economic,1,Flexible Joints,1,Flexible pipes,1,floors,1,Flow charts,1,Fly ash,1,Foundation analysis,1,Foundations,1,framed openings,1,Free over fall spillway,1,FRP,1,FRP advantages,1,FRP disadvantages,1,FRP technology,1,full length bar,1,General Notes,1,Geophone sensor,1,Hammer Schmidt Type,1,HDP,1,Health and Safety procedures,1,High Early Strength Portland Cement,1,High quality additives,1,high rise / tower,1,highly effective,1,Histograms,1,hooked bars,1,Horizontal steel,1,Human Comfort,1,hydraulic,1,hydraulic jump,1,Hydraulic resistance,1,Hydro technical tunnels,1,IBC/ASCE,1,immediate reaction,1,importance of Plasticizers,1,Importing,1,IMS,1,Inspection Checklist,6,INSTRUMENT CALIBRATION,1,inter-story drift,1,interest payments,1,IT engineer responsibilities,1,Jack-up Platforms,1,Jacking Systems,1,Japanese code for escalators,1,Kicker,1,largest man-made machine,1,largest man-made machine on earth,1,largest oil platform,1,lateral forces,1,lateral loads,1,LFD,1,lifting hooks,1,Load Factor Design,1,load resisting elements,1,load-bearing wall,1,Loading,1,Loads and Resistances,1,LRFD,1,Maintain contract database,1,Maintains close scrutiny,1,maintenance cost,1,Makes recommendations,1,manage,1,manufacturer,1,manufacturing process,1,Maximum allowable slopes,1,maximum deflection,1,maximum difference,1,maximum pressure,1,maximum reinforcement,1,maximum temperature,1,Mechanical couplers,1,Mechanical damage,1,membrane floors,1,Metal sleeves swaged,1,Method of dissipation,1,METHOD OF TESTING,1,Method statement,2,Mineral Admixtures,1,minimize the seepage,1,minimizing the cost,1,minimum eccentricity moment,1,Minimum reinforcement,1,mixing concrete,1,modelling in Etabs,1,Monitors performance,1,monthly invoice,1,Monthly Safety Report,1,multi-storey buildings,1,multistory buildings,1,Natural frequency,1,Necessity of tunnel lining,1,new structural systems,1,O&M,1,of concrete block buildings,1,office buildings,1,Office Tall Buildings,1,offshore platforms,1,oil platform,1,oil rigs,1,on beams from loaded slab can be achieved by defining the slab as a membrane,1,opening reinforcement,1,ordinary Portland cement,2,Other bars,1,Overlap,1,overlap locations,1,Oversee and review,1,palm trees weight,1,parallel threads,1,parapet,1,Perform data backups,1,Performance Bonds,1,Performs design drafting,1,physical properties,1,Pile Dynamic Test,1,Pile Head Preparation,1,Pile Integrity Testing,1,Pile Shaft Overbreak,1,Pindos,1,Pipe Classifications,1,PLACING,1,Placing boom,1,Plan and prioritize work,1,Planning Engineer,1,plant and equipment,1,Plant and Equipment Engineer,1,plaster walls,1,Platform types,1,pneumatic,1,Post-Tensioning Grouting,1,Pour strip,1,precast panel,1,Prepares monthly report,1,Pressure Ratings,1,Prestressed Concrete,1,prevent uplift,1,principal load resisting,1,procedure of fixing,1,Project Coordinator,1,Project manager assignment,1,project schedule,1,project's compliance,1,Provides technical expertise,1,provisional Sum,1,PT slabs,2,pump,1,PVC,1,QA,1,QA/QC Engineer,1,QC,1,Quality,1,raft foundations,1,Raft Slab Inspection Checklist,1,reaction as an engineer,1,rebound hammer,1,recommended tests,1,Recorded experience,1,Reinforced concrete columns,1,reinforcement,1,Reinforcement at openings,1,reinforcing bars,2,reinforcing-steel,1,Residential Tall Buildings,1,RESISTING SYSTEMS DAMAGE,1,Retaining Wall Inspection Checklist,1,Retaining walls,1,retarder,1,Review contract documents,1,review contracts,1,review expiring contracts,1,Reviews accidents,1,reviews contract drafts,1,Reviews shop drawings,1,Reviews the terms and conditions,1,Rice husk ash,1,rigid foundation,1,Rigid pipes,1,Road layers,1,Robot Millennium,1,Roles and Responsibilities,8,Roller bucket,1,Rough Order of Magnitude,1,Rules of thumb,1,saddle beams,1,Safe 14,1,Safety Manager,1,sample letter,3,sand,1,SAP2000,1,Schmidt Hammer,1,Seismic,1,Seismic Design Principle,1,Seismic force,1,SEISMIC RESISTING SYSTEMS,1,seismic zone factor,1,Semi-structural welding,1,Semi-submersible Platforms,1,Senior Architect,1,Senior Contracts Engineer,1,Sequential Loading,1,Set work program,1,Seven Basic Quality Tools,1,shallow foundation,1,Shell,1,Ship-board Rigs platforms,1,shortening of columns,1,Shrinkage,1,Shrinkage and Temperature,1,Side channel spillway,1,simply supported,1,Site engineer responsibilities,1,site facilities,1,SK Gosh,1,Ski-jump,1,slab assignment,1,slabs,2,Slabs Inspection Checklist,1,slings,1,slip forms,1,Slip-form,1,Slip-form construction,1,slip-forming,1,smooth finish,1,soffit slabs,1,Soil classification,1,Soil Sloping Systems,1,speed of erection,1,Spring Force,1,standard size bolts,1,Static load,1,Static load multiplier,1,steel beam,1,Steel Columns,1,steel quantity,1,steel stress,1,Stiffness,1,stiffness and resistance,1,stilling basin,1,Strap footing,1,Strength and Stability,1,Stress on soil in etabs,1,Stressing sequence,1,Striking formworks,2,Strip footing,1,Strong Column,1,structural construction process,1,structural design spreadsheet,1,Structural Details,1,structural engineers,1,Structural Provisions,1,structural purposes pipes,1,strukts spreadsheets,1,Subcontract Agreement,1,Super-plasticizers,2,surfactants,1,Tack welding,1,Tall Building,1,tall buildings,1,taper-cut threads,1,Tdr Test Accuracy,1,Technical Engineer,1,technical submittals,1,test hammer,1,Test on Piles,1,Test specimens,1,TESTING,1,Thermal Expansion,1,threaded rods with nuts,1,time for completion,1,Top bars,1,torsion-load test,1,Total Shortening,1,tower cranes,1,Tower cranes installation,1,Transform AUTOCAD drawings,1,trough spillway,1,Trump Tower,1,Tunnel,1,tunnel lining,1,type of concrete,1,Types of contracts,1,types of foundation,1,Types of shallow foundation,1,Types of spillways,1,Types of waterproofing,1,Ultra Ever Dry,1,Uniform loads Safe 14,1,uniform thickness,1,Uplift Force,1,uplift test lateral-load test,1,vertical load resisting,1,Voided Biaxial Slabs,1,wall openings,1,walls,2,Warning,1,Water curing,1,Weak Beam Concept,1,Wedge locking sleeves,1,weekly and monthly program,1,weekly and monthly report,1,Welding of reinforcement,1,Welding procedures,1,What teachers never taught us,1,wind and seismic,1,Wind loads,1,Wind simulation,1,WOOD SHEAR WALL,1,workability,2,Workshop repair,1,
ltr
item
Strukts: Fundamentals of Defects Affecting Carbon Steel
Fundamentals of Defects Affecting Carbon Steel
Strukts
https://www.strukts.com/2019/07/fundamentals-of-defects-affecting.html
https://www.strukts.com/
https://www.strukts.com/
https://www.strukts.com/2019/07/fundamentals-of-defects-affecting.html
true
7606260228666216043
UTF-8
Loaded All Posts Not found any posts VIEW ALL Readmore Reply Cancel reply Delete By Home PAGES POSTS View All RECOMMENDED FOR YOU LABEL ARCHIVE SEARCH ALL POSTS Not found any post match with your request Back Home Sunday Monday Tuesday Wednesday Thursday Friday Saturday Sun Mon Tue Wed Thu Fri Sat January February March April May June July August September October November December Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec just now 1 minute ago $$1$$ minutes ago 1 hour ago $$1$$ hours ago Yesterday $$1$$ days ago $$1$$ weeks ago more than 5 weeks ago Followers Follow THIS PREMIUM CONTENT IS LOCKED STEP 1: Share to a social network STEP 2: Click the link on your social network Copy All Code Select All Code All codes were copied to your clipboard Can not copy the codes / texts, please press [CTRL]+[C] (or CMD+C with Mac) to copy