Carbon Equivalent Limitation for Weldability of Steels 3

[johnthy]

Hell, in Wikipedia Carbon Equivalent Limitation for Weldability of Steels is defined as:

Carbon equivalent (CE) Weldability
Up to 0.35 Excellent
0.36–0.40 Very good
0.41–0.45 Good
0.46–0.50 Fair
Over 0.50 Poor

I looked through AWS D1.1 and AWS D1.4, but i failed to find the definition of Carbon equivalent for weldability of steel. So I want to know in which code could i find the definition for Carbon Equivalent Limitation for Weldability of Steels

Thank you!!

 

[metengr]

In the US, there is no specific guidance in Codes and Standards for how CE relates to weldability, this information can be found in technical literature, and is subjective. Also, see below

faq330-1077

 

[SJones]

Some standards do have restrictions on CE variability, i.e. an essential variable, NACE SP0472 for example, but not as an indicator for weldability.

Steve Jones
Materials & Corrosion Engineer

http://www.oilandgaspeople.com/cv/11499664

http://www.linkedin.com/pub/8/83b/b04

 

[rneill]

A commonly applied criteria in sour service is that materials shall have a CE of no more than 0.43. This limit is referenced in NACE Report 8X194.

 

[gtaw]

There are several carbon equivalency formulas, each with its own guidelines.

A simple definition of weldability is the ability to be welded without cracking. A simplistic definition, but good enough for many situations.

In general, as the CE increases there is more concern for cracking due to decreases in ductility (as strength and hardness increase, ductility decreases) and increased potential for cracking. One of the more serious issues and potential causes for cracking problems in a carbon steel alloy is the diffusible hydrogen introduced into the molten weld puddle from various sources such as flux coverings, granulated flux, surface contamination, etc. One means of reducing the potential for hydrogen induced cracks is to ensure the weld is ductile, i.e., ensure the microstructure isn't hard and brittle. Other activities include preheating before welding, maintaining high interpass temperatures, and performing post weld heat treatments to reduce residual stresses.

When the CE is low, little if any preheat is required. As CE increases, higher preheat is needed, as the CE increases even more, low hydrogen welding practices are needed in addition to high preheat and maintenance of high interpass temperature, etc.

Each carbon equivalency has its own set of guidelines. It is important to use the proper guidelines and do not apply the guidelines intended for one CE formula to different formula.


Best regards - Al

 

[MOB1]

Here in Australia we have standards AS1554 parts 1 to 6 covering the welding of all types of steel. Part 1 gives guidelines on the Carbon Eqivalent calculation giving a Group number and the relationship between this and combined joint thickness,joint weldability index,arc energy and minimum preheat temperature depending on welding process and whether hydrogen is controlled

 

[ajh1]

Various ASTM material standards show formulas for determining carbon equivalence. A6 and A529 come to mind. The formula varies depending upon whether you are looking at a carbon steel, high strength low alloy steel, or an alloy steel.

 

[TomEun]

Carbon Equivalent (Ceq) is used for the guideline for the decision of minimum preheating temperature as well as materials purchasing in order to prevent the crack of carbon steel during welding and/or on service in cracking environments (sour, caustic, etc.).

1. Carbon Equivalent of Cast Iron (Ceq) – element: weight %

Ceq/ = C + (Si + P) / 3

2. Carbon Equivalent of Carbon Steels (Ceq. %) – element: weight %
(1) Ceq = C + Mn /6 + (Cr + Mo + V) /5 + (Ni+Cu) /15 ; BS 2642 and IIW
(2) Ceq : C + Mn /4 + Ni /20 + Cr /10 + Cu /40 + Mo /50 + V /10 ; AWS
(3) Ceq = C + Mn /6 + Si /24 +Ni /40 + Cr /5 + Mo /4 + V /14 ; Japan JIS G 3106 & 3115
(4) Ceq = C + F [Mn/6+Si/24+Cu/15+Ni/20+(Cr+Mo+V+Nb)/5 + 5B] ; CSA Z245.1
F is a factor per Ceq.
(5) Others ; Several different formulas from lab studies.

3. Carbon Equivalent (Crack Parameter in Welding -Pcm , %)
Pcm is more appropriate than conventional carbon equivalent (Ceq) for steels, such as low carbon steels, HSLA (high strength low alloy steels) or TMCP (thermo mechanical controlled process steels). Pcm carbon equivalent formula was developed for steels with low carbon contents (<0.10%) and with tensile strengths of 60 to 130 ksi in Japan.

Pcm = C + Si /30 + (Mn + Cu + Cr) /20 + Ni /60 + Mo /15 + V /10 + 5 x B

Thomas Eun

 

[dik]

Attached Spreadsheet... use at your discretion...