Brittle to Ductile transition temperature of steel S450GD

  • #1
Hi guys,

I'm having an issue at the minute with rolled coil steel, cracking and fracturing when being rolled into a profile. The material certs are within ISO specification, i.e. chemical composition analysis and the mechanical properties etc.

The carbon equivalent may be a little high, but still be in specification. As the temperature of the steel being rolled is somewhere around 2-4 Degrees C, It may be closer to the brittle zone. Steel grade S450GD

Can anyone provide any further information on this? It's a phenomena I know little about, and unable to find any resources on the internet. A book, or study conducted would be a good pointer.

Many thanks,

Connor
 

Answers and Replies

  • #3
jim hardy
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Steel grade S450GD

hope this helps. I'm no NDTT expert, just am aware from my reactor days that it is a property of steel.

i gather there's a "sub-grade" that defines the temperature at which 'toughness' is measured ?

clicking this link
upload_2019-1-11_18-32-54.png

at https://www.steelconstruction.info/Steel_material_properties#Toughness
installed a pdf file that looks informative
it has a tutorial on brittle fracture.

two snips:

upload_2019-1-11_18-37-16.png


========================

upload_2019-1-11_18-35-32.png



do your procurement documents include a sub-grade ?


old jim
 

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  • #4
Astronuc
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with rolled coil steel, cracking and fracturing when being rolled into a profile. The material certs are within ISO specification, i.e. chemical composition analysis and the mechanical properties etc.

The carbon equivalent may be a little high, but still be in specification. As the temperature of the steel being rolled is somewhere around 2-4 Degrees C, It may be closer to the brittle zone. Steel grade S450GD
The S450 grade indicates relative high strength, min Sy = 450 MPa with a min elongation (ductility) of ~14% in longitudinal direction. If the local deformation exceeds 14%, then one may find an increased probability of tearing or cracking. Depending on the manufacturing route, there may be carbides and sulphides that promote cracking.

See also, https://www.thefabricator.com/article/stamping/die-science-splitting-or-cracking-

The chemical composition of the steel grades in max. % by mass:

C ≤ 0.20%, P ≤ 0.10%, Si ≤ 0.60%, S ≤ 0.045%, Mn ≤ 1.70 %
from https://www.stahl-online.de/wp-cont...ot-Dip-Coated-Steel-Strip-and-Sheet_final.pdf (p. 16)

The upper limits of P and S on commercial standards are too high in my opinion.

What kind of formability test does one organization perform, e.g., bend or punch test? Is microscopy performed on the material?
 

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