Brittle to Ductile transition temperature of steel S450GD

In summary, Connor's issue is with the rolled coil steel cracking and fracturing when being rolled into a profile. The material certs are within ISO specification, however, the carbon equivalent may be a little high. It is possible that the steel is closer to the brittle zone at around 2-4 degrees Celsius.
  • #1
conrad dunk
7
3
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
 
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  • #3
conrad dunk said:
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:

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upload_2019-1-11_18-35-32.png
do your procurement documents include a sub-grade ?old jim
 

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  • #4
conrad dunk said:
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-content/uploads/2013/10/CM-095E_Continuously-Hot-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?
 

FAQ: Brittle to Ductile transition temperature of steel S450GD

What is the brittle to ductile transition temperature of steel S450GD?

The brittle to ductile transition temperature of steel S450GD is the temperature at which the material transitions from a brittle to a ductile state. This means that at temperatures below this transition point, the steel will behave in a brittle manner, meaning it is more prone to breaking or fracturing without significant deformation. At temperatures above the transition point, the steel will behave in a more ductile manner, meaning it can deform and bend without breaking.

Why is the brittle to ductile transition temperature important for steel S450GD?

The brittle to ductile transition temperature is important for steel S450GD because it affects the material's mechanical properties. At temperatures below the transition point, the steel may become too brittle to be used in certain applications, as it may be more prone to failure. On the other hand, at temperatures above the transition point, the steel may become too ductile and lose its strength, making it unsuitable for certain applications as well.

How is the brittle to ductile transition temperature of steel S450GD determined?

The brittle to ductile transition temperature of steel S450GD is typically determined through a series of mechanical tests, such as Charpy impact testing. This involves subjecting the steel to different temperatures and measuring its ability to withstand sudden impacts. The temperature at which the steel exhibits a significant decrease in impact strength is considered the brittle to ductile transition temperature.

What factors can affect the brittle to ductile transition temperature of steel S450GD?

The brittle to ductile transition temperature of steel S450GD can be affected by various factors, including the composition of the steel, the rate of cooling during production, and any heat treatments the steel may undergo. Additionally, environmental factors such as temperature and humidity can also impact the transition temperature. It is important to consider all of these factors when determining the appropriate use and application of steel S450GD.

How can the brittle to ductile transition temperature of steel S450GD be improved?

The brittle to ductile transition temperature of steel S450GD can be improved through various methods, such as altering the composition of the steel or implementing heat treatments. For example, adding certain elements such as nickel or manganese can help improve the steel's toughness at low temperatures. Additionally, controlling the cooling rate during production can also help improve the steel's transition temperature. It is important to consult with experts and conduct thorough testing to determine the most effective methods for improving the transition temperature of steel S450GD.

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