WCB NT & QT tensile fail...

[RAJMETALLURGY]

Sometimes WCB Normalized (920 Deg C), Tempered (640 Deg C) & Quenched (920 Deg C), Tempered (640 Deg C) also getting ail in tensile test.

Required value: 485 - 655 MPa
Actual Value: 465 MPa

Please give your input for the same.

 

[jwhit]

Can you list the composition for some of the failed heats? Your temperatures look like they should work without problem, so I suspect a chem issue, or possibly a raw materials issue. Is there any evidence of defects in the broken test bar halves, for instance gas or shrinkage? Rough looking fractures would indicate dirty or excessively remelted material. If you are getting a good cup and cone fracture with good elongation and reduction I would look to the chemistry, Carbon or Manganese to low for example.

 

[jwhit]

I just looked at your additional posts, take a good hard look at your raw materials and also how much revert goes into your furnace charge.

 

[arunmrao]

Check your trace elements, pouring temperature and grain refiners addition.

I'm just one step away from being rich, all I need now is money.
( read somewhere on the internet)

 

[metengr]

Have you checked or verified the chemical composition against WCB? What is the carbon content?

 

[weldstan]

In addition to checking the Carbon Equivalent, lower the tempering temperature by 20 C-25 C.

 

[RAJMETALLURGY]

Carbon & Carbon equivalents are within the specification

Carbon: 0.21 %

Carbon Equivalent : 0.40

I have lowered the tempering temeperature to increase the strength but still its not working. Pouring temperatures are similar and only slight variations observed.

Tramp elements ? what kind of grain refiners has to be added ???

Sn, Sb, As are < 0.003 %
We are adding FeTi so Ti will be 0.035 %
FeSiZr, Misch Metal, CaSi & Selenium to some extent.

 

[metengr]

Aluminum content? I think your carbon content might be low. For Grade WCB, I would rather see 0.25%

 

[weldstan]

I would also recommend lowering the normalizing temperature to 900C. What was the %Mn? I have seen some disturbingly low Mn contents (< 0.5%) in the past year.

 

[Dalinus]

What is the test block thickness? Is the test block and the sample preparation always the same?
How the tensile test bar looks after the test(clean,microshrinkage porosity,...)
Are you adding so much Ti because there is a big wall thickness(>200 mm) of the casting and you are afraid of AlN cracks (rock candy)?
The hardenability of the material with so low CEV will also be minimal.

 

[jwhit]

You should not be having issues with a carbon of 0.21% and a CE of 0.40. This would fall within the requirements for NACE material, if it is for oilfield useage. Fracture appearance of the failed test bars would be good to see. What is your aluminum content? You don't want to exceed about 0.07 due to forming aluminum nitride and also causing weldability issues later on.