Effect of cold work on toughness 2

[GRoberts]

In general, on low alloy steels, (API 2Y gr. 50 for instance), what is the effect of cold work on toughness. If for example you cold bend a plate and strain the outer fiber 5-10%, how would CVN tests compare to unstrained plate?

 

[sayee1]

Material: API 2H Grade 50 S1 S4, 60mm Thk
SUMMARY OF THE MECHANICAL TEST VALUES FOR ROLLED CAN
WITH FIBER STRAIN OF 5.17%
TEST UNITS VIRGIN PLATE ROLLED CAN
IMPACT @ -20°C (LONG) JOULES 299(Avg.) 291(Avg.)
IMPACT @ -20°C (TRANS) JOULES 299(Avg.) 274(Avg.)
Y.S (LONG-1) PSI 48200 45300
T.S (LONG-1) PSI 81600 79500
ELONG % 31% 35%

Y.S (LONG-2) PSI 51800 56700
T.S (LONG-2) PSI 79100 82600
ELONG % 37% 28%
Y.S (TRAN-1) PSI 48200 51300
T.S (TRAN-1) PSI 81800 82700
ELONG % 35% 34%

Y.S (TRAN-2) PSI 49500 47700
T.S (TRAN-2) PSI 80800 82100
ELONG % 34% 28%

Hope that answers your query.

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
End of all knowledge is the attainment of immortality!

 

[GRoberts]

Thanks, that is helpfull info!

 

[sayee1]

A related question:
When AWT specimens are removed from a small dia pipe (In my case from a 6.625" OD, 6.7 mm WT API 5L X70 welded with 80 ksi consumables, due to the curvature of the pipe the AWT specimen has to be straightened. This not only reduces the % elongation (The ductility of the material drops due to the work hardening), but the YS also drops. What is expected for the UTS and any explanations for the drop in the YS?

Thanks and regards
Sayee Prasad R CEng MWeldI MIOMMM


If it moves, train it...if it doesn't move, calibrate it...if it isn't written down, it never happened!

 

[metengr]

sayeeprasadr;
The yield strength of metals is established during a tensile test based on the application of stress along a single direction, and one direction only. By definition, this is the yield strength of the metal.

However, if additional stresses are present either applied or residual, it is the effective stress and not the principal stress that determines if yielding will occur in metals. The effective stress is determined using the familiar von Mises criteria for yielding;

Effective stress = {[(?1-?2)^2+(?2-?3)^2+(?3-?1)^2]0.5}/?2

If the effective stress caused by the application of the principal and residual stress is higher than the yield strength, the material will yield. So, the measured stress in one direction can be a lower value because of the added residual stresses that were induced during straightening of the test specimen.

The UTS is typically not affected by residual stress because after the yiled point has been reached, the fracture strength is governed by strain along a principal direction until fracture.

 

[metengr]

sayeeprasadr;
Unfortunately, when I copied the von Mises equation for some reason the math functions and symbols did not transfer properly. The equation should read

sigma effective stress = [{(sigma 1 - sigma 2)^2 + (sigma 2 - sigma 3)^2 +(sigma 3 - sigma 1)^2}^0.5]/square root 2

 

[sayee1]

Thanx Metengr, a star for yr replies.

Thanks and regards
Sayee Prasad R CEng MWeldI MIOMMM


If it moves, train it...if it doesn't move, calibrate it...if it isn't written down, it never happened!