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Product Show
High collapse tubing and casing

Definition
High collapse casing is the casing whose collapse resistance is above 15% over the standard data of  API 5C2.

Design principle
In accordance with the requirements of API BUL 5C3 for casing collapse and the requirement of inspection and device of oil field, we take the following measurements when the specification and grade is fixed.
A.Decrease the residual stress of casing
B.Improve the accuracy of wall thickness
C.Improve the material’s yield strength
D.Control pipe body conicity

Raw materials
After reserch and trial production, the raw material for the production is limited to two brands 25 Mn2V and 30CrMo. The mechanical property of 25 Mn2V can fully meet the requirement of collapse resistance of the high collapse casing.
30CrMo has better material stability and as a kind of steel its hardenability is better owing to high content of elements like Cr, Mo and Mn. Meanwhile, carbon content is low and can undergo water quenching and oil quenching.
Our company choose 25 Mn2V as the raw material for the production of high collapse casing.

Performance & Parameter
A. Mechanical property

Size

Yield Strength   (MPa)

Tensile Strength   (MPa)

Elongation

(%)  

Impact

(J)

114.3×6.35

871~1062

≥948

≥15

≥52

114.3×7.37

B. Residual stress control
Residual stress control or yeild strength 20%

Property
A. Mechanical property

Size

Yield Strength   (MPa)

Tensile Strength   (MPa)

Elongation    (%)

Impact            (J)

114.3×6.35

955

980

19

65

114.3×7.37

930

973

18.5

94

B. Measurement of residual stress
Test of residual stress adopts Cutting Ring Method and the length of cuting ring is 3 times of the extermal diameter. Residual stress calculation formula is as below :

Σr=ES(1/Do-1/Df)/(1-μ)

ΣrResidual stress of the pipe body surface, MPa
EModulus of elasticity, E=2X10Pa
SAverage thickness, mm
DoAverage value of external diameter before slotting, mm
DfAverage value of external diameter after slotting, mm
μPoisson’s ratio,μ=0.3

Sample No.

Yield Strength   MPa

Residual           MPa

Residual/Yield Strength    %

114.3×6.35

955

14.3

15.0

114.3×7.37

930

13.8

14.8

 
 
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