Our Sour Service grades demonstrate improved resistance to Sulfied Stress Corrosion Cracking through their steel microstructure and tight mechanical properties.
Grades to resist sour environments
Tenaris has developed sour service grades for oil and gas operations in sour environments. The grades in our SS Series exhibit improved resistance to Sulphide Stress Corrosion (SSC).
An unfavorable combination of H2S dissolved in water, low pH, susceptible structure and high loads, will cause cracks to occur in the steel pipe, which will propagate until failure occurs. Our SS grades are designed to prevent Sulfide Stress Corrosion Cracking (SSC) failures.
The improved resistance to SSC is obtained by the specific design of the steel microstructure and tight control of the mechanical properties .
Our Sour Service steel grades are available in minimum yield strengths ranging from 80Ksi to 125Ksi.
Mechanical Properties
| Grade | Min. Yield Strength (Ksi) | Max. Yield Strength (Ksi)
| Min. Tensile Strength [Ksi] | Max. Hardness Reading HRC | NACE Method A Threshold % SMYS |
|---|
| TN 80SS |
80 |
95 |
95 |
22 |
90 |
| TN 90SS |
90 |
105 |
100 |
24 |
90 |
| TN 95SS |
95 |
110 |
105 |
25 |
90 |
| TN 100SS |
100 |
115 |
110 |
27 |
85 |
| TN 110SS |
110 |
125 |
115 |
29 |
85 |
| TN 125SS |
125 |
140 |
130 |
36* |
85** |
| TN 80S |
80 |
95 |
95 |
22 |
85***
|
| TN 90S |
90 |
105 |
100 |
24 |
85***
|
| TN 95S |
95 |
110 |
105 |
25 |
85***
|
Elongation according to API formula.
*Difference among three hardness readings within the same radial wall thickness line shall be < 3 HRC
**Test solution B; initial pH 3,5; 3%H2S
***Threshold, the product will be tested upon request. |
Maximum Through-Wall Highness Variation [HRc]
| WT < 0.5" | 0.5" < WT < 0.75" | 0.75" < WT < 1.0" | WT > 1.0" |
|---|
| 3 |
4 |
5 |
6 |
Parameters for excellent ssc resistance
The steelmaking process must provide products with the following characteristics:
- Clean steel, with a very low level of residual elements and oxygen to minimize the quantity of inclusion and specifically oversize oxides.
- Chemistry design: a balanced chemical composition to ensure high hardenability. Together with adequate quenching, the chemistry ensures over 95% martensite.
- Fine-grained microstructure through rolling and heat treatment
- Heat treatment ensuring a very fine microstructure and high final tempering temperature to promote a recovery process eliminating high-energy sites.
Corrosion testing capabilities worldwide
Each Tenaris mill has its own corrosion lab where the different NACE/ISO corrosion tests are regularly performed to guarantee the quality of pipes manufactured for sour service environments.
