OREANDA-NEWS. January 22, 2013. ArcelorMittal Lazaro Cardenas, Mexico, has recently launched production for slabs which will be used in pipelines that transport sour gas, reported the press-centre of ArcelorMittal.

Strengthening its position in this niche market, the Mexican site is consolidating its position as a leading producer of world-class steel slabs.

Since the start of its operations, Lazaro Cardenas has always put a great emphasis on providing customers with high quality, value-added steel, serving more and more niche markets which competitors have found difficult to enter. Launching production of this new product was a major step in that direction.

The new value added product will be used in pipelines that will transport sour gas, a natural gas containing significant quantities of toxic gases such as hydrogen sulfide (H2S), carbon dioxide (CO2), or similar contaminants.

In order to be suitable for this use, the steel slabs must present very stringent technical specifications, including a high resistance against hydrogen-induced cracking (HIC). For this reason, best technological practices were implemented at Lazaro Cardenas for the site to be able to produce defect-free slabs with a reduced centre segregation rate, in order to increase its share of the growing market for API (American Petroleum Institute) pipes.

The H2S present in the sour gas poses a major challenge: this compound reacts with water creating a corrosion mechanism due to the release of hydrogen in diatomic and monatomic form. The monatomic hydrogen diffuses through the steel and becomes trapped in voids in the metal microstructure, giving rise to brittle areas when these atoms recombine to form hydrogen molecules. This creates pressure mechanisms, leading to the formation of blisters and subsequently micro-cracking which can result in the failure of the metal with potentially disastrous consequences.

To test the steel’s resistance, an HIC test – developed by the US association of corrosion engineers (NACE) – is carried out: the steel is placed in an acid bath for 96 hours to see if cracking occurs. If that is the case, cracks are measured against an index based on two criteria: the crack length ratio (CLR) and the crack sensitivity ratio (CSR). The tolerance level is dictated by the customer, in this case the pipes producer, but average ratios are between 10-15% for CLR, and between 2-5% for CSR.

After undergoing several tests, ArcelorMittal Mexico met all the requirements of its customers in this project - world leading tube manufacturer Welspun Corp in India, and leading coils plate producer Ternium in Mexico - with the internal quality of the slabs exceeding expectations.

To maintain its leading position in the market, Lazaro Cardenas is determined to keep the focus on the quality of its high value-added products, which only very few steel producers are able to offer.