Hydrogen resistance increase of the X70 steel type

• Autorzy: Rucká Z. , Mazancová E.
• Konferencja: Międzynarodowe Sympozjum: Metody oceny struktury oraz własności materiałów i wyrobów (XXIII ; 22-24.10.2008 ; Jarnołtówek, Polska)
• Języki publikacji: EN

Abstrakty

EN

Increasing requirements of oil and gas production as well as transport of these substances resulting from this tendency lead to the call to increase the material-technical properties of gas and oil pipelines guaranteeing both the increased mechanical properties and high hydrogen induced cracking resistance (HIC), simultaneously. For steel sheets being used for welded tubes and pipelines production classification of susceptibility is one of the important quality criteria. The most often detected being orientated with surface parallelly. In summary it is to possible to say that analyse of material hydrogen degradation in carbon or low-carbon microalloyied steel depends on below mentioned parameters a) hydrogen activity level in steel; b) exposition temperature; c) chemical steel composition; d) micro-structural and strength level; e) mechanical stress method; f) exposition time. As known, hydrogen activity depends upon its heterogeneous distribution in basic steel matrix. To a great extent this is connected with heterogeneity in the steel and in this way with different local formability. The manganese and carbon segregations can be observed. Beside the mentioned metallurgical parameters as chemical and steel purity there is also important type of microstructure. In this connection, there the microstructural parameters play an important role. This is characterized with rolling conditions and also with selected variant of thermo-mechanical processing during the deformation process. Moreover there is expected that produced steel sheets can be used in as rolled condition without another heat treatment application representing additional production expenses [1,2]. Further, attention is concentrated both on the role of chemical composition and evaluation of metallurgical purity, non-metallic inclusions, especially. Firstly, the question is well-balanced carbon and manganese content. Influence of sulphur content is also relevant. Currently its content is kept on very low values, but that does not mean guarantee of a lover susceptibility to hydrogen brittleness of given material. Low sulphur content can be reached with intensive desulphurization being standard process at present time. Moreover calcium having higher affinity to sulphur leads to fine globular inclusions formation and to suppressing of very long sulphide strips simultaneously. Globular inclusion shape is the decisive characteristic. For maximum effect of this action the lowest oxygen content is necessary, so that none more dimensional calcium oxides (or oxides complexes, e.g. on MnS base) in higher volume fraction would be formed. Those can act as potential places for initiation and/or HIC development. Usually, the central segregate zone is enriched with manganese and according to level of purity also with residual elements. Manganese content does extremely relevant role in superposition with phosphorus, eventually. Manganese can increase its local concentration up to 50%, with following consequences influencing the austenite decomposition properties during cooling process from the finishing rolling temperature. This effect is getting stronger according to cooling conditions and carbon atoms redistribution. Those can diffuse to the areas with increased manganese content resulting in lover carbon activity. The problem becomes very dangerous in case of slower cooling process (in the air especially) being realized from finish rolling temperature.

• Wydawca: Oficyna Wydawnicza Politechniki Opolskiej
• Czasopismo: Zeszyty Naukowe. Mechanika / Politechnika Opolska
• Rocznik: 2008
• Tom: z. 92
• Strony: 57--58
• Opis fizyczny: Bibliogr. 2 poz.

Twórcy

autor

Rucká Z.

autor

Mazancová E.

• VŠB-TU Ostrava

Bibliografia

• [1] MAZANCOVÁ E.: Rozbor vlivu nejduležitejších fyzikálne metalurgických a technologických faktoru ovlivnujících odolnost plechu z ocelí jakostí X50 až X70. Dílcí zpráva projektu evidencní c. FI-IM 3/159, VŠB-TU Ostrava, 2006.
• [2] GOUNÉ M., BOUAZIS O., PIPARED J. M., MAUGIS P.: Revue de Metallurgie, vol. 103, 2006, 10, p. 465.