Features of Phase Transformations in Martensitic Class Steel for Oil Grade High-Strength Corrosion-Resistant Pipes

• Published in: Metallurgist (New York) Vol. 65; no. 11-12; pp. 1245 - 1254
• Main Authors: Pumpyansky, D. A., Pyshmintsev, I. Yu, Bityukov, S. M., Alieva, E. S., Gusev, A. A., Mikhailov, S. B., Lobanov, M. L.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-03-2022; Springer; Springer Nature B.V
• Subjects: Austenite; Carbon dioxide; Casing; Characterization and Evaluation of Materials; Chemical composition; Chemistry and Materials Science; Chromium; Corrosion; Corrosion effects; Corrosion resistance; Corrosion resistant steels; Crystallization; Delta ferrite; Equivalence; Heat treatment; Inhomogeneity; Iron compounds; Martensitic stainless steels; Materials Science; Mechanical properties; Metallic Materials; Microstructure; Nickel; Phase composition; Phase transitions; Pipes; Room temperature; Steel; Steel structures; Steel, High strength; Temperature; Transformation temperature; phase transformation temperatures; chromium equivalent; nickel equivalent; austenite; martensitic class; ferrite-forming elements; phase transformation diagram; δ-ferrite; austenite-forming elements; dilatometric curve; crystallization; phase composition; chemical composition
• DOI: 10.1007/s11015-022-01270-w
• EISSN: 1573-8892
• ISSN: 0026-0894

The effect of chemical composition on features of phase transformation in martensitic stainless steels based on 13 wt.% chromium containing 0.04–0.1 wt.% carbon additionally alloyed with nickel (2.0– 5.2 wt.%) and molybdenum (0–1.20 wt.%) is studied by calculation (using a Thermo-Calc program) and experimental approaches. The effect of nickel Ni
equ
and chromium Cr
equ
equivalents for test steel chemical compositions on types of crystallization (peritectic or single-phase mechanism with δ-ferrite formation), phase transformation temperatures, and regions of different phases (δ-ferrite, γ -austenite, α -ferrite) is identified. An increase in ferrite-forming element concentration over values of the chromium equivalent up to ≥ 16 wt.% or more leads to steel transition into the martensitic-ferritic class. An increase in the content of austenite-forming elements, primarily nickel, reduces the lower boundary of the temperature range for inverse α → γ transformation and leads to formation of stabilized austenite within the microstructure. Results of modeling phase transformation are compared with the microstructure and phase composition of two grades of industrial steel. It is established that chemical inhomogeneity of the two-phase (δ + γ )-structure formed during crystallization is retained at room temperature. Heat treatment regimes connected with heating in the lower half of the two-phase (α + γ )-region are determined when stabilized austenite is fixed in the steel structure at room temperature affecting mechanical properties. Research facilitates development of new steel compositions at TMK Group plants for the producing seamless casing and pump-compressor pipes of P110 type 13Cr strength group, resistant to carbon dioxide corrosion, including operation in cold macroclimatic conditions.