SEAMLESS HIGH-STRENGTH PIPE FROM STAINLESS STEEL OF OIL-FIELD RANGE AND METHOD OF ITS MANUFACTURING Russian patent published in 2020 - IPC C22C38/54 

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy, namely to seamless high-strength pipe of oil-field range from stainless steel. Pipe has a yield point of 862 MPa or more and a composition containing the following in wt%: C: 0.05 or less; Si: 0.5 or less; Mn: 0.15–1.0; P: 0.030 or less; S: 0.005 or less; Cr: 14.5–17.5; Ni: 3.0–6.0; Mo: 2.7–5.0; Cu: 0.3–4.0; W: 0.1–2.5; V: 0.02–0.20; Al: 0.10 or less; N: 0.15 or less; B: 0.0005–0.0100, balance – Fe and unavoidable impurities. Following conditions are met for steel components: -5.9×(7.82+27C-0.91Si+0.21Mn-0.9Cr+Ni-1.1Mo+0.2Cu+11N)≥13.0 and Cu+Mo+W+Cr+2Ni≤34.5, where C, Si, Mn, Cr, Ni, Mo, Cu, W and N represent content of each element, wt%. Pipe has a structure containing more than 45 vol% phase of martensite as a primary phase, 10–45 vol% phase of ferrite and 30 vol% or less phase of residual austenite as a secondary phase. Ferrite grains, measured by electron backscattering diffraction in a continuous region of 100 mm², have size of 500 mcm or less, wherein grains with crystal orientation difference of not more than 15° represent the same grains.

EFFECT: high low-temperature impact strength, corrosion resistance to carbon dioxide, resistance to sulfide corrosion cracking under stress (SCC) and resistance to sulphide cracking under stress (SSC).

5 cl, 2 tbl