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OwnerTakahiro Kushida, Kaori Miyata +2inventors
InventorsTakahiro Kushida, Kaori Miyata, Kunio Kondo, Tomohiko Omura
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A low alloy steel for oil country tubular well which has a yield stress of 110 ksi or above, and excellent sulfide stress cracking resistance. The low alloy steel comprises, by weight, 0.2 to 0.35% carbon, 0.2 to 0.7% chromium, 0.1 to 0.5% molybdenum, 0.1 to 0.3% vanadium, 0 to 0.5% silicon, 0 to 1% manganese, 0 to 0.1% aluminum, 0 to 0.1% niobium, 0 to 0.05% titanium, 0 to 0.005% boron, 0 to 0.1% zirconium, 0 to 1% tungsten, 0 to 0.01% calcium, 0.025% or less phosphorus, 0.01% or less sulfur, 0.01% or less nitrogen, and 0.01% or less oxygen. The low alloy steel further comprises a total amount of precipitated carbides between about 2 to 5% by weight, and a ratio of the MC type carbide to the total amount of the precipitated carbides is between about 8 to 40% by weight.
A low alloy steel comprising, by weight, 0.2 to 0.35% carbon, 0.2 to 0.7% chromium, 0.1 to 0.5% molybdenum, 0.1 to 0.3% vanadium, 0 to 0.5% silicon, 0 to 1% manganese, 0 to 0.1% aluminum, 0 to 0.1% niobium, 0 to 0.05% titanium, 0 to 0.005% boron, 0 to 0.1% zirconium, 0 to 1% tungsten, 0 to 0.01% calcium, 0.025% or less phosphorous, 0.01% or less sulfur, 0.01% or less nitrogen, and 0.01% or less oxygen, with the balance iron and impurities, the low alloy steel further comprising a total amount of precipitated carbides between about 2 to 5% by weight, the precipitated carbides including an MC carbide, wherein a ratio of the MC carbide to said total amount of the precipitated carbides is between about 8 to 40% by weight.
A process for manufacturing a low alloy steel comprising the steps of:
Dependencies are inferred from the claim text.