Nippon Steel Corporation

Nippon Steel & Sumitomo Metal Corporation

Naoya Shirasawa

Yasuyoshi Hidaka

Yusaku Tomio

Hiroki Kamitani

Yasuto Higashida

Shohei Ikeda

Tatsuya Miyai

Seiya Okada

Nobuaki Komatsubara

Yuichi Yamanari

The seamless steel pipe according to the present disclosure includes a base material and a decarburized layer formed on the surface of the base material. The chemical composition of the base material consists of, in mass %, C: 0.20 to 0.50%, Si: 0.05 to 0.50%, Mn: 0.01 to 1.00%, P: 0.0300% or less, S: 0.0100% or less, Al: 0.005 to 0.100%, Cr: 0.30 to 1.20%, Mo: 0.30 to 1.50%, Ti: 0.002 to 0.050%, V: 0.01 to 0.30%, Nb: 0.002 to 0.100%, B: 0.0001 to 0.0050%, N: 0.0100% or less, O: 0.0050% or less, and with the balance being Fe and impurities. The base material has a yield strength of 655 MPa or more, and a yield ratio of 85.0% or more. The decarburized layer has a depth of 150 μm or less.

Seamless steel pipe suitable for use in sour environment

A piercer plug with increased recyclability is provided. A piercer plug () has a chemical composition of, in mass %: 0.15 to 0.30% C; 0.4 to 1.2% Si; 0.2 to 1.5% Mn; 0.1 to 2.0% Ni; 0 to 4.0% Mo and 0 to 4.0% W, where the total content of Mo and W is 1.0 to 6.0%; higher than 1.0% and not higher than 4.0% Cr; 0 to 0.2% B; 0 to 1.0% Nb; 0 to 1.0% V; 0 to 1.0% Ti; and balance Fe and impurities, the plug including a tip portion () and a trunk portion () made of the same material as the tip portion () and contiguous to the tip portion (). The trunk portion () includes a cylindrical portion () having a hole used to mount a bar. The tip portion () is harder than the cylindrical portion ().

Piercer plug and method of manufacturing the same

A piercer plug having good base-material deformation resistance is provided. A method of manufacturing a piercer plug () includes the steps of; preparing a plug body () including a tip portion () and a cylindrical portion () having a hole () usable to attach a bar and located rearward of the tip portion (); forming a build-up layer () on the surface of the tip portion (); and heating the plug body () such that the temperature of the tip portion () with the build-up layer () formed thereon is not lower than the austenite transformation temperature and the temperature of the cylindrical portion () is lower than the austenite transformation temperature.

Method of manufacturing piercer plug

Growing community of inventors

Tokyo, Japan

Naoya Shirasawa