(1) the main importing countries are: Germany, Japan, Romania, Czech, Italy, the United Kingdom, Austria, Switzerland, the United States, Argentina, and Singapore. Import standards refer to the American Petroleum Institute standard 5AX, API5A, 5AC. Steel grade is H-40, J-55, N-80, P-110, C-75, C-95, etc.. Specifications are mainly 139.77.72R-2177.89.19R-2244.58.94R-2244.510.03R-2244.511.05R-2, etc..

(2) API provides three kinds: that is, the R-1 is 4.88 ~ 7.62m, R-2 for 7.62 ~ 10.36m, R-3 for 10.36m to longer.

(3) some imported goods are marked with the words of LTC, That is a long thread casing pipe.

(4) imported from Japan in addition to the use of API standard casing, and a small part of the Japanese standard (such as iron, Sumitomo, Kawasaki, etc.) steel is NC-55E, NC-80E, NC-L80, NC-80HE etc..

J55 steel - oil casing is an important equipment for oil drilling equipment, which mainly include drilling pipe, tube and casing, drill collar and small diameter drilling pipe etc.. Domestic casing to geological drilling with steel after hot rolling or cold drawn steel made by "geological" (DZ) said that the steel grade are commonly used DZ40, DZ55, DZ753.