According to the American Petroleum Institute standard APISPEC5CT 1988 first edition, casing steel grades are H-40, J-55, K-55, N-80, C-75, L-80, C-90, C-95, P- There are 10 types of 110 and Q-125. The casing pipe
should be supplied with thread and coupling, or supplied in any of the following pipe end forms: flat end, round thread without coupling or coupling, buttress thread with coupling or without coupling, direct connection -Shaped thread, special end processing, sealing ring structure.
There are many kinds of oil casing materials, the common ones are ordinary carbon steel, J55, L80, N80, P110, etc.; more special materials, such as 3Cr, 9Cr, 13Cr, 22Cr, etc., mainly carbon dioxide; and hydrogen sulfide Material, such as 90SS, 95SS, etc.
In addition, higher grades include nickel-chromium alloy pipes, which have different numbers according to different manufacturers. There are also some special needs, such as materials for high anti-extrusion use. Some manufacturers will add TT to indicate anti-extrusion.
General steel grades such as: J55, K55, N80, etc., the materials used are: 37Mn5, 36Mn2V.
The J55, K55, and N80 indicate steel grades, for example: J55, which means that the average tensile strength of the steel grade is 550KN/mm2. J55 and K55 steel grades generally use 37Mn5 materials; N80 steel grades generally use 36Mn2V materials.