API 5CT, steel grade of oil casing, API 5CT steel grade classification

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API 5CT steel grade classification

There are twenty different steel grades and types of oil casing, including H40, J55, K55, Mg65, N80 (n80-1, n80ql80 (l80-1, l80-9cr, l80-13cr), C90 (c90-1, c90-2), T95, C95, P110, q125. In order to distinguish different steel grade strength and thread type, different color codes and symbols are used to represent the steel grade and thread of oil casing.


The two or three digits after the color code and English letters represent the minimum yield strength of the steel grade of oil and casing. For example, J55 represents the minimum yield strength of 55000 lb / in2 (379jpa), the maximum yield strength of 80000 lb / in2 (552mpa), P110 the minimum yield strength of 110000 lb / in2 (758mpa) and the maximum yield strength of 140000 lb / in2 (965mpa).

H. J, K and N represent general strength oil casing,

C. L, m and t represent the oil casing with limited yield strength, which has certain sulfur corrosion resistance.

K55 and J55 are generally normalized with 36m2v and 37Mn5,

L80 quenched and tempered with 25n2q

P110: 30CMo

J55 / K55: 37Mn5, 36Mn2V normalizing heat treatment

N80: 36mn2v

L80: 13Cr, 25mn2-q quenching and tempering heat treatment