Which came first the X42 pipe or the X52 pipe and what year?

The X42 pipe came first, introduced in the early 1970s, while the X52 pipe was developed later, in the late 1980s. The X42 designation corresponds to a lower yield strength compared to X52, which has a higher yield strength requirement. These designations are part of the American Petroleum Institute (API) specifications for line pipes used in the oil and gas industry.