The techniques for manufacturing API 5L steel pipes were derived from the making of seamless steel pipes which can be traced back to the early 1900s. At the time the London government made the decision to install a coal burning system in the city. Therefore, quality, durable pipelines were needed badly to link various supply station and to transfer gas. Thanks to the great efforts of a group of scientists and technicians, the earliest seamless steel pipes were introduced and put to mass production.
Traditionally, to make a seamless steel pipe, workers need to drill a hole through a round billet and has it melted down in the furnace. Then the melting iron was poured into the mold and was elongated to the length as required by customers. Although this method used in the old days was hardly cost-effective, it is still inspiring and creative for later inventors and scientists. During 1960s and 70s, API 5L steel pipes were introduced to transfer gas across regions. Since then, the manufacturing techniques of API 5l steel pipe have undergone remarkable development.
In general, there are three steps in the making of API steel pipes. To begin with, round billets of carbon steel are cut into suitable length according to customers' requirements and are heated in the furnace where the temperature can reach as high as 2400℃. Quenching and tempering control the hardness of the pipes and yield certain physical qualities. Therefore, different grades of API steel pipes undergo different types of quenching and tempering in order to change their micro-structure to improve strength or other properties. Next the billet is rolled over a reel, producing curled hollow shells at one end, which is sent to be cooled. Then the surfaces of the semi-products are pickled, coasted and lubricated to accelerate the following drawing process. Depending on the requirements, the pipes may be subjected to single, double or even triple drawing, after which the pipes are straightened and cut to the required sizes. Finally, API steel pipes are sent to be tested for quality before delivery.
Nowadays in many major API steel pipe plants, high-end technology is adopted to manage every aspect of the production. For instance, real-time communication between the control room and machine operators guarantees precise regulation of each step, from charging furnaces with raw materials to timing, testing and transport. And most manufacturers carefully monitor their production process according to the standards made by ASTM or ISO to meet diversified customer demands.
