Hot-rolled seamless process and cold-rolled seamless process
In the API 5CT 10th edition standard, the L80-13Cr steel grade pipe is required to be manufactured using a seamless process and delivered in a quench + temper heat treatment state. After receiving L80-13Cr orders, Nantong Zhencheng generally has two manufacturing methods: hot-rolled seamless process and cold-rolled seamless process. The following text uses the specification 114.3*7.37 as an example to compare the two manufacturing methods in terms of process flow, manufacturing efficiency, first-pass yield, overall yield, and material yield, in order to select the most suitable manufacturing process.
The hot-rolling process generally involves the following steps
Inspection of pipe billets, hot-rolling production, quenching and tempering heat treatment, physical and chemical testing, finishing, dimensional inspection, appearance inspection, internal and external grinding, re-dimensioning and appearance inspection, non-destructive testing, hydrostatic testing, and measurement of length and weight of each pipe.
The cold-rolling process generally involves the following steps
Inspection of pipe billets, hot piercing, annealing treatment, inspection of rough pipes, internal and external grinding, cold-rolling production, quenching and tempering heat treatment, physical and chemical testing, finishing, dimensional inspection, appearance inspection, non-destructive testing, hydrostatic testing, and measurement of length and weight for each pipe.
From a process flow comparison, hot-rolling production is more efficient than cold-rolling production.
However, because hot-rolling is more efficient and the 13Cr steel grade is air-hardening, which makes it prone to surface defects during production, both the first-pass yield and overall yield of hot-rolled products are lower than those of cold-rolled products. For example, in Nantong Zhencheng’s past production practices for the 114.3*7.37 specification, the first-pass yield for hot-rolled products is about 50%, while the overall yield can reach 90%. In contrast, the first-pass yield for cold-rolled products can exceed 90%, with the overall yield even reaching over 95%.
Regarding material yield, due to the lower yield rates of hot-rolled products compared to cold-rolled products, the material yield is also lower for hot-rolled products. For the 114.3*7.37 specification, the material yield for hot-rolled products is about 85%, while cold-rolled products can achieve around 89%.
Considering all these factors, including manufacturing costs and delivery times, Zhencheng Steel generally prefers the cold-rolling manufacturing process on 13 chrome material pipes.
