Development of Large Diameter Thick Walled TP347H Stainless Steel Pipe

Literature Overview

This technical paper by Yin Renjie, Wang An'e, Bian Huachuan, Li Xu, and Zhang Tao from Pangang Group Chengdu Steel and Vanadium Co., Ltd. (2009) documents the successful development of Φ355.6mm × 42.8mm TP347H stainless steel pipe using a combined centrifugal casting and Pierger rolling process. Published in Steel Pipe (Volume 38, Issue 6, pp. 34-37), the work represents a significant advancement in domestic production of large-diameter thick-walled stainless steel piping.

Process Route and Technical Approach

The manufacturing process combines two distinct technologies to achieve the required specifications. The first step involves centrifugal casting to produce the initial pipe blank with controlled wall thickness and microstructure. The second step employs a Pierger rolling mill for hot rolling and final shaping to achieve precise dimensional tolerances. This dual-process approach leverages the advantages of both methods: centrifugal casting provides good material homogeneity and reduced material waste, while Pierger rolling ensures dimensional accuracy and improved mechanical properties.

Technical Specifications and Performance Verification

Key Technical Insights

The TP347H grade is a high-temperature creep-resistant austenitic stainless steel containing niobium and molybdenum, commonly used in power generation applications such as superheater tubes and boiler components. The wall thickness of 42.8 mm represents a substantial challenge for manufacturing, as thick-walled stainless steel pipes are prone to center segregation, incomplete recrystallization, and inconsistent mechanical properties through the wall thickness.

The successful achievement of uniform longitudinal and transverse properties is particularly noteworthy. In thick-walled pipes, transverse properties are often weaker than longitudinal properties due to the rolling direction effects. The combination of centrifugal casting and Pierger rolling appears to mitigate this issue effectively by providing a more isotropic starting microstructure and controlled deformation during the rolling stage.

Engineering Significance

The successful domestic production of this specification reduces dependence on imported large-diameter thick-walled stainless steel pipes, which have historically been limited in availability and subject to long lead times. For power plant engineering, this development enables more economical procurement of critical components for ultra-supercritical boiler systems. The process innovation demonstrated here could potentially be extended to other alloy grades and dimensions, opening new possibilities for domestic heavy-wall pipe production.

Study Reflections

This work demonstrates that process innovation in steel pipe manufacturing can overcome dimensional and material limitations. The centrifugal casting plus hot rolling route offers a viable alternative to traditional solid billet piercing for large-diameter thick-walled products. Engineers should consider this approach when specifying large-diameter alloy and stainless steel pipe components, particularly where wall thickness exceeds conventional piercing capabilities. The key lesson is that process combination strategies can unlock new product possibilities that single-process routes cannot achieve.