WhitepaperApril 7th, 2023
Adjusting the Mechanical Properties of the Alloy to Solve Quality Issues - Unleashing an Alloy’s potential to Improve Quality.
This Whitepaper outlines quality constraints experienced by steel castings during the hydrostatic pressure testing. It also discusses how the yield and tensile strength of WCB can be adjusted so that WCB becomes compliant with ASTM A148 grade 80/50.
This whitepaper highlights the importance of quality control during the manufacturing process, particularly in critical processes such as hydrostatic pressure testing. It emphasizes the value of innovation in solving manufacturing issues, leading to cost-effective and time-efficient solutions. The paper also also talks about the importance of considering all aspects of an alloy's composition, such as the role of Mn as an important alloy strengthener in carbon and low alloy steels.
Hydrostatic pressure testing is a critical process for finished machined castings. When the testing exceeds the maximum allowable working pressure, plastic deformation in the form of casting distortion can occur, leading to a perfectly sound casting becoming scrap. To avoid this, some machine shops try to mitigate the issue by semi-finishing the casting and leaving machining stock on areas prone to distortion.
However, this approach is time-consuming, expensive, and not always successful. Carbon steel castings, such as the split pump casings are prone to this type of distortion. To solve this issue, a modified WCB grade with improved mechanical properties was developed, providing the subject casting with the extra strength required to undergo pressure testing without any plastic deformation.
The modified version of WCB aims to prevent deflection during hydro pressure testing, making the alloy compliant with all requirements of ASTM A216, including the 0.50% max Carbon Equivalent per S11.1. The goal was to create a cost-effective alloy with similar or better weldability, machinability, and comparable ductility. The WCB-Mn grade was created by moving the aimed range for Mn towards the upper permissible limit, resulting in increased tensile and yield strength while not significantly impacting the ductility of the alloy.