Life Improvement of Pot Hardware in Continuous Hot Dipping Processes Final Report

Technical Report · Wed Jan 18 00:00:00 EST 2006

DOI:https://doi.org/10.2172/876590· OSTI ID:876590

Liu, Xingbo

The process of continuous galvanizing of rolled sheet steel includes immersion into a bath of molten zinc/aluminum alloy. The steel strip is dipped in the molten bath through a series of driving motors and rollers which control the speed and tension of the strip, with the ability to modify both the amount of coating applied to the steel as well as the thickness and width of the sheet being galvanized. There are three rolls used to guide the steel strip through the molten metal bath. The rolls that operate in the molten Zn/Al are subject to a severely corrosive environment and require frequent changing. The performance of this equipment, the metallic hardware submerged in the molten Zn/Al bath, is the focus of this research. The primary objective of this research is to extend the performance life of the metallic hardware components of molten Zn/Al pot hardware by an order of magnitude. Typical galvanizing operations experience downtimes on the order of every two weeks to change the metallic hardware submerged in the molten metal bath. This is an expensive process for industry which takes upwards of 3 days for a complete turn around to resume normal operation. Each roll bridle consists of a sink, stabilizer, and corrector roll with accompanying bearing components. The cost of the bridle rig with all components is as much as $25,000 dollars just for materials. These inefficiencies are of concern to the steel coating companies and serve as a potential market for many materials suppliers. This research effort served as a bridge between the market potential and industry need to provide an objective analytical and mechanistic approach to the problem of wear and corrosion of molten metal bath hardware in a continuous sheet galvanizing line. The approach of the investigators was to provide a means of testing and analysis that was both expeditious and cost effective. The consortium of researchers from West Virginia University and Oak Ridge National Laboratory developed several test apparatuses that were designed to work in concert so that the process of developing and evaluating new materials and material combinations could be carried out in the most effective manner. ORNL focused on the long-term effects of static and dynamic corrosion on the hardware. Their efforts have yielded corrosion data in terms of mass loss for a large database of materials for immersion times in excess of 6000 hours. In addition, they have developed a new series of alloy, designated ORNL Alloy 4-x. Several variants of Alloy 4 were tested for corrosion and wear performance. Another effective method for protecting bearing components is through the use of weld overlays or laser cladding. ORNL worked with several project partners to develop a weld overlay process for cladding of 316L stainless steel with metallic materials that are much more corrosion and wear resistant. This method provides super-alloy performance that is more affordable. WVU was tasked to study wear of the bearing materials along with mechanisms of dross buildup on the roll surface. A small scale screening test apparatus was developed for the purpose quickly evaluating wear performance of candidate superalloys, ceramics, and coatings through the use of a ball-and-seat testing combination. This combination uses a fraction of the material used in full-scale bearing applications. With this system, WVU has been able to conduct hundreds of tests on various combinations of materials that mimic a wide variety of operating conditions for the galvanizing lines. The small scale wear tester was used to perform both direct correlation to galvanizing line conditions and to act as a screening mechanism for prototype-scale testing at WVU?s airport bearing materials testing facility. In addition, the studies on the effect of contact pressure and velocity on the bearing wear rate lead to the design and subsequent patent application for a fixed-shaft roll design that has the potential for increasing the bearing life by a factor of 2. The prototype-scale bearing test apparatus was donated by one of our project partners and was relocated to the WVU airport hanger at Morgantown Municipal Airport. This test apparatus uses full-scale sleeve and bushing dimensions and is designed to more accurately mimic the galvanizing line conditions. Through the combination of corrosion, wear, and dross buildup testing, as well as material modeling and thermodynamic analysis, the research team has been able to show that an order of magnitude improvement in material performance is a realistic goal.

• Research Organization: West Virginia University Research Corp. on behalf of West Virginia University
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: FC36-01ID14042
• OSTI ID: 876590
• Report Number(s): DOE/EE/14042-1; TRN: US200712%%187
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
ALLOYS
BEARINGS
BUSHINGS
CERAMICS
COATINGS
CORROSION
HEAT RESISTING ALLOYS
HOT DIPPING
LASERS
MARKET
MATERIALS TESTING
MOTORS
STAINLESS STEELS
STEELS
TESTING
THERMODYNAMICS
THICKNESS
VELOCITY
Liquid metal corrosion
wear
galvanizing
pot hardware