Navigating the Steps to a New Alloy
Every journey has a beginning and a natural progression. It starts with a request, and is followed by careful consideration, before a decision is finally made whether to attempt the new venture. When a customer requests a new alloy from a foundry, the foundry can take a scientific approach to develop that alloy to fit existing processes and capabilities. In the example described in this article, a customer requested a cast aluminum bronze material. These are the steps the metalcaster identified for achieving successful production of castings in the new material that met the customer’s requirements, including delivery.
Step One: Assessment
Following the customer’s request, a series of risk-based decisions should be asked, assessed, and finally acted on. A comparison of the chemistry and mechanical properties is part of the assessment because if the foundry makes something similar successfully, the risks may be low. If the new material is like historically troublesome alloys, a deeper dive is necessary to look for truths and issues about this new alloy.
Strategizing to make a dimensionally compliant and volumetrically sound casting in a new material requires experience. Having a solid model that can be used with solidification software allows the development of gating and risers. But, if the alloy is not in the catalog for the foundry’s solidification software, another approach must be taken: reliance on past practice and experience. This includes first article process, use of filters, pouring temperatures, and other testing techniques as ordered from foundry engineering.
Before the alloy details are hammered out, other things require consideration, beginning with an evaluation of the material specifications and quality programs the customer requires. It might also make sense to expand the opportunity by qualifying to multiple specifications and/or programs. When qualifying a welding procedure, shoot for compliance to multiple welding codes from one plate (ASTM, ASME, NAVSEA and EN/ISO). Ensure that special processes work in harmony with necessary heat treatment, non-destructive testing, and welding codes. It is better to have a complete plan rather than just a plan.
A serious discussion on the desired outcomes you are looking to achieve with the alloy in development is warranted. First, once the desired specification is selected, control ranges need to be established. The development of heat sheets needs to be discussed, as well as the volume of the heat that will be made with returns or percentages of ingot. Finally, the desired microstructure needs to be addressed. The microstructure can be a result of microstructural balance with the chemical aims, as well as pouring temperatures.
Step Two: Melt Practice
One of the most important variables to keep constant is the melting practice that you employ. Selecting the furnace, ladle-type late additions, and other variables need to be documented and followed each time you pour the new alloy being trialed. Considerations must be made into the cleanliness practices to keep the metal bath free of large inclusions, oxides, and other deleterious elements. A gas or liquid argon cover is always wise to consider. Having a technical representative present at all times when pouring high and new alloys is mandatory to observe process controls.
Step Three: Chemistry, Mechanical Properties, and Microstructure Verifications
For success in the short and long term, all your attributes need to be documented, and controlled procedures need to be created. Data sheets catalog all technical and general information of the alloy being produced. These sheets contain aim/range chemistry, actual mechanical properties your organization achieves with the alloy, metallurgical and physical constants, foundry engineering parameters, and general microstructure, as well as general industry usage of the alloy.
Step Four: Inspection Methods
Inspection programs require a thorough understanding of the new alloy and its base material specification. Typically, the QA department would probe the customers interested in the new alloy once the foundry becomes comfortable pouring it. When the customers see the tests and inspections performed, as well as acceptance criteria, the foundry will need to ensure that the produced parts meet these requirements. A few common codes for testing and inspection are in Table 1.
Destination: Accreditation, Certification and Qualification Process
With a repeatable foundry process in place to produce a new material, the metalcasting company can look to add it to different compliance codes and directives for certification and market it to industry specific applications. For instance, the aluminum bronze alloy that Stainless Foundry & Engineering developed could apply to the ASME Boiler & Pressure Vessel Code, Section IIb for nonferrous materials or the European Union’s Pressure Equipment Directive 2014/68/EU. There are other qualifications such as NORSOK M-630 for material data sheets and M650 for program and test methods to qualify materials. Many of these events need to be witnessed or sourced for proof that the foundry properly completed them. An ISO registration agency can either certify these materials to the selected codes and directives or direct you to the appropriate agency for certification.
Bringing a new alloy (or family of alloys) on board is time consuming. It requires finances as well as an appropriate level of technical staffing to achieve success. Many meetings, much lab time, and several experimental melts are required to optimize results. Additionally, it is essential to be able to sustain the process and repeat your process as necessary. Having performed a proper risk assessment and then documenting all steps, you should be able to repeat quality results. Involving numerous technical persons, such as metallurgists, process engineers, foundry engineers, and quality engineers, makes the process much more obtainable and successful.