Casting Quality into YOUR part
The most important aspect in guaranteeing the reliability of a precision investment cast component is a casting quality verification process that is both meticulous and detail oriented. Based on our investment casting engineering efforts the casting quality verification process starts with direct customer interaction and part design optimization. The results are then shared with the customer and inputted into the final tooling investment casting design stages. Prior to the final stage of the metal being poured into the ceramic shell, further pre-production quality measures and visual inspection criteria are designed to ensure premium casting quality throughout the production process. Due to these casting quality procedures, we are on “dock-to-stock” programs with many of our customers; this eliminates their need for the direct casting quality inspection process, which saves them time and money.
Aero Metals, Inc. is your #1 source for exceptional precision investment cast parts. We offer a wide variety of in-house casting quality verification and product testing services (such as NDT) designed to provide our customers with the highest quality cast product. No matter what the intended application, every precision investment cast component is examined, inspected, and approved before leaving our building.
Visual Casting Quality Inspection
In accordance with the investment cast industry standards, specific industry regulations, and/or the customer’s specified quality instructions, visual inspection is required to ensure genuine casting quality from start to finish. In terms of casting quality this means that we make sure parts are properly filled with metal (no cracking, tearing, holes or voids, non-fill, etc.). Our casting quality control experts also meticulously inspect each part, making sure there are no distortions or bends before moving forward in the casting quality process. During the final phase of inspection, parts are inspected and compared to the casting quality control plan and written process instructions. Lastly, the casting quality results are documented and stored for future use by production department staff and process engineers.
Dimensional Casting Quality Inspection
Variance in cast dimension(s) is an inherent part of the manufacturing process. Due to these differences, it can be difficult to expect exacting dimensions throughout the production lot. These discrepancies in casting quality can be caused by the heat and hydraulic pressure of molten metal being poured into the ceramic mold, which can cause the metal to contract (move) as it cools or after post-cast heat treatment. The toolmaker compensates for these expansions and contractions when designing the mold. Also, due to these slight variations in casting quality, Investment Cast Industry Standards are used as a guide by setting a range of values that the casting dimensions can fall within. We also take into consideration critical part dimensions, given to us by the customer, during the planning and inspection phases. We then verify the dimensions of the parts by using micrometers, thread and plug gauges, CMM machine diagnostics, and other approved functional gauges. The accuracy of these measuring tools adds to the dimensional consistency and casting quality of the manufactured parts.
Mechanical Properties Casting Quality Inspection
To confirm the properties of the metal cast part are correct, mechanical testing is performed to approve the metal of the casting. The testing confirms the properties comply per the specified mechanical requirements. The below mechanical properties testing is done to confirm proper casting quality.
- Hardness testing: A non-destructive procedure that demonstrates the alloy’s machinability and wear resistance.
- Tensile testing: A destructive casting quality test that provides ultimate tensile strength, yield strength, elongation and reduction of the material test specimen.
- Load testing: This test is performed on the entire casting lot to evaluate its casting quality, and to verify that the cast part can carry (deflect) the required or specified structural load when applied. Pressure-containing parts can be hydraulically tested to a proof load or destruction maximum limit.
Chemical Composition Casting Quality Inspection
The chemical composition of every alloy melt is tested and recorded in our database. We then electronically store the records for an indefinite period. This test is performed to ensure the alloy performance properties are to the specification(s) of the customer. Casting alloys are typically specified per ASTM, AMS and SAE alloy specifications. The alloy composition is analyzed by spectrographic atomic absorption (spectrometer), or x-ray fluorescence analysis. Aero Metals currently runs two of these analyzers in our metallurgy lab. Before the metal is poured from the melting pot, a sample of molten metal is poured in to a small “coupon” mold and the casting quality is evaluated in the spectrometer. If needed, minor alloying elements are added to the material to bring the alloy melt into required specification. Then another coupon is tested and certified to ensure proper chemical composition.
Non-Destructive Casting Quality Testing and Inspection
Aero Metals Inc. performs non-destructive casting quality testing (NDT) on-site, which allows us the capability of assuring the quality of a casting without destroying it. Our NDT in-house facility is fully staffed with both Level II and Level III resident technicians. We are also NADCAP Certified in Dye (Liquid) Penetrant Testing, Magnetic Particle Inspection, and Radiographic (x-ray) Inspection. The on premise NDT facility allows Aero Metals to perform the most common combinations of non-destructive testing and inspection methods required by many high-profile industries, such as Aerospace. Each industry has its own set of inspection criteria, or allowance, for defects noted by Class and Grade. The most common methods available are described below.
- Dye (Liquid) Penetrant Testing: Some things are hard to detect by the human eye, such as tiny cracks, pores or other surface imperfections. Liquid dye penetrant testing is a casting quality test used for both ferrous and nonferrous alloy castings. In this inspection process, a colored dye solution is applied to the surface of the casting. The dye, which is suspended in penetrating oil, finds its way into the surface defects. When a special developer is applied, the defects are clearly indicated under a special “blue” light. The idea is to detect any cracks or other surface defects due to porosity or gas that have come up to the surface because of metal tearing or stress.
- Magnetic Particle Inspection: Magnetic particle casting quality inspection is quick, inexpensive and sensitive to defects, particularly shallow (0.003 in.) surface cracks and other lineal indications. It detects small cracks on or near the surface of ferrous alloys that can be magnetized. Cracks and defects have differing magnetic properties than those of the surrounding material. Their presence will interrupt the magnetic field, causing distortion, which indicates the shape and position of the crack or void.
- Radiographic (x-ray) Inspection: This inspection process is the best non-destructive method for detecting internal defects, such as shrinkage and inclusions. In this procedure, a casting is x-rayed and part of the radiation is then absorbed by the cast while the remaining portion of the radiation exposes the film. Denser materials show up or give the film a lighter appearance. Less dense materials correlate to darker areas on the film. Therefore, any hole, crack or inclusion that is less dense than the casting alloy is revealed as a dark area.
Contact Aero Metals to learn more about our in-house quality inspection and testing capabilities for your cast parts.