ULTREX™ – Ultrasonic (UT) Inspection

Almex’s specially designed Ultrex™ Testing Methods for casting and quality inspection of the cast and machined billet or slab fall in the following two categories:

Ultrex™ I – “Hot” Testing Method

Inspection of billet & slab for detection of cracks while casting is in progress. This is a “hot” inspection method using high temperature couplant for the “pulse-echo” technique to detect major inconsistencies in the cast product (post wiper emergence) such as cracks, including sub-surface and centerline cracks.

Instantaneous detection of cracks assists in controlling cast house costs. If a crack is detected, depending on it’s location and spread, a corrective action can be immediately implemented to arrest the growth of the crack or a decision can be taken to “abort” the drop, thus saving substantial remelt cost and down stream handling cost. With 2XXX and 7XXX alloys, early detection of cracks can also enhance the safety of the cast house.

An optional bar code writer is available with the system which will automatically print and apply a detailed bar code to the inspected billet per customer specifications before the inspected billet is discharged from the inspection table. This system also provides both automatic marking of defective billets and the specific location of the identified defect. The defective billets are also indented with red ink spray at the top / bottom end face for easy recognition.

Ultrex II™ – “Cold” Testing Method

The Ultrex II™ “non-submerge” ultrasonic instrumentation was developed by Almex for inspection of scalped slabs and machined billets. The unit detects internal defects of extremely fine size. It is based on the “pulse-echo” principle but uses a larger probe of 25 mm dia and works at the 2.25 Megahertz frequency. It is well known that a defect in the cast product of the size of 75 microns (0.003”) is “large” enough to cause a rejection of finished forging, extrusion or a rolled plate as the original defect undergoes substantial enlargement in size during the subsequent thermo-mechanical working of the material.

Hence, Almex’s Ultrex II™ ultrasound testing equipment and procedure is designed to inspect such “small” sizes of discontinuities in the material.

Typically in aluminum 2XXX and 7XXX series alloys, these discontinuity indications on the ultrasonic testing screen provide a reflection of the following types of defects:

• Agglomerated gas porosity
• Non-metallic inclusions
• Metallic INCLUSIONS (such as early precipitates of Ti-B-Zr and Chromium)
• Salt particles
• Very large primary phase segregation
• Incipient melting during homogenization
• Insufficient homogenization;

Note that all of the above are causes for rejection in aircraft metal and therefore Almex’s Ultrex II is designed to assure inspection of the machined billet to the highest possible resolution. Machined surface should conform to 250 RMS number.

The attenuation of the machine is designed such that the subtle changes on the screen can be seen in the “baseline” of the reflection. The controlled gain amplification of the signal coupled with a noise reduction hardware module allows the operator to discriminate clearly between a “defect” in the metal and just the “baseline noise”.

Depending on the diameter of the billet to be inspected, a series of custom-made standards is furnished with the equipment. These standards are traceable to standards lab specified in the US military Ultrasonic Standard MIL-2154 Class AA.