ASTM B311 Density of Powder Metallurgy Materials Containing less Than two Percent Porosity

• Material type: Powder metallurgy materials with less than two percent porosity and cemented carbides. 
• Purpose: Determination of density for quality control and material verification. 
• Property measured: Density using the water displacement method. 
• Method: Measuring specimen mass in air and apparent mass in water, then calculating density. 
• Result: Report density in grams per cubic centimetre (g/cm³). 
• Test Limitations: The method is not applicable if the specimen gains mass when immersed in water, which indicates surface-connected porosity. 
• Units: Density values use g/cm³, and mass values use grams (g) units as the long-standing industry practice. 
• Applications: Powder metallurgy structural components, sintered metal parts, automotive PM components, aerospace precision parts, cemented carbide tooling and wear parts. 

What are the Uses of ASTM D4186 Testing?

ASTM B311 testing helps manufacturers and quality control laboratories assess the density of powder metallurgy products and cemented carbides. The test results are used for quality control, material checking, and product development. The standard is widely used in the powder metallurgy, automotive, aerospace, and tooling industries. This standard-

• Gives an indication of whether PM parts have been densified sufficiently.
• Detects major composition variations in cemented carbide.
• Helps with quality assurance within the PM component manufacturing process.
• Facilitates the verification and certification of materials.
• Helps develop products and optimizes processes.
• Helps standardize the density measurements in various laboratories.
• Ensures material meets specifications. 

Which materials can be tested under ASTM B311?

ASTM B311 is used for powder metallurgy materials with under 2% porosity and cemented carbides. The test method is applicable to near-full-density PM components and grades of carbide. The common applications are automotive PM components, aerospace structural parts, cemented carbide tooling and wear parts, metal injection molded (MIM) parts, and powder forged (PF) parts.

 Why is ASTM B311 important? 

A standard method for measuring the density of powder metallurgy materials and cemented carbides by water displacement is described in ASTM B311. The test method sets requirements for testing that assist manufacturers in checking densification and composition deviations. The standard provides a consistent procedure for testing and interpretation of test data throughout laboratories. The correlation of density with composition is simple for straight grades of tungsten carbide cobalt grades. With complex carbide grades, the situation is more complex – density measurements help determine if the composition is outside specified limits. If the density measured is outside the specified density range, the composition is outside of the specified composition range. This standard is used by quality control engineers to maintain product quality and material performance.

ASTM B311Testing Process and Data Collection

The first step in testing is to clean the specimen to remove surface contaminants. The technician precisely weighs the dry specimen using a precision analytical balance and records its weight in air. They place the specimen in distilled or deionized water and determine its apparent mass, making sure the specimen is completely submerged and that there are no air bubbles. They measure and record the water temperature to know the proper water density. Analysts calculate the density based on the mass in air, apparent mass in water, and water density at the measured temperature.  Laboratories collect data for quality control, material verification, and product development. 

Common Challenges and Troubleshooting

Some typical issues with ASTM B311 testing are surface-connected porosity, surface air bubbles, and wrong temperatures. These problems can impact density determination. Surface-connected porosity means the specimen takes in water and gains weight, leading to an incorrect reading of its density. Air bubbles can cause an erroneous determination of apparent mass, and improper temperature readings can result in an incorrect determination of water density. Evacuation, boiling or ultrasonic agitation of the water will degas the water, thus minimizing the air bubbles on the specimen. These problems can be minimized by proper examination of the specimens, careful immersion, and correct temperature readings. 

ASTM B311 Analysis Results and Interpretation

The report summarizes the density determination test performed for the tested material (powder metallurgy or cemented carbide). It shows the measured values, units, and specimen information. The interpretation compares these measured values against specification requirements or performance benchmarks. Quality control engineers use these results to ensure material compliance and product performance.

• The laboratory reports density in grams per cubic centimetre (g/cm³) to the nearest 0.01 g/cm³.
• The laboratory provides dimensional measurement records, mass measurement data, and quality control reports.
• Results for PM materials show whether the part has been densified to the desired level, while results for cemented carbides pinpoint key composition differences.
• If the measured density falls outside specified limits, the composition falls outside the specified limits.
• A measured density within the desired limits does not guarantee correct composition, as compensation between constituents may lead to the desired density with the wrong composition, and the grade of a cemented carbide cannot be determined by density alone.

Link to ASTM B311