ASTM A370 specifies impact testing over a wide range of temperatures. This standard allows for several types of impact testing to be performed as long as the same impact test method is used for all samples throughout the experiment. At least three pieces of the steel called coupons must be impact tested at each temperature. At lower temperatures, like room temperature, the steel is brittle. The impact causes the steel to fracture. The amount of deformation and fracture appearance are measured with each impact. Then the temperature is increased. The mechanical properties of the steel like the tensile strength and yield stress are found via this process.
Types of Impact Testing
"Damage Mechanisms and Life Assessment of High-Temperature Components" states "the Charpy V-notch impact test is undoubtedly the test most commonly used to characterize the ductile to brittle transition in steel." ASTM E23 defines how to perform Charpy impact testing on steel. Notched Izod impact testing can also be performed.
As temperature rises, the fracture appearance rate declines. At high temperatures, the material is considered ductile. Fracture appearance is a measure of what percentage of damage is in the form of fractures or cracks in the steel compared to deformation. Fracture appearance transition temperature, or FATT, is the temperature when half of the impact is fractured. FATT can be used as the transition temperature from brittle to ductile. According to "Selection and Use of Engineering Materials", "if a given steel is to be a candidate material for a given application, its measured transition temperature must be lower than the temperature of intended service."
ASTM A833 is the standard for using comparison hardness testers on metals. ASTM E110 describes how to test the indentation hardness of metals using portable hardness testers. ASTM E4 defines how to verify the force generated by the impact testing machine. ASTM E10 describes how to perform the Brinell hardness test on metals. ASTM E18 gives the standard test method for the Rockwell hardness test. The American Water Works Association (AWWA) requires testing by ASTM A370 to prove the tensile strength of steel water pipe.