ASTM A327M - Impact Testing of Cast Irons (Metric)
Impact Testing of Cast Irons: Understanding ASTM A327M
1. Introduction
Impact testing is a crucial evaluation method to assess the mechanical properties and fracture toughness of materials. In the context of cast irons, including gray iron, white iron, malleable iron, ductile iron, and austempered ductile iron, impact testing plays a significant role in determining the material's ability to withstand sudden loading and impact forces. This article discusses the ASTM standard test methods for impact testing of cast irons and outlines the procedures for conducting Charpy-type impact tests on different types of cast iron.
2. Scope
The ASTM standard for impact testing of cast irons covers apparatus, test specimens, and procedures for various types of cast iron. The test methods included in this standard are applicable to gray and white irons, malleable and ductile irons, and austempered ductile irons. It is important to note that the standard does not encompass chilled rolls or rolls with white iron skins. The values provided in the standard can be expressed in either SI units or inch-pound units, with each system to be used independently.
3. Referenced Documents
The ASTM standard for impact testing of cast irons references the following documents:
ASTM A327M Test Methods for Impact Testing of Cast Irons (Metric)
ASTM E23 Test Methods for Notched Bar Impact Testing of Metallic Materials
Test Method A - Round Bar Charpy-Type Impact Test for Gray and White Irons
4. Apparatus
The Charpy-type impact test for gray and white irons is conducted using a pendulum-type impact machine with a capacity of at least 150 J [110 ft·lbf]. This apparatus is similar to the one used for the simple beam test for steel described in Test Methods E23.
5. Test Specimens
The test specimens for the Charpy-type impact test shall have a plain cylindrical form, machined or ground to a smooth finish, and must adhere to specific dimensions. Two types of test specimens are used:
Type A: Diameter of 28.572 ± 0.050 mm [1.125 ± 0.002 in.], Length of 200 ± 13 mm [8.0 ± 0.5 in.], Span of 152.0 ± 0.7 mm [6.00 ± 0.03 in.]
Type M: Diameter of 20.00 ± 0.03 mm [0.787 ± 0.001 in.], Length of 120 ± 2 mm [4.73 ± 0.08 in.], Span of 100.0 ± 0.5 mm [3.937 ± 0.020 in.]
6. Procedure
The test bars are placed on the spans indicated in the tabular data of the test specimens. The Charpy-type impact test for gray and white irons should conform to the appropriate requirements of Test Methods E23, with the test conducted at room temperature. To ensure accuracy, at least three specimens should be tested to characterize the fracture toughness of any cast iron.
7. Report
The test results should be reported as ____J [ft·lbf] cast iron Charpy impact with ____ mm [in.] diameter bar.
Test Method B - Standard Charpy-Type Impact Test for Malleable and Ductile Irons
8. Scope
The standard Charpy-type impact test can be conducted on malleable and ductile irons. The selection of the type of bar (notched or unnotched) depends on the specific material being evaluated.
**8.2 Both types of Charpy bars have been designated to characterize the fracture toughness of irons. The unnotched Charpy bar will produce substantially higher energy values than the notch bar type. As a result, the unnotched bar is specified for testing irons that have low fracture toughness characteristics.
Conclusion
Impact testing is a critical method for evaluating the mechanical properties and fracture toughness of cast irons. The ASTM standard test methods provide standardized procedures for conducting Charpy-type impact tests on different types of cast iron. By adhering to these procedures, engineers and researchers can obtain reliable data to assess the suitability and performance of cast iron materials in various applications.