ASTM B754 - Measuring Flatness in Copper and Copper Alloy Strip
Understanding ASTM B754: A Comprehensive Guide to Measuring Deviations from Flatness in Copper and Copper Alloy Strips
When it comes to producing close tolerance parts, ensuring that the copper and copper alloy strips used are flat and free of distortions is essential. ASTM B754, a standard issued by ASTM Committee B05 on Copper and Copper Alloys, outlines a meticulous method for measuring and recording deviations from flatness in these materials. This article aims to provide an in-depth understanding of this critical standard.
Scope and Applicability
ASTM B754 is tailored for measuring distortions such as dish, wavy edges, buckle, longitudinal corrugation, and herringbone in thin metal strips. However, it’s worth noting that this test method is not applicable for measuring coil set, longitudinal curl, camber, edgewise curvature, or twist.
The focus is on metal strips ranging from 0.003 to 0.020 inches in thickness and not exceeding 6.0 inches in width. The values stated in inch-pound units are standard, with the SI units provided for informational purposes only.
Safety First
Safety cannot be overlooked. Users of this standard are responsible for establishing appropriate safety and health practices and determining the regulatory limitations applicability.
The Test Method
A test specimen, prepared from a specific wrought copper or copper alloy sheet or strip, is placed on a surface plate. The test method involves measuring the length and height of the irregularity and calculating the percentage of deviation from flatness.
Equipment Needed
A surface plate, micrometer, height gauge, and steel rule are essential apparatus for this test method. The surface plate should be flat within 0.0002 inches per inch, and the micrometer and height gauge should be graduated in 0.0001-inches and 0.001-inches increments, respectively.
Procedure
The thickness of the specimen is measured at six locations, and the average reading is used in subsequent calculations. The specimen is then placed unrestrained on the surface plate, and any irregularities are compared with standard illustrations to determine the type of distortion and measurement technique.
The highest point of each irregularity is measured using the height gauge, and the length between the points where the outer radii of the most significant irregularity touch the surface plate is measured with the steel rule. This process is repeated as necessary to satisfy quality level requirements.
Calculating Deviations
The percentage of deviation from flatness is calculated using the formula:
Deviation from flat, %=�×2��×100Deviation from flat, %=LH×2T×100
where,
�H = height of the irregularity,
�T = thickness of the specimen,
�L = length of the irregularity.
Reporting
The report should include the nominal thickness, width, temper, alloy number, and form of the product. Furthermore, the number and type of distortions measured, and their thickness, height, length, and percent deviation from flatness should also be detailed.
In Conclusion
ASTM B754 is a pivotal standard ensuring the flatness of copper and copper alloy strips used in manufacturing close tolerance parts. By adhering to this standard, manufacturers can mitigate difficulties associated with feeding through close-fitting dies and other equipment, ensuring optimal production efficiency and quality of the final products. Always ensure to refer to the most current edition of the standard as published by ASTM for accurate and updated information.