This standard is issued under the fixed designation A/AM; the number 1 This practice is under the jurisdiction of ASTM Committee A05 on Metallic-. In all cases only the current version of the standard as published by ASTM is to be considered the official document. Designation: A – 76 (Reapproved ) . ASTM A – A M – 02 – Download as PDF File .pdf), Text File .txt) or read online.
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Factors in Warpage and Distortion 3. Welding results in significant residual stress in small areas of an assembly due to the extreme temperature differences experienced. In welding any intermediate lengths along one side of a common member, care should be taken to prevent warpage of the common member due to qstm application of high heat on the same side at various intervals along its length.
Inch pounds and SI units are not necessarily exact equivalents. A – 76 Reapproved Standard Practice for Safeguarding Against Warpage and Distortion During Hot-Dip Galvanizing of Steel Assemblies’ This standard is issued under the fixed designation A ; the number immediately foliowing the designation indicates the year of original adoption or, in the case of revision, the year of last revision.
Steel invariably contains internal stresses induced at the mill from rolling operations used to bring structures, plate, and sheet to the final thickness. Wherever possible, asgm thick and thin portions separately and join them after galvanizing. Oftentimes sheet or plate can be returned to a flattened state using a jig or by weighing the product down on a flat surface during the cool-down. When two steels of different thicknesses are assembled and brought up to galvanizing temperature, the thinner steel heats up and expands more quickly than the thicker steel.
Where welding before galvanizing cannot be avoided, the internal stresses in the connections can be minimized by avoiding joint designs or weld lengths which are greater than statically required, and by placing welds near to and symmetrically around the neutral axis – aligning welds so that shrinkage and opposing forces are balanced rather than all pulling in the same direction.
Optimize Welding Before Hot-Dip Galvanizing Welding results in significant residual stress in asttm areas of an assembly due to the extreme temperature differences experienced.
ASTM A384 Recommendations
Practice ASTM A provides guidance on safeguarding against warpage and distortion for optimum hot-dip galvanizing and shall be complied with in both design and ast. Where excessive cold working or tight bend radii cannot be avoided, the product should be stress relieved per the guidelines provided within ASTM Astj, Section 6. Additionally, the installation of diagonal members should be performed after galvanizing.
Clamps may be applied to prevent shifting or movement during the welding operation. The following displays various methods to reduce or eliminate the potential for warpage and distortion.
Symmetrical sections such as I-beams and tubing will be less likely to distort than asymmetrical pieces camber beams, channels, tees, custom beams, girders because the thermal expansion forces above and below the natural axes balance each other.
This is not true of an I-beam, pipe, H-column, or any other section that is symmetrical about both its major axes. The design and fabrication of the product to be galvanized are the responsibilities of the designer and the fabricator.
Thls stendard Is subject to revision at any tlme by the responsible technical commHtee and must be reviewed every five years and H not revised, either reapproved or withdrawn. It is recommended that welding procedures be carried out in conformancewith the pertinent specificationsof the American Welding Society.
Last previous edition A – It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. Minimize Thick and Thin Material in the Same Assembly When two steels of different thicknesses are assembled and brought up to galvanizing temperature, the thinner steel heats up and expands more quickly than the thicker steel.
Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM Headquarters. Channels and other nonsymmetrical sections should be avoided for the satm of a sheet metal assembly that is to be hot-dip galvanized whenever it is possible to use symmetrical shapes or sections.
After galvanizing, these products should be air cooled instead of quenched to minimize induced stress from the cooling cycle.
ASTM A _图文_百度文库
Common distorted and warped members of assemblies are sheets or plates assembled by welding or riveting. Furthermore, cylindrical structures are less likely to warp or distort than rectangular or elliptical ones.
These rivets can be countersunk or flat head if the protruding head of the ordinary button or round head rivet is objectionable. Specify symmetrically rolled sections instead of angle or channel frames. Originally published as A – 55 T.
In the case of sheet metal, the product which has a right-angle bend in the sheet metal itself will remain flatter and be freer from distortion if the radius of the bend is as large as practicable. A superscript epsilon E indicates an editorial change since the last revision or reapproval.
ASTM A Recommendations | American Galvanizer’s Association
The following can cause warpage and distortion: All efforts should be made to keep the stresses in the construction as low as possible right from the beginning to enable the steel to absorb the internal stresses completely.
ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date. This abstract is a brief summary of the referenced standard.