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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Steel invariably contains internal stresses induced at the mill from rolling operations used to bring structures, plate, and sheet to the final thickness. 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 satm rather than all asttm in the same direction.
Channels and other nonsymmetrical sections should be avoided for the framework 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. Current edition approved Oct. Qstm the angie steel frame and sheets are punched prior to galvanizing the recommended procedureaxtm use of drift pins to bring the holes into alignment should be avoided as far as possible at the time the sheets and frame are assembled.
Therefore, steel thicknesses should vary as little as possible throughout the assembly. Suggested corrections for panel fabrication are detailed. I the a834 frame has to be dipped one half at a time, it will be better to have the sheets galvanized, rolled flat after asstm, and assembled to the galvanized frame by the use of aluminum alloy or galvanized rivets.
Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard. Where excessive cold working or tight bend radii cannot be avoided, the product should be stress relieved per the guidelines provided within ASTM A, Section 6.
Additionally, the installation of diagonal members should be performed after galvanizing. This is not true of an I-beam, pipe, H-column, or any other section that is symmetrical about both its major axes.
Suggested Corrections for Panel Fabrication 4. Asymmetrical Design Symmetrical sections such as I-beams and tubing will be less likely to distort than asymmetrical pieces awtm beams, channels, tees, custom beams, girders because the thermal expansion forces above and below the natural axes balance each other. This abstract is a brief summary of the referenced standard. In nearly every case, regardless of size, channels require straightening after galvanizing.
ASTM A _图文_百度文库
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.
It is informational only and not an official part of the standard; the full text of atm standard itself must be referred to w384 its use and application.
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. 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. Inch pounds and SI units are not necessarily exact equivalents. These rivets can be countersunk or flat head if the protruding head of the ordinary button or round head rivet is objectionable.
ASTM A384 Recommendations
This specification deals with safeguarding against warpage and distortion during hot-dip galvanizing of steel assemblies. Last previous edition A – 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 the application of high heat on the same side at various intervals along its length.
Optimize Welding Before Hot-Dip Galvanizing Welding results in significant residual stress in small areas of an assembly due to the extreme temperature differences experienced. Clamps may be applied to prevent shifting or movement during the welding operation. It is recommended that welding procedures be carried out in conformancewith the pertinent specificationsof the American Welding Society.
Avoid Susceptible Thin Sheet Steels Steel invariably contains internal stresses induced at the mill from rolling operations used to bring structures, plate, and sheet to the final thickness. 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 fabrication.
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. The following displays various methods to reduce or eliminate the potential for warpage and distortion. This will prevent the rusting of the surfaces which are so connected that molten zinc cannot circulate through the crevices to galvanize the contacting surfaces.
Within the text of this specification and where appropriate, SI units are shown in parentheses.
Furthermore, cylindrical structures are less likely to warp or distort than rectangular or elliptical ones. Historical Version s – view previous versions of standard.
ASTM does not give aatm warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date. Originally published as A – 55 T. A number in parentheses indicates the year of last reapproval.
Welding results in significant residual stress in small areas of an assembly due to the extreme temperature a84 experienced.
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.
Link to Active This link will always route to the current Active version of the standard. Specify symmetrically rolled sections instead of astn or channel frames. 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 w384 heats up and expands more quickly than the thicker steel.
The following can cause warpage and distortion: Wherever possible, galvanize thick and thin portions qstm and join them after galvanizing. The design and fabrication of the product to be galvanized are the responsibilities of the designer and the fabricator. Factors in Warpage and Distortion 3. Necessary precautions to fabricate properly and prepare the material for galvanizing to prevent embrittlement are described in Practice A