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A182 VS A479 sstainless steelthread330-267557

JAYDEE23 (Materials) 16 Mar 10

9:14

I am about to look into this further so i figured i would post here also. I know A182 is forging and A479 is bar. Can you eloborate more on the differences of the two. Most of my mill certs state both. What factors must met in order to classify a bar as both?

metengr (Materials) 16 Mar 10

11:02

JAYDEE23; Do you have both ASTM specifications to review? If not, you need to obtain them to review side by side. If you have a materials background you will see the stated differences in terms of manufacture, required mechanical tests, marking, etc. The A 479 is a standard stainless steel bar specification, where products supplied under A 479 can be certified under A 182 provided the weight size is followed in the Scope statement of A 182.

JAYDEE23 (Materials) 16 Mar 10

14:28

Metengr, I do not have a materials backround i do however have the specs. After reviewing what i am familar with in the 2 specs i see no mentionable differences is chemical, machanical, grain size, hardness requirements..etc.. not for 304 anyway Even ASME section II allowable stresses @ temps are the same. i see a difference in reduction of area % min..thats all my untrained eye spots. Reason i am inquiring is...im pressed for time on a project that requires sa-182 piping component I fabricate. Time only allows me to get 479 in time. I dont see any reason i can not use 479. I am curious as what reason could be given to reject 479.

rneill (Mechanical) 16 Mar 10

14:36

Background Info: "Directional strength is the direct result of the forging process. In the forging process, controlled deformation results in greater metallurgical soundness and improved mechanical properties of the material. In most cases, forging stock has been pre-worked to remove porosity

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resulting from the solidification process. This produces directional alignment (or grain flow) for important directional properties in strength, ductility and resistance to impact and fatigue. These properties are deliberately orientated in directions requiring maximum strength. Working the material achieves recrystallization and grain refinement that yields the maximum strength potential of the material with the minimum property variation, piece to piece. Properly developed grain flow in forgings closely follows the outline of the component. In contrast, bar stock and plate have unidirectional grain flow; any changes in contour will cut flow lines, exposing grain ends, and render the material more liable to fatigue and more sensitive to stress corrosion" From a code perspective, ASME B31.3 (and other design codes) do not always list bar stock materials whereas they typically do always list forging material. Check Table A-1 of B31.3 to see if your material is listed or not. If your specific material is not listed in Table A-1 the client could reject it as an "unlisted" material.

JAYDEE23 (Materials) 16 Mar 10

14:55

Also I am wondering why "sa-182 chemical only" is stated on some certs and not others...seem to meet all mechanical requirements also...

rneill (Mechanical) 16 Mar 10

15:06

Perhaps because A182 requires that forgings meet all the requirements specified in A961 whereas A479 does not and the material does not meet these requirements. Consequently, a forging made to A182 can have significantly better properties and be of higher quality than A479 bar stock material despite the fact that the specified chemistry and minimum mechanical properties shown on the MTR might appear to be the same. Note that A961 does not allow barstock material to be used for flanges, elbows, return bends, tees and only allows it to be used for other hollow cylindrical parts up to NPS 4 provided the axial length of the part is approximately parallel to the metal flow lines of the starting stock. If the manufacturer has not certified the material as A182 (without limitation) then it is not A182 material and does not meet the customers specification nor Code requirements if that is what they asked for. You could ask the original manufacturer to review and issue you a new MTR certifying it as A182 material someone other than the manufacturer can not regrade the material on the basis of information presented on an MTR. There is just not sufficient information presented on an MTR to fully assure that all requirements of the original material specification (e.g., A182, A961) were met.

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Page 2 of 2Metal and Metallurgy engineering - A182 VS A479 sstainless steel

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