Along with shear plates and round malleable washers, malleable beveled washers are made with ASTM A47 cast malleable iron. See the following excerpts from ASTM A47.
11.3 Castings that have been repaired by the welding shall be reannealed so that the microstructure will comply with Section 8. (Section 8 of ASTM A47 lays out specific requirements for the microstructure of the casting, as well as testing and inspection.)
X1.4 If malleable iron castings are welded, the microstructure of the iron is markedly affected, particularly in the heat-affected zone. Therefore, since this may adversely affect the properties of the casting, the welding of malleable iron castings should be done under strict metallurgical control, followed by appropriate post-weld heat treatment, to minimize the substantial reductions in ductility, impact resistance, and machinability that could result, particularly in the vicinity of the weldment. Nevertheless, it is generally considered inadvisable to join castings to similar castings or to other materials, by fusion welding out in the field, or in manufactured assemblies, without fully testing the entire completed part.
It would seem that ASTM A47 does appear to be weldable, due to these excerpts, but additional steps may need to be necessary to ensure the structural integrity of the casting after welding. If welding does take place, the casting would need to be reannealed to restore the original grain structure in order to comply with the specification. However, the specification also mentions that welding to castings is generally a bad idea and must be performed under strict supervision of an expert who is aware of the complex issues that may arise, not only with the initial welding but also with the eventual final use of the part. As with many complex questions that arise on projects and jobsites, an engineer needs to be consulted on any critical decisions involving structural integrity, especially concerning welding.
Since ASTM A47 is the specification that applies to malleable beveled washers, shear plates, and round malleable iron washers, this welding information applies to all three items. A similar product, ogee washers, however are manufactured to ASTM A48 (gray iron castings). A48 also has a similar section containing information about welding. See the below excerpt…
X1.5 If iron castings are welded (see 9.2), the microstructure of the iron is usually altered, particularly in the vicinity of the weldment. Therefore, the properties of the casting may be adversely affected by welding. Where practical, appropriate post weld heat treatment may reduce this effect of welding. (Section 9.2 refers to getting written permission from the purchaser before welding or plugging can occur for repairs.)
Although ogee washers are made to a different casting specification, ASTM A48, the same kind of welding precautions apply.