Manufacturing method of platinum or platinum-rhodium belt and sheet

The invention provides a method for manufacturing platinum or platinum-rhodium strips and sheets, which comprises the following steps of: (1) smelting: taking 0-30 percent by weight of rhodium powder and the balance of pure platinum ingots, mixing and smelting to obtain liquid alloy; (2) casting: casting the liquid alloy to obtain a cast ingot; (3) primary rolling is conducted, specifically, the cast ingot is subjected to hot forging thickness reduction, after a shrinkage cavity part is cut off, the cast ingot is subjected to cold rolling through a two-roller rolling mill to reach the thickness of 1.00-1.50 mm, and a primary rolled plate is obtained; (4) finish rolling is conducted, specifically, the primarily-rolled plate is cold-rolled to the thickness of 0.15-0.30 mm through a four-high rolling mill, the plate is cold-rolled to the thickness of 0.05-0.10 mm through the four-high rolling mill after being cleaned and annealed, and semi-finished belts and sheets are obtained; (5) hot joining: applying the sem