Buttweld fittings are used to connect pipes of various sizes and shapes, and are typically welded to the pipes for a strong and leak-free connection. Here are some of the most common grades and specifications for buttweld fittings:

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1. Carbon Steel: Carbon steel buttweld fittings are made from carbon steel, which is known for its strength and durability. The most common grades of carbon steel used for buttweld fittings are ASTM A234 WPB, ASTM A234 WPC, and ASTM A420 WPL6. Carbon steel buttweld fittings are available in a range of sizes, from 1/2" to 48", and in various wall thicknesses.

2. Stainless Steel: Stainless steel buttweld fittings are made from stainless steel, which is known for its corrosion resistance and strength. The most common grades of stainless steel used for buttweld fittings are ASTM A403 WP304, ASTM A403 WP316, and ASTM A403 WP321. Stainless steel buttweld fittings are available in a range of sizes, from 1/2" to 48", and in various wall thicknesses.

3. Alloy Steel: Alloy steel buttweld fittings are made from alloy steel, which is a type of steel that has additional alloying elements such as chromium, molybdenum, and nickel. The most common grades of alloy steel used for buttweld fittings are ASTM A234 WP5, ASTM A234 WP9, ASTM A234 WP11, ASTM A234 WP22, and ASTM A234 WP91. Alloy steel buttweld fittings are available in a range of sizes, from 1/2" to 48", and in various wall thicknesses.

4. Copper Nickel: Copper nickel buttweld fittings are made from copper nickel alloys, which are known for their excellent corrosion resistance in seawater and other harsh environments. The most common grades of copper nickel used for buttweld fittings are ASTM B466 C70600 and ASTM B466 C71500. Copper nickel buttweld fittings are available in a range of sizes, from 1/2" to 24", and in various wall thicknesses.

In addition to the grades of buttweld fittings, they come in various specifications such as type, size, and schedule. The most common types of buttweld fittings are elbow, tee, reducer, cap, and stub end. The size and schedule of buttweld fittings depend on the application requirements and can vary widely. The schedule refers to the thickness of the wall of the pipe, and the most common schedules are Sch 10, Sch 40, Sch 80, and Sch 160.