When it comes to stainless steel tubing and piping, selecting the right grade is essential. ASTM A312 and ASTM A240 both provide specifications for stainless steel products but differ in their purposes. ASTM A312 is a standard specification for seamless, welded, and heavily cold-worked austenitic stainless steel pipes. At the same time, ASTM A240 is a standard specification for chromium and chromium-nickel stainless steel plate, sheet, and strip for pressure vessels and general applications. This blog post highlights the fundamental differences between ASTM A312 and ASTM A240 and explains why they matter.
What Is Astm A312 And Astm A240
ASTM A312 is a standard specification for seamless, welded, and heavily cold-worked austenitic stainless-steel pipes used for high temperature and general corrosive service. On the other hand, ASTM A240 specification covers chromium, chromium-nickel, austenitic stainless steel plate, sheet and strips for pressure vessels and general applications. This includes both ferritic grades of steel, which can also be used in aircraft engine components, and martensitic grades of steel generally found in industrial machines. Both standards are extensively utilized in numerous industries, such as petroleum refining and chemical processing.
Difference Between Astm A312 And Astm A240
The major difference between ASTM A312 and ASTM A240 is that the former is a specification for seamless and welded austenitic stainless steel pipes, while the latter is an alloy specification. ASTM A312 covers two varieties of austenitic stainless steel pipes which support high-temperature and pressure applications. It also has several requirements related to chemical composition, mechanical properties, testing etc. On the other hand, ASTM A240 contains requirements regarding chemical & mechanical properties, hardness tests & impact tests for a wide variety of alloys (ferritic (400 series), martensitic (400 series) or austenitic (300 series)). In summary, both are different specifications, each designed for different types of materials with specific requirements in terms of their properties.
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Purpose and Applications
As mentioned earlier, ASTM A312 is used for various purposes, including processing chemicals, refineries, paper mills, and shipbuilding. It covers seamless, straight-seam welded, and heavily cold-worked welded austenitic stainless steel pipe intended for high-temperature and general corrosive service. On the other hand, ASTM A240 is used to specify the quality of stainless steel plates, sheets, and strips for general applications, such as architectural, building, construction, and kitchen equipment industries. It also covers pressure vessels and tanks.
Chemical Composition
ASTM A312 stainless steel pipes are made from austenitic steel that contains a high percentage of chromium and nickel, along with other elements like molybdenum, titanium, and copper. The primary focus is on the chemical composition of steel, which determines its properties. On the other hand, ASTM A240 stainless steel plates, sheets, and strips are also made from chromium and nickel steel but have a different composition to meet the requirements for their intended applications.
Manufacturing Process
ASTM A312 pipes can be manufactured using two different methods, seamless and welded. The seamless pipes are made from solid steel billets and are subjected to heat treatment to achieve the desired properties. The welded pipes can be made using high-frequency induction and electric resistance welding. Conversely, ASTM A240 products can be produced through hot-rolling and cold-rolling processes. Hot rolling is used for plates, and cold rolling is used for sheets.
Dimensions and Sizes
The most significant difference between these two standards is their range of sizes and dimensions. ASTM A312 provides a broader range of sizes, from 1/8″ to 30″ in diameter, while ASTM A240 is limited to plates between 0.1875″ and 3″. ASTM A312 products are designed to withstand high temperatures and are generally thicker than ASTM A240. In contrast, ASTM A240 products are thinner and used for structural applications.
Cost and Availability
Cost is a critical factor when selecting between ASTM A312 and ASTM A240. ASTM A240 is usually cheaper than ASTM A312 because it is thinner and less heat-resistant. However, the availability of each product can also depend on the location. ASTM A312 pipes are commonly used in heavy industries, so that they may be more conveniently available in industrial areas.
Conclusion:
In conclusion, ASTM A312 and ASTM A240 are essential standards for stainless steel products. While they are similar in composition, their manufacturing processes, dimensions, and applications differ. It’s important to know their differences when selecting the right stainless steel product for your intended purpose. By familiarizing yourself with each standard’s specifics, you can make an informed choice about which option will meet your requirements.
