What are the differences between f6a, 13cr, and 410?

This post was last edited by Liu Jiajia on 2017-4-13 at 09:03. 1. First, let’s talk about 13Cr: 13Cr is a type of steel with a chromium content of 13%; it includes grades such as 0Cr13 (06Cr13), 1Cr13 (12Cr13), 2Cr13 (20Cr13), 3Cr13 (30Cr13), and 4Cr13 (40Cr13). The numbers in parentheses represent the new grade designations (as per GB/T20878-2007). Among them, 0Cr13 (06Cr13) is a ferritic stainless steel, while 1Cr13 (12Cr13), 2Cr13 (20Cr13), 3Cr13 (30Cr13), and 4Cr13 (40Cr13) are all martensitic stainless steels. Although 0Cr13 (06Cr13) is classified as a martensitic stainless steel in GB/T20878-2007, this is debatable. The normal microstructure of 0Cr13 (06Cr13) is ferrite, unless the carbon content increases or specific heat treatment is applied. Otherwise, a martensitic structure will not form. 2. F6a F6a is a material grade specified in ASTM A182/A182M. It belongs to the 13Cr type of martensitic stainless steel mentioned above, and is commonly used to manufacture components for valves operating in non-corrosive or slightly corrosive environments, such as parts that come into contact with the medium like valve stems, valve seats, and valve discs. The equivalent grade in our country is the 1Cr13 (12Cr13) mentioned above. This steel grade exhibits excellent high-temperature oxidation resistance, with a maximum oxidation resistance temperature of 750°C, but its heat strength is only 500°C. Therefore, when used at high temperatures, it is necessary to pay attention to strength verification; especially for components under stress such as valve stems, special attention must be given to their stiffness and strength. It is generally recommended for use as internal components in carbon steel valves at temperatures of 425°C or less. Three points should be noted: 1) F6a has four grades, namely CL1-CL4, each with a specified hardness value; for details, refer to the ASTM A182 standard. The hardness values for these four grades are the requirements for F6a material, not the hardness values required for the valve stems of the products. For example, API 600 and API 602 specify that the hardness of 13Cr valve stems should be between 200HBW and 275HBW, whereas none of the hardness levels for the four grades of F6a meet the requirements specified by API 600 and API 602. Therefore, API 600-2009 and subsequent versions replaced 13Cr valve stems with ASTM A276 410, allowing the required hardness and mechanical properties of the components to be achieved by adjusting the tempering temperature through heat treatment. 2) F6a is applicable to the heat treatment requirements in acidic environments containing H2S. Martensitic stainless steels used in acidic environments associated with H2S-containing natural gas extraction or in petroleum refining processes involving H2S-containing hydrocarbon gases must comply with the specifications of NACE MR 0175/ISO 15156 or NACE MR 0103. The hardness of such steels after heat treatment shall be less than or equal to 22 HRC, and they must undergo a three-step heat treatment process. Step 1: Austenitization and air cooling after quenching ； Step 2: Temper at a minimum temperature of 621°C ； Step 3: Temper at a minimum temperature of 621°C, but below the temperature used for the first tempering, and then cool to room temperature. For details, refer to the NACE MR 0175/ISO 15156 and NACE MR 0103 standards. 3) Welding repairs to forge defects are permitted in accordance with the relevant provisions in ASTM A182/A182M, but welding repairs are not allowed for F6a CL3 and CL4. 3. Finally, regarding 410, the United States has a unified numerical code for steel materials, namely UNS (UNIFIED NUMBERING SYSTEM). This numbering system was jointly developed in 1967 by the Society of Automotive Engineers (SAE) and the American Society for Testing and Materials (ASTM) with the aim of replacing or at least supplementing the product designation systems used in existing standards. If you are interested, you can take a look at ASTM E527. The F6a mentioned above has an UNS number of S41000, abbreviated as 410. Just like the 304 stainless steel that we usually refer to, its UNS number is S30400; we commonly abbreviate it as 304.

:victory::handshake

Great post, thumbs up – a real expert in materials.

F6a is the forging designation and material for 13Cr； 13Cr refers to a series – a general term for martensitic stainless steels containing 13% or more chromium – and is not a specific grade ； 410 refers to the plates and bars of the 13CR series

:victory: The 3rd floor post explained it in great detail! Digging posts!

Very detailed – what are the differences between 13Cr and Cr13? Is it the same meaning?

F6a is the forging designation and material for 13Cr； 13Cr refers to a series – a general term for martensitic stainless steels containing 13% or more chromium – and is not a specific grade ； 410 refers to sheets and bars of the 13CR series. 13Cr denotes the martensitic stainless steel series; in our factory, Cr13 is considered to be the type of material used for internal components, and it generally refers to valve stems. For the double-sealed surfaces of 13CR materials, welding materials made of CR13 are used (such as sealing materials like D507 + D507MO)