Stainless Steel Pipe Supplier Wenzhou Kaixin China
Processing characteristics:
2205 duplex stainless steel is similar to 316L in many aspects, but there are still some important differences. The cold forming operation must take into account the high strength and high work-hardening characteristics of duplex stainless steel. The forming equipment may require higher load capacity, and 2205 stainless steel will show higher resilience than the standard austenitic stainless steel grade in the forming operation. The high strength of 2205 duplex stainless steel makes it more difficult to cut than 316L.
The welding method of 316L stainless steel can be used for 2205 duplex stainless steel. However, the heat input and interlayer temperature must be strictly controlled to maintain the desired austenitic-ferrite phase ratio and avoid the precipitation of harmful intermetallic phases. A small amount of nitrogen in the welding gas can help to avoid these problems. When evaluating the welding procedure of duplex stainless steel, the commonly used method is to evaluate the austenitic-ferrite ratio by using a ferrite tester or through metallographic examination. ASTM A 923 test method is usually used to verify the existence of harmful intermetallic phases.
The recommended weld filler metal is ER2209 (UNS S39209, EN 1600). Self-fusion welding without filler metal can only be used if the weld can be solution annealed after welding to restore corrosion resistance. During solution annealing, heat the parts to a temperature of at least 1040 ° C, and then rapidly cool them.
The penetration and fluidity of duplex stainless steel such as 2205 are worse than 316L stainless steel, so the welding speed is slower. Due to the poor penetration of 2205 duplex stainless steel, the shape of the joint needs to be modified. 2205 duplex stainless steel needs wider groove angle, larger root gap and smaller blunt edge than 316L stainless steel in order to obtain complete penetration weld.
If the welding equipment allows the use of filler wire, 2209 filler wire can be used for rail welding of 2205 stainless steel pipe. It is also possible to use consumable inserts with proper alloying composition without filling welding wires. Table 3 summarizes the insert materials used for welding 2205 duplex stainless steel pipes.
Electrolytic polishing of duplex stainless steel
Many pharmaceutical and biotechnology applications require electrolytic polishing of the surface in contact with the product. Therefore, the ability to provide high-quality electrolytic polishing surface has become an important material property. 2205 duplex stainless steel can be electropolished to 0.38 μ m or higher finish, which meets or exceeds the surface finish requirements of ASME BPE standard for electropolished surface. Although 2205 duplex stainless steel can easily meet the requirements of pharmaceutical and biotechnology industries for surface finish, the surface of 2205 stainless steel after electrolytic polishing is not as bright as that of 316L stainless steel after electrolytic polishing. This difference is due to the slightly higher metal dissolution rate of ferrite compared with that of austenite phase in the electrolytic polishing process.
Standard specifications and quality control standards
Many industrial and national standards include 2205 duplex stainless steel. ASTM A 240 currently lists two grades of 2205 duplex stainless steel, S31803 and S32205. The minimum content of chromium, molybdenum and nitrogen in S32205 is slightly higher, but it is still within the chemical composition range of S31803. The purpose of developing this brand is to solve the problem of potential corrosion resistance and toughness loss in the heat affected zone (HAZ) of some S31803 welds. Therefore, it is recommended that users specify S32205 brand. If S31803 is required, sometimes because it is included in ASME standards, users should require that all chemical components of S31803 also meet the composition requirements of S32205, so as to maintain consistent performance.
Processing characteristics:
2205 duplex stainless steel is similar to 316L in many aspects, but there are still some important differences. The cold forming operation must take into account the high strength and high work-hardening characteristics of duplex stainless steel. The forming equipment may require higher load capacity, and 2205 stainless steel will show higher resilience than the standard austenitic stainless steel grade in the forming operation. The high strength of 2205 duplex stainless steel makes it more difficult to cut than 316L.
The welding method of 316L stainless steel can be used for 2205 duplex stainless steel. However, the heat input and interlayer temperature must be strictly controlled to maintain the desired austenitic-ferrite phase ratio and avoid the precipitation of harmful intermetallic phases. A small amount of nitrogen in the welding gas can help to avoid these problems. When evaluating the welding procedure of duplex stainless steel, the commonly used method is to evaluate the austenitic-ferrite ratio by using a ferrite tester or through metallographic examination. ASTM A 923 test method is usually used to verify the existence of harmful intermetallic phases.
The recommended weld filler metal is ER2209 (UNS S39209, EN 1600). Self-fusion welding without filler metal can only be used if the weld can be solution annealed after welding to restore corrosion resistance. During solution annealing, heat the parts to a temperature of at least 1040 ° C, and then rapidly cool them.
The penetration and fluidity of duplex stainless steel such as 2205 are worse than 316L stainless steel, so the welding speed is slower. Due to the poor penetration of 2205 duplex stainless steel, the shape of the joint needs to be modified. 2205 duplex stainless steel needs wider groove angle, larger root gap and smaller blunt edge than 316L stainless steel in order to obtain complete penetration weld.
If the welding equipment allows the use of filler wire, 2209 filler wire can be used for rail welding of 2205 stainless steel pipe. It is also possible to use consumable inserts with proper alloying composition without filling welding wires. Table 3 summarizes the insert materials used for welding 2205 duplex stainless steel pipes.
Electrolytic polishing of duplex stainless steel
Many pharmaceutical and biotechnology applications require electrolytic polishing of the surface in contact with the product. Therefore, the ability to provide high-quality electrolytic polishing surface has become an important material property. 2205 duplex stainless steel can be electropolished to 0.38 μ m or higher finish, which meets or exceeds the surface finish requirements of ASME BPE standard for electropolished surface. Although 2205 duplex stainless steel can easily meet the requirements of pharmaceutical and biotechnology industries for surface finish, the surface of 2205 stainless steel after electrolytic polishing is not as bright as that of 316L stainless steel after electrolytic polishing. This difference is due to the slightly higher metal dissolution rate of ferrite compared with that of austenite phase in the electrolytic polishing process.
Standard specifications and quality control standards
Many industrial and national standards include 2205 duplex stainless steel. ASTM A 240 currently lists two grades of 2205 duplex stainless steel, S31803 and S32205. The minimum content of chromium, molybdenum and nitrogen in S32205 is slightly higher, but it is still within the chemical composition range of S31803. The purpose of developing this brand is to solve the problem of potential corrosion resistance and toughness loss in the heat affected zone (HAZ) of some S31803 welds. Therefore, it is recommended that users specify S32205 brand. If S31803 is required, sometimes because it is included in ASME standards, users should require that all chemical components of S31803 also meet the composition requirements of S32205, so as to maintain consistent performance.