AWS D10.18M-D10.18:2018 pdf download.Guide for Welding Ferritic/Austenitic Duplex Stainless Steel Piping and Tubing
1.1 Scope. The ferritic/austenitic duplex stainless steels (DSSs) discussed in this document have proven to be weldable using proper welding procedures. The processes GTAW, GMAW (includes all transfer modes), SMAW, FCAW, and SAW have all been used with success on these alloys. Automatic and mechanized welding such as orbital welding with the GTAW, GMAW, and FCAW processes have also been used with success on duplex alloys. Manual welders that have experience with austenitic stainless steels should be able to apply many of the techniques they have learned from these alloys to the welding of duplex stainless steels, while of course keeping in mind the exceptions to be noted within this document.
1.2 Units of Measure. This standard makes use of both the International System of Units (SI) and U.S. Customary Units. The latter are shown within brackets ([ ]) or in appropriate columns in tables and figures. The measurements may not be the exact equivalents; therefore, each system must be used independently.
To identify nominal pipe sizes in both SI and U.S. Customary Units, the following designations are used:
(1) DN (Diameter Nominal) is the SI designation, and
(2) NPS (Nominal Pipe Size) is the U.S. Customary designation.
Work performed in accordance with this standard may involve the use of materials that have been deemed hazardous,and may involve operations or equipment that may cause injury or death. This standard does not purport to address all safety and health risks that may be encountered. The user of this standard should establish an appropriate safety program to address such risks as well as to meet applicable regulatory requirements. ANSI Z49.1 should be considered when developing. the safety program.
4. Material Compositions and Specifications
4.1 Material Compositions. The duplex stainless steels (DSSs) have a microstructure of approximately equal parts of ferrite and austenite. Consequently, in welding and fabrication, the duplex alloys exhibit some characteristics of both ferritic and austenitic stainless steels. As a result, the welding procedures for the duplex alloys require different parame-ters than ferritic or austenitic stainless steels.
Beneficial features of DSSs include a yield strength about double that of the austenitic grades, while maintaining ductil-ity and toughness approaching that of the austenitics. DSSs are especially resistant to chloride stress corrosion cracking,pitting, crevice corrosion, and erosion corrosion. The useful service temperature range is more restricted than the austen-itics and varies with the particular duplex alloy. In general, the duplex range is - 40°C [- 40°F] to 280°C [536°F].
4.2 Specifications. The wrought DSSS are often classified into three families (lean, standard, and super) based on com-position. The compositions of the wrought alloy families are shown in Tables 1, 2, and 3. Cast alloys are shown in Table 4. Type 2205 is the most widely used of the DSSs and is estimated to represent 80% of DSSs used. Most literature refer-ences to welding DSSs refer to 2205, however details of welding procedures for the three groups are discussed in later subclauses.AWS D10.18M-D10.18 pdf download.