Astm A928 716k1r

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This specification covers standard requirements for ferritic/austenitic (duplex) stainless steel pipe that is electric fusion welded with addition of filler metal suitable for corrosive service. Heat treatment shall be performed after welding and in accordance with specified temperature and quench conditions. Several grades of ferritic/austenitic steel shall conform to the requirements of the applicable specification and grade designation. Heat and product analyses shall be conducted and shall conform to the requirements for the particular grade. The plate used in making the pipe shall conform to the required tensile properties. The steel pipe shall undergo several mechanical tests including transverse tension test, transverse guided-bend test, nondestructive test, hydrostatic test, and nondestructive electric test. This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standar d; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.

Ô 1.1 This specification covers electric-fusion-welded steel pipe suitable for corrosive service. Note 1²The dimensionless designator NPS (nominal pipe size) has been substituted in this specification for traditional such as nominal diameter, size, and nominal size. 1.2 This specification covers grades of ferritic/austenitic steel as indicated in Table 1. The selection of the proper alloy and requirements for heat treatment shall be at the discretion of the purchaser, dependent on the service conditions to be encountered. 1.3 Five classes of pipe are covered as follows: 1.3.1 Class 1²Pipe shall be double welded by processes using filler metal in all es and shall be radiographed completely. 1.3.2 Class 2²Pipe shall be double welded by processes using filler metal in all es. No radiograph is required. 1.3.3 Class 3²Pipe shall be single welded by processes using filler metal in all es and shall be radiographed completely. 1.3.4 Class 4²Same as Class 3, except that the weld exposed to the inside pipe surface is permitted to be made without the addition of filler metal (see 6.2.2.1 and 6.2.2.2). 1.3.5 Class 5²Pipe shall be double welded by processes using filler metal in all es and shall be spot radiographed. 1.4 Supplementary requirements covering provisions ranging from additional testing to formalized procedures for manufacturing practice are provided. Supplementary Requirements S1 through S4 are included as options to be specified in the purchase order when desired.

1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. The inch-pound units shall apply unless the M designation of the specification is specified in the order.

purchase separately)

The documents listed below are referenced within the

subject standard but are not provided as part of the standard.

c A240/A240M Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications A480/A480M Specification for General Requirements for Flat-Rolled Stainless and HeatResisting Steel Plate, Sheet, and Strip A941 Terminology Relating to Steel, Stainless Steel, Related Alloys, and Ferroalloys A999/A999M Specification for General Requirements for Alloy and Stainless Steel Pipe E426 Practice for Electromagnetic (Eddy-Current) Examination of Seamless and Welded Tubular Products, Austenitic Stainless Steel and Similar Alloys c SectionIX,WeldingQualifications c A5.30 Consumable Weld Inserts for Gas Tungsten Arc Welding

! arc welded steel pipe; corrosive service; duplex (austenitic-ferritic) stainless steel; fusion welded steel pipe; steel pipe; welded steel pipe; Austenitic stainless steel pipe--specifications; Corrosive service applications--pipe (steel); Duplex stainless steel--specifications; Electricfusion-welded steel pipe; Ferritic steel pipe--specifications; Filler metals; Stainless steel pipe-specifications; ICS Number Code 25.160.40 (Welding ts and welds)

! Duplex stainless steels are called ³duplex´ because they have a two-phase microstructure consisting of grains of ferritic and austenitic stainless steel. The picture shows the yellow austenitic phase as ³islands´ surrounded by the blue ferritic phase. When duplex stainless steel is melted it solidifies from the liquid phase to a completely ferritic structure. As the

material cools to room temperature, about half of the ferritic grains transform to austenitic grains (³islands´). The result is a microstructure of roughly 50% austenite and 50% ferrite.

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The duplex structure gives this family of stainless steels a combination of attractive properties:

& "' Duplex stainless steels are about twice as strong as regular austenitic or ferritic stainless steels. &" (' Duplex stainless steels have significantly better toughness and ductility than ferritic grades; however, they do not reach the excellent values of austenitic grades. ' As with all stainless steels, corrosion resistance depends mostly on the composition of the stainless steel. For chloride pitting and crevice corrosion resistance, their chromium, molybdenum and nitrogen content are most important. Duplex stainless steel grades have a range of corrosion resistance, similar to the range for austenitic stainless steels, i.e from Type 304 or 316 (e.g. LDX 2101©) to 6% molybdenum (e.g. SAF 2507©) stainless steels.

)& ' Duplex stainless steels show very good stress corrosion cracking (SCC) resistance, a property they have ³inherited´ from the ferritic side. SCC can be a problem under certain circumstances (chlorides, humidity, elevated temperature) for standard austenitics such as Types 304 and 316. 'Duplex stainless steels have lower nickel and molybdenum contents than their austenitic counterparts of similar corrosion resistance. Due to the lower alloying content, duplex stainless steels can be lower in cost, especially in times of high alloy surcharges. Additionally, it may often be possible to reduce the section thickness of duplex stainless steel, due to its increased yield strength compared to austenitic stainless steel. The combination

can lead to significant cost and weight savings compared to a solution in austenitic stainless steels.

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uplex stainless steels have a mixed microstructure of austenite and ferrite, the aim usually being to produce a 50/50 mix, although in commercial alloys the ratio may be 40/60. Duplex stainless steels have roughly twice the strength compared to austenitic stainless steels and also improved resistance to localized corrosion, particularly pitting, crevice corrosion and stress corrosion cracking. They are characterized by high chromium (19±28%) and molybdenum (up to 5%) and lower nickel contents than austenitic stainless steels. Duplex grades are characterized into groups based on their alloy content and corrosion resistance. Lean duplex refers to grades such as UNS S32101 (LDX 2101), S32304, and S32003. The standard duplex is 22% chromium with S31803/S32205 known as 2205 being the most widely used. Super duplex refers to 25% chromium grades such as S32760 (Zeron 100), S32750 (2507), and S32550 (Ferralium). Hyper duplex refers to higher chromium grades such as S32906. The properties of duplex stainless steels are achieved with an overall lower alloy content than similar-performing super-austenitic grades, making their use cost-effective for many applications.