ASTM A789 S32205 S31803 Stainless Steel Tubes Material Purchase Specification

Stainless Steel Feed Material

Preference for Yongxing Special Materials Technology or similar quality manufacturer (to be nominated if not Yongxing)

Feed material certificates to be issued to the buyer for approval prior to commencing production

PREN Pitting Corrosion Equivalent

• Adequate corrosion resistance shall be achieved by ensuring the pitting resistance equivalent (PRE) exceeds 36 for all tubes.
• The pitting resistance equivalent shall be calculated as follows and reported for each heat.
  PRE = %Cr + (3.3 x %Mo) + (16 x %N)

Dimensional Tolerances

• Outside Diameter – 38.1mm +/- 0.25mm
• Wall Thickness – 1.65 +/-0.17mm
• Length – 7315mm -nil +5mm

Surface Condition

• All tubes shall be free of mill scale or any other oxide form that may reduce corrosion resistance in service.

Chemical Composition

• The stainless steel shall STRICTLY conform to the chemical requirements of UNS S32205

Critical Pitting Temperature Corrosion Test

A sample from each lot shall be tested in accordance with ASTM A923 Test Method C, at 35°C for a 24-hour test period.

• The resultant corrosion rate shall be less than 10mg/dm2 and the results shall be reported.

Microstructure

The microstructure shall consist of ferrite and austenite and the volume fraction of ferrite shall be in the range of 40 – 60% in with ASTM E563, the presence of any intermetallic phase in the microstructure is strictly prohibited.

Mechanical Properties

• The tensile and hardness properties shall conform to those nominated by ASTM A789M for UNS S31803.
• Flaring tests as specified by ASTM A789M shall also be conducted.
• Conformance to these requirements shall be reported for each production lot.

Integrity Testing

• Hydrostatic testing or appropriate non-destructive tests shall be undertaken to assure tube integrity in accordance with ASTM A789M
• The manufacturer shall nominate the preferred method of testing

PMI Testing

100% PMI testing required

Material Certification

• EN 10204 3.1 Mill certificates required and shall clearly document the results of the tests and inspections nominated by the Technical Specification Requirements and the requirements of ASTM A789M and shall be supplied for buyers approval prior to packing and despatch of the consignment ex-mill.
• Specification numer – QM22-004-02 REV 5 to be clearly noted on the material certificate
• In addition to the 3.1b certificate/s the manufacturer shall provide additional reports for;

· Critical Pitting Temperature (copy of complete test report required)
· Microstructure (copy of test complete report required)
· Integrity Test Method and Results (Hydrostatic Test or Eddy Current Test)

Sample Testing

3 samples per heat (500mm long) of the finished tube/s to be made available to the buyer upon completion of production to enable independent third party testing this will be performed at buyer cost.

Inspection

Buyer reserves the right to appoint at it’s own cost an independent third party to carry out inspection/s both during production and final inspection prior to packing.