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API RP 2Z-2005 pdf free download

API RP 2Z-2005 pdf free download.Recommended Practice for Preproduction Qualification for Steel Plates for Offshore Structures.
3 Qualification for HAZ Toughness 3.1 Each pre-qualification shall consist of preparation of three butt welds using test plates with either a K-bevel or single-bevel joint preparation (See Figure 1), subjection to agreement between purchaser and manufacturer. The weld shall be parallel to the final rolling direction and at mid width of mother plate. Test plates shall be of the maximum thickness intended for inclusion within the scope of the pre-qualification. 3.1.1 Pre-qualification test welds shall be made in the flat position using mechanized SAW process except that other mecha- nized welding process may be employed for the root pass and for the lowest heat input. The maximum angular distortion after welding and release of restraint shall not be greater than two degrees. 3.1.2 The welding consumables for pre-qualification welding shall be selected so that the CTOD fracture toughness of the weld metal in the final heat-treatment condition exceeds the required CTOD of the HAZ materials by at least 0.13 mm (0.005 in.) at –10°C (14°F), or at the temperature selected. To determine the CTOD value of weld metal, 100% of the fatigue crack should sample weld metal over the entire thickness and should be targeted to be within 1 – 2 mm (0.04 – 0.08 in.) of the fusion line over the central 2 / 3 of specimen thickness. In addition, the hardness of the weld-metal deposit should be measured and should equal or exceed the hardness of the base material. These weld requirements are intended to ensure (1) that low weld metal toughness does not interfere with the interpretation of low CTOD results in the HAZ, and (2) that during HAZ testing, fatigue crack propagation into soft weld metal is not promoted. The weld metal toughness requirement contained in this section is not intended as a specifi- cation for production welding procedures. 3.1.3 The three butt welds shall be welded with pre-heat, heat input, and interpass temperature that span the pre-qualification range. The heat input (arc energy) range for pre-qualification shall encompass at least 0.8 to 4.5 kJ/mm (21 to 114 kJ/in.), unless the manufacturer elects a more restrictive heat input range for their particular steel supply (see 1.3.6). One weld shall be made at the lowest heat input to be pre-qualified with the lowest preheat/interpass temperature to be qualified in Section 4 [100°C (212°F) or lower] at the start of each weld pass adjacent to the tested HAZ. Preheat/interpass may increase 60°C (140°F) for weld passes further from HAZ. Another weld shall be made at the highest heat input to be pre-qualified with preheat/interpass temperature at 250°C (482°F) or higher at the start of each weld pass. The third weld shall be made with heat input at 3.0 kJ/mm (76 kJ/in.); the preheat temperature shall be 100°C (212°F), and the interpass temperature shall be allowed to build naturally, but not to exceed 250°C (482°F). Suitable equipment shall be employed for measuring these parameters quantitatively (temperature-indicating crayons are not acceptable). The heat input may be varied temporarily for initial or final passes if of practical necessity to com- plete a weld of the desired shape. 3.3 CTOD TESTING For the lowest heat input weld, a minimum of eight valid CTOD tests are required, and for the 3.0 kJ/mm (76 kJ/in.) weld and the highest heat input weld, five valid CTOD tests are required. All CTOD tests will be performed at –10°C (14°F), or at the lowest anticipated service temperature (LAST). All CTOD tests shall be in accordance with either British Standard BS 7448 Part 1 & 2 or ASTM E1290 (at Manufacturer’s option), employing the preferred (Tx2T) test specimen (See Note 1) with a through-thickness notch and fatigue precrack extending halfway through the specimen width, nominally. The CTOD specimen length dimension shall be perpendicular to the weld and plate rolling direction (T-L orientation). The straight side of the weld should be straight enough so that a through-thickness notch can be placed normal to the plate surface and intersect the etched HAZ for at least 75% of the notch length over the central 2 / 3 of the specimen thickness. More specimens than the number of required valid specimens may be necessary to allow for invalid results (per the CTOD test method) or failure to meet the notch placement criteria. The weld reinforcement may be removed, and the original plate surfaces cleaned to remove scale and superficial roughness, prior to the preparation of the specimens.

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