5.1. Carbon steel plates (including plates for heads)
The following requirements shall apply to pressure vessels and heat exchangers fabricated ofunalloyed carbon steel.
5.1.1. Manufacturing process
The plates shall be produced by a low sulphur and low phosphorus refining process such as inan electric furnace, with double deslagging, or in a basic oxygen furnace. The steel shall be vacuumdegassed while molten; if manufactured by the continuous casting method, preference is given formagnetic stirring and squeeze rolling to prevent centerline segregation.
Plates shall be supplied in the normalized condition
Controlled rolled or quenched andtempered plates are not acceptable except by special arrangement (acceptance based on HIC testresults).
The Steel shall be shape control treated by Calcium except for low sulphur content equal or lessthan 0.002%, which shall be left at steel manufacturer’s option. Calcium addition shall not exceed 3times the sulphur content. Specific treatment by rare earth metals is not permitted.
Repair of defects by welding is not permitted.
5.1.2. Particular inspection of finished products
In addition to what is already required in the plate material specification, the followingexamination must be performed:
5.1.2.1. Ultrasonic examination
All plates of thickness greater than 3/8 inch (10mm) shall be examined by Ultrasonic inaccordance with ASTM A 578 with supplementary requirements S1. Acceptance criteria level C shallapply.
5.1.2.2. Micro-examination
The plates shall be checked for microstructure from the full thickness, at the center, quarterwidth, and at each edge, for confirmation of effectiveness of shape control of the inclusions. Thesample shall be typical of normal production material. Plates rolled from continuous cast materialshall be checked at one end of each plate. Plates rolled from ingots shall be checked at both ends ofeach plate. The examination method shall conform to the ASTM E 45 standard (microscopicallymethod, method D, with [A + B + C + D] < 20).
5.1.2.3. Through-thickness tension tests
Plates 25 mm and over in thickness shall be tested perpendicular to the rolled surface fordetermination of reduction of area according to ASTM A770. Minimum reduction of area shall notbe less than 35%.
5.1.3. Chemical composition
The chemical analysis (ladle) of plate materials shall be within the following limits (all value inpercent, by weight):
Elements
%
Maximum
Carbon 0.21
Manganese 1.00
Silicon 0.40
Sulphur 0.003
Phosphorous 0.015
Copper 0.35
Oxygen 0.002
Nickel 0.30
Chromium 0.20
Molybdenum 0.20
Deliberately added micro alloying elements shall require prior approval of Company.
Microalloying elements are considered as deliberately added when the values of Niobium (Nb),
Vanadium (V), and Titanium (Ti) are greater than 0.01 % and Boron (B) greater than 0.0005 %.
Deviation from the above mentioned limits shall require prior Company approval and shall be
followed by modification of WPS and qualification test, if necessary.
5.1.4. Material certificates
Material certificates shall be of the EN 10204 Type3.1 type and shall give the followinginformation:
• Full chemical analysis
• Mechanical properties (as required in the material specification)
• Steel making process, desulfurization technique
Casting method and size of ingots/slabs
Rolling procedures
• Results of ultrasonic inspection.
Forgings (for flanges)
6.5.1. Process of manufacture
Cold work or machining from bars is not permitted.
Hot work operations must be followed by an appropriate heat treatment with the followingdecreasing order to preference:
• Quenching and tempering
• Normalization and tempering
• Normalization.
6.5.2. Chemical analysis
The chemical analysis (ladle) of forgings shall be within the following limits (all values inpercent, by weight):
• C < 0.20
• Mn < 1.30
• P < 0.020
• S < 0.015
• Nb ≤ 0.005
• V ≤ 0.0051
• CE (IIW) ≤ 0.420
Hardness = 22 HRC ( MAX)