This procedure covers the repair welding of several types of alloy steel components with materials meeting VIWI MS3 or MS5 specification.
2.0 DEFECT REMOVAL
The defect may be removed by carbon-arc, chipping, grinding or machining. Carbon-arc is the most practical. Flame cutting is not recommended due to the high heat input. When carbon-arc is used the temperature of the base metal should be at least 212° F (100° C).
It is imperative that the defect be completely removed to sound metal, free from cracks, shrinkage or porosity. The use of magnetic-particle or dye-penetrant inspection of the cavity is strongly recommended.
3.0 PREHEAT TEMPERATURE
The minimum preheat temperature is 400° F (205° C). The part should be preheated in a temperature-controlled furnace. The heating rate is 100° F/hour (40°C/hour) maximum, and the holding time is one (1) hour/inch (25min/cm) of thickness, but not longer than six (6) hours.
Localized preheating is not recommended, but may be used if furnaces are not available. The area preheated must be at least 24 inches (60cm) from the edge of the cavity. The rate of heating must be not over 100° F/hour (40° C/hour). Holding times should be one (1) hour/inch (25min/cm), but not over six (6) hours. The temperature of the part can be checked by temperature-sensitive markers such as “Tempil-Sticks”.
4.0 INTERPASS TEMPERATURE
The maximum interpass temperature is 600° F (320° C). It is important not to exceed this temperature.
5.0 WELDING PARAMETERS
The “shielded metal arc welding” process (SMAW) should be used for all welding.
(A) Welding Current
Direct-current, reverse-polarity (DCRP) is required for the electrodes recommended. The voltage and amperage settings should be based upon the recommendations of the manufacturer. In the absence of specific instructions, the following guide may be used:
Electrode Amperage Voltage Diameter Flat Position Flat Position 1/8″ (3mm) 120 22/26 5/32″(4mm) 160 23/27 3/16″(5mm) 240 24/29
NOTE: The use of smaller electrodes and corresponding lower amperage is recommended.
There are two (2) electrodes that may be used, AWS E-10018-M or E-10018 D2. These are iron-powder electrodes but the corresponding EXXX15 or EXXX16 low- hydrogen electrodes with mineral coating may be used. No other substitution of electrodes should be used.
No special technique is required. The weld bead should be the stringer type and slag should be removed from the bead by chipping, peening and wire-brushing.
7.0 POST-WELDING HEAT TREATMENT
Due to the hardenability of these steels, stress relief after welding is required. This should be done in a temperature- controlled furnace–heating with gas torches or space heaters is not recommended. The component should not be allowed to cool below 212° F (100° C) before placing it in a furnace heated to 400° F (205° C). The component should be held at this furnace temperature for one (1) hour minimum. The part should be then heated gradually–for parts less than 5″ (125mm) thick, the heating rate should be 200°F/hr (95°C/hr), for parts more than 5″ (125mm) thick, 100° F/hr (40°C/hr). In either case, the maximum temperature achieved should be 1100° F (600°C). Once this temperature is reached, it should be held for one hour per inch (25 minutes per centimeter) at this temperature, but in no case longer than ten (10) hours. Cooling should be done in still air. The piece should neither be held in nor furnace cooled through the temperature range of 600-1000°F (320-540°C), as temper embrittlement and subsequent loss of impact resistance may occur.