Shielded Metal Arc Welding, Flux Cored Arc Welding, Gas Metal Arc Welding, Submerged Arc Welding
For Hardfacing
█ A guide for selecting welding consumables
Weld metal microstructure and main alloying elements determine the performances of welding
consumables for hardfacing as summarized in Table 1. In addition, PF-200S/US-63B is good
for reclamation of mill rolls.
Table 1 Welding consumables and their characteristics
Weld metal Type of wear
(1)
microstructure Hv Features SMAW FCAW GMAW SAW
and alloying formula MTM ABR HTW CAV COR HRT IMP
HF-240
200- ▪Good crack resistance HF-260 DWH-250 MG-250 G-50 ⁄ USH-250N
Pearlite ○ △ × - - × ○
400 ▪Good machinability HF-330 DWH-350 MG-350 G-50 ⁄ USH-350N
HF-350
HF-450
G-50 ⁄ USH-400N
HF-500 DWH-450
G-50 ⁄ USH-450N
350- HF-600 DWH-600
Martensite ▪Good wear resistance ○ ○ △ - × △ △ - G-50 ⁄ USH-500N
800 HF-650 DWH-700
MF-30 ⁄ USH-550N
HF-700 DWH-800
MF-30 ⁄ USH-600N
HF-800K
▪Good resistance to
13%Cr stainless 350- oxidation, heat and
○ △ ○ ○ ○ ○ △ HF-13 - - -
steel type 500 corrosion
▪Good wear resistance
500- ▪High toughness and
Semi-Austenite ○ ○ △ △ △ △ △ HF-12 - - -
700 good wear resistance
▪High toughness and
150- good impact wear
13%Mn × ○ × △ × × ◎ HF-11 DWH-11 - -
500 resistance
High Mn ▪High work hardenability
Austenite
▪High hardness at high
16%Mn- 200-
temperatures ○ △ ○ ○ ○ ○ ○ HF-16 DWH-16 - -
16%Cr 400
▪High toughness
▪Excellent erosion
600- resistance DWH-30
High Cr-Fe △ ◎ ◎ × ○ ○ × HF-30 - -
800 ▪Good resistance to DWH-30MV
corrosion and heat
800- ▪Excellent resistance to
Tungsten carbide type × ◎ × × × × × HF-950 - - -
1200 heavy abrasion
Note (1) MTM: Metal-to-metal wear, ABR: Abrasion, HTW: High temp. wear, CAV: Cavitation,
COR; Corrosion wear, HRT: Heat resistance, IMP: Impact wear
◎: Excellent resistance, ○:Good resistance, △: Slightly inferior, ×: Inferior,
-: Not used for general application
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Shielded Metal Arc Welding, Flux Cored Arc Welding, Gas Metal Arc Welding
For Hardfacing
█ Tips for better welding results
4) Postweld heat treatment:
Common to individual welding processes Postweld heat treatment (PWHT) at 550-750°C is effective to prevent cold cracking and distortion in
service, and to improve properties of the welds. It is important to set the PWHT conditions taking into
Important points in hardfacing are to obtain sufficient hardness and to minimize cracking. In order to account that the hardness of the weld is normally decreased by PWHT.
achieve them, proper selection of welding consumables and proper welding procedures mentioned
below are necessary. 5) Underlaying:
Underlaying is effective to prevent cracking in welds where low-alloy steel having high hardenability is
1) Preparation of base metal: hardfaced or where high-hardness weld metal is deposited on carbon steel. For underlaying, mild steel
Rust, oil and soil attached on the base metal may cause blowholes. Cracks in the base metal may type welding consumables or austenitic stainless steel type welding consumables should be used.
cause cracking of the weld metal; therefore, they must be removed completely beforehand.
6) Penetration:
2) Preheat and interpass temperature: In hardfacing, the properties of the weld metal will considerably be affected by welding penetration into
In order to minimize cracking, control of preheat and interpass temperature is a key technique. Table 1 the base metal, because the chemical composition of the welding consumable is generally very
shows a rule of thumb for proper preheat and interpass temperatures in relation to the carbon different from those of the base metal. In order to use sufficiently the desired properties of the welding
equivalent of the base metal. In practice, size of work, type of welding consumable and method of consumable, welding penetration must be controlled by using an appropriate welding procedure, for
hardfacing should be taken into consideration to determine the most appropriate temperatures. instance, multi-layer welding.
7) Welding distortion:
Table 1 A rule of thumb for preheat and interpass temperature in relation to Intermittent and symmetrical welding sequences are effective to minimize welding distortion. Restraint
base metal carbon equivalents of the work is also effective to minimize welding distortion.
Carbon Preheat and interpass
Type of steel (1)
SMAW
equivalent temperature (°C)
Less than 0.3 100 max.
0.3-0.4 100 min. 1) Control the arc length as short as possible.
0.4-0.5 150 min. 2) Use the backstep method for arc starting to prevent blowholes.
Carbon steel and 3) Control the weaving width less than 3-4 times the diameter of a covered electrode.
0.5-0.6 200 min.
Low alloy steel 4) Re-dry covered electrodes before use.
0.6-0.7 250 min.
0.7-0.8 300 min.
Over 0.8 350 min. FCAW, GMAW
Use no preheat and cool
High-Mn steel (13%Mn steel) 1) Control shielding gas flow rates within 20-25 I/mm for general applications. Note that poor shielding
each weld pass with water
Use no preheat and control due to low flow rates and wind can cause blowholes and pits in the weld metal.
Austenitic stainless steel the interpass temperature 2) Refer to proper currents for individual wire sizes as shown in Table 2.
150℃ or lower
High alloy steel (e.g., High-Cr steel) 400 min. Table 2 Proper welding currents
Diameter Welding current
Type of wire Polarity
Note (1) Carbon equivalent = C + Mn/6 + Si/24 + Cr/5 + Mo/4 + Ni/15 (mm) (A)
1.2 DC-EP 120-360
DWH series
1.6 DC-EP 200-420
3) Immediate postweld heating: 1.2 DC-EP 120-320
Heating the weldment at 300-350°C for 10-30 minutes just after welding was finished is effective to MG series
1.6 DC-EP 200-420
prevent cold cracking. Control the temperature carefully, or the hardness of the weld will be decreased
by excessive heating.
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