LOW ALLOY STEEL—FLUX CORED WIRE

1.SELECTION RECOMMENDATION：

According to AWS A5.29, low alloy steel flux cored wire can be classified, by characteristic, to T1, T4, T5, T6, T7, T8, T11, TG. These are to define welding position, shielding gas, polarity, single or multiple beads. If to be classified by weld metal, the classification is similar to covered electrodes. The features are as follows：

 

Classification	Characteristic	Group	Features
Carbon molybdenum steel	Heat resistant	A1	1.The heat resistance and anti-corrosion abilities increase because of adding 0.5%Mo, however the impact toughness decreases. 2.Suitable for the welding for steel plates of ASTM A204 or pipes of A355 P1.
Chrome molybdenum steel	Heat resistant	B1、B2、B3、B6、B8	1.The heat resistance and anti-corrosion abilities increase because of adding 0.5%~10%Cr - 0.5%~1.2%Mo, however the impact toughness decreases. 2.Suitable for the welding for steel plates of ASTM A387 or pipes of A213 or A335. 3.By using L grade consumables(e.g. B1L, B2L), the hardness of beads decreases because of low carbon, but high temperature strength and creep resistance decreases as well.
	Heat resistant	B9	1.The creep resistance under high temperature, anti-fatigue, and anti-corrosion abilities increase because of adding 9% Cr–1% Mo and minor Nb&V 2.Suitable for welding ASTM A387 Gr.91, A213 T91, and A335 P91. 3.The heat input, temperature control, and PWHT should be strictly managed.
Nickel steel	Low Temperature	Ni1、Ni2、Ni3	1.The material is with 1~3.5%Ni , and classified to 3 grades. With excellent impact toughness when the temperature ranges –73℃~room temperature. Not required PWHT for regular usage in case of high temperature brittle. 2.Suitable for the welding for steel plates of ASTM ASTM, A352 LC1, A352 LC2, A302 and A734.
Manganese Molybdenum Steel	Special purpose	D1、D2、D3	1.The material, with 1~2%Mn - 0.3~0.5%Mo, has better performance of tensile strength and impact toughness than Carbon molybdenum steel and Nickel molybdenum steel. 2.PWHT is required for D2 grade.
Nickel molybdenum steel	Special purpose	K1、K2、K3、K4、K5、K6、K7、K8、K9	1.The material, with 1.0~3.5%Ni – 0.2~0.5%Mo and minor V, is for high tensile strength under special circumstance. Normally used for requirement of high tensile strength and low temperature impact toughness, such as military or oil pipe. 2.PWHT is not required.
Atmospheric Corrosion  Resistant	Anti-pitting corrosion	W2	1.With 0.5%Ni – 0.5%Cr - 0.5%Cu, to improve Anti-pitting corrosion. 2.Designed for the welding of Atmospheric Corrosion Resistant steel (e.g ASTM A242 or A588)
Regular	Multi-classification	G	1. The material of G series requires that P, S, Si need to be under the upper limit, and for the other chemical composition, only need one of them meet the requirement of AWS.  2.The material composition of G series need to be confirmed and classified, in case of misuse.

 

 

 

2.Welding Operation:：

(1)Storage：

①This classification cannot be re-baked with high temperature like covered electrodes, so should be avoid stored in the environment of high temperature and humidity, and damage of packing. This can prevent the consumable from the moisture.

 

②Most flux cored wires are with seam, so the requirement of moisture resistance is more than seamless ones. If the storage environment of high temperature and humidity is unavoidable, the aluminum foil packing is recommended. 

 

 

(2)Note：

①The heat input and temperature of as weld for low alloy steel should be relatively stricter than carbon steel, to prevent the beads from crack and life reducing of assembly or equipment.

 

②If the surface of groove or base metal are not clear, there will easily be crack and porosity for beads. The pre-work need to be carried out. 

 

③The welding suggestion is that in workable situation, lower the current, stick-out-length, and the width of weaving, to prevent the alloy from burned and cell enlargement.