LB-52NSU日本神钢焊条 低合金低温钢高强钢焊条进口焊条进口焊丝

西安骏焊专业销售日本神钢焊条焊丝

4.1.  LB-52NSU

When pipe root pass welding must be conducted from outside rather than inside in order to form the back bead inside the pipe, GTAW or SMAW are generally favored. Kobe Steel has long marketed FAMILIARC™ LB-52U as well as FAMILIARC™ LB-62U for this purpose, and they still serve as Kobe’s most reliable, “one and only” products worldwide.

In addition to meeting the always-changing and diverse specifications of pipelines, TRUSTARC™ LB-52NSU has been developed specifically for root pass welding of pipes for low temperature service. It is a covered, low hydrogen type electrode equivalent to AWS A5.5 E7016-G. It offers superb notch toughness at -60°C and very low diffusible hydrogen content of about 3.0ml/100g. The chemistries, mechanical properties of all weld metal and diffusible hydrogen content of TRUSTARC™ LB-52NSU are shown in Tables 3, 4 and 5 respectively.

Table 1: Covered electrodes for girth welding

API 5L pipe grade	Welding pass	Low hydrogen type		High cellulose type
		Vertical upward position	Vertical downward position
X42-X52	Root	LB-52U LB-52NSU	LB-78VS	KOBE-6010
	Hot	LB-52-18 LB-52NS
	Filler & Cap
X56-X60	Root	LB-52U LB-52NSU		KOBE-6010 KOBE-7010S
	Hot	LB-52-18 LB-52NS		KOBE-7010S
	Filler & Cap
X65	Root	LB-52U	LB-88VS	KOBE-7010S KOBE-8010S
	Hot	LB-62 LB-62D
	Filler & Cap			KOBE-8010S
X70	Root	LB-62U		KOBE-7010S KOBE-8010S
	Hot	LB-62 LB-62D
	Filler & Cap			KOBE-8010S
X80	Root	LB-62U	LB-98VS LB-108VS	——
	Hot	LB-65D LB-106
	Filler & Cap
X100	Root	——	LB-118VS	——
	Hot	LB-80L LB-116
	Filler & Cap

Table 2: TIG and MAG wires for girth welding

API 5L pipe grade	Welding pass	Temperature (°C)
		-20	-40	-60
X42-X56	Root & Hot	TG-S50 MX-100T	TG-S1N MX-A55T
	Filler & Cap	DW-A50 DW-A50SR	DW-A55E DW-A55ESR	DW-A55L DW-A55LSR DW-A81Ni1
X60	Root & Hot	TG-S62	TG-S60A
	Filler & Cap	DW-A55E DW-A55ESR		DW-A55L DW-A55LSR DW-A81Ni1
X65	Root & Hot	TG-S62	TG-S60A
	Filler & Cap	DW-A55E DW-A55ESR		DW-A55L DW-A55LSR DW-A81Ni1
X70	Root & Hot	TG-S62	TG-S60A
	Filler & Cap	DW-A70L		DW-A55L DW-A81Ni1
X80	Root & Hot	TG-S80AM
	Filler & Cap	DW-A70L		——
X100	Root & Hot	TG-S80AM
	Filler & Cap	DW-A80L	——	——

Table 3: Chemistries of TRUSTARCTM LB-52NSU all weld metal (mass %)

C	Si	Mn	P	S	Ni	Ti	B
0.06	0.62	1.25	0.016	0.004	0.50	0.014	0.0027

Table 4: Mechanical properties of TRUSTARCTM LB-52NSU all weld metal

Tensile properties				Notch toughness
0.2% PS (MPa)	TS (MPa)	EI (%)	RA (%)	Absorbed energy:J (Brittle fracture: %)			FATT (°C)
				-80°C	-60°C	-40°C
511	598	32	78	43(60) 55(60) 41(60) Av.46(60)	44(55) 72(55) 58(52) Av.58(54)	70(50) 137(35) 144(35) Av.117(40)	-53

Table 5: Diffusible hydrogen content of TRUSTARCTM LB-52NSU (ml/100g)

Electrode dia (mm)	1	2	3	4	Ave.
3.2	2.8	3.3	3.5	3.0	3.2

Note: Tested method: According to AWS A4.3.(Gas chromatography)
            Welding current: 120 A (DCEP)
            Welding atmosphere: 21°C x RH10%

In welding a butt joint on a 25 mm thick plate, 3.2 mm dia. TRUSTARC™ LB-52NSU was used for the root pass with DC 95 amp, and 3.2 mm dia. TRUSTARC™ LB-52NS was used for the second pass onwards with DC 110 amp in the vertical upward position. The preheating and interpass temperatures were kept between 115 and 135°C. Figure 3 shows the groove shape and the pass sequence and Figure 4, the macrostructure of the weld metal. The chemistries and the tensile properties are shown in Tables 6 and 7, respectively and the notch toughness properties and the transition curve of the butt joint weld metal are shown in Table 8 and Figure 5, respectively. (Note: both TRUSTARC™ LB-52NSU and TRUSTARC™ LB-52NS are specified as AWS A5.5 E7016-G).

Table 6: Chemistries of butt joint weld metal (mass %)

Location	C	Si	Mn	P	S	Ni	Ti	B
Face	0.07	0.31	1.40	0.008	0.003	0.50	0.013	0.0022
Reverse	0.08	0.30	1.36	0.009	0.003	0.43	0.014	0.0023

Table 7: Tensile properties of butt joint weld metal

Location	Tensile properties
Center	0.2%PS (MPa)	TS (MPa)	El (%)	RA (%)
	506	577	25	81