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 b 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 bl 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 b	Vertical downward b
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 bl (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 bl

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 b: 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 b. 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 bl. 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 bl 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 bl (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 bl

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