CN105643137A

CN105643137A - Flux-cored wire for 9Ni steel gas shielded welding and welding metal

Info

Publication number: CN105643137A
Application number: CN201410730435.1A
Authority: CN
Inventors: 潘登
Original assignee: Haining Ruiao Metal Technology Co Ltd
Current assignee: Haining Ruiao Metal Technology Co Ltd
Priority date: 2014-12-05
Filing date: 2014-12-05
Publication date: 2016-06-08

Abstract

The invention discloses a flux-cored wire for 9Ni steel gas shielded welding and welding metal. The flux-cored wire is composed of a metal skin and inner powder. The powder comprises, by weight, 5-25% of molybdenum powder, 5-20% of ferrochromium, 0.50-10.0% of ferromanganese powder, 1.0-10% of ferrotitanium powder, 1.0-10% of potassium fluoride, 0.2-1.5% of sodium carbonate, 0.1-1.5% of potassium oxide, and the balance other alloy. The welding metal prepared by Ar+CO2 mixed shielding gas shielded welding and used for a welding connector comprises 0-0.05% of C, 0.05-0.25% of Si, 1.0-3.5% of Mn, 0-0.008% of P, 0-0.005% of S, 5-15% of Cr, 5-20% of Mo, 5-12% of Fe, 0-0.01% of Nb, and the balance Ni. The tensile strength of the welding metal is greater than or equal to 700 MPa, and the impact toughness of the welding metal at minus 196 DEG C is greater than or equal to 100J.

Description

9Ni steel gas shield welding flux-cored wire and weld metal

Technical field

The invention belongs to field of welding material, particularly relate to a kind of low temperature 9Ni steel gas shielded welding flux-cored wire and weld metal.

Background technology

Along with gradually decreasing of traditional fossil energy resource, receiving extensive concern with the clean energy resource that liquefied natural gas (LNG) is representative, its ratio in energy consumption structure gradually steps up, and has therefore driven LNG to store the development with transportation equipment. LNG storage tank is typically under the cryogenic conditions of-162 DEG C to use, generally adopt 9Ni steel making for the tank body stored.

During current tank body is built, being generally adopted manual electric arc welding, TIG and submerged-arc welding and carry out the construction welding of 9Ni steel, stick electrode has American Standard AWS5.11NiCrFe-2, NiCrMo-6, four trades mark of NiCrFe-9 and NiMo-8, welding wire for submerged-arc welding has two trades mark of AWSA5.14NiCrMo-3 and NiMo-8.

Flux-cored arc welding can realize all-position welding, and welding efficiency is high, therefore instead of stick electrode arc welding gradually in fields such as shipbuildings. But contain higher oxygen content owing to flux-cored arc welding joint is compared to the welding point that other welding method obtains; the heat cracking sensitivity of Ni-based system weld metal can be increased; and reduce low-temperature flexibility; thus affecting quality of weld joint, limiting flux-cored wire gas and protecting the application being welded in 9Ni steel.

So far, 9Ni steel gas shield welding is rarely had to connect the report with flux-cored wire application.

Summary of the invention

For the deficiencies in the prior art, it is an object of the invention to provide a kind of flux-cored wire used for gas shield welding suitable in 9Ni and weld metal, use the tensile strength >=700MPa of weld metal that this welding wire prepares;-196 DEG C >=100J; can realizing all-position welding, welding bead molding is good, zero defect.

For achieving the above object, present invention employs following technical scheme:

Flux-cored wire is rolled formed by metal sheath and internal core material; Metal sheath, by weight percentage, including: C��0.03%, Ni20-80%, S��0.01%, P��0.01%, surplus is other alloy and inevitable impurity; Described medicated powder includes: molybdenum powder 5-25%, ferrochrome 5-20%, ferromanganese powder 0.50-10.0%, titanium-iron powder 1.0-10%, potassium fluoride 1.0-10%, sodium carbonate 0.2-1.5%, potassium oxide 0.1-1.5%, other oxide and fluoride 0.5-5.5%, other alloy 5-25%.

It occur frequently that the heat cracking caused due to element segregation in nickel-base alloy system weld metal cooling procedure after welding. Result of study in recent years shows, crack sensitivity is relevant with the fragility solidification temperature region (BTR) of weld metal, and predicts heat cracking sensitivity by its size, and accuracy rate is higher.

BTR (K)=38.7+358.7*C+29.3*Si-0.3*Mn+212.7*P+330.8*S+2.6*Cr+1.0*M o+14.5*Nb+2.9*Fe, wherein constituent content adopts percentage by weight, and BTR numerical value big explanation crack sensitivity is big.

The sensitivity coefficient of C, P and S is maximum three, therefore strictly to control its content in flux-cored wire and weld metal, to suppress weld crack to produce, improves welding quality;

Meanwhile, Alloying Design is being carried out while improving weld metal intensity and low-temperature flexibility, will avoid adopting the alloy design of Si and Nb.

Flux-cored wire inner core powder proportioning and content illustrate as follows:

Adding molybdenum powder and can be effectively improved intensity and the low-temperature flexibility of weld metal, mechanism is by reducing austenite phase transition temperature and refinement transformation tissue. Molybdenum interpolation simultaneously is also beneficial to reduce fire check sensitivity, improves quality of weld joint, and its preferred proportion is 5-25%.

Adding ferrochrome powder to be mainly used in improving weld metal intensity, with the reasonably combined key being to control weld metal intensity and low-temperature impact toughness of molybdenum, its preferred proportion is 5-20%, and its content must not be higher than molybdenum powder.

Adding ferromanganese powder is improve the Mn content in weld metal further, reaches to improve the purpose of intensity and toughness. Manganese and nickel are to expand austenitic area element simultaneously, add a certain proportion of manganese and are conducive to the austenite structure of weld seam stabilizing metal, and its preferred proportion is 0.5-5.0%.

Adding titanium-iron powder, being utilize Ti element metallurgical reaction to occur in welding pool, forms dystectic slag, thus improving the welding technological properties of its all-position welding; Guarantee pore-free and slag inclusion on the one hand, improve the surface quality of welding bead on the other hand, it is preferable that its content is 1.0-10.0%.

Add potassium fluoride mainly for generation of fluorion, and react with the hydrion in welding process, to reduce the residual hydrogen of weld metal, it is preferable that its content is 1.0-10.0%.

Add potassium oxide and sodium carbonate is mainly used in controlling arc stability, it is preferable that content is 0.2-1.5% and 0.1-1.5% respectively.

The element of the weld metal that the gas shield welding adopting above-mentioned welding wire prepared connects and content illustrate as follows:

C, P, S and Nb are impurity or base metals dilution introducing, and its content is less than 0.05%, 0.008%, 0.005% and 0.01% respectively.

Ti is mainly used in welding pool deoxidation, has material impact for controlling droplet shape, fusion penetration and welding bead surface quality, and when content is higher than 1.0%, weld metal viscosity is relatively big, and popular reduction is unfavorable for welding quality control, and processability reduces; When its content is lower than 0.05, the mobility of weld metal is better, is unfavorable for overhead welding and vertical downward weldering. It is therefore preferable that its content is 0.05-1.0%.

Si is mainly used in, with Ti, welding pool is carried out combined deoxidation, impact is had for improving weld metal mobility, droplet transfer behavior and slag blanket structure, it is unfavorable for that fire check sensitivity controls when Si too high levels, the de-slag on welding bead surface then it is unfavorable for, it is preferable that its content is 0.05-0.25% when but being below 0.05%.

Mn is mainly used in strengthening weld metal, belongs to austenitic area together with Ni and expands element, can partly replace Ni and add, and owing to its price is one of 1/6 of Ni, therefore from cost angle, interpolation Mn replaces Ni superiority;But meanwhile, Mn, Si and Ti has together decided on weld metal deoxidation, droplet transfer behavior and slag blanket structure, and welding technological properties is had a direct impact, it is thus preferred to its content is 0.8-3.5%.

Cr and Mo is used for strengthening weld metal, belongs to ferrite area and expands element, and both and the solidification behavior of Ni Resistance of Weld Metal, phase in version and segregation have material impact; The above two are unfavorable for low-temperature flexibility and fire check sensitivity, and the latter is expensive, and the above two content and ratio determine the intensity of weld metal, toughness and fire check sensitivity, it is preferable that content is 8-3.5% and 5-12% respectively.

Fe is introduced by mother metal weld dilution, it is preferable that content is 5-12%.

Other alloy 0.5-5.0%, for increasing weld metal intensity further, increases welding technological properties.

The metal sheath of flux-cored wire of the present invention is made through operations such as smelting, continuous casting and rollings; Then require preparation medicated powder in proportion, and medicated powder is wrapped up with metal skin, rolls, be drawn into the welding wire of certain diameter; Then carry out gas shield welding to connect test, can be prepared by weld metal, it may be achieved all-position welding, and the intensity of weld metal and excellent in low temperature toughness.

Compared with prior art, welding wire of the present invention beneficial effect at least that:

1. providing to low temperature 9Ni steel and a kind of realize the flux-cored wire that all positon gas shield welding connects, welding quality stable is reliable;

2. adopt the outside foreskin of high alloy content, the strict control of C, S and P, ferro-titanium powder to add, by reducing brittle transition temperature interval and TiO₂It is the design of high-melting-point slag, it is achieved that all-position welding, and welding quality is good, welding bead surface quality is good;

3. have benefited from the design of Mo-Cr-Mn alloy so that the tensile strength >=700MPa of weld metal ,-196 DEG C of impact flexibility >=90J, it is achieved that wlding mates with the equal strength of mother metal steel plate.

Detailed description of the invention

Below in conjunction with preferred embodiment, technical scheme is further described.

Embodiment 1:

Adopting the metal sheath of thickness 0.8mm, its chemical composition contains: C0.01%, Ni52%, S0.003%, P0.006%, and surplus is inevitable impurity.

Described medicated powder includes: molybdenum powder 24%, ferrochrome 19%, ferromanganese powder 5.5%, titanium-iron powder 4.5%, potassium fluoride 2.1%, sodium carbonate 1.1%, potassium oxide 0.8%, and remainder is Fe and other alloy.

Through filling, roll, be drawn into the welding wire of diameter 1.2mm.

Test mother metal is 9Ni steel plate thick for 20mm, and its yield strength 588MPa, tensile strength 726MPa ,-196 DEG C of ballistic works are 122J.

Adopting above-mentioned welding wire and mother metal to carry out welding crack sensibility evaluation test, design parameter is as follows:

(1) bevel for welding is monolateral V-type, and angle is 60 ��, root face 10mm, and groove gap is 2mm;

(2) without preheating, downhand welding, stem elongation 20mm, protective gas is Ar+20%CO2 mixing gas;

(3) welding current respectively 160,200,240,280,320 and 360A; Speed of welding 8,16,24,32,40,48 and 56cm/min.

Postwelding is placed 48 hours, and then ultrasonic inspection does not find defect; Carry out metallographic observation from the section of face of weld down 1mm, 2mm position simultaneously, do not find the defects such as crackle.

Embodiment 2:

Adopting the metal sheath of thickness 0.8mm, its chemical composition contains: C0.01%, Ni60%, S0.003%, P0.006%, Cr18%, and surplus is inevitable impurity.

Described medicated powder includes: molybdenum powder 20%, ferrochrome 8%, ferromanganese powder 6.5%, titanium-iron powder 6%, potassium fluoride 2.4%, sodium carbonate 0.9%, potassium oxide 0.9%, titanium dioxide 3.5%, and remainder is other alloy.

Through filling, roll, be drawn into the welding wire of diameter 1.2mm.

Test mother metal is 9Ni steel plate thick for 30mm, and its yield strength 585MPa, tensile strength 726MPa, elongation percentage 21% ,-196 DEG C of ballistic works are 128J.

Adopting gas protection welding process, bevel for welding is bilateral V-type, and angle is 40 ��, without preheating, interlayer temperature��200 DEG C, vertical-up welding, multiple tracks multilayer welding; Welding current 170A, speed of welding 7.8cm/min, protective gas is Ar+20%CO₂Mixing gas.

Postwelding is placed 48 hours, and then ultrasonic inspection does not find defect.

Through inspection: the tensile strength of weld metal is 736MPa, and-196 DEG C of ballistic works are 106J.

Embodiment 3:

Adopting the metal sheath of thickness 0.6mm, its chemical composition contains: C0.015%, Ni55%, S0.004%, P0.007%, Cr6%, Mn1.6%, and surplus is Fe and inevitable impurity;

Described medicated powder includes: molybdenum powder 23%, ferrochrome 10%, ferromanganese powder 3.5%, titanium-iron powder 9.0%, potassium fluoride 3.8%, sodium carbonate 0.6%, potassium oxide 1.2%, titanium dioxide 3.2%, and remainder is other alloy.

Through filling, roll, be drawn into the welding wire of diameter 1.2mm.

Test mother metal is 9Ni steel plate thick for 38mm, and its yield strength 576MPa, tensile strength 718MPa ,-196 DEG C of ballistic works are 138J.

Adopting gas protection welding process, bevel for welding is bilateral V-type, and angle is 45 ��, without preheating, interlayer temperature��200 DEG C, and vertical downward welds, multiple tracks multilayer welding; Welding current 165A, speed of welding 7.2cm/min, protective gas is Ar+20%CO2 mixing gas.

Through inspection: the tensile strength of weld metal is 726MPa, and-196 DEG C of ballistic works are 112J.

Embodiment 4:

Adopting the metal sheath of thickness 0.8mm, its chemical composition contains: C0.015%, Ni35%, S0.004%, P0.006%, and surplus is Fe and inevitable impurity;

Described medicated powder includes: molybdenum powder 19%, ferrochrome 16%, ferromanganese powder 8%, titanium-iron powder 9.0%, potassium fluoride 7.2%, sodium carbonate 0.6%, potassium oxide 1.5%, other oxide and fluoride 4.5%, and remainder is iron powder and other alloy.

Through filling, roll, be drawn into the welding wire of diameter 1.2mm.

Test mother metal is 9Ni steel plate thick for 24mm, and its yield strength 592MPa, tensile strength 754MPa ,-196 DEG C of ballistic works are 126J.

Adopting gas protection welding process, bevel for welding is bilateral V-type, and angle is 45 ��, without preheating, interlayer temperature��200 DEG C, downhand welding, multiple tracks multilayer welding; Welding current 260A, speed of welding 12.6cm/min, protective gas is Ar+20%CO2 mixing gas.

Through inspection: the tensile strength of weld metal is 736MPa, and-196 DEG C of ballistic works are 116J.

By above example; the weld metal adopting flux-cored wire of the present invention, utilizing gas shielded welding to prepare; tensile strength >=700MPa;-196 DEG C of impact flexibility >=100J; the welding manufacture of low temperature LNG storage tank 9Ni steel can be satisfied with, overcome heat cracking sensitivity and the technical barrier of low-temperature flexibility deficiency.

Claims

1. a 9Ni steel gas shield welding flux-cored wire, including metal sheath and internal medicated powder, it is characterised in that: by weight percentage, metal sheath composition includes: C��0.03%, Ni20-60%, S��0.01%, P��0.01%, surplus is other alloy and inevitable impurity;Internal medicated powder includes: molybdenum powder 5-25%, ferrochrome 5-20%, ferromanganese powder 0.50-10.0%, titanium-iron powder 1.0-10%, potassium fluoride 1.0-10%, sodium carbonate 0.2-1.5%, potassium oxide 0.1-1.5%, remainder is other alloy.

2. the weld metal of a 9Ni steel gas shield welding flux-cored wire, it is characterised in that: by weight percentage, the chemical composition of weld metal includes: C��0.05%, Si0.05-0.25%, Mn0.8-3.5%, P��0.008%, S��0.005%, Cr5-15%, Mo5-12%, Fe5-12%, Nb��0.01%, other alloy 0.5-5.0%, surplus is Ni.

3. the weld metal of the gas shield welding of flux-cored wire according to claim 2, it is characterised in that: tensile strength >=700MPa ,-196 DEG C of impact flexibility >=100J.