Fluxfor steel bar electroslag pressure
welding
1 scope
This technology is applicable for
industrial and civil reinforced concrete structure in diameter 14~ 40mm ⅰ-ⅱ level
vertical or oblique (slant range 4:1) steel connections.
2 construction preparation
2.1 materials and equipment:
2.1.1 steel: steel grade, diameter must
conform to the design requirements, certificate and retest report of the
factory. Import steel chemical retest should also form, its chemical
composition requirements should be met, and solderability testing.
2.1.2 flux.
2.2.2.1 flux performance should meet the
requirements of GB5293 carbon fluxes for submerged arc welding. Flux model is
HJ401, commonly used for smelting high manganese high silicon fluoride flux
Silicon manganese or high and low fluoride flux.
2.1.2.2 flux should be stored in dry
warehouses, preventing moisture. If exposed to moisture, use ~ 300℃ before
baking 2H.
2.1.2.3 using flux recovery should remove
slag and impurities, and new flux and mix before use.
2.1.2.4 the flux factory certificate.
2.1.3 equipment:
2.1.3.1 Manual electro-slag pressure
welding equipment include: welding power source, control box, welding jigs,
solder tank and so on.
2.1.3.2 automatic electro-slag pressure
welding equipment (priority) include: welding power source, control box, box,
welding machine, and so on.
2.1.3.3 the welding power source. Fluxfor
steel bar electroslag pressure welding should use secondary no-load voltage is
high (over TSV) AC or DC power source. (General steel welding up to the
diameter of 32mm, 600A for welding power sources could be used; 32mm nm in
diameter and above steel welding, 1000A for welding power sources should be
used). When welding capacity is small, can also be used with smaller capacity
models, with the performance of the parallel use of two welding machines.
2.2 operating conditions
2.2.1 the welder qualification test of
welders must hold a valid certificate.
2.2.2 equipment should meet the
requirements. Welding fixtures shall have sufficient rigidity, maximum
allowable loads should move freely, convenient operation. Flux tank diameter
commensurate with welded steel bar diameter, not burned during the welding process.
Voltage meter, the time display should be equipped so that operators accurately
where the welding parameters.
2.2.3 power supply should meet the
requirements. When the supply voltage drops greater than 5% are not suitable
for welding.
2.2.4 site safety measures, formulation and
implementation of safety measures, strengthen the protection of welders,
prevent the occurrence of Burns, electric shock, fire, explosion and burn
machines such as accidents.
2.2.5 Note header location, pay attention
to the same percentage of the sector in the joint area of steel, not in line
with the concrete structure construction and acceptance specification of the
relevant provisions of the regulations, to resize the header location before
welding.
3 operational processes
3.1 process:
Bar end preparation check the device, power
supply →
→ options → install the welding parameters welding fixtures and steel →
Place wire balls (can also be omitted) → place flux
filling, filling the flux → try welding → welding parameters were determined for specimens →
Welding flux → recovery → → remove fixture
quality checks
3.1.1 electroslag welding process:
The circuit arc arc process → → → → the electroslag
process squeezing power
3.2 check the device, power supply to
ensure that at any time in the normal state, do not overload.
3.3 bar end preparation:
Reinforcement before installing welding and
electrode contact jaw (150mm sections) of reinforcing steel bar rust, grease,
and other debris on the surface should be clean, end if bent, twisted, or
straightening should be removed, but not with hammer straightening.
3.4 selecting welding parameter:
Welding of steel bar electroslag pressure
welding parameters include: welding time and welding current and welding
voltage, see table 4-23.
Different diameter steel welding, select a
parameter by small diameter bars, weld time about 10%.
3.5 installing the welding fixtures and
steel: fixture end part under the lower jaw should be clamped in place, usually
lower-1/2 solder pot height 5~10MM, to ensure that the welds of flux there is
enough depth of submergence.
After the steel bar into the clamp JAWS on,
starting point of alignment clamp head, the upper and lower steel welds on the
same axis,
Steel bar electroslag pressure welding
parameter table 4-23
Welded steel welding voltage (v) weld time
(s)
Diameter
(Mm) current
(A) electric arc processes
U2-1 of electroslag process
U2-2 arc
T1 electroslag process
t2
16 200~250 40~45 22~27 14 4
18 250~300 40~45 22~27 15 5
20 300~350 40~45 22~27 17 5
22 350~400 40~45 22~27 18 6
25 400~450 40~45 22~27 21 6
28 500~550 40~45 22~27 24 6
32 600~650 40~45 22~27 27 7
36 700~750 40~45 22~27 30 8
40 850~900 40~45 22~27 33 9
Before clamping bars.
Bar clamp, to prevent shaking, so that the
upper and lower steel fixture deformation and dislocation.
3.6 deposit arc wire balls (or omitted).
Place flux tank, filling the flux.
3.7 test weld, as a specimen, determines
the welding parameters: in advance of the official steel bar electroslag
pressure welding, try welding and the welding parameters must be selected in
accordance with a specimen to test in order to determine the reasonable
parameters. After passing the official production. When using semi-automatic
and automatic welding equipment, should be determined in accordance with the
parameters set the device control data, to ensure that the quality of welded
joints.
3.8 welding operation.
3.8.1, arc closed loop: the joystick or the
switch on the control box, turn on welder the welding current circuit and power
input circuit and ignite the arc between the end and start welding.
3.8.2 arc: after ignition arc, should
control the voltage value. Take ribs joystick keep a certain distance between
the upper and lower end, delay the process of arc, flux continuous melting and
forming the necessary depth of slag pool.
3.8.3 electroslag process: then send
reinforcement, so that the upper end of slag pool are inserted, the arc goes
out into the electroslag process delays, the accelerated melting of steel
section.
3.8.4 squeezed off: end of electroslag
process and quickly send reinforcement, which end with end surfaces to touch
each other and hot removal of slag and molten metal. And cut off the power.
3.8.5 welded should stop after the 20~30s
(when welding in cold area, rest time shall be extended appropriately),
recycled solder and remove the welding fixture.
3.9 quality checks: in the production of
steel bar electroslag pressure welding, welders should be carefully performing
a self-test, if eccentric, bend, burn, weld package full weld defects such as,
excision of joint welds and find out why, to eliminate. Remove connector should
be removal of the heat-affected zone of steel, away from the weld is
approximately 1.1 times times the bar diameter within the length of the part
should be removed.
4 quality criteria
4.1 guarantee project;
4.1.1 the variety and quality of steel
bars, you must comply with the design requirements and the relevant provisions
of the standards.
Note: imported rebar should first undergo
chemical testing, welding, comply with the relevant requirements before they
can weld.
Inspection method: quality inspection
certificate and test report.
4.1.2 steel specifications, weld joint
location, within the same section of a joint bar area percentage, you must meet
the requirements of specification for design and construction.
Inspection method: observation or standard
checks.
4.1.3 the mechanical properties of
electro-slag pressure welding testing must be qualified.
Mechanical property testing and cut
randomly from each connector 3 Connector for tensile test.
4.1.3.1 the general structure, with 300
level splices as a batch.
4.1.3.2 reinforced multilayer structure,
with each floor or splices at the same level as a number of construction
sector, still less than 300 joints as a batch.
Inspection method: check the weld sample
test report.
4.2 basic items: steel bar electroslag
pressure welding should be carried out by a Visual inspection result shall
conform to the following requirements:
4.2.1 welding package is uniform,
highlights at least above the bar surface 4mm.
4.2.2 electrode contact with the bars, no
obvious burn problems.
4.2.3 joint bending angle of not greater
than 4 °.
4.2.4 joint axis offset should be less than
0.l times the bar diameter and not more than 2mm.
Visual inspection failed joints should be
cut off welding, or to take remedial action.
Inspection method: Visual observation or
measurement.
5 finished product protection
Welded should stop 20~30s to remove the
fixture to avoid joint bent.
6 quality problems to be noticed
6.1 in the production of steel bar
electroslag pressure welding, should be attached to any part of the welding
process. Joint should be cleaned; steel installation should be unity; fastening
fixture to prevent shaking; arc processes to reliable arc process delay full,
electroslag process short and stable extrusion process, appropriate pressure.
If abnormal. 4-24 find out why should refer to table and cleared in a timely
manner.
6.2 electro-slag pressure welding can be
carried out at the negative temperature conditions, but when the ambient
temperature is below-20 ℃, it would be inappropriate for welding.
On rainy days, snowy days should not be a
welding must be when welding, covered measures to be effective. Not cooling
after welding joints, encountered snow and ice should be avoided.
7 quality records
This standard shall meet the following
quality records:
Steel quality certificate or test report
7.1.
7.2 flux certification.
7.3 steel mechanical properties the second
interview report.
7.4 import steel chemical composition and
solderability test report the test report. Domestic steel processing occurs
during brittle fracture is obviously not normal, poor welding performance and
mechanical properties, chemical composition inspection report.
7.5 splices in tensile test report.
Electroslag welding weld defects and
prevention measures table 4-24
Welding defect prevention
1. the straightened end part
2. install clamps and bars
3. avoid too much squeezing force
4. timely repair or replacement fixtures
1. the straightened end part
2. install and support reinforcement
3. after welding to avoid the quick release
clamp
4. repair or replacement fixtures
3
Welding thin, large 1. Reducing the top
pressure speed
2. reduce the welding current
3. reduced welding time
1. reduce the welding current
2. shorten the time of welding
3. pay attention to the starting point for
the upper jaw to ensure steel extrusion on
5
No welding
1. increasing the welding current
2. avoid weld time too short
3. repair fixtures to ensure steel on send
free
6
Uneven welding package
1. reinforced face to smooth
2. filling the flux uniformity
3. extended welding time increasing melting
capacity
7
Stomata
1. According to the required baking flux
2. welded parts rust
3. ensure that the buried depth of welding
flux in
1. reinforced conductive parts away rust
2. clamping bars
1. completely sealed flux tank leak
2. avoid fast recovery after welding fluxes
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