Steel manual metal arc welding

1 scope

This technology is applicable to general industry and civil engineering in the manufacture and installation of manual metal arc welding of steel structure engineering.

2 construction preparation

2.1 materials and equipment:

2.1.1 electrode: the mode according to the design requirements, must have the certificate of quality. After baking before brazing as required. Prohibited the use of coating loss, cores rusty electrode. Designs provided, timely E43 series carbon steel welded Q235 steel welding rod welded 16Mn steel up E50 series low-alloy structural steel welding rod welding important structures for the times using the low hydrogen type electrode (basic electrodes). According to the manufacturer's instructions after baking, into the cooler, ad-taking. Alkaline and acid electrodes the electrode mixed use is not allowed.

2.1.2 arc: arc-Groove connection required, arc Groove configuration and material should be identical to the weld.

2.1.3 equipment: welding machine (AC and DC), welding wire, welding gun, mask, hammers, electrode oven, welding rods, wire brushes, asbestos insulation barrel, temperature sensors, etc.

2.2 operating conditions

2.2.1 familiar with the drawings, welding technology gives the low-down.

2.2.2 welding welder certificate should be checked before expiry, should demonstrate that the welder can bear the welding work.

2.2.3 power supply should meet the electricity requirements for welding on site.

2.2.4 environmental temperature below 0 ° c, Preheat, thermal temperature should be determined according to the test.

3 operational processes

3.1 process

Ready → arc welding (welding, welding, welding, Heng Yang-welding) → weld inspection

3.2 electric arc welding of steel structure:

3.2.1 flat welding

3.2.1.1 selecting appropriate welding electrode diameter welding current, welding, arc length, and so on, by welding procedure test.

3.2.1.2 clean up welding: welding, Assembly clearance check Groove whether it meets the requirements, solid welding, without oil, rust around the weld.

3.2.1.3 baking temperature of welding electrodes shall be in conformity with the provisions and time, remove the electrodes from the oven, placed within the electrode insulation barrel, ad-taking.

3.2.1.4 welding current: according to the thickness of weld, welding, welding type, diameter, welder's proficiency and other factors, appropriate choice of welding current.

3.2.1.5 arc: Arc Weld fillet weld ends, should be greater than 10MM, we should not make any arc, immediately after ignition arc welding rods away from the weld zone, arcing 2~4mm gap between electrodes and component. Docking weld and the docking and angle received combination weld, in weld ends set introduction arc Board and leads Board, must in introduction arc Board Shang introduction arc Hou again welding to weld district, Midway joint is should in weld joint ahead 15~20mm at sparking introduction arc, will welding pieces Preheat Hou again will electrode returned to weld starting at, put melt pool fill to requirements of thickness Hou, party can forward Shi welding.

3.2.1.6 welding speed: the speed requirement welding to ensure uniform thickness, width of weld from the mask in molten pool of molten iron and slag equidistant (2~3mm).

3.2.1.7 welding arc length: depending on the electrode type and determine, generally require a constant arc length, and acid electrodes are generally 3~4mm, basic electrode is generally 2~3mm.

3.2.1.8 welding angle: according to two welding pieces of thickness determine, welding angle has two Hooke′s joints surface, a is electrode and welding forward direction of angle for 60~75 °; II is electrode and welding around angle has two species situation, dang welding pieces thickness equal Shi, electrode and welding pieces angle are for 45 °; Dang welding pieces thickness ranging Shi, electrode and more thick welding pieces side angle should is greater than electrode and more thin welding pieces side angle.

3.2.1.9 arc: each seam welded to the end of the crater should be full, towards the direction of welding with arc in the opposite direction, the crater left in the weld case crater eat. Welding and ARC cutting resection should be used, and flat grinding, no hammer down.

3.2.1.10 cleaning: after the whole weld out clear the slag, welders self test (including appearance and dimension, and so on) without problems, before relocation to continue welding.

3.2.2 welding: basic operating processes and welding the same, but should pay attention to the following issues:

3.2.2.1 in the same condition, than flat welding current welding power supply 10%~15%.

3.2.2.2 using short-arc welding, arc length is generally 2~3mm.

3.2.2.3 electrode angle according to the weld thickness. Two pieces of equal thickness, welding rods and electrodes around angles to 45 °; when two unequal thickness, welding rods and thick weld one side of the angle should be greater than the thinner side of the angle. Welding rod should be vertical planes formed 60 ° ~80 ° angle, arc slightly upward, towards bath Center.

3.2.2.4 arc: when welded to the end of the line arc method fill crater, Central stop ARC ARC moved to the weld pool. Is prohibited to crater and swing to one side. In order to prevent the bites of meat, lower electrode arc transform angle perpendicular to the electrode and weld or arc blow slightly downward.

3.2.3 cross weld: same as the flat welding, welding current adjustment of welding current 10%~15% arc long 2~4mm. Electrode angle of horizontal position welding electrode should be downward-sloping angle of 70 ° ~80 ° to prevent drop of molten iron. According to the thickness of two different angle could adjust electrode, welding electrodes and welding direction was 70 ° ~90 °.

3.2.4 overhead welding: cross basic welding, welding the same angle between the electrode and weld, and weld thickness, welding electrodes and welding direction into a 70 ° ~80 ° angle, suitable for low current, short-arc welding.

3.3 welding of low temperature in winter:

3.3.1 in the ambient temperature is lower than 0 ℃ when arc welding conditions, in addition to complying with relevant provisions of normal temperature welding, you should adjust the welding parameters, the weld seam and heat-affected zone of slow cooling. Wind turbines more than 4 levels, measures should be taken from the wind; not cooling after welding joints, encountered snow and ice should be avoided.

3.3.2 to prevent weld cracking of steel structures, Preheat and Preheat to control temperature. When the place of work when the temperature is below 0 c should be studied in order to determine the appropriate preheating, heat temperature.

4 quality criteria

4.1 project

4.1.1 welding materials should comply with the design requirements and the relevant provisions of the standards, quality certificate, and records should be checked.

4.1.2 the welder must be approved by the examination, inspection certificates of welders welding conditions and examination dates.

4.1.3 level ⅰ and ⅱ welds shall be subject to inspection and should comply with the design requirements and the provisions of the code for construction and acceptance of, check the weld inspection reports.

4.1.4 weld surface ⅰ, ⅱ degree weld shall not crack, tumor, burn, weld crater and other defects. Grade welds without surface pores, slags, arc, arc pits, cracks, defects such as bruising, and class I weld shall not undercut, joints and other defects.

4.2 Basic project

4.2.1 weld appearance weld shape uniform, weld and weld, weld and base metal between the transition smooth, clean slag and spatter.

4.2.2 surface blowhole: ⅰ, ⅱ degree weld is not allowed; ⅲ seam weld in the allowed diameter ≤ 0.4t 50mm length and 3mm holes 2; hole spacing less than 6 times times the aperture.

4.2.3 undercut: class I weld is not allowed.

Grade seam: the depth of undercut ≤ 0.05t and 0.5mm in continuous length ≤ 100mm and undercut weld length total length ≤ 10% on both sides.

Grade seam: the depth of undercut ≤ 0.lt and ≤ LMM.

Note: t-joints with thin thickness.

4.3 allowable deviation, as shown in table 5-1.

Table 5-1

Tolerance (mm) test

Method of class ⅰ ⅱ ⅲ

Weld reinforcement b<20 0.5~2 0.5~2.5 0.5~3.5

1 butt welds (mm) b ≥ 20 0.5~3 0.5~3.5 0~3.5

<0.1T and <0.1T and <0.1T and welding

Less than 2.0 is not more than 2.0 are not greater than 3.0

Fillet weld size HF ≤ 6 0~+1.5 gap

2 fillet welds (mm) HF>6 0~+3

Weld reinforcement HF ≤ 6 0~+1.5 control

(Mm) HF>6 0~+3 test

3 combination welding t-joint, joints, corner joints >t/4 check

Fillet weld size lifting capacity 50T, intermediate working crane beams t-joint t/2 and Michael Jackson-10

Note: b-width, t-joints with thin thickness, HF for fillet weld size.

5 finished product protection

5.1 welding allowed to hit after hit joint, don't just finished welding the steel of watering. Low temperature slow cooling measures should be taken.

5.2 no free on material outside the weld arc.

5.3 members just before the welding and shall not move the horns and clamps to avoid causing component tolerances. Hidden parts of the weld must finish handling covert acceptance procedures, can be carried out under the covert operations.

5.4 low temperature welding no immediate cleaning, weld after cooling.

6 quality problems to be noticed

6.1 size exceeds the allowed deviation: lack of length, width, thickness of the seam, centerline offset bending deviation, should strictly control the relative position of welds, qualified before welding, welding careful operation.

6.2 weld cracking: in order to prevent cracks, you should select a suitable welding parameters and welding procedures, avoid high amperage, not stalling, weld joints should be taking 10~15mm, wood allows moving, percussion welding in the welding.

6.3 surface porosity: the electrode according to the required temperature and time to bake, welding area must be cleared, select the appropriate welding current during welding, reduced speeds, the escape of gas in molten pool full.

6.4 weld slag: multi-layer welding slag should be layers clean up operation times right, arc length is appropriate. Note the slag flow direction, when adopting a basic electrodes, keep slag in slag on the back.

7 quality records

This standard shall meet the following quality records:

7.1 welding materials quality certificate.

7.2 certification of welders and a serial number.

7.3 the welding procedure test report.

7.4 welding quality inspection reports and inspection reports.

7.5 design changes, record of negotiation.

7.6 conceal engineering acceptance record.

7.7 other technical documents.