Horizontal reinforcement construction technology of narrow-gap welding

Horizontal steel narrow gap welding

1 scope

This technology is applicable to industrial and civil reinforced concrete structure in the 20mm and above level ⅰ and ⅱ in hot-rolled 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 electrodes: welding rod trademark should comply with the design requirements. Design provided shall comply with the requirements in table 4-17, welding quality should meet the following requirements:

Table 4-17 of grades of steel used by arc welding electrode

Steel level narrow-gap welding

1

2

3 grade

ⅱ

Grade III E5003

E5016

E6016—D1

Note: does not contain heat treatment of grade ⅲ steel.

2.1.2.1 Administration should be no defects such as cracks, pores, uneven skin, and may not have the eccentricity of the naked eye can see.

Welding in 2.1.2.2, stable arc, coating melts evenly, dropping the main block.

2.1.2.3 electrode drying must according to the electrode manufacturer's instructions before use.

2.1.2.4 electrode must have a factory certificate.

2.1.3 equipment

2.1.3.1 welding: welding power sources can use styling products on the market, its size should have access to 300A, no-load voltage 75V and above.

2.1.3.2 u-shaped copper: u-shaped copper from copper, limited support, fastening device consisting of a special die. U-shaped copper copper plate available to suppress or copper rods manufactured by, electrolytic copper casting can also be used after a little processing. Die sizes should be commensurate with the welded steel bar diameter. Similar to that of a copper is suitable only for two diameter steel welding. Copper must be of a certain thickness and volume.

2.1.3.3 other equipment: cables, electrode holders, welding masks, pads, wire brushes, non-toothed saws etc.

2.2 operating conditions:

2.2.1 the welder must have a valid test certificate.

2.2.2 fitting location should be in order.

2.2.3 power supply should meet the requirements.

2.2.4 site safety facilities should, as well as fire protection and ventilation measures necessary to prevent the occurrence of accidents such as burns, electrocution, poisoning and fires.

2.2.5 familiar with the drawings, technical clarification.

3 operational processes

3.1 process

Check device → selection → welding parameters welding test for simulated specimens → send → test determines the welding parameters →

Welding → quality control

3.2 check the power supply, welding machines and tools: good contact welding ground should be reinforced to prevent arcing and burning steel.

3.3 selection of welding parameters according to diameter reference table 4-18 selection of welding parameters.

Horizontal steel bar welding parameters for narrow gap welding 4-18

Bar diameter (mm) clearance (mm) electrode diameter (mm) welding current (a)

20 10~12 3.2 100~110

22 10~12 3.2 100~110

25 12~14 4.0 150~160

28 12~14 4.0 150~160

32 12~14 4.0 150~160

36 13~15 5.0 220~230

40 13~15 5.0 220~230

3.4 welding test, simulated specimens: in each batch of steel before welding, welding 3 simulated specimen tensile testing, after passing the test, set welding parameters can be mass-produced.

3.5 welding operation:

3.5.l end surface should be smooth, surface and perpendicular to the axis. Steel using tooth saws or pneumatic welding special cutting machine cutting. Steel welded parts of the rust, oil dirt, water and needs cleaned up.

3.5.2 steel fastening devices fixed firmly, should die on both sides of the axis line to prevent axial-inclination or bend joints defects.

3.5.3 steel narrow gap welding, the process is as follows: first step, insert an electrode clearance side bar at the bottom end ignition arc and reinforcement end full penetration took metals and molten pool of more than 1/2 clearance. Then, arc moves to the bottom end on the other side of the gap. Repeat the above welding. If necessary, alternate to welding metal molten pool integrated in a timely manner, complete base weld welding. The second step, Rod shipped in the gaps around the arc, continuous sequence, gradually deposited metal to fill gap end 4/5 high. The third step, after welding to weld thick 4/5, weld gradually widen, if necessary, change

Continuous welding for intermittent welding, to avoid overheating. Weld reinforcement should be less than 3mm, and gentle transition to the steel surface.

3.5.4 remove mold. According to the temperature determines time of stripping. Summer open die after welding ends 3min, 5min after form removal in winter. 10 deg also covered arc-shaped metal cover plate or rock wool thermal insulation. Premature removal can cause the weld to lose heat insulation and joints become brittle.

3.6 quality checks: welders in welding production should be carefully one by one joint performing a self-test, if defects are found, should find the cause to eliminate, failed and irreparable joints should be removed after the heat-affected zone of welding.

4 quality criteria

4.1 project:

4.1.1 the variety and quality of the steel, electrode grades, performance, 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.

Inspect; check the factory certificate and test report.

4.1.2 the specification, location of the welded joint of steel bars, the same percentage of area within a segment of joint reinforcement, must meet the requirements of specification for design and construction.

Inspection method: observation or standard checks.

4.1.3 the mechanical properties of narrow-gap welding testing must be qualified.

Mechanical property testing and cut randomly from each connector 3 connector tensile test; according to project needs, can also take the 3 connectors for bending test.

Welding conditions in factories, to 300 joint type, with levels of splices for a number of.

In field conditions, each to the two floors with 300 in the same connector type, with steel connector level as a group, when there are less than 300, still as a batch.

Inspection method: check the weld sample test report.

4.2 basic item: horizontal bars narrow gap welding should be carried out by a Visual inspection result shall conform to the following requirements:

4.2.1 joint seams shall be full, no cracks, no depth greater than 0.5mm of undercut.

4.2.2 the joint axis deviation must not exceed 0.1 times times the bar diameter and not more than 2mm.

4.2.3 bending of the joints is not greater than 4 °.

4.2.4 joint weld is 2~3mm.

4.2.5 weld porosity and slag in number and size of all the welds on the surface does not exceed 2 and 6mm2.

Visual inspection failed joints, repair or reinforcement may be submitted after the second inspection. No connector cannot remedy should be removed after the heat-affected zone of welding.

Inspection method: Visual observation or measurement.

5 finished product protection

Pay attention to the protection of steel skeletons you have binding, not randomly stepped on to dismantle it, non-stick oil, removed during the construction of the skeleton should be carefully repaired to ensure steel skeleton reinforced in the correct position.

6 quality problems to be noticed

6.1 should take the shortest possible arc welding, to avoid holes.

6.2 has a direct effect of welding current on weld, brittle organizations make the weld current is overheating, small currents can produce pores, inclusions, incomplete penetration defects. To select the appropriate current when welding, and maintain the current stability.

6.3 welding a great influence on the quality, qualified welding rod should be used. Welding ⅱ and ⅲ class reinforced using electrodes of low-hydrogen alkaline welding before welding, electrode be baked according to the manufacturer's instructions, and put the insulating tube spare. Insulation tube into the site after receiving the electric welding machine, keep the inside temperature is 150 degrees centigrade. Welding electrode using 1 get 1, cold electrodes can be baked again, but not baking the 3rd.

6.4 rainy, snowy and foggy days do not allow open-air welding.

6.5 in the ambient temperature is below-5 ° c under conditions of welding for reinforcing bars at low temperature welding, cold welding, the welding current increases slightly.

7 quality records

This standard shall meet the following quality records:

Steel quality certificate or test report 7.1.

7.2 steel mechanical performance test report.

7.3 import steel chemical composition and solderability test report the test report. Made in steel in the process of brittle fault, poor weldability and mechanical properties significantly abnormal, chemical composition inspection report.

7.4 tensile test for steel joint report.

7.5 welding electrode factory certificate.

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