1 scope
This technology is applicable for industrial and civil construction steel bars and submerged-arc welding.
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. Embedded parts of the anchor fluke ⅰ and ⅱ steel bar. Bars should be no old rust and grease.
2.1.2 steel: embedded parts of steel shall not crack, rust, marks, deformation, its dimensions and mechanical properties, the design requirements.
2.1.3 electrodes: welding rod trademark should comply with the design requirements. Design provided shall comply with the requirements in table 4-14, welding quality should meet the following requirements:
Table 4-14 of grades of steel used by arc welding electrode
Steel level lap welding, welding Groove
1 I E4303 E4303 E4303
2 E4303 II E4303, E5003
3 grade ⅲ E5003 E5003 E5503
4 ⅰ, ⅱ and welded steel E4303
Note: no 25MnSi bar.
2.1.3.1 coating defects such as cracks, pores, uneven, and may not have the eccentricity of the naked eye can see.
2.1.3.2 the welding process, stable arc, coating melts evenly, dropping the main block.
2.1.3.3 electrode drying must according to the electrode manufacturer's instructions before use.
2.1.3.4 electrode must have a factory certificate.
2.1.4 arc welding machine, welding cable, welding clamps, masks, cutting, wire brushes, RASP, hammer, steel codes and so on.
2.2 operating conditions:
2.2.1 the welder must hold the examination certificate.
2.2.2 dimensions, Groove, steel head clearance, should comply with the provisions of joint and steel axis.
2.2.3 power supply should meet the requirements.
2.2.4 site has security protection facilities, 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 exchanges.
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 selecting welding parameter. According to steel grade, diameter, joint type and position, select the appropriate diameter of electrode and welding current, welding layers to ensure fusion of weld metal and steel good.
3.4 welding test, a simulation test. In each batch of steel before welding, welding 3 simulated specimen tensile testing, after passing the test, can determine the mass production of welding parameters.
3.5 welding operation:
3.5.1 arc: joints with pads or help, arc should be carried out on plates or help. No pads or no splices, Arc Weld can be formed in part to prevent burn main bar.
3.5.2 positioning: brazing welding before welding anchor again.
3.5.3 weaving: weaving of straight-forward, swaying and sent to the electrode of the three actions to coordinate smooth.
3.5.4 arc: when arc and weld pool should be filled, when you pull out the arc and weld pool should be filled, be careful not to cause arc on the working surface scrapes.
3.5. more than 5 layers: a larger diameter, when the need for multi-layer welding should be layered discontinuous welding, after each welding layer should be cleaning before welding the next layer. Should ensure that the height and length of the weld.
3.5.6 Fusion: welding process should have adequate penetration. Main seams and tack combining well to avoid porosity and slag inclusion defects and burn, and the formation of cracks.
3.5.7 flat: flat note when welding slag and hot metal mixed phenomena, preventing the flow in front of molten iron molten slag. Weld pool should also be controlled into an oval, generally use the right welding electrode and the work surface into a 70 °.
3.5.8 welding: vertical welding, hot metal and slag easily separated. To prevent the molten pool temperature is too high, fall of hot metal forming-welding, and when perpendicular to the electrode and surface forming 60 ° ~80 ° angle. The arc slightly upward, towards bath Center. When weld first should arc up weaving, while for a small sway, the rest of the layer with a semi-circular swaying up and pick the arc method of welding.
3.5.9 horizontal welding electrodes tilted 70 ° ~80 ° to prevent molten iron sank into the gravity on the Groove. Transported uphill mouth not to arc stop, quickly take to the downhill root minor horizontal stabilizing action, followed by uniform welding.
3.5.10 overhead welding: overhead welding time by low current short-arc welding, solution should be thin, should ensure that base metal fusion sound. First weld with short arc for push-pull action, direction of electrode and welding into 8 ° ~90 ° angle. Other electrode yaw, and pauses in the Groove side arc stability, assurance on both sides fused.
3.5.11 steel weld:
3.5.11.1 steel welding applied ⅰ, ⅱ, ⅲ class reinforced bar. Steel bar welding should be used double-sided welding, as shown in Figure 4-27 (a), not when welded on both sides, or one side welding, as shown in Figure 4-27 (b).
Figure 4-27 steel welded joints
Help and reinforcement should be used with level, with equal diameter steel production, its length l see table 4-15. Helping level with main bars are the same, the diameter can be smaller than the diameter of main bar of a specification. Such as help and reinforcement diameter is the same as steel can be one level lower than the main bar.
3.5.11.2 steel joint weld thickness should be not less than 0.3D h, width b is not less than 0.7d, as shown in Figure 4-28.
Bar length table 4-15
Item bar-level type of weld length l
One-side welding
Double welded 8d
≥4d
One-side welding
Double welded 10d
≥5d
Note: the d bar diameter.
Figure 4-28 dimension diagram
A-width; h-weld depth chart 4-29
3.5.11.3 steel for welding, assembling and welding of steel reinforcement shall conform to the following requirements:
A ... between the two main bar ends should be left 2~5mm gap.
B. between reinforcement and fastened with a four-point position, tack should help end more than 20mm.
C. when welding, arc should begin at the end, on steel end arc, crater fill. First layer weld should have enough penetration welds and tack, especially at the tack and the beginning of a Terminal, fuse is good.
3.5.12 rebar lap welding:
3.5.12.1 lap welding steel: suitable for ⅰ, ⅱ, ⅲ class reinforced bar. When welding, use double welded, as shown in Figure 4-29 (a). When wood can be welded on both sides, or one side welding, as shown in Figure 4-29 (b). Lap length l should be the same length, as shown in table 4-15.
3.5.12.2 lap joint weld thickness should be not less than 0.3D h, width b is not less than 0.7d.
3.5.12.3 lap welding, Assembly and welding of steel shall meet the following requirements:
A. overlap welding, steel should bend, to ensure the two axis of the bars on a axis.
Prefabricated installation conditions at the site, nodes when lap welding steel such as rebar bending is difficult, may be appropriate to bend.
B. overlap welding with two fixed points, positioning welding lap ends 20mm.
C. when welding, arc should begin at the end of lap bars, on lap steel end arc, crater fill. First layer weld should have enough penetration welds and tack, especially at the tack and the beginning of a Terminal, fuse is good.
3.5.13 arc welding embedded parts of t-joint: arc welding embedded parts of t-joint joint form of fillet welding and piercing a plug weld two kinds, as shown in Figure 4-30.
Figure 4-30 embedded parts of t-joint
(A) fillet weld (b) perforation
When welding, shall meet the following requirements:
3.5.13.1 the plate thickness δ is not less than 0.6D, and should not be less than 6mm.
3.5.13.2 ⅰ and ⅱ in steel should be used. Anchoring bar diameter should not be less than 8mm, structural anchorage bar diameter should not be less than 6mm. Anchor bar diameter is less than 6~25mm, use the fillet weld; anchor when the diameter is 20~32mm, perforated plug should be used.
When 3.5.13.3 the use of grade ⅰ reinforcement, fillet weld k not less than 0.5d used when grade steel, weld toe k not less than 0.6D.
3.5.13.4 welding current should not be too large, no Burns steel.
3.5.14 lap welding steel plate and steel: lap steel plate and steel welding, joints form as shown in Figure 4-31. The lap length l of grade ⅰ reinforcement not less than 5d. Weld width b is not less than 0.5d, weld thickness h is less than 0.35d.
Figure 4-31 take the steel plate and steel connector
3.5.15 installation of Assembly frames, welded steel shall meet the following requirements.
Two steel axis offset 3.5.15.1 is larger, suitable for cold bending correction, but not with the hammer. Have difficulty bending correction, correction after using oxy-acetylene flame heating, heating temperature must not exceed 850 ° c, to avoid burns steel.
3.5.15.2 welding, should be a reasonable selection of welding sequence for between nodes can be symmetrical, to reduce the deformation of the structure.
3.5.16 welded steel at low temperature:
3.5.6.1 in ambient temperatures below-5 ° c under conditions of welding for reinforcing bars at low temperature welding. Low-temperature welding, 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. When the wind exceeds 4, should have the wind measure. Meet ice not cooling after welding the joint should be avoided.
3.5.16.2 steel at low temperature electric arc welding, the welding process, the following requirements:
A. for flat welding welding or bonding, the first layer weld, first from the arc in the Middle, and then shipped to both ends of the arc made welding, first shipped in from above the middle of the arc, and then shipped arc from the bottom to the Middle, to make junctions of steel bar reaches a certain temperature working. In each subsequent layer welds when welding, stratified temperature welding. Interpass temperature control between 150~350℃, to play a role in cooling.
B. ⅱ and ⅲ class reinforced multilayer welding the arc-welded, using "temper bead welding method", that is, temper bead weld at each end to shorten length than the previous layer 4~6mm, as shown in Figure 4-32, to eliminate or reduce the front bead and overheated zone hardened tissue, improve the performance.
Figure 4-32 sketch map of steel at low temperature temper bead welding
(A) help weld; (b) lap; (c) Groove
C. welding current increases slightly, appropriate welding speed slows down.
4 quality criteria
4.1 project:
4.1.1 the variety and quality of the steel, electrode grades, performance and joint use of steel plates and steel, are required to 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: check the factory certificate and test report.
4.1.2 the specification, location of the welded joint of steel bars, percentage of joints within the same section must comply with the design requirements and the provisions of the code.
Inspection method: observation or standard checks.
4.1.3 arc welding strength testing must be qualified.
From each batch of finished product obtained tensile test 5 connectors. Fabricated of welded joints of structural joints, production conditions can produce a simulated specimens.
Welding conditions in a factory, with 300 joints of the same type (with the bar level, with joint type) for a group.
Installation conditions, every one to two floors with 300 in connectors of the same type (same reinforcement level, joint type, welding position), when there are less than 300, still as a batch.
Inspection method: check the weld sample test report.
4.2 basic items: operators should check one by one after the joint clearing weld appearance quality and the inspection result shall conform to the following requirements:
4.2.1 the welding surface, must not have larger dents, welding tumor.
4.2.2 without cracking at the joint.
4.2.3 bit depth, number and size of the blowhole, slag, and dimension deviations shall not exceed the values set out in table 4-16.
Steel arc dimension deviations and defects allowed value (mm) table 4-16
Project tolerance test
1 longitudinal offset along the center line of joint 0.5d standard
Joint bending
Embedded parts of t-joint rebar spaced 4 °
Not more than 10
3 steel joint axis offset 0.1d and not more than 3 feet
+0.05d
0
0.1d
0
Standard
6 length of weld -0.5d
7 horizontal undercut visual assessment of depth of 0.5
Number and size of weld porosity and slag in 2D welding
Joint embedded on the surface of t-joint hole 2, 6mm23 x,
Diameter is not more than 1.5
Note: 1. D for diameter.
2. the negative temperature, biting edge depth is not greater than 0.2mm.
Visual inspection failed joints, repair or reinforcement may be submitted after the second inspection.
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 in the construction of frame carefully repaired, ensure the steel skeleton reinforced in the correct position.
6 quality problems to be noticed
6.1 check dimensions, Groove, steel, steel head clearance axial-inclination, as well as surface quality of steel, does not meet the requirements without welding.
6.2 taking good contact wiring and steel, are not free to take to prevent arcs.
6.3 joints with plates or help, arc should be carried out on plates or help. Without plates or help joints, Arc Weld can be formed in, are not free to arc to prevent burn main bar.
6.4 according to steel grade, diameter, joint type and position, select the appropriate electrode diameters and the welding current to ensure fusion of weld metal and steel good.
6.5 cleaning of welding process, welding surface smooth and weld appearance, reinforcement of weld should be smooth transition, crater fill.
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 embedded parts of steel bar tensile test of t-shaped joint report.
7.6 electrode factory certificate.
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