焊缝要求（Weldrequirement）

焊缝要求（Weld requirement）
Two welding requirements of 2010-08-20 15:40:21| classification: welding material | Tags: | font
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Two welding requirements
A butt weld in grade one and grade two, weld the main difference is what?
GB 50205-2001 "steel structure construction quality acceptance" table 5.2.4 have clearly stated, a level detection ratio of 100%, while the two level inspection proportion requirement is 20%.
In the project of butt weld of the more commonly used for level two, but the component, fatigue calculation in need of heavy duty and the weight of more than 50 tons of specific parts is equal to the intermediate duty crane beam component is required by a butt weld. In the "standard" steel structure design should have a detailed provisions.
(GB 3323-87) according to the relevant provisions of weld quality:
16.1 according to the nature and number of defects, the weld quality is divided into four levels.
The internal 16.1.1 grade I weld without crack, lack of fusion, lack of penetration and stripe slag.
The internal 16.1.2 II weld without crack, incomplete fusion and penetration.
Internal 16.1.3 grade weld without crack, lack of fusion and double welding and welding pad added in unweld. One side welding without backing the nonpenetration allowed according to the length of grade evaluation table 10 stripe slag length.
16.1.4 weld defects than level III for class IV.
Welding inspection
1. qualification
In the steel structure of NDT personnel must meet with issued by relevant government departments and their work qualifications, to detect the need to detect the parts according to the specification.
2. in addition to routine check, the steel structure sampling check points, factory production and installation of weld seam of two kinds of checks.
3. visual inspection
A. all welds should be cooled to ambient temperature after visual inspection, weld class II and III steel to be welded is completed after 24 h examination results as the basis for
acceptance.
There shall be no unfilled B., a root of weld shrinkage, undercut and joint defects such as bad, there shall be no surface porosity slag crack and arc scratch defects such as a weld and two weld, the weld height 0--4 mm.
C. two weld weld fully equal to or less than 1 mm, 1 mm less than the root contraction, the undercut is less than or equal to 0.5 mm, continuous length is less than or equal to 100 mm, cracks, scratches, arc surface porosity and surface slag is not allowed.
D. three weld weld fully equal to or less than 2 mm root contraction is less than or equal to 2 mm, the length is not limited; bite edges are less than 1 mm, the length is not limited, allowing the existence of crack length is less than or equal to 5 mm, arc scratch, surface porosity and surface slag allows the existence of individual number. The weld height 0-5 mm.
E. when using the manual electric arc welding (SMAW) for stud welding, weld appearance inspection in accordance with the following requirements of fillet weld:
Weld shape: 360 degree range, high weld seam width > 1mm > 0.5mm; no pores, slag; undercut depth is less than 0.5mm, the height of the allowable deviation of positive and negative 2mm.
4. nondestructive testing
A. nondestructive testing should be carried out in appearance
inspection.
B. weld NDT report issued by the staff must have the corresponding control methods of injury level II or above grade II qualification certificate.
C. test of full penetration welds shall be 100% of the level,
The ultrasonic flaw detection method (UT).
D. two weld (UT) sampling, sampling ratio of not less than 20%.
E. three weld can perform nondestructive testing, visual inspection only.
The welding procedure qualification and qualification of welders.
According to the < steel fusion welding technology assessment (JB/T6963) is less than or equal to or over specification for welding of steel structure (AWSD1.1) for evaluation of welding process components, welding technology of steel structure welding process in accordance with the qualification for making.
Welder qualification: engaged in the installation of steel structure welding welder must have the required specification for welding welder certificate, and all qualified in the scope of the project.
1. H type frame column installation welding
Choose the reasonable form of the weld thickness according to the requirements of design drawings and plates
The welding process requirements:
A. welding groove available flame cutting or mechanical processing method;
Remove weld surface water, B. welding scale, rust, oil cleaning; quality check assembly and surface welding parts such as do not meet the requirements, should repair welding, passing before welding;
C. welding must be a corresponding certificate of welder welding, the welding material and welding quality requirements and the same formal welding, weld thickness should not exceed the design of weld thickness 2/3, positioning weld length should be greater than 40 mm, 500-600 mm spacing, and should fill the crater, welding preheating temperature should be higher than the formal welding preheating temperature; (1\ steel butt welding weld weld steel butt welding seam welded steel pipe is a spiral plate or skelp end to end. 2\ weld butt welding: the circular weld two section steel pipes are connected together and formed. <3\: is the final weld before welding seam for fixed butt edge).
D. group to avoid forced, assembled joints to be inspected, to welding;
E. groove bottom bead using shielded metal arc should be not
more than 4 mm of the electrode welding, the maximum thickness of the underlying root bead should not exceed 6 mm;
F. thick multilayer welding, continuous welding, each weld bead should be completed after the clean welding slag and spatter surface in a timely manner, in case of interruption of welding, should take appropriate measures after heat insulation, again re welding, preheating temperature should be higher than the initial preheating temperature;
The 2. H shaped steel composite steel column installation welding
The welding head, and according to the design requirements with full and partial penetration weld full penetration weld groove form should be used with single V groove plate.
The welding of H beams
The combination of H beams welding installation requested from the box section member flangeplate and web interface staggered should be greater than 500 mm, the upper and lower flange welding should adopt V groove plate with one side welding.
The 4. frame column and beam welding rigid connection,
The beam flange and cantilever beam flange groove with application of V single plate full penetration weld connection.
5. tube - tube installation welding connection
In the delta is not greater than 6 mm, available I groove with
a base plate, a single full penetration weld connection, delta >
6 mm, available V groove plus plate single full penetration weld connection.
6. steel structure installation process, T joint and cross joint, corner joint welding plate to prevent tearing.
Seven
The control of welding deformation
A. using reasonable welding sequence to control the deformation, long weld should adopt backstep welding or more symmetrical welding method and use;
B. uses skip welding method to avoid the local centralized heating,
C. uses the reverse deformation control of angular deformation.
D. on the common components available at the same time limit fixed position of welding deformation of large thick plate welding structure should be increased when the rigid rigid fixation of large structures should adopt segment assembly welding, respectively after deformation correction assembly or construction method of connection.
8. post weld stress relief treatment
Site installation weld should adopt the hammering method to
eliminate stress, eliminate the middle layer welding stress by hammering method should be used, or a small vibration ball peen hammer tool, should not the root weld, the parent metal cap weld seam edge or the hammer.
9. stud welding (Shuan Ding)
A. will (Shuan Ding) end welding nail and plate (pipe) surface contact electric arc, the contact surface to be melted to stud (Shuan Ding) pressure welding.
B. select the appropriate reasonable welding bolt, bolt welding type, supporting the use of specifications. In the process of welding, welding nail note extension length and lifting height changes, flat, vertical, change back position welding.
C. The scene simulation of welding stud welding technology evaluation report, record, bending test after welding, the technology assessment report as the basis for guidance of field welding.。