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JGJ 18-2012 English PDF (JGJ18-2012)

JGJ 18-2012 English PDF (JGJ18-2012)

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JGJ 18-2012: Specification for welding and acceptance of reinforcing steel bars

This Specification was formulated with a view to adopting reasonable welding procedure and unified quality acceptance criteria, achieving construction safety, guaranteeing quality, advanced technology, material and energy conservation in the welding procedure of reinforcing steel bars.
JGJ 18-2012
JGJ
INDUSTRY STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
UDC
Record No.: J 253-2012
P JGJ 18-2012
Specification for Welding and Acceptance of
Reinforcing Steel Bars
ISSUED ON: MARCH 01, 2012
IMPLEMENTED ON: AUGUST 01, 2012
Issued by: Ministry of Housing and Urban-Rural Development of the
PEOPLE Republic of China
INDUSTRY STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
Specification for Welding and Acceptance of
Reinforcing Steel Bars
Approved by: Ministry of Housing and Urban-Rural Development of the PEOPLE Republic of China
IMPLEMENTED ON: AUGUST 01, 2012
2012 Beijing
Table of Contents
Foreword ... 6
1 General Provisions ... 8
2 Terms and Symbols ... 8
2.1 Terms... 8
2.2 Symbols ... 11
3 Materials ... 14
4 Welding of Reinforcing Steel Bar ... 16
4.1 Basic provisions ... 16
4.2 Resistance spot welding of reinforcing steel bar ... 21
4.3 Flash butt welding of reinforcing steel bar ... 22
4.4 Flash butt welding of stirrup ... 25
4.5 Arc welding of reinforcing steel bar ... 27
4.6 Electroslag pressure welding of reinforcing steel bar ... 33
4.7 Gas pressure welding of reinforcing steel bar ... 36
4.8 Submerged-arc pressure welding of reinforcing steel bar at prefabricated components ... 38
4.9 Submerged-arc stud welding of reinforcing steel bar at prefabricated components ... 40
5 Quality Inspection and Acceptance ... 42
5.1 General requirements ... 42
5.2 Welded frame and welded fabric of reinforcing steel bar ... 46
5.3 Flash butt welded joint of reinforcing steel bar ... 48
5.4 Flash butt welded joint of stirrup ... 49
5.5 Arc welded joint of reinforcing steel bar ... 49
5.6 Electroslag pressure welded joint of reinforcing steel bar ... 51
5.7 Gas pressure welded joint of reinforcing steel bar ... 52
5.8 T-joint of reinforcing steel bar at prefabricated components ... 53 6 Examination of Weldor ... 55
7 Welding Safety ... 59
Appendix A Quality Acceptance Record of Welded Joints Inspection Group of Reinforcing Steel Bar ... 62
Appendix B The Certificate of Weldor Examination for Reinforcing Steel Bar 69 Explanation of Wording in This Specification ... 72
List of Quoted Standards ... 73
Specification for Welding and Acceptance of
Reinforcing Steel Bars
1 General Provisions
1.0.1 This Specification was formulated with a view to adopting reasonable welding procedure and unified quality acceptance criteria, achieving construction safety, guaranteeing quality, advanced technology, material and energy conservation in the welding procedure of reinforcing steel bars.
1.0.2 This Specification is applicable to welding procedure of reinforcing steel bars and the quality inspection and acceptance in generally industrial and civil construction engineering concrete structure.
1.0.3 Welding procedure of reinforcing steel bar and the quality inspection and acceptance shall not only be carried out according to this Specification, but also comply with the provisions of relevant current national standards.
2 Terms and Symbols
2.1 Terms
2.1.1 Hot rolled plain bars
Finished reinforcing steel bar that is formed by hot rolling, generally with circular cross section and smooth surface.
2.1.2 Hot rolled bars
Reinforcing steel bar that is delivered according to hot-rolled state, whose metallographic structures are mainly ferrite and pearlite and shall be free from other microstructures (such as tempered martensite microstructure on base circle) with influence on service performance.
2.1.3 Hot rolled bars of fine grains
Reinforcing steel bar of fine grains that is formed through controlled rolling and cooling process in the hot-rolled process, whose metallographic structures are mainly ferrite and pearlite and shall be free from other microstructures (such as tempered martensite microstructure on base circle) with influence on service performance; their grain size A kind of fusion welding method that welding wire is regarded as one electrode and reinforcing steel bar as another electrode; and carbon dioxide gas is regarded as arc medium to protect metal drop, welding pool and hot metal in weld zone. Carbon-dioxide arc welding is hereinafter referred to as CO2 welding.
2.1.12 Electroslag pressure welding of reinforcing steel bar
A kind of pressure welding method that two pieces of reinforcing steel bars are placed in vertical butting form; by direct or indirect arc initiation method, in utilization of welding current and through clearance between end faces of the reinforcing steel bars; arc process and electroslag process are formed below flux layer to generate arc heat and resistance heat so as to melt the reinforcing steel bars and complete the pressurization. 2.1.13 Gas pressure welding of reinforcing steel bar
A kind of pressure welding method that oxyacetylene or oxygen-liquefied petroleum gas flame (or other flames) is adopted to heat the joint of the two reinforcing steel bars so as to make them reach thermoplastic state (solid-state) or melted state; then complete the pressurization.
2.1.14 Submerged-arc pressure welding of reinforcing steel bar at prefabricated components
A kind of pressure welding method that reinforcing steel bar and steel plates are placed in the form of T-shaped joint to generate arc below the flux layer in utilization of welding current, form molten pool and complete pressurization.
2.1.15 Submerged-arc stud welding of reinforcing steel bar at prefabricated components
A kind of welding method that reinforcing steel bars are inserted into the molten pool at the right time to form a T-shaped joint after arc stud welding gun is used to clamp reinforcing steel bars so as to make the reinforcing steel bars vertically aligned with steel plates and stud welding power equipment is adopted to generate high current and welding arc in a short time so as to generate molten pool between end faces of welding of reinforcing steel bars and steel plates under the protection of flux layer. 2.1.16 Waiting weld stirrup
Semi-finished stirrup that the aligned reinforcing steel bars are adopted to make shape specified in the design according to inner clear dimension and angle of stirrup and are waiting for flash butt welding.
2.1.17 Butt welded stirrup
Closed-loop stirrup that is formed through flash butt welding of waiting weld stirrup. F ?€? HRBF500 hot-rolled ribbed bar of fine grains.
2.2.2 Dimension and symbols for welded joints of reinforcing steel bar
??g - the inside clear length of stirrup;
b - the width of weld surface;
bg - the inner clear width of stirrup;
bh - the temper bead;
br - the contour weld bead;
d - the diameter of reinforcing steel bar (stirrup);
dy - the pressed depth;
fy - the pressure weld surface;
hy - the excess weld metal;
K - the dimension of weld leg;
l - the length of auxiliary rod and overlap length;
Lg - the blanking length of stirrup;
S - the effective thickness of weld.
2.2.3 Symbols of welding procedures
A - the burn-off allowance;
??1 - the left burn-off allowance;
??2 - the right burn-off allowance;
A1 - the primary burn-off allowance;
??1.1 - the left primary burn-off allowance;
??2.1 - the right primary burn-off allowance;
A2 - the secondary burn-off allowance;
??1.2 - the left secondary burn-off allowance;
??2.2 - the right secondary burn-off allowance;
t3.2 - the upset current-off time;
??? - the total welding allowance.
2.2.4 Symbols for mechanical property test of reinforcing steel bar
A - the percentage elongation after fracture;
ReH - the upper yield strength;
ReL - the lower yield strength;
Rm - the tensile strength.
3 Materials
3.0.1 Chemical composition and mechanical property of welded reinforcing steel bar shall comply with the provisions of relevant current national standard. 3.0.2 Low carbon steel or low alloy steel may be adopted for steel plates and section steel in welded joint of reinforcing steel bar at prefabricated components as well as molten tank auxiliary rod and groove welded joint; and the mechanical property and chemical composition shall comply with the provisions of the current national standards Carbon Structural Steels (GB/T 700) or High Strength Low Alloy Structural Steels (GB/T 1591).
3.0.3 Welding rod adopted for shielded metal arc welding of reinforcing steel bar shall comply with the provisions of the current national standard Carbon Steel Covered Electrodes (GB/T 5117) or Low Alloy Steel Covered Electrodes (GB/T 5118). Welding wire adopted for carbon-dioxide arc welding of reinforcing steel bar shall comply with the provisions of the current national standard Welding Electrodes and Rods for Gas Shielding Arc Welding of Carbon and Low Alloy Steel (GB/T 8110). Models of the covered electrodes and welding wires shall be determined according to the design; where there are no provisions in the design, it may be selected according to those specified in Table 3.0.3.
4 Carbon dioxide gas shall comply with the provisions of high-class products in the current industry standard Carbon Dioxide for Welding (HG/T 2537).
3.0.5 Among electroslag pressure welding as well as submerged-arc pressure welding and submerged-arc stud welding of reinforcing steel bar at prefabricated components, HJ 431 fused flux may be adopted; in submerged-arc stud welding, SJ101 fluorine- alkali agglomerated flux may also be adopted.
3.0.6 Welded reinforcing steel bars and steel plates shall be provided with quality certificate; welding rods, welding wire, oxygen, dissolved acetylene, liquefied petroleum gas, carbon dioxide gas and flux shall be provided with product certificate.
When the reinforcing steel bars are approaching the construction site, test pieces shall be taken according to the requirements of national current relevant standards for the inspection of mechanical property and weight deviation; and the inspection results must comply with the provisions of relevant current national standard.
Inspection quantity: it is determined according to approaching lot and product sampling inspection plan.
Inspection method: inspecting product certificate, exit-factory inspection report and site reinspection report.
3.0.7 Welding materials shall be sorted for storage, and handled appropriately; the measures against rust and deterioration through moisture shall be taken. 4 Welding of Reinforcing Steel Bar
4.1 Basic provisions
4.1.1 During welding of reinforcing steel bar, application scope of welding methods shall comply with the provisions specified in Table 4.1.1.
mixture with new flux.
4.1.7 Flash butt welding, electroslag pressure welding or gas pressure welding may be carried out for two pieces of reinforcing steel bars with the same designation and different diameters. Where the flash butt welding is carried out, diameter difference of reinforcing steel bar shall be no greater than 4mm; where electroslag pressure welding or gas pressure welding is carried out, the diameter difference of reinforcing steel bar shall be no greater than 7mm. Larger welding parameters for large-and-small-diameter reinforcing steel bars may be selected. The axis of two pieces of reinforcing steel bars shall be in the same straight line and the permissible value for axis deviation shall be calculated according to the reinforcing steel bar with smaller diameter. Butt joint strength shall be calculated according to the reinforcing steel bar with smaller diameter. 4.1.8 Flash butt welding, arc welding, electroslag pressure welding or gas pressure welding may be carried out for two pieces of reinforcing steel bars with the same diameter and different designations; the designation of reinforcing steel bar shall be within the range specified in Table 4.1.1 of this Specification. Welding rod, welding wire and welding parameters shall be selected according to the reinforcing steel bar with higher designation; and the butt joint strength shall be calculated according to the strength of reinforcing steel bar with lower designation.
4.1.9 Where resistance spot welding, flash butt welding, submerged-arc pressure welding and submerged-arc stud welding, the supply voltage fluctuation shall be observed at any time: where the reduction of the supply voltage is greater than 5% and less than 8%, measures to increase grade of welding transformer shall be taken; where it is greater than or equal to 8%, welding shall not be carried out.
4.1.10 Where welding is carried out under below -5??C ambient temperature, the welding procedure shall meet the following requirements:
1 Where flash butt welding is carried out, preheating flash welding or flash- preheating flash welding should be adopted; the overhanging length may be increased. Where relatively low grade of transformer is adopted, preheating times and interval time are increased.
2 Where the arc welding is carried out, welding current should be increased while the welding speed should be reduced. Where arc auxiliary-rod welding or overlap welding is carried out, the arc initiation shall be carried out from the middle for the first layer of weld, and welding shall be carried out toward both ends. For subsequent layers, the welding is carried out through temperature control; the interlayer temperature shall be controlled between 150??C~350??C. Where
welding is carried out in multiple layers, temper bead may be adopted for welding. 4.1.11 Where the ambient temperature is less than -20??C, various welding shall not be carried out.
procedure. Where continuous flash welding is carried out, the flash process shall be relatively long and the burn-off allowance shall be equal to severely-crushed cutter knife edge (including roughness of end face) where two pieces of reinforcing steel bars are fractured plus 8mm~10mm; where flash-preheating flash welding is carried out, primary burn-off allowance and secondary burn-off allowance shall be distinguished. The primary burn-off allowance shall be no less than 10mm while the secondary burn-off allowance shall be no less than 6mm; 3 Where preheating needs to be carried out, resistance preheating method should be adopted. The preheating allowance shall be 1mm~2mm and the preheating frequency shall be 1~4 times; each preheating time shall be 1.5s~2s while the interval time shall be 3s~4s;
4 Upset allowance shall be 3mm~7mm and shall be increased with increasing diameter and designation of reinforcing steel bar. Thereinto, the current-on upset allowance accounts for about 1/3 while the current-off upset allowance
accounted for about 2/3; welding must be controlled properly. Where HRB500 reinforcing steel bar is welded, the upset allowance should be increased slightly so as to ensure welding quality.
4.3.5 Where the flash butt welding is carried out for HRBF335, HRBF400 and HRBF500 or RRB400W, compared with hot rolled bars, the overhanging length shall be reduced, grade of welding transformer shall be increased and the heating time shall be shortened for rapid upset forging to form rapid-heating and rapid-cooling conditions so as to make length of heat-affected zone controlled within the range of 60% diameter of reinforcing steel bar.
4.3.6 Grade of transformer shall be selected according to specific conditions such as grade and diameter of reinforcing steel bar, welder capacity and welding procedure. 4.3.7 Where HRB500 and HRBF500 reinforcing steel bars are welded, preheating flash welding or flash-preheating flash welding procedure shall be adopted. Where joint tensile test results with brittle fracture, or bend test fail to meet requirements, post-weld heat treatment shall be carried out on the welder.
4.3.8 During the flash butt welding production, in case of abnormal phenomena or welding defect, the causes shall be found out and measures shall be taken to timely eliminate it.
4.4 Flash butt welding of stirrup
4.4.1 Position of welding spot for flash butt welding of stirrup should be arranged in the middle of the stirrup side with relatively small stress. Position of butt-welding points for scalene polygonal column stirrup should be arranged in the middle of two sides. 4.4.2 The blanking length of stirrup shall be reserved with total welding allowance (???), ??g - inside clear length of stirrup; bg - inside clear width of stirrup; ??? - total welding allowance; Ft - elastic pressure;
Figure 4.4.3 -- Waiting Weld Stirrup
4.4.4 Processing quality inspection, which belongs to intermediate quality inspection, shall be carried out for semi-finished waiting weld stirrup. Waiting weld stirrups completed according to the same shift and designation of reinforcing steel bar as well as the same processing equipment is regarded as an inspection lot; 5% shall be randomly inspected for each lot. The inspection items shall comply with the following provisions:
1 End faces of two reinforcing steel bar heads shall be closed without bevel connection.
2 The joint shall have certain elastic pressure.
4.4.5 Flash butt welding of stirrup shall comply with the following provisions: 1 100kVA special butt welder for stirrup should be used.
2 Preheating flash welding should be adopted; welding parameters, operation points, formation of welding defects and the elimination measures shall be in accordance with the relevant provisions of subclause 4.3 in this Specification. 3 Grade of welding transformer shall be properly increased and the secondary current shall be slightly greater.
4 After upset forging of two pieces of reinforcing steel bars is closed, the fixture shall be loosened after several seconds.
4.4.6 In the process of flash butt welding of stirrup, in case of abnormal phenomena or welding defect, the causes shall be found out and measures shall be taken to timely eliminate it.
4.5 Arc welding of reinforcing steel bar
4.5.1 Where arc welding of reinforcing steel bar is carried out, shielded metal arc welding or carbon-dioxide arc welding procedures may be adopted. The carbon- dioxide arc welding equipment shall be consisted of 5 parts -- welding source, wire feed system, welding gun, air supply system and control circuit.
4.5.2 Where carbon-dioxide arc welding of reinforcing steel bar is carried out, the following welding parameters shall be selected according to conditions such as welder property, shape of welded joints and welding position:
1 Welding current;
4.7 Gas pressure welding of reinforcing steel bar
4.7.1 Gas pressure welding may be used for butt welding of reinforcing steel bar at vertical, horizontal or inclined positions.
4.7.2 Gas pressure welding may be divided into solid-state and molten-state ones according to different heating temperatures and procedures and methods. The construction organization shall select it according to conditions such as equipment. 4.7.3 Gas pressure welding may be divided into oxyacetylene and oxygen-liquefied petroleum gas ones according to different fuel gases for heating flame. The heating temperature of oxygen-liquefied petroleum gas flame is on the low side and the construction organization shall select it according to specific conditions. 4.7.4 Gas pressure welding equipment shall comply with the following provisions: 1 Air feeder shall include oxygen cylinder, dissolved acetylene cylinder or liquefied petroleum gas cylinder, decompressor and rubber hose. The dissolved acetylene or liquefied petroleum gas cylinder outlet shall be installed with dry tempering preventer.
2 The welding fixture shall be able to clam...

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