Some standard content:
Engineering Construction Standard Full-text Information System
UDC691.328:621.791.56
National Standard of the People's Republic of China
GB12219—89
Gas pressure welding
Gas pressure welding of reinforcing steel barConstruction Standard
Published on 1990-01-04
Implementation on 1990-09-01
Published by the State Bureau of Technical Supervision
W Engineering Construction Standard Full-text Information System
National Standard of the People's Republic of China
Gas pressure welding of reinforcing steel bar
Gas pressure welding of reinforcing steel bar 1 Subject content and scope of application
This standard specifies the construction technical conditions for gas pressure welding of steel bars and the quality requirements for joints. GB12219—89
This standard applies to the construction and quality acceptance of gas pressure welding of steel bars in reinforced concrete structures of buildings and structures. 2 Reference standards
GB1499 Steel bars for reinforced concrete
GB3863
Industrial gaseous oxygen
GB6819 Dissolved acetylene
GB9448 Welding and cutting safety
GBJ204 Specification for construction and acceptance of reinforced concrete engineering 3 Terminology
3.1 Gas pressure welding of steel bars: A method of heating the joints of two steel bars with an oxyacetylene flame until they reach a plastic state, and then applying appropriate pressure to form a firm butt weld.
3.2 Multi-nozzle annular tube heater: A heating device composed of an oxygen-acetylene mixing chamber and a heating ring. 3.3 Pressurizer: A pressure source device composed of an oil pump, an oil pressure gauge, an oil pipe, a top pressure oil cylinder, etc. 3.4 Welding fixture: a fixture used to ensure the clamping, installation and positioning of the steel bar and to apply axial pressure. 3.5 Pressure welding surface: the surface where the two steel bar end faces in the joint meet each other. 3.6
Upset area: the section of the parent material in the joint that is upset. 3.7 Upset diameter: the maximum diameter of the upset area. 3.8 Upset length: the length of the upset area.
3.9 Eccentricity: the distance between the axes of the two steel bars on the pressure welding surface. Pressure welding surface offset: the distance between the pressure welding surface and the maximum diameter section of the upset area. 3.10
3.11 Circumferential crack: a crack perpendicular to the axis of the steel bar. 4 General provisions
Scope of application of steel bar gas pressure welding
Steel bar gas pressure welding can be used for butt connection of grade 1 and grade I steel bars with a diameter of 16 to 40 mm in vertical, horizontal or inclined positions.
When the diameters of the two steel bars are different, the difference between the two diameters shall not exceed 7mm. 4.2 Technical training and job qualifications
The construction unit shall select technical personnel who have received technical training to be responsible for the construction of steel bar gas pressure welding, and shall assign welders who have passed the examination and have a certificate of qualification to operate the steel bar gas pressure welding heating operation. 4.3 Implementation plan
Approved by the State Administration of Technical Supervision on January 4, 1990 and implemented on September 1, 1990
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The technical personnel responsible for the construction shall formulate a steel bar gas pressure welding implementation plan in advance in combination with the actual project, including welding process, quality inspection and safety technology measures.
4.4 Welding process test
Before the project starts formal welding production, the steel bar gas pressure welding process performance test must be carried out under on-site conditions. The steel bars used are cut from the actual steel bars entering the site. Each batch of steel bars welds 6 joints. After the appearance inspection, 3 joints are subjected to tensile tests and 3 joints are subjected to bending tests. The test methods and requirements are the same as those for quality acceptance. After passing the test, welding shall be carried out according to the determined process. 4.5 Welding environment
4.5.1 During on-site welding, when the wind speed exceeds 5.4m/s, effective wind-blocking measures must be taken. 4.5.2 It is not suitable to carry out steel bar gas pressure welding construction on rainy and snowy days. When welding is necessary, effective shielding measures should be taken. 4.5.3 When constructing at negative temperatures, appropriate insulation and anti-freezing measures should be taken for the gas source equipment. When welding below -15℃, preheating and insulation and slow cooling measures should be taken for the steel bar joints. When the ambient temperature is lower than -20℃, welding shall not be carried out. 4.6 Equipment maintenance
Steel bar gas pressure welding equipment should be maintained according to equipment requirements and regularly inspected to keep it in good condition and ensure normal use. 5 Materials
5.1 Steel bars
5.1.1 Steel bars used for gas pressure welding of steel bars must have a material certificate, and all properties and quality should comply with the relevant provisions of GB1499. 5.1.2 When other varieties and specifications of steel bars are used for gas pressure welding, steel bar welding performance tests should be carried out. The test methods and requirements refer to A6 in Appendix A (Supplement); they can only be used after passing the test. 5.2 Oxygen
The quality of gaseous oxygen (O2) used should comply with the technical requirements of Class I or Class I Grade I specified in GB3863. 5.3 Acetylene
The acetylene (C2H2) used should preferably be bottled dissolved acetylene, and its quality should comply with the requirements specified in GB6819. 5.4 Calcium carbide
When acetylene is directly produced using an acetylene generator, the quality of the calcium carbide used should comply with the requirements of superior grade or grade I specified in the relevant standards. wwW.bzxz.Net
6 Equipment
6.1 Gas supply device
6.1.1 The gas supply device shall include oxygen cylinders, dissolved acetylene cylinders (or medium-pressure acetylene generators), dry flashback arresters, pressure reducers and hoses.
6.1.2 The use of oxygen cylinders and dissolved acetylene cylinders shall comply with relevant national regulations. Note: The use of oxygen cylinders shall comply with the relevant provisions of the "Gas Cylinder Safety Supervision Regulations" issued by the former State Bureau of Labor; the use of dissolved acetylene cylinders shall comply with the relevant provisions of the "Dissolved Acetylene Cylinder Safety Monitoring Regulations" issued by the former State Bureau of Labor. 6.1.3 The gas supply capacity of dissolved acetylene cylinders must meet the gas supply requirements for welding the largest diameter steel bars on site; if it does not meet the requirements, multiple cylinders can be used in parallel.
6.2 Multi-nozzle ring pipe heater
6.2.1 The gas supply of the oxygen-acetylene mixing chamber shall meet the gas consumption requirements of the heating coil. 6.2.2 The multi-mouth annular tube heater should be equipped with heating rings of various specifications to meet the needs of welding steel bars of different diameters. 6.2.3 The multiple flames of the multi-mouth annular tube heater should burn evenly and be easy to adjust. 6.3 Pressurizer
6.3.1 The pressurizing capacity of the pressurizer should reach the axial pressure required for welding the largest diameter steel bar on site. 6.3.2 There are two types of pressurized oil pumps, manual and electric. When welding large diameter steel bars, electric pressurized oil pumps should be used. W. Engineering Construction Standard Full Text Information System
6.4 Welding Clamp
6.4.1 The welding clamp should ensure that the steel bar is clamped; and when the steel bar is subjected to the maximum axial pressure, there is no relative slip between the steel bar and the clamp. 6.4.2 The welding clamp should facilitate the installation and positioning of the steel bar and maintain sufficient rigidity during the welding process. 6.4.3 The moving clamp in the welding clamp should be concentric with the fixed clamp; and when welding steel bars of different diameters, they should still remain concentric. 6.5 Auxiliary equipment
Necessary auxiliary equipment should be equipped during the construction of steel bar gas pressure welding, which is used to cut steel bars, grind steel bar ends, remove corner burrs and end surface oxide film, etc.
7 Construction
7.1 Operators
7.1.1 The person in charge of the steel bar gas pressure welding team must be a gas pressure welder. 7.1.2 Heating operations must be performed by gas pressure welders; pressurization operations should be performed by gas pressure welders. 7.1.3 The operating skill qualifications of gas pressure welders are divided into three levels. Their qualification assessment is shown in Appendix A. The grades and diameters of steel bars allowed to be welded are shown in Table 1.
Rebars allowed to be welded
Operational skill qualifications
Diameter, mm
7.1.4 Auxiliary workers should have relevant knowledge and experience in steel bar gas pressure welding and master the quality requirements of steel bar end processing and steel bar installation. 7.2 Inspection before welding
Before formal welding, the steel bar gas pressure welding equipment and safety technical measures should be carefully checked to ensure normal operation. 7.3 Processing of steel bar ends
7.3.1 The end face of the steel bar should be cut flat and perpendicular to the axis of the steel bar. If the end of the steel bar is bent or twisted, it should be corrected or cut off. 7.3.2 Before welding, if there are cement and other attachments within the length of twice the diameter of the steel bar end, they should be removed. The burrs on the corners of the steel bar and the rust, oil stains and oxide film on the end face should be cleaned and polished to reveal the metallic luster, and no oxidation should be allowed. 7.4 Installation of steel bars
7.4.1 The setting of the steel bar gas pressure welding joint in the component should meet the design requirements; when there is no design requirement, it should comply with the relevant provisions in GBJ204.
7.4.2 When installing the welding fixture and steel bar, the two steel bars should be clamped separately and the axes of the two steel bars should be in the same straight line. 7.4.3 After the steel bar is installed, it should be pressed and tightened. The local gap between the two steel bars shall not be greater than 3mm. The shape of the steel bar end face shall comply with the provisions of (a) or (b) in Figure 1.
When it is found that it does not meet the requirements after inspection, such as (c) or (d) in Figure 1, it should be reprocessed and installed. W.bzsoso.coI Engineering Construction Standard Full Text Information System
7.5 Steel bar gas pressure welding operation
a Correct
c Unqualified
b Qualified
d Unqualified
Figure 1 Steel bar end face shape
7.5.1 When gas pressure welding steel bars, the welding process of equal pressure method, secondary pressure method or tertiary pressure method should be selected according to the specific conditions such as steel bar diameter and welding equipment.
7.5.2 During the process of gas pressure welding of steel bars, the axial pressure applied to the steel bar should be 30~40MPa according to the cross-sectional area of the steel bar. 7.5.3 In the initial stage of gas pressure welding of steel bars, it is advisable to use a carburizing flame, aim at the joint of the two steel bars for concentrated heating, and let the inner flame cover the gap to prevent oxidation of the steel bar end face.
7.5.4 After confirming that the gap between the two steel bars is completely sealed, a neutral flame should be used instead, with the pressure welding surface as the center, and reciprocating wide heating within the length of one steel bar diameter on both sides.
7.5.5 The appropriate heating temperature of the steel bar end face should be 1150~1250℃; the heating temperature of the steel bar forging rough zone surface should be slightly higher than this temperature, and it should be determined according to the temperature gradient caused by the steel bar diameter. 7.5.6 In gas pressure welding of steel bars, the final heating and pressurization should make the upsetting zone of the joint form the specified appropriate shape; then stop heating, delay slightly, release the pressure, and remove the welding fixture. 7.5.7 During the heating process, if the fire extinguishing is interrupted before the gap between the steel bar ends is completely sealed, the steel bar should be removed, re-grinded, and installed, and then the flame should be ignited for welding. If it occurs after the gap between the steel bar ends is completely sealed, heating and pressurization can be continued to complete the pressure welding operation.
8 Quality Acceptance
8.1 Quality Inspection Items
The quality inspection and acceptance of steel bar gas pressure welding joints should be carried out in batches. The quality inspection should include two parts: appearance inspection and mechanical property inspection. 8.2 Inspection Batch
8.2.1 The batch for appearance inspection is all joints. 8.2.2 For mechanical property inspection, in general structures, 200 joints are considered as a batch. In cast-in-place reinforced concrete house structures, 200 joints are considered as a batch on the same floor. Joints less than 200 are still considered as a batch.
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8.3 Number of test pieces
When inspecting mechanical properties, randomly cut 3 joints from each batch of joints for tensile test. According to the needs of the project, another 3 joints can be cut for bending test. 8.4 Appearance inspection
8.4.1 When inspecting appearance, the welder should first self-check all the welded joints, and then the quality inspector should check them one by one. 8.4.2 The method of appearance inspection is mainly visual inspection; if necessary, vernier calipers or other special tools can be used. 8.4.3 Appearance inspection items and quality requirements are as follows: a.
The eccentricity e shall not be greater than 0.15 times the nominal diameter of the steel bar, and shall not be greater than 4mm, see Figure 2. Weld surface
Figure 2 Eccentricity
When steel bars of different diameters are welded, the smaller steel bar diameter shall be used for calculation. When the limit is exceeded, it should be cut off and re-welded.
The bending angle of the two steel bar axes shall not be greater than 4 degrees. When the limit is exceeded, it should be reheated and corrected. The upset diameter d㎡ should not be less than 1.4 times the nominal diameter of the steel bar, see Figure 3. When it is less than this limit, it should be reheated and forged. Figure 3 Upset diameter
d. Upset length La should not be less than 1.2 times the nominal diameter of the steel bar, and the raised part should be smooth and round, see Figure 4. When it is less than this limit, it should be reheated and forged.
Figure 4 Upset length
The offset ea of the pressure welding surface shall not be greater than 0.2 times the nominal diameter of the steel bar, see Figure 5. Pressure welding surface
Maximum diameter section
Figure 5 Pressure welding surface offset
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The steel bar gas pressure welding joint shall not have circumferential cracks. If such cracks are found, they should be cut off and re-welded. f.
g·There shall be no serious burns on the surface of the upset area. 8.5 Tensile test
8.5.1 The test length L of the tensile test piece of the gas pressure welded joint of the steel bar shall be equal to 8 times the nominal diameter of the steel bar; the clamping length L shall be determined according to the diameter of the steel bar and shall generally be greater than or equal to 100mm, see Figure 6. Figure 6 Quality acceptance tensile test piece
L, - test length; L - clamping length; L - total length of the test piece8.5.2 Tensile test results The tensile strength of the three test pieces shall not be lower than the tensile strength value specified for this grade of steel bar in GB1499, and they shall break outside the pressure welding surface and show plastic fracture. 8.5.3 Tensile test results. If one test piece does not meet the requirements, 6 joints shall be cut for re-inspection. If there is still one joint that does not meet the requirements in the re-inspection results, the batch of joints shall be judged as unqualified products. 8.6 Bending test
8.6.1 The length of the bending test piece of the gas pressure welded joint of the steel bar shall not be less than the value specified in Table 2. Table 2
Steel bar diameter
Test piece length
8.6.2 The diameter of the bend core during the bending test of the steel bar gas pressure welded joint shall comply with the provisions of Table 3. Table 3
Steel bar grade
Note: & is the nominal diameter of the steel bar.
Bending core diameter
d>25mm
8.6.3 The bending test should be carried out on a universal testing machine or a manual hydraulic bending tester. The raised part of the pressure surface of the test piece should be removed and flush with the outer surface of the steel bar. The pressure welding surface should be at the center of the bend and bent to 90 degrees. The test piece should not break on the pressure welding surface. 8.6.4 If one test piece does not meet the requirements in the bending test results, 6 joints should be cut for re-testing. If one test piece still does not meet the requirements in the re-test results, the batch of joints will be judged as unqualified products. W Engineering Construction Standard Full Text Information System
8.7 Quality Inspection Certificate
In the construction of steel bar gas pressure welding, after each batch of steel bar welding joints passes the quality inspection, a quality certificate should be filled in. The certificate should include columns such as project number, batch number, actual batch, joint position, steel bar grade and diameter, appearance inspection results and mechanical property test results. The welder and quality inspector should sign on the certificate. 9 Safety Technology
9.1 Equipment Use and Operation Safety
The equipment use and operation safety technology of steel bar gas pressure welding should refer to the gas welding safety regulations in GB9448. The working pressure of oxygen shall not exceed 0.8MPa; the working pressure of acetylene shall not exceed 0.1MPa. 9.2 Construction Site Safety
9.2.1 An operating platform must be set up at the construction site, and the scaffolding should be firmly supported and equipped with guardrails to ensure that the steel bar gas pressure welding operation can be carried out in a stable state.
9.2.2 When working on the upper and lower floors, protective measures should be taken. 9.2.3 There should be no flammable and explosive materials near and below the construction site. 9.2.4 There should be no oil leakage at all joints of the entire hydraulic system, such as the oil pump, oil pressure gauge, oil pipe and top pressure cylinder. Oil mist spraying due to micro cracks in the oil pipe should be prevented from causing combustion or explosion.
9.2.5 Firefighting equipment should be installed at the construction site. 9.2.6 Welding operators should wear gas welding protective glasses. Safety belts should be worn when working at height. 9.2.7 After work, all welding equipment should be properly collected to prevent damage. W.bzsoso.con Engineering Construction Standard Full Text Information System
A1 Welder Registration Conditions
Appendix A
Welder Examination Rules
(Supplement)
A1.1 Students who have completed the special training course for steel bar gas pressure welding can apply for the steel bar gas pressure welding welder examination and apply for the assessment of Class D operating skill qualification.
A1.2 Class D operating skill qualification welders who have been in actual operation for more than 3 months can apply for the Class C qualification examination; Class C operating skill qualification welders who have been in actual operation for more than 6 months can apply for the Class B qualification examination. A2 Technical Training Units
A2.1 Only companies, factories, scientific research, training centers and other units that have been approved by the construction departments of provinces, municipalities directly under the Central Government, autonomous regions or relevant ministries with the ability to train steel bar gas pressure welding welders are qualified to organize and establish steel bar gas pressure welding welder training courses. A2.2 The welder technical training unit should formulate a clear teaching syllabus, be equipped with qualified teachers, and have welder training materials and various equipment and conditions for welding operations.
A3 Welder Examination Unit
A3.1 Units with the technical strength to conduct welder examinations approved by the provincial, municipal, autonomous region or relevant ministry’s competent construction department are qualified to organize and establish a welder examination committee and issue qualification certificates. A3.2 The welder examination committee should be responsible for conducting technical examinations on welders who apply for the examination and assessing their operating skills qualifications. A3.3 The welder examination unit shall establish and improve relevant technical files for each welder who applies for the examination, and regularly compile a list of welders who have been issued with qualification certificates and submit it to the relevant competent construction departments of the province, municipality, autonomous region or ministry for record. A4 Examination content
The welder examination content includes two parts: basic knowledge examination and operation skill examination. Only welders who have passed the basic knowledge examination can take the operation skill examination.
A5 Basic knowledge examination scope
The basic principle of steel bar gas pressure welding;
The grade, diameter and basic properties of steel bars; the performance, adjustment, use and maintenance methods of steel bar gas pressure welding equipment; the basic properties and use of oxygen, acetylene and calcium carbide; the preparation before welding and the precautions to ensure the welding quality; the steel bar gas pressure welding process and its characteristics, the adjustment of the flame and the calculation of the pressure; the quality inspection methods and requirements of steel bar gas pressure welding joints; the causes and preventive measures of welding defects; h.
The composition and performance of welding joints;
Safety technical knowledge.
A6 Operational Skills Test
A6.1 When welders take the operational skills test, each welder shall weld 10 test pieces according to the declared qualification level. After the appearance inspection is qualified, 5 pieces shall be subjected to tensile test and 5 pieces to bend test.
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A6.2 The grade, diameter, length and number of sections of steel bars used in the welder operational skills test are shown in Table A1. Table A1
Operational Skills Qualification
A6.3 The welding position during the welder test shall be determined by the examination committee. According to the requirements of the welder who applied for the test, an assistant may be provided to assist in pressurization. Rebar
Number of tensile test pieces Number of bending test pieces
A6.4 The items and requirements for the appearance inspection of the test pieces are the same as those for quality acceptance. For test pieces that fail the appearance inspection, they can be removed and re-welded, but only once.
A6.5 After the appearance inspection, the test piece shall be machined on the test part. The test section diameter, test length and bend center diameter shall comply with the requirements of Table A2. The shape of the test piece is shown in Figures A1 and A2. Table A2
Operational skill qualification
Rebar diameter
Test section diameter
Tensile specimen
Test length
Test section diameter
Figure A1 Welder test tensile specimen
L,-test length; Lj-clamping length L-full length of specimen Bending specimen
Test length
Bending center diameter
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Test section diameter
Figure A2 Welder test bending specimen
Ls-Test length
A6.6. According to the tensile test results, the tensile strength of the five specimens shall not be lower than the tensile strength value specified for Grade I steel bars in GB1499, and they shall show plastic fracture.
A6.7 Bend test results: 5 test pieces shall not break when bent to 90 degrees. A6.8 When only one test piece fails to meet the specified requirements in the tensile test or bending test, a group of 5 test pieces may be re-welded for re-testing, but only once. The test requirements are the same as the initial test. A7
Welder's test certificate
A7.1 Welder's operation skill test results: If both the tensile test and the bending test meet the specified requirements, the test is considered to be passed, and the operation skill qualification level is assessed.
A7.2 See Appendix B for the welder's test certificate template. A8 Invalidation
If a welder who has obtained a test certificate produces two batches of unqualified products within 3 months of production, his certificate shall be revoked. A9 Re-examination
A welder who has passed the examination shall be re-examined every two years. If a welder who has been away from the production post for more than half a year returns to the steel bar gas pressure welding operation, a re-examination shall be conducted first. The retest can be exempted from the basic knowledge test and only the operation skill test will be conducted. W.bzsosO.coI Engineering Construction Standard Full Text Information System
Plastic Certificate Cover
Rebar Gas Pressure Welding Welder Examination
Year Month Day
Certificate Number:
Welder Examination Unit
Appendix B
Welder Examination Certificate Sample
(Reference)
Year Month Day
Plastic Certificate Cover
Page 15
Examination Results
Basic Knowledge Examination:
Operation Skill Examination:
Rebar Grade Test Piece Tensile Test Piece
Branch Diameter Number
Bending Test Degree
Evaluation of Welder Operation Skill Qualifications for
Chairman of the Examination Committee
Year Month DaycoI Engineering Construction Standard Full Text Information System
Plastic Certificate Cover
Rebar Gas Pressure Welding Welder Examination
Year Month Day
Certificate Number:
Welder Examination Unit
Appendix B
Welder Examination Certificate Sample
(Reference)
Year Month Day
Plastic Certificate Cover
Page 15
Examination Results
Basic Knowledge Examination:
Operation Skills Examination:
Rebar Grade Test Piece Tensile Test Piece
Branch Diameter Number
Bending Test Degree
Assessment of Welder Operation Skills Qualifications for
Chairman of the Examination Committee
Year Month DaycoI Engineering Construction Standard Full Text Information System
Plastic Certificate Cover
Rebar Gas Pressure Welding Welder Examination
Year Month Day
Certificate Number:
Welder Examination Unit
Appendix B
Welder Examination Certificate Sample
(Reference)
Year Month Day
Plastic Certificate Cover
Page 15
Examination Results
Basic Knowledge Examination:
Operation Skills Examination:
Rebar Grade Test Piece Tensile Test Piece
Branch Diameter Number
Bending Test Degree
Assessment of Welder Operation Skills Qualifications for
Chairman of the Examination Committee
Year Month Day
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