Abstract : The welding process is a key process in the manufacture and installation of steel structures. A quality assurance system is established at the manufacturing and installation site of hydraulic steel structures to make the installation and installation of hydraulic steel structures from tooling design, process development, material procurement, and resource allocation. Welding, inspection, etc. are all carried out under controlled conditions to ensure the quality of the manufacturing and installation of hydraulic steel structures and to ensure the safe and reliable operation of the metallurgical equipment.

Key words: hydraulic steel structure; welding; quality; control

The welding process is a key process in the manufacture and installation of steel structures. The quality of the steel structure directly affects the reliability of the safe operation of the metallurgical equipment; especially the uncertainty of the influence of the welding of the hydraulic steel structure installation site: the operation area Small, dark and damp, complicated construction, wide range, and difficult to manage... Therefore, all relevant hydraulic steel structure design, manufacturing, installation and acceptance procedures have given full attention to the welding process and construction The quality indicators are clearly defined. From the analysis of the accidents occurring in the current steel structure, most of them are directly related to the quality of steel structure manufacturing and installation in the weld and heat affected zone. Establish a quality assurance system at the manufacturing and installation site of hydraulic steel structure, so that the manufacturing and installation of hydraulic steel structure is carried out under controlled conditions from tooling design, process formulation, material procurement, resource allocation, welding, inspection, etc., thus ensuring hydraulic engineering. The quality of the manufacture and installation of steel structures.

1 Welding quality control system

The welding quality control system is a sub-system of the quality assurance system for the fabrication and installation of hydraulic steel structures. The establishment of this system must meet the following conditions.

(1) Appoint and match the personnel responsible for welding each position.

(2) There is a set of welding management system that is suitable for the company and the construction site. Such as: welding construction preparation rules, welding process evaluation, product welding test board management system, welding process and construction, welding materials, welding equipment, welding technology, weld rework, welder training and qualification and certificate and quality cost, etc. Management system, etc.

(3) Establish a set of effective working procedures, work basis, work standards and work vouchers, and follow them.

Work procedures refer to a series of welding quality control standards such as process evaluation, process modification, weld repair, quality problem handling and prevention, product welding test board inspection, sample processing and testing.

Work basis refers to the process, drawings, etc., such as the welder's work is based on the welding general code of practice and the welding process card; the welding technician's work is based on the construction drawing, process evaluation report, etc.; the welding quality inspector's work is based on the construction drawing, welding Work instructions, welding quality assessment standards, etc.

Working standards refer to corporate standards, industry standards, national standards and international standards. For example, the weld quality inspector checks the appearance quality of the weld mainly according to the standard DL5017-93 Table 6.4.1 or DL/T5018-94 Table 4.4.1.

Work vouchers refer to various forms, reports and original records in welding management, weld appearance quality inspection records, welding technology record, welding rod baking records, welding rod collection and recovery records, welding construction records, weld non-destructive testing reports , weld non-destructive testing orders, weld repair notices, etc.

2 Welder management

To ensure the quality of welding, there must be a team of welders with both a certain quantity and a certain quality. The main contents of the welder management work of hydropower construction enterprises are: welding salary quality review and certification, formulation and implementation of welder training plan and welder training technical management, quality assurance of welder management work and establishment and improvement of various systems, welder assessment and certificate Management, training quality supervision and inspection and management of welder files. The management program for welder training is shown in Figure 2.

2.1 Welding Training Management

The core of training management is to conscientiously implement the "SL35 Hydraulic Metal Structure Welder Examination Rules" or the Ministry of Labor "Boiler and Pressure Vessel Welder Examination Rules". Measuring and testing the training results is based on the test pass rate and the welder's quality in the production. When the standard is reached, the corresponding qualification certificate - welder certificate is issued.

2.2 Management of welder technical files

The comprehensive and complete technical archives enable the personnel engaged in welder management to have a comprehensive and systematic understanding of the welder's technical status and welder performance. A relatively complete technical file should contain: 1 basic conditions of the welder; 2 overall status of the welder; 3 training materials; 4 welding quality status records; 5 qualified welder skills files and other aspects.

3 Welding process management

The preparation and testing of welding processes and process qualification are an important management task that is essential to guide welding operations.

3.1 Review of welding process design

For the hydraulic steel structure, the review of the welding process design mainly includes: 1 visibility and reachability of the welded joint position, weldability and reliability of non-destructive testing after welding; 2 welding groove standardization, special design welding Joint type and groove form, dimensional accuracy of processability, economy, but also should consider its degree of restraint and the possibility of crack formation; 3 welding method, the correctness of welding material selection; 4 the definition of welding joint category and Whether the selected acceptance criteria are reasonable and so on.

3.2 Preparation of welding process plan

According to the welding process design provided by the construction drawing of the meeting, the welding construction process plan shall be prepared. The main contents of the welding process plan shall include: 1 pretreatment method of material; 2 blanking process of blank; 3 processing method of groove; 4 welding method Selection; 5 welding material and welding parameters selection; 6 welding sequence; 7 welding preheating and post-weld heat treatment methods and parameters selection; 8 welded joint quality inspection methods, quantity and qualification standards; 9 welded joint surface treatment Claim.

3.3 Welding procedure qualification

Welding procedure qualifications should be based on reliable steel weldability testing and completed prior to product welding. The welding procedure qualification shall be carried out according to the following procedures: 1 The technician shall submit the process evaluation task book (welding method, test project and standard); 2 the welding responsibility engineer shall review the task book and formulate the welding procedure qualification instruction book (welding process specification parameters); The responsible engineer shall arrange the task book and the instruction book to organize the implementation of the person in charge of the welding laboratory; 4 the welding responsibility engineer shall supervise the basis according to the provisions of DI5017-93 or DL/T5018-94 or JB4708-92 "Steel Pressure Vessel Welding Process Evaluation". The skilled welder shall weld the test piece and the test and test of the test piece and sample; 5 the person in charge of the test room shall be responsible for assessing the test of the sample, and shall summarize the test results and submit the welding process evaluation report; 6 After being approved by the welding responsible engineer and approved by the chief technical officer of the enterprise, it is formally used as a reliable basis for the preparation of the welding process.

The equipment and instruments used in the welding process assessment shall be in normal working condition. The steel and welding consumables shall comply with the corresponding standards. The test specimens shall be welded by the skilled welders with qualified certificates.

The quantity of process evaluation shall be subject to the needs of the construction and production of the enterprise, not as many as possible. Refer to the process evaluation criteria, list the minimum number of assessments for a project in the enterprise, and maximize the coverage of individual assessment projects.

3.4 Welding instructions

The welding operation instruction sheet is also called the welding process card. It is formulated according to the relevant parameters of the process evaluation comprehensive report after the welding process evaluation. It is the technical document of the product welding process and is the basis for guiding the welder to engage in product welding. It is to overcome An important means of random welding process and strict implementation of process quality requirements is a reliable guarantee for improving the quality of welding engineering. The preparation should follow the principles of effectiveness, practicability, scientificity, and rigor, and should be sent to the welder before the engineering welding or welder training or examination, or to explain clearly to the welder in a technical way to facilitate implementation.

4 Management of welding materials

According to the relevant national regulations, “welding materials should have a factory certificate of conformity and a quality guarantee”. “When the material enters the factory, it shall be inspected and accepted according to its corresponding standards. If there is any doubt about the material, it shall be re-examined and used only after passing the test.” “The welding rod, welding wire and flux should be placed in a dedicated, ventilated and dry warehouse. The temperature is kept above 5 °C, and the relative humidity is not more than 50%." "The welding rod library should be established in the manufacturing plant or construction site. The welding rods should be kept by special personnel, baked and distributed, and the measured temperature and welding rod should be released in time. And recycling records, baking temperature and time should be strictly in accordance with the specifications of the welding rod" and so on. This clearly sets out specific requirements for the use and storage of welding materials for hydraulic steel structure manufacturing and installation companies. The hydraulic steel structure safety construction enterprise must strictly manage the procurement, acceptance, storage and use of welding materials to ensure the welding quality.

The storage, distribution, use and recycling of welding materials must be carried out in strict accordance with the welding technical conditions, the corresponding welding material standards, the product welding process instructions and JB3223 "Quality Management Regulations for Welding Materials". At the construction site of water conservancy and hydropower, we should focus on the secondary storage of welding consumables, the baking conditions of low-hydrogen welding rods, the number of repeated baking and the heat preservation during use, and the processing of expired welding rods.

5 Welding construction site management

On-site management of welding quality control of hydraulic steel structure installation, including product welding, weld rework and welding environment confirmation.

When welding products, quality inspectors and technicians must urge the welders to strictly enforce the process discipline and strictly follow the welding instructions. For the first and second types of welds, the welding records signed by the quality inspectors are required.

Weld seam repair means that welds with excessive defects must be treated by welding. SL36 "General Technical Conditions for Welding of Hydraulic Metal Structures" and DL5017, DL/T5018, etc. stipulate that "the number of repairs at the same location of welds should not exceed two times. The third repair must be approved by the chief technical officer and will be repaired. Record in the product quality file." Therefore, the weld repair must have a rework process and record, and if necessary, a rework process qualification should be in place to ensure that the weld rework is carried out under controlled conditions. The repair process shall be formulated according to the material, equipment technical parameters, defect nature, location, size and causes of the weld and the characteristics of the weld stress, and shall be subject to approval. Otherwise, it shall be deemed invalid and shall not be implemented.

Welding environment. According to SL36-92, DL5017-93, DL/T5018-94, etc.: When the following conditions exist in the welding environment, and there is no effective protective measures, welding construction is prohibited: 1 open-air welding in rainy and snowy days; The welding site wind speed is greater than five (8m / s); 3 ambient temperature is lower than -10 ° C; 4 relative humidity is greater than 90%. Since the installation and construction of hydraulic steel structure is basically open-air operation, and the construction period is tight and there are many cross-operations, it is necessary to ensure that the welding environmental conditions meet the welding technical requirements during construction, thus creating favorable conditions for ensuring the welding quality of the products.