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Semi-automatic cutting machine to improve the automatic fillet welding and welding process assessment method

In the case of a newly constructed steel ship, the welding of stiffened plates such as spherical flat steel is carried out on each of the bulkheads, generally requiring double-sided fillet welds and welding in the case of prefabricated slabs. Usually using carbon dioxide gas shielded welding (FCAW), commonly used in two ways. First, the use of all manual welding. This approach is less costly. But there are obvious shortcomings, production efficiency is very low; welding quality fluctuations, weld forming unsightly, it will cause a lot of rework, waste of labor, waste materials; thin bulkhead deformation is also large, firework correction workload. This also increases the cost. Another method is the use of professional angle welding equipment. This method is fast, high efficiency; forming good, repair less; but the equipment is more expensive, equipment operation on the workers demanding, such as equipment damage repair more trouble, the high cost. Generally only in the demanding use of steel welding, the hull sub-production used, it is not worth. The pursuit of maximum profit is the theme of enterprise development, in order to improve the welding efficiency, reduce production costs as the starting point, improve and apply the shipbuilding process of welding technology, and to ensure product quality at the same time, can reduce costs and improve efficiency. In the project Boskalis-SMIT (Boat No. ZPMC1040) constructed by Zhenhua Heavy Industry, an effective method was adopted, which was to transform the semi-automatic small-size cutting machine, which was cheap and easy to operate, into an automatic fillet welding machine. Practical application, the effect is quite good. However, this new welding method is not recognized as a manual or professional welding equipment, according to classification societies requirements, the new welding method requires the assessment of the welding process, through the assessment can be used in shipbuilding projects.

1. Semi-automatic cutting machine transformed into automatic fillet welding

Semi-automatic cutting machine is mainly used in steel plate cutting, by the cutting system, body, adjusting device, track and other major components. One body is driven by the internal motor drive wheel in the track after walking; body panels are speed adjustment, front and rear direction selection switch, power switch, in order to achieve the control of the car walking. According to the characteristics of semi-automatic cutting machine, the cutting machine has the following improvements:

(1) Remove the original cutting system of external components (internal retention, can also be used for cutting), instead of card gas welding gun installed.

(2) The power switch inside the fuselage, the use of 2-pin socket with 2-wire cable connected to a wire, wire and welding machine control cable connection (without welding gun trigger switch and control cable), thus To achieve the same time walking car can be welded.

(3) in the fuselage side of the installation of lateral guide wheel, in order to use the car to achieve fillet welding, to ensure that the car to meet the shape of welding. After the transformation of the semi-automatic cutting machine in the function has been able to fully meet the needs of automatic fillet welding, only one worker can easily operate.

2. The welding process assessment

This modified fillet welding application, which is different from manual welding, is also different from the professional welding of welding trolleys, this welding method of welding procedures need to be approved by the classification society in order to apply in the corresponding project . First of all, welding process engineers, according to experience and the corresponding norms of the preparation of the "Welding Process Planning" (WPSP), submitted to the classification societies authorized surveyors to review, the surveyor will WPSP materials, joints, welding position , Welding methods, welding consumables and other requirements are reviewed one by one, in addition to the relevant parameters are also reviewed, such as current, voltage, welding speed, but also to confirm whether the size of the test board to meet the requirements and so on. After approval by the Surveyor, the WPSP will be submitted for approval, and the shipyard will proceed in accordance with the approved plan.

1, witness test board cutting. The shipyard invites the surveyor to witness the cutting of the test panels and provides a material warranty to the surveyor for approval. The surveyor will check the information of the steel plate, after correcting in each piece of board knocked on the stamp of classification society. (Usually more than a set of test boards to cut back.)

2, witnessed welding. When everything is ready, the shipyard invites the surveyor to witness the entire welding process. The surveyor first checks the test plate stamping, groove conditions, pre-spell quality, welder qualification certificate, welder ammeter, voltmeter test certificate, a variety of testing equipment in the test cycle and its test certificate and so on. Arrange the corresponding qualification of the welder for preheating, welding work. Welding process, the shipyard and the surveyor arranged to survey and record a variety of parameters and data, such as current and voltage, welding process but also to measure the preheating temperature, welding temperature. Upon completion of the welding, the surveyor shall check whether the appearance of the weld meets the requirements. All ends, finishing all records, the surveyor signature confirmation. If there is a problem, such as weld appearance does not meet the requirements, it is necessary to arrange re-welding, re-invite the witness to witness.

3, witness NDT. The surveyor is required to do the MT and invite the surveyor to witness. The operator's qualifications are submitted to the surveyor for inspection. If qualified, issue a MT report to the Surveyor. If not qualified, you need to re-welding, repeat the above steps.

4, witnessed the mechanical properties of test block sampling. Each block must be stamped on the classification society stamp. And then cutting to the laboratory for processing.

5, Seal transfer. During the processing of the test block, the original classification society's stamping needs to be processed, requiring the surveyor to carry out the stamping transfer.

6, to witness the mechanical properties test. When everything is ready, the surveyor is invited to witness the mechanical properties of the test block, mainly tensile and impact tests. The surveyor shall check the test equipment certification and laboratory qualification certificate, check the steel stamp, impact temperature and so on. At the end of the test, the surveyor will be required to sign the test data and then the laboratory will prepare a formal test report. Such as mechanical performance does not meet the requirements, according to regulatory requirements is to re-arrange the performance test, or direct assessment of failure, and then in accordance with the above steps to re-arrange the assessment.

7, check the macro-corrosion. After consultation with the surveyor, corrosion is carried out in advance. Corrosion requirements must be met. The surveyor is invited to inspect the corrosion and the surveyor signs the corrosion report.

8, to witness the hardness test. Upon request, the surveyor is invited to witness the hardness test of the test block. Submit the test equipment and laboratory qualification to the Surveyor. At the end of the test, the surveyor will need to sign the test data. The laboratory provides a formal test report. If the hardness does not meet the requirements, assessment failure, the need to re-do the above steps assessment.

9. To compile and report all data and prepare a "PQR" (PQR), according to the PQR, prepare a formal "Welding Procedure" (WPS). And submit to the surveyor for approval. After verification by the Surveyor, the seals are signed and sealed. This WPS takes effect. After the above assessment, the welding method can be formally used in the project.

3.The improved automatic fillet welding

(1) easy to configure; car light, individual use or move alone; easy to operate, the operator does not have high requirements.

(2) the car can be positive and negative direction of operation, two-way welding, to reduce the air range.

(3) a wide range of applications. Not only can be used in the construction of ships, in other large box structure can also be applied.

(4) its weld appearance, welding quality is high, reduce rework.

(5) due to semi-automatic cutting machine low prices, and other more expensive compared to the special welding car, can reduce the cost of equipment inputs. Not for welding can also be changed back into a cutting machine can be a dual-purpose machine, saving costs.