Ductile iron pipe fittings are a class of materials widely used in contemporary industry or architecture. Compared to ordinary iron castings, the addition of graphite materials effectively improves the toughness and strength of the materials, and their comprehensiveness is comparable to that of steel. Ductile iron pipe fittings are produced by pouring and molding molten metal. During the pouring process of molten metal, some issues should be carefully addressed in order to produce ductile iron castings with high quality, toughness, and strength.
For the production materials of nodular cast iron pipe fittings, the most important thing to be careful about is their strength. If the strength does not meet the requirements, it will lead to a decline in the performance of the product, and in addition, it will also reduce its utilization compliance. On the other hand, it is also necessary for the product to meet good toughness requirements.
"Only when it reaches its toughness can its performance prevail in the time it is used. With such products, there is often a sign of breakage during the time they are used, which is due to the fact that they do not meet the requirements in terms of toughness. Finally, it is also related to their useful life, which means that they must achieve good performance.".
During the pouring process, we usually follow the guidelines of high temperature tapping and low temperature pouring. This pouring method can largely melt the mixture, which is conducive to the floating of molten slag, preventing defects such as slag inclusion and air holes in the casting, affecting the quality of the casting, and also conducive to slag removal and degassing.
In order to ensure the quality of castings and high-quality production, we should follow the following principles in our meticulous work during the pouring process of ductile iron castings.
1. Before using, we need to adequately dry a series of pre pouring agents such as inoculants and spheroidizing agents.
2. Master the accurate pouring rate, slow first and then fast, which not only reduces the impact of molten metal on the sand mold, facilitates gas extrusion, but also prevents the appearance of cold insulation signs. Strictly follow the principles of slow, fast, and slow.
3. For those with a large specific force between liquid shrinkage and consolidation shrinkage, supplementary pouring is conducted from the gate or riser in real time after pouring.
Preparation before installation of ductile iron pipe fittings:
1、 Complete various contents of foundation engineering design, while completing the following work:
(1) The foundation control line and foundation bottom elevation line have been marked;
(2) Composite foundation, pile foundation, etc. have passed the inspection by the testing unit;
(3) The foundation treatment plan requires approval documents.
2、 After the completion of the foundation project, the construction unit has inspected the project quality, confirmed that the project quality conforms to relevant laws, regulations, and mandatory standards for engineering construction, and meets the requirements of the design documents. It has also submitted a construction unit (foundation) report on the quality of the construction project, which has been reviewed and signed by the project manager and relevant principals of the construction unit;
3、 The supervision unit has conducted a quality assessment of the foundation works, provided complete supervision data, and submitted a supervision and evaluation report on the foundation acceptance of Tianjin construction projects, which has been reviewed and signed by the Chief Supervision Engineer and relevant principals of the supervision unit;
4、 The survey and design units have inspected the survey and design documents and the notice of design change signed by the design unit during the construction process, and have submitted a quality inspection report, a project quality inspection report of the survey and design unit, and a project quality inspection report of the design unit, which have been reviewed and signed by the person in charge of the survey and design unit and the relevant person in charge of the survey and design unit;
5、 Complete technical archives and construction management data are available and meet the quality data archiving requirements of Tianjin Construction Engineering Quality Supervision and Management Station;
6、 All issues ordered to be rectified by the District Planning and Construction Administration and its entrusted District Construction Engineering Quality Supervision Station have been rectified.