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Importance of Defect Repair and Heat Treatment of Ductile Iron Parts

Mar. 01, 2020

Ductile iron parts as shaft parts require comprehensive mechanical properties with high strength and good toughness. The process is: the cast iron is heated to a temperature of 860-900 ° C to keep the matrix austenitized, and then cooled in oil or molten salt to achieve quenching, and then tempered at 500-600 ° C to obtain a tempered sorbite structure. (Generally, there is still a small amount of massive ferrite), the shape of the original spherical graphite does not change. After processing, the strength and toughness are well matched, which is suitable for the working conditions of shaft parts.

Ductile Iron Bollard

Ductile Iron Lamp Post

Due to various factors, ductile iron lamp post often has defects such as pores, holes, slag inclusions, cracks, and pits. Common repair equipment is argon arc welding machine, resistance welding machine, cold welding machine, etc. Its advantages are mainly reflected in the small heat affected area, no pre-heating of ductile iron parts, cold welding repair at room temperature, so no deformation, undercuts and residual stress, no local annealing, and no change in the metal structure of nodular cast iron parts. Therefore, the cold welding machine is suitable for repairing the surface defects of precision ductile iron parts.

The cold welding welding repair range is Φ1.5-Φ1.2mm welding repairing point repeatedly melting and accumulation process. In the repair process of large-area defects, repair efficiency is the main factor restricting its wide application. For large defects, the composite application of traditional welding repair process and casting defect repair machine is recommended. But sometimes we do n’t have a lot of defects, so we do n’t need to invest a lot of cost. We can repair it with some repairing agents. For example, for iron materials, we can use JS902 to repair it. It can be used later if it is not finished.

Sometimes ductile iron lamp post will be severely deformed and cracked. On the basis of inspection of its structure, you can place ribs and stiffeners in places that are deformable and cracked. Without affecting the casting geometry and performance requirements, increase the fillet size at the transition. In the design of the casting casting system, more than two straight runners can be set up for castings with larger weight and larger volume, so that the molten metal can quickly and smoothly enter the casting mold, thereby forming a high quality.

In addition, nodular cast iron parts will also have serious sand sticking, which will cause the quality of castings to decline. The solution is to start with the paint, because the fire resistance, strength and adhesion of the paint directly affect the sand sticking phenomenon. Careful inspection should be performed before painting. At the same time, properly increasing the vibration force, negative pressure and adjusting the pouring temperature will also help to improve the problem of sand sticking.

Ductile iron castings are high-quality precision castings or sand castings. Reasonable design, precise processing and perfect quality control make the Aomi pump have the characteristics of low vibration, low noise, high efficiency and long life. Ductile iron parts are widely used in electronic light industry and can be used for instruments.

Processing of light industry, standard parts, bearing industry, auto parts industry and other parts. Abrasion resistance and dimensional stability directly affect the accuracy of the machine tool. Ductile iron parts of machine tools are ground with water grinding technology. In order to prevent rusting of machined ductile iron parts after processing, rust-proof water is required for grinding. Ductile iron parts of machine tools are filled with vinyl chloride. Ductile iron parts of machine tools must be sanded after they have been dried. After each grinding, the refining slurry and dust must be completely removed. After the nodular cast iron parts of the machine tool are cleaned after the putty is polished, it is necessary to spray a second primer of vinyl chloride, which can improve the flatness of the paint film and the gloss of the paint film.

The aluminum electric motor shell supplier believes that, as a new type of cast iron material in the 21st century, isothermally quenched ductile iron castings (ADI) have excellent comprehensive mechanical properties, which are comparable to alloy forged steel, and their unit mass and strength The ratio and the relative cost per unit yield strength are the lowest in cast aluminum, ductile iron, cast steel and forged steel, with obvious performance and cost advantages.

Ductile iron parts should be used after heat treatment. Due to casting defects such as pores, cracks, shrinkage and shrinkage, coarse grains, uneven structure and residual internal stress in the nodular cast iron parts in the as-cast condition, the strength, especially plasticity and toughness, of the nodular cast iron parts are greatly reduced.

Ductile iron parts require higher hardness as bearings, often quenched and tempered at low temperatures. The process is: various castings are heated to a temperature of 860-900° C, and the original matrix is fully austenitized by heat preservation, and then cooled in oil or molten salt to achieve quenching. After heating and tempering at 250-350° C, the original matrix is converted For tempered martensite and retained austenite structure, the shape of the original spherical graphite does not change. The treated casting has high hardness and certain toughness, retains the lubricating performance of graphite, and further improves the wear resistance.