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Defects in castings and forgings

Release time:

2023-05-11 16:19

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The defects produced in the casting and forging process are similar to the defects produced in the ingot, but they are still process defects, including pores, inclusions, shrinkage holes, loose holes, cracks, etc.

Pores (bubbles): The metal liquid contains too much air, the model is wet, and the air permeability is poor to form pores (bubbles). The pores of castings are divided into monodisperse pores and dense pores. Inclusions: Inclusions are divided into non-metallic inclusions and metallic inclusions. Non-metallic inclusions are the chemical reaction products between metal and gas environment in the smelting production process, or the inclusions that can be formed by mixing refractory materials, molding sand and the like into molten steel in the process of pouring system. Metal inclusions are inclusions that form when different metals occasionally fall into the foundry water and cannot be dissolved. Shrinkage cavity: Shrinkage cavity is a defect that cannot be supplemented by volume shrinkage after cooling and solidification of liquid metal. Shrinkage is mostly located near the riser and large cross-section or abrupt cross-section. Looseness: due to the defects in the smelting process of students, the design of mold shape and inappropriate reasons, the research on the development of fine grain boundary cracks in the middle of the wall thickness of castings and forgings or the internal structure of loose tissues formed by learning some fine voids in grain boundaries, this part can be analyzed by analyzing the combination between grains. China's enterprise culture is quite weak (cloud-like dark shadow is formed on the radiographic film). Crack: Crack refers to the internal stress (thermal stress and tissue stress) caused by local cracking due to excessive low melting point impurities and the formation of casting defects during cooling. Under the size of casting and forging, the stress concentration is serious and easy to crack.

The process defects of casting and forging have the characteristics of complex shape, and the use defects of casting and forging are mainly fatigue cracks, including mechanical fatigue cracks and thermal fatigue cracks. The organization is uneven. After the liquid metal is injected into the mold, the liquid metal layer contacting the mold wall becomes finer particles due to the rapid temperature drop. With the increase of the distance of the die wall, the influence of the die wall gradually begins to weaken, and the crystal grows into a parallel columnar analysis crystal along the direction perpendicular to the die wall. In the central part of the casting, there is no obvious direction of heat dissipation, and it can grow freely in all directions until it contacts each other to form an equiaxed crystal region. It can be seen that the organization of the casting is not uniform, in general, the grain is relatively rough. The tissue is not dense. The liquid metal crystallizes in the form of branches, and the liquid metal between the branches finally solidifies, but the branches are difficult to be completely filled with liquid metal, resulting in a general lack of compactness of the casting. In addition, if the liquid metal injected into the mold shrinks in volume during cooling and solidification, it is not fully replenished, and pores or even shrinkage cavities may be formed. The graphite in cast iron often appears in flake, spherical or other large-sized shapes, and can also be regarded as a non-dense structure. The surface is rough. Surface quality management general enterprise development is still a relatively rough, can not be compared with the machining surface information technology level, the shape is also more complex

How to maintain planter accessories

Production of castings and forgings

The correct use and maintenance of the disc harrow: in operation, the technical condition of the rake, scraper, square shaft, bearing, angle adjuster and connecting parts should be checked frequently, especially the end nut of the disc harrow group and the fixing bolts of each bearing. If it is found loose, tighten it in time, and remove the weeds and dirt on the workpiece in time.

How to maintain planter accessories

Planter A planting machine using crop seeds as a planting object. Planters for a certain type or crop are usually named after the crop type, such as wheat planter, cotton planter, etc. Planter accessories are very effective in farmland operations, so the planter accessories are easily damaged. Next, the planter manufacturer will introduce how to maintain the planter accessories. Before using the planter, we should have a simple and comprehensive understanding of the principles of all planter accessories. The planter manufacturer stated that it can be effective as long as the maintenance is carried out on the correct accessories to ensure the normal use of the planter accessories. The planter will extend its life.

Defects in castings and forgings

Production of castings and forgings

Castings and forgings must be melted by electric furnaces, mainly electric arc furnaces and induction furnaces. According to the different lining materials and slag system, can be divided into acidic furnace and alkaline furnace. Carbon steel and low alloy steel can be smelted in any furnace, but high alloy steel can only be smelted in alkaline furnaces.

Inspection of Casting and Forging

The complex information system management interface of casting and forging, such as poor ultrasonic penetration, coarse grain, uneven organization, etc., all enhance the scattering of an ultrasonic wave by students, and the energy can be effectively attenuated, so that the detectable thickness is smaller than that of forgings.

What are the advantages and disadvantages of casting and forging

One of the advantages of casting and forging is the flexibility of design. Personnel design has a large degree of freedom of design choice for the shape and size of castings, especially for parts with complex shapes and hollow sections. Steel castings can be manufactured using a unique process known as core assembly.

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