Dongming fasteners are actually a kind of connectors (connectors), but due to their wide variety and wide application, they are only one type in actual use, and are even referred to as standard parts. At present, the materials of standard parts on the market are mainly divided into carbon steel, stainless steel, brass and aluminum alloy.

Dongming fasteners are widely used in automobile, aerospace, construction, shipbuilding, medicine and health and other fields. They play a very important role in people's production and life. With the development of the times, the quality requirements for Dongming fasteners are also constantly improving. More and more aerospace standards directly regard non-destructive testing as a necessary process for Dongming fastener manufacturing. Dongming fastener defects are mainly divided into raw material defects and manufacturing process defects.

Defects in raw materials (mainly bars, wires, and tubes) include folds, delaminations, cracks, and non-metallic inclusions. Unqualified raw materials can be removed by non-destructive testing.

In the manufacturing process, upsetting (cold heading, hot heading, stamping, etc.) may cause defects such as drawing marks, cracks, and folding, grinding may cause grinding cracks, rolling threads may cause folding, and heat treatment may cause quenching cracks .

The non-destructive testing method can find the substandard products in Dongming fastener products as soon as possible, reduce the cost, improve the manufacturing process and improve the reliability of the products.

Non-destructive testing in the manufacturing process of Dongming fasteners

Commonly used non-destructive testing methods for Dongming fasteners

Magnetic particle inspection

Surface and near-surface defects (such as cracks, inclusions, hairlines, wrinkles, pores, porosity, etc.) can be found through magnetic particle inspection, and the shape of the defect can be visually displayed? It can roughly judge the nature of the defect, with high detection sensitivity, and the minimum width of the detectable defect is about 1 μM. As long as the proper magnetization method is used, almost all parts of the surface of Dongming fasteners can be detected, which is not only fast, but also easy to operate? It is especially suitable for detecting various surface and near-surface longitudinal defects of ferromagnetic Dongming fasteners.

The main limitation of magnetic particle inspection is that it can only detect Dongming fasteners of ferromagnetic metal materials, but not austenitic stainless steel? Aluminum copper? Dongming fasteners made of non-magnetic materials such as magnesium and titanium. The sensitivity of magnetic particle detection is closely related to the direction of magnetization. If the defect direction is parallel to the magnetization direction or the angle with the surface of the Dongming fastener is less than 20°, it is difficult to display the defect, and the surface scratches are shallow? Deep buried holes are not easy to find.

In addition, if there is a covering layer on the surface of Dongming fasteners, such as a paint layer, it will adversely affect the detection sensitivity. The thicker the covering layer, the greater the influence; if the surface of Dongming fasteners is shot peened, it will also have an adverse effect on the detection sensitivity.