The specific heat capacity of NdFeB material was determined by differential scanning calorimetry (DSC) method. The optimal test conditions were explored from the aspects of crucible selection, standard sample mass and sample weight. Meanwhile, the Curie temperature of NdFeB material was determined by the abnormal turning point of the specific heat capacity near the Curie temperature. The optimal testing conditions were obtained as below: the aluminum (Al) crucible was selected; the mass of sapphire standard sample was 43.3 mg; the sample weight was about 43.3 mg. The results showed that the Curie temperature (T_C) of NdFeB material determined by DSC was consistent with that of typical NdFeB magnetic steel (310 ℃). The Curie temperature of NdFeB materials with different grades was in range of 290-330 ℃, and the Curie temperature of NdFeB magnetic material obtained by this method was in the range of 243-386 ℃ of the third generation of rare earth permanent magnet materials R₂Fe₁₄B series compounds.

In the practical application of phased array ultrasonic testing technology, the coupling methods of probe and workpieces mainly include contact method and water immersion method. In the contact detection method, the probe is in direct contact with the workpiece, and the detection effect is affected by the workpiece surface roughness and near field region. For the water immersion method, there is a water layer between the probe and the workpiece, which not only has good coupling effect, but also has no near-field influence, so the detection effect is good. This paper analyzed the defect imaging characteristics of the two detection methods, and verified the imaging effect of the same defect through comparative experiments. It showed that the water immersion method of phased array ultrasonic detection had better defect display effect and higher signal-to-noise ratio than the contact method.

This article mainly introduced a high-temperature static Poisson's ratio test method using mechanical axial and transverse extensometers through axial tension. Compared to traditional high-temperature static Poisson's ratio measurement methods, the proposed method had the advantages of more convenient, low-cost, and intuitive displacement measurement. The static Poisson's ratio tests of various materials were conducted at room and high temperatures. Moreover, the data were compared with dynamic Poisson's ratio data under the same conditions. The results showed that for GH49, 316L, GH4720Li, and K6509 materials, there is a certain numerical difference between high-temperature dynamic Poisson's ratio and static Poisson's ratio, and even under temperature changes, the trend of change does not show correlation.

The mapping of elements in the non-stick pan inner coating were analyzed using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) under acceleration voltage of 10 kV. The results showed that the overlapping between the K spectrum series of F element and L spectrum series of Fe occurred led to the difficulty to distinguish F and Fe elements in the mapping. By changing the spectrum series of Fe from L to K or employing the TruMap function of EDS software, the true distribution of Fe element could be obtained. By combining the point spectrum fitting with quantitative analysis results, the true position of F element in the mapping was determined.

The application of LED UV-A lamp is more and more common. Its performance indicators are quite different from the high-pressure mercury vapor arc lamp, and the improper application will directly lead to the missing inspection of defects. Based on the performance index of the UV-A lamp, its use characteristics were discussed so as to facilitate the correct use of the UV-A lamp by technicians. The contents included the production certificate of the UV-A lamp, the integrity and cleanliness of the filter and the inspection method, the radiation intensity of the UV-A lamp, the leakage of the white light of the UV-A lamp, the minimum working distance, the effectiveness of the LED lamp bead work. The requirements and test methods of the UV-A lamp were analyzed in details in order to guide the inspectors to correctly grasp its use characteristics and test requirements. This study was conducive to the correct implementation of the detection, which could ensure the reliability of the defect detection results.

During the grinding and inspection stage, some surface-initiated turtle-back cracks were observed on the connecting rod neck of φ135 mm 48MnV steel crankshaft after surface induction hardening and tempering. These surface cracks were analyzed by optical microscope, scanning electron microscopy equipped with an energy dispersive spectrometer, and microhardness tester. The results indicated that the observed cracks were grinding cracks. The cracks only existed on the surface layer of the hardened layer, with a depth of about 340-510 μm. The surface layer of the hardened layer had the lowest hardness. Then it firstly increased and then leveled off, and gradually decreased to the hardness of connecting rod journal substrate. The microstructure of the connecting rod journal from the hardened layer to the substrate was: quenched martensite + residual austenite → tempered martensite + tempered troostite → tempered martensite → ferrite + pearlite.

A rainwater grate in one residential area fractured during use. The intact rainwater grates and fractured ones collected from the site were analyzed and compared by metallographic examination, scanning electron microscopy, and mechanical property testing. By combining with finite element simulation analysis, it was found that the material of the fractured rainwater grate was gray cast iron, which had relatively poor mechanical properties. Additionally, due to the existence of old damage in the fractured rainwater grate, its strength could no longer meet the requirements for pedestrian stepping, posing a safety hazard, and leading to breakage accidents when stepped on by pedestrians.

The X80 grade pipeline steel products have been widely used in domestic oil and gas pipeline transportation engineering. The X80M hot-coiled produced by a steel factory had some defects such as edge warping, which led to the unqualified problem of batch flaw detection after pipe manufacturing. The typical defects were selected for macro and micro analysis and energy spectrum analysis, and according to the results of slab nickel nail test, it was found that the defects were mainly caused by the large temperature drop of hot-coiled edge in the rolling process. By adopting various measures, such as corner cutting and grinding of the slab, optimizing the hot rolling secondary model, reducing descaling passes in rough rolling, and modifying the vertical roll pass, the proportion of hot-coiled with scaly skin defects had decreased to less than 5%. The scaly skin defect was also reduced, and the improvement effect was remarkable.

The motorcycle′s frame riser made by 20# seamless steel tube was cracked during use. The cause was investigated through metallographic examination, chemical composition analysis, hardness test and scanning electron microscope. The results showed that the chemical composition of frame riser could meet the requirements of national standards, and there was no abnormality in the hardness and microstructure. Martensite was found in the welding heat affected zone of tested surface. The existence of martensite increased the brittleness and reduced the toughness of riser support. The hardness difference between martensitic structure and matrix structure formed stress concentration. Therefore, the main reason to cause cracking of frame riser was the martensite which was generated during welding.

The unsatisfactory low-temperature impact performance of Q345qD bridge slabs produced by one company was observed successively. The unqualified slabs were mainly concentrated in the thickness of 16 mm. Through a series of analysis and testing on the unqualified samples submitted for inspection, the main reasons for the unqualified low-temperature impact performance of Q345qD steel plate were identified, i.e., the severe segregation in the center of the sample as well as the presence of bainite structure in the segregation zone. At the same time, the nonmetallic inclusions in the sample also affected the low-temperature impact performance of the plate. The corresponding improvement measures were also proposed.

The leaking of some tubes in heat exchanger was observed in a secondary tower′s top condenser in one certain distillation deisobutanizer. In order to find out the failure cause and prevent the similar incidents from recurring, the chemical composition, mechanical properties, metallographic structure, and microscopic morphology of the tubes were analyzed to identify the reasons for leaking. The results showed that the heat exchanger tubes had a serious uniform corrosion and local point corrosion perforation, leading to the leaking of tubes. Moreover, the corrosion morphology had the characteristics of microbiological corrosion. Meanwhile, the large size nonmetallic inclusions in heat exchanger tubes accelerated the process of point corrosion perforation of tube wall.

The 40CrNiMoA alloy steel billet produced by a certain forging factory was forged into wear-resistant plate ring billet by forging hammer. After quenching and tempering heat treatment, it was found that there were many crack defects on the surface of the ring forgings. In order to investigate the causes of surface crack defects in 40CrNiMoA ring forgings, samples were dissected and analyzed for chemical composition, metallographic examination and scanning electron microscopy. The analysis results indicate that the crack in the 40CrNiMoA ring forging originates from the end face of the ring forging, and the crack propagation mode is a single transgranular propagation. The formation of the crack belongs to the stress crack of heat treatment quenching.