One tungsten-nickel-copper alloy with trademark of 93WNiCu was selected for damp heat test. The sample was treated according to the requirements (30-60 ℃ and humidity of 98%) of damp heat test in GJB150.9A. Some abnormal corrosives appeared on the material surface after treatment, and the color of gray green was visible. A series of characterizations of such abnormal corrosives were conducted, including surface morphology analysis, cross-section morphology analysis and elemental analysis, to analyze the causes and mechanisms of corrosive formation. The results showed that the attached matters on the surface of tungsten rods were the corrosion and oxidation products which were precipitated from the substrate during the damp heat test. The corrosives contained W, O, Ni, Cu, and C. The distribution of such precipitates was discontinuous and the thickness was nonuniform. The maximum thickness of the corrosion products observed was about 70 μm.

Metallographic inspection is an important approach for quality control of steel products. The quality problems can be reflected through classifying and rating of nonmetallic inclusions, grain size, microstructure, decarburized layer and nitrided layer. Then the corresponding measures are made to optimize the smelting and rolling production process. The rating process of metallographic inspection relies entirely on manual reference to the standard rating map, which has some disadvantages such as large influence of human subjective factors, low accuracy and low efficiency. The rapid development of artificial intelligence technology provides a realistic basis for the automatic identification and rating in metallography. The application status and research progress of artificial intelligence image recognition technology in metallographic inspection were summarized. Its development direction and challenges were discussed.

With the rapid development of spallation neutron source large-scale scientific facility technologies, the neutron beam flux that can be obtained has been significantly enhanced, and the neutron imaging technique has been also further developed. Due to the limitation of neutron beam flux, the conventional neutron imaging techniques require neutron beam with wide wavelength range to obtain relatively high flux conditions. In recent years, the high-flux pulsed neutron beam has been obtained via the large accelerator spallation neutron source. The energy (wavelength) resolved neutron imaging technique based on Bragg-edge effect, i.e., neutron Bragg-edge transmission imaging technology, has showed a wide application potential due to its high energy resolution, high spatial resolution and the ability to detect the crystallographic information. The fundamental principle of this technology was briefly introduced. Some application cases in residual strain, phase composition, dislocation density and oriented structure characterization were reviewed to play a positive role in the popularization of relevant techniques.

The cracking accidents of fuel spray nozzle seat manufactured with martensitic stainless steel occurred for several times during use. Moreover, the cracking positions of nozzle seat were almost same. In order to find out the cracking reasons, the cracked nozzle seats were examined by fracture analysis, chemical composition analysis and microscopic structure analysis. In addition, the residual stress analysis was also conducted for the same batch of valve seats. The testing results showed that the chemical composition of the cracked nozzle seats could meet the requirements, and there was no abnormality in microscopic metallographic structure. However, the dendritic cracks distributed along with the grain boundary were observed around the fracture position. The fracture analysis showed that the cracking of nozzle seats was dominant in intergranular fracture, and the muddy patterns appeared in the fracture surface. The energy spectrum analysis indicated the presence of a large quantity of chloride ions in the muddy patterns. The residual stress measurement showed that there was a certain residual compressive stress on the surface of unwelded nozzle seats, while there was obvious residual tensile stress near the cracking position of welded nozzle seats. The comprehensive analyses indicated that the cracking of fuel spray nozzle seat belonged to stress corrosion cracking.

In view of the brittle fracture problem of 65Mn hot rolled steel strip for cold rolling base material in the process of slitting and rewinding during the production of a saw blade enterprise, the failure reasons were comprehensively analyzed by means of composition analysis, metallographic observation and Brinell hardness test. The results showed that the chemical composition and tensile properties of the brittle fracture steel strip could meet the standard requirements. The Brinell hardness was 244-271HBW with large local fluctuations. The structure was mainly in pearlite with grain size of grade 6.5-7. There was a network or semi network ferrite wrapped pearlite phenomenon, leading to the decrease of grain boundary energy, which was the main cause of brittle fracture. By fully slow cooling or annealing hot rolled coils, the phenomenon of brittle fracture could be significantly improved. Pre-annealing was performed before cold rolling of subsequent steel strips to reduce deformation resistance. The rolling force was stabilized at 10-14 MN, which could significantly improve the cold rolling efficiency and performance stability.

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.

The corrosion behavior of 6061-T6 aluminum alloy laser-GMAW composite welding joint in 3.5%NaCl solution was studied using the scanning electron microscope (SEM), the energy dispersive scanning (EDS) and X-ray diffraction (XRD). The results showed that the grains in the microstructure of 6061-T6 aluminum alloy elongated along the rolling direction. The small black blocks and dots with dispersed distribution inside of the grains were the main reinforcing phase of the 6061-T6 alloy, i.e., Mg₂Si phase. The part with light color was α-Al matrix. Few larger black particles were the Al-Fe-Si phases, and there were few precipitated phases at the grain boundaries. The corrosion process of 6061-T6 in 3.5%NaCl solution could be divided into three stages, i.e., the pitting induction stage, the pitting development stage, and the corrosion product film growth stage. It had been transformed from a high-frequency capacitive reactance-low-frequency inductive reactance system to a high-frequency capacitive reactance-low-frequency Warburg impedance system.

The laboratories that participated in proficiency testing of ultrasonic inspection of defects inside forgings were assessed and analyzed. Firstly, the z-score statistics were carried out based on the results returned from the laboratories. Then the factors affecting the accuracy of the test results were analyzed and summarized. Moreover, the data of questionable and unsatisfactory laboratories were analyzed. Through the implementation of proficiency testing scheme, the testing level of relevant domestic laboratories could be reflected truly and objectively. It could also help the laboratories find out the problems in the daily testing and further improve the internal quality control, thus improving the testing level. This study provided basis for the laboratory supervision by the laboratory certification and accreditation management department.

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.

The liquid penetrant inspection is required for the weld of tube-tube sheet in steam generator product which was used in the main system of the pressurized water reactor nuclear power plant nuclear island. The selection of liquid penetrant inspection method, the requirements for the inspection devices, and the verification of inspection sensitivity were investigated. Through experiment comparison analysis, the inspection control process for water-washed liquid penetrant inspection of densely arranged tube-tube sheet welds was determined. Moreover, the product inspection results showed that when the liquid penetrant inspection was performed using the densely arranged and numerous tube sheet welds, the most efficient inspection method was the water-washed type dye penetrant inspection method under the condition that the sensitivity requirements were met.

The effects of testing forces, indentation diagonal direction, and indentation location on the measurement results of Vickers hardness for nickel-based single crystal superalloy were investigated. The results indicated that the testing force and the indentation location (either at dendrite arm or in interdendritic region) had little influence on the Vickers hardness measurement results, while the indentation diagonal direction had a certain impact. On the {100} crystal plane, the hardness value was the highest when the indentation diagonal direction lied along the <001> crystal orientation, and the lowest along the <011> crystal orientation. The difference was about 35HV. On the {111} crystal plane, the hardness value was between the above maximum and minimum values. The nickel-based single crystal superalloy exhibited anisotropy so that there were significant differences in the elastic modulus and other factors on different crystal orientations, which affected the measurement results of Vickers hardness.

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.

There was low local hardness of P91 main steam pipe in one thermal power unit. The non-destructive testing, thickness measurement, Brinell hardness testing and metallographic examination were conducted on site. The reasons for the low hardness were analyzed by combining with the unit maintenance and operation data. Moreover, the non-destructive life assessment and operation strategy formulation were performed. The results showed that the metallographic structure of the low hardness region was coarse, and the characteristic of martensite was nonobvious. One of the main causes was the improper preparation or execution of heat treatment procedures for welding line. According to the safety factor of 1.5, the residual life of the low hardness region was short. If the safety factor was further reduced, the corresponding residual life would increase, but the safety risk of continuous operation was also increased. It was necessary to reduce the operation parameters to ensure the safety of subsequent operation.

The temperature field of S355NL cylindrical casting billet (the height-to-diameter ratio was 1.05) in air-cooling process was studied by thermocouple temperature measurement experiments and simulation analyses. The proportion of convective heat transfer and radiation heat transfer was calculated, respectively. It was found that the convective heat transfer accounted for about 40%. The effect of workpiece inclination angle on heat transfer was investigated. The temperature distribution of the workpiece gradually increased along the opposite direction of gravity. For the inclined cylindrical forging billet, the temperature gradually increased along the axis direction. It was due to the thickening of the thermal boundary layer, which resulted in a reduction in heat transfer efficiency. The distribution law of local Nusselt number was opposite to that of temperature distribution. The average temperature of the workpiece surface gradually increased with the increase of inclination angle.

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.

After rough machining of X22CrMoV12-l alloy thick-walled forgings, the ultrasonic flaw detection indicated that there were long strip defects. The defects had a great impact on the life of the forgings, and were easily exposed to the surface of forgings during the finishing process, thus affecting the normal use of the forgings. In order to understand the cause of the defects, the flaw detection defects of alloy thick-walled forgings were analyzed by metallographic inspection, scanning electron microscopy and energy spectrum analysis. The anatomical defect characteristics belonged to the typical slag inclusion defect. In the closed thick-walled ring forgings, the defects were in the shape of long strips. After forging deformation, the defects had the bifurcation and crack extension morphology. There were abnormal particles inside the defects, and the contents of O, Al, La and Ce were abnormal. Therefore, it could be inferred that the defect was the brittle oxide defect.

For the ø300 mm YG1600 ultra-high strength stainless steel produced by double vacuum smelting and forging process, it was found that the fracture toughness index was on the low side during the mechanical property test. The microstructure of sample with low fracture toughness index was analyzed by metallographic microscope and scanning electron microscope. The results showed that there were microscopic cracks in the plane along the cracking direction of fracture toughness sample. The cracks were along the boundary of the martensite lath. The length of the martensite lath was not uniformly distributed between 20-80 μm, which was the reason to cause low fracture toughness of the bar. After a series of process analysis and process simulation, the original production process was adjusted. The vacuum arc remelting speed was reduced from 4.85-5.2 kg/min to 3.8-4.15 kg/min; the last fire heating temperature of forging was reduced from 1 100-1 130 ℃ to 1 060-1 100 ℃; the last fire forging ratio was increased from 2.25-2.77 to 3.36-4. Through the adjustments above, the fracture toughness of YG1600 ultra-high strength steel increased by 30-40MPa·m^1/2.

The influence of crack source weld bead welding methods on the drop weight NDT temperature was studied using the drop weight testing machine and optical microscope. Different heat dissipation methods, different magnitudes of welding current, different weld bead lengths, and different weld bead widths were selected and investigated. The results showed that the heat dissipation method and welding current had a significant influence on the drop weight NDT temperature, while the length and width of weld bead had no significant impact. Meanwhile, the melting depth, the area of heat affected zone, and the area of coarse grain zone were the essential reasons to affect the drop weight NDT temperature.

In order to fully play the role of low magnification inspection in quality control of continuous casting billets, each process of low magnification inspection was studied. A low magnification laboratory that met the requirements of the management system was redesigned. The automatic low magnification inspection process was formulated. The low magnification inspection processes were designed, including the sample processing and transportation, acid etching process, scanning imaging process, and environmental protection process. The suggestions for the overall layout of the process, civil engineering, materials, and laboratory management involved in the construction of the low magnification laboratory were proposed, which provided reference for the physical inspection quality management personnel and low magnification laboratory design and construction personnel in steel enterprises.

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.

Fracture occurred for a 10 mm NM500 steel plate in the cold bending test process. In order to study the cause of fracture, the bending test fracture steel plate and qualified steel plate were used for comprehensive analysis including cold bending process parameters, tensile properties, microstructure and inclusions type, fracture morphology, and energy spectrum detection comparison. The results showed that the large size MnS inclusions and agglomerated TiN inclusions with irregular morphology destroyed the continuity of the steel plate, and the micro-cracks appeared in the cold bending process. With the increase of stress, the micro-cracks expanded and finally led to cold bending fracture of the steel plate.

In order to assess the laboratory's detection ability in Rockwell hardness of metal materials, a proficiency testing was conducted. Firstly, the samples were sent to the China Institute of Metrology for verification. Then, the metallographic microscopic analysis and hardness testing were conducted at different positions. It was proved that the quartering cutting did not affect the hardness value of the sample. Moreover, the uniformity and stability were good. The difference method was used for proficiency testing evaluation of the laboratory using the maximum allowable value of hardness block uniformity as the reference value. The satisfaction rates for 9 A-scale, 10 B-scale, and 15 C-scale participating laboratories using this method were 33.3%, 50%, and 53.3%, respectively, which were significantly lower compared to other evaluation principles. It demonstrated that employing this evaluation principle could identify the potential issues in the laboratory and assist in enhancing its testing capabilities. Finally, a detailed technical analysis was conducted on the results of this proficiency testing. It was concluded that the hardness tester and personnel operation were the primary factors that affected the experimental results. This analysis provided effective improvement measures and basis for laboratories with issues in proficiency testing.

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 issue of surface plating leakage on bake-hardened steel BH180 products produced by a hot-dip galvanizing production line in a domestic steel plant was analyzed and studied. The formation mechanism of plating leakage was analyzed by observing the macroscopic and microscopic morphology of defects as well as detecting the composition of defects. It was found that there were numerous pits on the surface of substrate where the defects appeared as orange peel shapes. Even after cleaning, the grease mixture residue remained in these pits. The organic residues were carbonized and deposited within the pits during annealing, which reduced the wettability of zinc solution and inhibited the formation of Fe₂Al₅ inhibition layer on the substrate surface. As a result, the plating leakage defects were generated. By comparing the composition of the defective coil substrate with that of the normal coil substrate, it was found that the boron content in the defective substrate exceeded the standard. The trace boron elements were segregated at the grain boundaries, which led to the existence of mixed structure of coarse block and long grain and fine grain in the substrate. The hot-rolled substrate with mixed grain structure would form orange peel pits after pickling and cold rolling. After strictly controlling the boron content in BH180 substrate and improving the process efficiency of galvanized cleaning section, the problem of plating leakage of BH180 could be effectively solved.

In order to improve the accuracy of phase transformation test data for metal materials, the thermal expansion method was employed to analyze various influencing factors in phase change tests using one kind of hot formed steel as the example. The results showed that the factors such as heating speed and top rod material had a significant impact on the test results, while the surface treatment method, zero displacement, vacuum degree, parallelism at both ends of the sample, and distance between thermocouple wire welding points had a relatively low influence on the test results. The development of appropriate experimental techniques and rigorous operational processes could reduce errors of the experimental data to a certain extent and improve the accuracy of experimental results.

In order to analyze the phases of superalloy and high-strength steel, the combination method of EDS and EBSD was adopted. The non-metallic inclusions in nickel-based master alloy were identified, and the oxide layer phases of 300M low-alloy high-strength steel were distinguished. The result showed that the mean angular deviation (MAD) of the center line inclination of the nickel-based master alloy Kikuchi band was 0.79°. The non-metallic inclusion was identified as Al₂O₃ by comparison with the simulation bands of selected phases in the database. After ion polishing, the phases in the 300M steel oxide layer and their distribution could be distinguished and determined by the EBSD technology. Most phases were Fe₃O₄ followed by Fe₂O₃, and the content of FeO was extremely low.

The passivation film of tinplate was characterized by X-ray photoelectron spectroscopy. The testing parameters were varied to investigate the influence of different conditions on the elemental analysis of passivation film of tinplate. The results showed that the larger the test spot size, the higher the peak intensity and the narrower the half-peak width of spectral peak. The pass energy of the full spectrum test was improved, and the effect was the best when the pass energy in high-resolution narrow spectrum test was controlled at 20-50 eV. The thickness of polluted carbon and passivation film of tinplate was studied by the depth profiling technique of X-ray photoelectron spectroscopy. The results showed that the thickness of polluted carbon film on tin plate surface was about 2 nm, and the thickness of passivation film was about 28 nm. The measure result of passivation film thickness was basically consistent with that obtained by glow discharge spectrometry.

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 austenite grain size display of 45 steel and 20CrMoH steel was optimized. The commonly used picrate corrosion method was selected for the detection of austenite grain size. The corrosion temperature and corrosion time were controlled to optimize the detection method of austenite grain size display for 45 steel and 20CrMoH steel, so that the austenite grain size display was clearer.

X-ray diffraction (XRD) is the most important and fundamental testing method for modern material analysis. However, there are many strict conditions for sample preparation and testing when the standard flat sample stage is used. For example, a certain amount of powder samples is required, and block sample should meet certain size requirements. To solve the problem of complex sample preparation process in flat sample stage, an XYZ program automatic 3-axis sample stage based on polycrystalline X-ray diffractometer was designed for experimental design of powder and bulk samples. The results showed that the testing could be normally performed when the amount of powder sample was little or the size of block sample was small. Moreover, the measurement data were accurate and the operation was simple. The three-axis sample stage effectively solved the problem of small sample amount for scientific research through the combination of laser positioning and manual positioning. It was sample friendly. The sample preparation time was greatly shortened, which provided convenience for more efficient open and sharing.

The production technology, process control and quality of SCM440 hot rolled coil for high grade cold heading standard parts were introduced. In the steelmaking process, the converter smelting, LF+RH refining, and continuous casting processes should be strictly controlled to ensure the chemical composition and purity of steel. Water cooling was adopted in the rolling process to maintain the coiling temperature at 840-870 ℃. Meanwhile, the cooling speed of the rolled coil was controlled below 2 ℃/s through the adjustments in insulation cover opening/closing and fan air volume. According to the testing, the hot rolled structure of Ø26 mm SCM440 hot rolled large coil was bainite + perlite + ferrite with a grain fineness number of 9-10. Additionally, the ratio of total decarburization layer was ≤1%, and the pass rate for 1/2 cold forging was 100%. The results indicated that SCM440 large coil could fully meet the processing requirements of grade 12.9 cold heading steel.

In view of the scratch defects on the surface of spring steel for railway spring bar, the experimental detection and analysis were conducted, and the reasons were discussed to find out the root causes of scratch defects. The results showed that the long scratches were the sliding friction between the guide groove between the exit of the rolled part and the finished product frame to the 3# shear and the conveying roller frame after the 3# shear. A groove was formed after long-term friction. The intermittent scratches were produced by contact friction between rolled pieces and skirt and skirt rollers with sharp corners during high-speed discharge. Combining with the quality problems existing in the production process, the improvement measures were put forward to effectively control the scratch defects on the surface of the spring steel for the railway spring bar. The quality of final products was good, which was recognized by the customers.

The water-immersion ultrasonic detection of titanium alloy structural component by direct laser deposition was conducted using water-immersion ultrasonic C-scan testing system. The corresponding testing procedures were also established. The results showed that the testing procedure had the characteristics of high sensitivity and high signal-to-noise ratio. The proposed testing procedure was applied to the ultrasonic detection of some titanium alloy products by direct laser deposition, and the results were compared with the radiographic testing and penetrant testing. The effectiveness of this testing procedure was verified.

The electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves (PDP), and localized electrochemical impedance spectroscopy (LEIS) were utilized to investigate the electrochemical behavior of as-forged and selective laser-melted (SLMed) TC4 alloys in 3.5wt.% NaCl solution. Additionally, Mott-Schottky test and X-ray photoelectron spectroscopy (XPS) were employed to analyze the properties of the passive films formed on the surface of the alloys. The results indicated that the as-forged TC4 alloy possessed an α+β dual-phase structure, whereas the SLMed TC4 alloy was mainly composed of acicular α' martensite. Compared to the SLMed TC4 alloy, the as-forged TC4 alloy exhibited a higher polarization resistance, a lower corrosion current density, and a thicker passive film. The passive films on both alloys were found to be n-type semiconductors, but the as-forged alloy had a lower carrier density. The content of TiO₂ in passive film was also higher, indicating that the corrosion resistance property of the as-forged TC4 alloy was better than that of SLMed TC4 alloy.

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.

Utilizing ultrasonic flaw detection technology, a comprehensive inspection was conducted on steel plates after rolling, and a systematic analysis was performed to identify the causes of flaw detection. The causes of cracks and inclusions result from Nb and Ti were elaborated, revealing the microstructures and maromorphology of these defects. Adopting KR hot metal desulfurization: The hot metal adopts a full slag removal process, with the incoming S less than 0.005%, hot metal temperature more than 1 340 ℃, converter compound blowing throughout the process with argon, endpoint carbon content controlled between 0.04%-0.06%, utilizing a slide gate for slag retention, and a steel tapping time more than 4 minutes, etc. The implementation of these measures is vital for ensuring the safety and reliability of steel used in ocean platforms and contributes to quality control in the steel industry.

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 patent application of household stainless-steel sinks in China was analyzed based on the perspective of patent. The application trend, type distribution, application subjects, technical types, and research topics of household stainless-steel sink patents were sorted out. A multifunctional detection equipment for household stainless-steel sinks was designed and developed. The relevant detection experiments were conducted according to the national standard GB/T 38474-2020 Household Stainless Steel Sinks. The results showed that the multifunctional detection equipment could achieve the installation of different specifications of sinks, and could also meet the testing standards for detection of indicators such as load-bearing performance, anti-condensation coating, and drainage mechanism performance. It significantly improved the work efficiency and reduced the labor costs, and also ensured the scientificity and accuracy of testing data.

The embedded flaws of butterfly valve steel castings were detected by ultrasonic testing technology. In the establishment of detection process, the appropriate single/double crystal longitudinal wave straight probe parameters were selected through comparative experiments by combining the unique acoustic characteristics of steel castings. Moreover, the key points of the detection process for single crystal and double crystal straight probes were elaborated separately. On the basis of testing experience, the waveform characteristics and mechanisms of four typical clustered internal defects commonly found in large butterfly valve steel castings were summarized. It was proven that the composite testing process using single/double crystal longitudinal wave straight probes as a practical non-destructive testing technology could ensure that the steel castings of butterfly valves entering the precision machining process meet the corresponding quality requirements.

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.