In industrial production,it is often necessary to remove the surface decarburization layer to prevent the work piece cracking during subsequent processing due to uneven hardness and structure. Therefore, the prediction of decarburization layer depth is of great significance. The decarburization behavior of 42CrMo steel was discussed at different holding temperatures,the differences in the morphology of decarburization layer was observed by metallographic microscope. Then the decarburization layer depths were statistically compared. Based on Fick′s second law and analyzing the decarburization kinetics behavior of 42CrMo steel at holding temperatures ranging from 1 023 to 1 373 K, a theoretical calculation model was established for decarburization layer depth of 42CrMo steel. At the same time, through the metal high-temperature oxidation theory combined with the oxidation weight gain experiment, the oxidation and loss behavior of 42CrMo steel at different holding temperatures was discussed, and the model was revised. Through metallographic analysis and microhardness distribution analysis, it was proved that the theoretical value of decarburization layer depth obtained from the corrected decarburization layer depth calculation model was basically consistent with metallographic test value, verifying the accuracy of the model. This indicated that the decarburization layer depth calculation model designed in this work could effectively predict the decarburization layer depth.

Aiming at the significant forming difficulties existing in Ti₂AlNb intermetallic compounds, the die forging forming process parameters were systematically optimized based on Deform-2D numerical simulation technology. Through systematic experimental verification and strict process implementation, the trial production of aero engine casing die forgings had been successfully achieved. The experimental results showed that the contour filling of die forging was full and complete. The overal properties analysis revealed that the range in mechanical properties between the high and low strain regions were controlled within 5%. The non-destructive clutter wave in ultrasonic testing reached ø1.2 mm-6 dB, demonstrating its excellent microstructure uniformity. This research achievement provided an effective process solution for the reliable manufacturing of key Ti₂AlNb die forgings for aero engines.

The selection of austenitizing temperature has a significant impact on the solid-state phase transformation of test steel. The microstructure transformation and properties of 40Cr2Ni4MoV steel at different austenitizing temperatures were investigated by analytical techniques such as quenching thermal dilatometer and laser confocal microscope. The results showed that as the continuous increase of austenitizing temperature, the microstructure gradually changed from a mixture of martensite and a small amount of bainite to all martensite. The undissolved carbides gradually changed from a few precipitations along the grain boundaries to a large number of precipitations, and eventually the precipitation mode developed into a combined precipitation at both grain boundaries and within the grains. The average hardness of samples also increased with the increase of austenitizing temperature. Therefore, under the condition of ensuring the microstructure and properties of 40Cr2Ni4MoV steel, the preferred austenitizing temperature was 920 ℃.

The research on the continuous cooling transformation behavior of Ti and Nb-Ti microalloyed steel for pallet container is of great significance for promoting the industrial application of this type of steel and improving the quality of pallet container equipment. The microstructure phase transformation behavior of Ti and Nb-Ti microalloyed steel for pallet container at different cooling rates was determined by dilatometric method combined with metallographic-microhardness method using thermal simulation testing machine. The dynamic continuous cooling transformation (CCT) curves of the two test steels were drawn, and the continuous phase transformation rules were analyzed. The results showed that the microstructure of both test steels transformed to bainite and the hardness increased with the increase of cooling rate. Due to the precipitation of particles such as Nb(C,N) and Ti(C,N), Nb-Ti test steel pinched the grain boundaries and refined the grains, delaying the bainite transformation and resulting in the appearance of martensite at higher cooling rates. Combined with the analysis of microstructure and precipitates, it indicated that when the cooling rate was 0.2-1 ℃/s, grain refinement dominated the hardness; when the cooling rate was 2-10 ℃/s, the hardness difference between the two test steels was small; when the cooling rate was 20-50 ℃/s, the hardness of Nb-Ti test steel reached 330HV 5 due to grain refinement, martensite transformation and precipitation strengthening, which was significantly higher than that of Ti test steel (290HV 5). In addition, the CCT curve of Nb-Ti test steel had a new martensite transformation zone, and the phase transformation temperature and critical cooling rate were better, which proved that Nb could effectively improve the microstructure density and hardness of steel.

A lightweight non-contact size measurement system is proposed in this paper, based on embedded image acquisition and MATLAB image processing, enabling rapid and accurate workpiece size measurements. In the hardware configuration, STM3F407ZGT6 is adopted as the main controller to operate the OV2640 camera for image acquisition, while the captured images are displayed in real-time on an liquid crystal display (LCD) screen. The software component is developed on MATLAB platform, realizing essential functions including system calibration, distortion correction, image denoising, and edge detection, thereby achieving accurate calculation of the distance between any two designated points in the image. Experimental results indicate that the system has good measurement repeatability, with standard uncertainty of 0.023-0.030 mm and relative error of 0.08%-0.43% in sample measurements. Compared to conventional contact-based measurement approaches, the proposed system has the characteristics of non-contact operation and operational simplicity, rendering it applicable in industrial settings where physical contact is not feasible or where efficient measurement is necessary.

Particle size distribution of nanopowder is one of the key factors affecting microstructure and propertie of materials, and the accurate characterization of their particle sizes has been a research hotspot in this field. A measurement method for accurately characterization of the particle size and distribution of nanopowder was discussed systematically based on atomic force microscopy (AFM), with a focus on key aspects such as sample preparation, image analysis, and statistical reliability. Taking metallic nickel powder and non-metallic zirconia powder as the research objects, the problem of measurement error caused by the high surface energy of nanoparticles and their tendency to agglomerate was solved. The results showed that the uniformly distributed nanoparticles could be obtained after the dispersed liquid was dropped onto mica and dried for 30 min, after simply dispersing in water or ethanol as the solvent and ultrasonically treating for 30 min. Using the significant height difference between particles and substrate in AFM height image, each particle could be precisely separated and extracted with Image Pro software, realizing precise measurement of parameters such as the diameter and aspect ratio of individual particle. This method was applicable and highly accurate for characterizing the particle size of powder with a diameter not more than 10 nm. By analyzing the relationship between the particles number and the average particle size stability, it was concluded that the measured particle number should be not less than 1 000 in order to ensure that the average particle size results had statistical representativeness and accuracy.

The film processor is a key equipment in darkroom processing stage of film radiographic detection technology. The film obtained after its processing is the sole medium for determining the detection results, and the film quality directly affects the detection result accuracy. Therefore, the correct use of film processor is the key for obtaining high-quality and qualified films. This article starts from the principle of film radiographic detection technology and combines the international aerospace Nadcap checklist requirements. The impact of film processor on film quality is discussed in detail from 8 aspects, including the material and cleanliness situation of transfer roller shaft in film processor, transmission speed, film development solution and its replenishment rate, developing solution temperature, drying temperature, darkroom environment, regular maintenance and servicing, and consistency verification of film processor. Through theoretical analysis and practical application experience, the following 5 measures were proposed to ensure that the film processor could produce high-quality and qualified film: the replenishment rate of film development solution, the control of developing solution temperature, the darkroom environment control, the regular maintenance and servicing of film processor, and the consistency verification of film processor.

There is a demand to image the simple internal structures of components by digital radiography (DR) technology in practical applications. This feasibility of DR technology in internal structure imaging was discussed in this paper. 4 samples with relatively simple internal structures were selected as test objects. Based on the optimization of parameters such as focus size, exposure tube voltage, tube current, magnification, and image acquisition mode, DR technology was used to image their internal structures. The results showed that for simple internal structures such as the distribution of single layer wiring harness inside a circular cavity, the deformation of metal coils inside a cylindrical cavity, the distribution of reinforcing fibers at the cross-section of composite bullet-resistant ceramics, and the bullet hole morphology after the target test of ceramic composite armor plates, DR technology could achieve good imaging results.

The corrosion causes of Hastelloy welding seam in melamine device were analyzed by field emission scanning electron microscope(SEM), metallographic microscope, and X-ray diffractometer, providing a reference for the anti-corrosion of melamine device. The macroscopic analysis indicated that the most severely corroded area was the welding seam. The chemical composition test results showed that the composition met the requirements of C-276 Hastelloy. The metallographic structure test results indicated that the material structure was normal. The X-ray diffraction results showed that the corrosion products on the outer surface of welding seam were mainly NiO. The scanning electron microscope energy spectrum results indicated that the contents of Mo, Cr, and W in the most severely corroded welding seam were the lowest. Through comprehensive analysis, the results showed that the alloying contents of Mo, Cr, and W alloy elements in Hastelloy alloy welding seam were lower than those of the base material, which was the reason for the severe corrosion of welding seam. The alloy element Cr formed a dense passivation oxide film on the surface, and a low Cr content reduced the oxidation resistance of welding seam; a low Mo content reduced the reduction resistance of welding seam; a low W content reduced the high-temperature strength and corrosion resistance of welding seam. To improve the corrosion resistance of welding seam area, it was recommended to use welding wire with a higher corrosion resistance level than the base material for welding.

The failure analysis research of rock drilling hammer heads is of great significance for improving the operational efficiency of rock drilling vessels, ensuring project progress and waterway safety. The microstructure, composition and mechanical properties of failed hammer heads were analyzed by means such as metallographic microscope, chemical testing and mechanical properties tests. The heat treatment process of hammer heads during manufacturing was simulated and calculated with JMatPro thermodynamic software. Then, the failure causes of the rock drilling hammer heads were discussed, and the specific measures for performance improvement were proposed. The results showed that the failure of rock drilling hammer heads was caused by the severe deformation of the base part of hammer heads. It was mainly due to the fact that the contents of Si and Cr in the base alloy of rock drilling hammer heads were lower than the required values specified in standard of GB/T 5680-2010 for ZGMn13Cr2 steel, while the contents of Mn and Mo were at the lower limit of standard requirement, resulting in insufficient strengthening effect of hammer heads. In addition, the water hardening treatment temperature of hammer heads was lower than the conventional water hardening temperature of high manganese steel ranging from 1 050 to 1 100 ℃, which had a limited strengthening effect on the hammer heads, causing the strength of hammer heads to fail to meet the standard requirements. The following measures could enhance the strength and hardness of hammer heads: increasing the content of alloy elements such as Si, Mn, Cr and Mo in hammer heads, and controlling them at the upper limit of standard requirement; raising the water hardening temperature to 1 060 ℃, and taking measures such as increasing the refining process, etc.

The inclined shaft skip pull rod of the raw coal lifting device for coal mines was made of 45 steel. After 35 d of use, a pull rod fracture accident occurred. The fracture morphology, chemical composition, hardness, impact properties, tensile properties and microstructure of the skip pull rod were analyzed by electron probe, direct reading spectrometer, hardness tester, impact testing machine, tensile testing machine and metallographic microscope, respectively, and the failure cause was discussed. The results showed that the failure mode of skip pull rod was brittle cleavage fracture. The main reason was that the metallographic microstructure of pull rod consisted of reticular ferrite, pearlite and widmanstatten structure with some local coarse grains, which led to a significant reduction in the impact resistance of skip pull rod. At R-angle of pull rod, there was a clear cutting tool mark processing defect, which intensified the stress concentration, and the skip pull rod undergoed an early cleavage fracture due to the impact force.

It is of great significance to investigate the scarring causes on SWRCH22A wire rod surface for improving the quality stability of steel for fastening piece and reducing the scrap rate in downstream processing. This paper aimed to clarify the scarring causes on SWRCH22A wire rod surface and formulate overall process improvement measures to effectively control the scarring defects. By collecting SWRCH22A wire rod samples with surface scarring, the distribution characteristics and macroscopic morphology of scarring were observed. The inclusions distribution and the matrix structure in the scarring areas were observed by metallographic analysis. The types and elemental composition of inclusions in the scarring areas were determined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), and the inclusions in the steel were rated. It indicated that aluminum oxide type (Class B) inclusions were the main scarring cause on SWRCH22A wire rods surface, resulting from insufficient flotation of deoxidation products in the molten steel and the formation of large particle accumulations. Through measures such as converter steel pouring slag control, optimization of deoxidation system, development of dedicated refining slag system (with w(CaO)/w(Al₂O₃) ranging from 1.3 to 1.8 and w(Al₂O₃) ranging from 25% to 35%), control of w(Ca)/w(Al) more than 0.1 in the steel, strengthening continuous casting protection pouring and optimizing protective slag, the inclusions in the steel were significantly reduced, the wire rod scarring rate decreased from 0.63% to 0, and there was no flocculation during the continuous casting process, effectively improving the product quality stability.

Taking 120 t LF furnace as the research object, a new temperature prediction and control model combining mechanism model and linear regression method was designed, to address the insufficient control accuracy of molten steel temperature and hysteretic nature of manual adjustment during LF refining process. This model aimed to achieve high-precision prediction and dynamic control of molten steel temperature, in order to meet the strict requirements for temperature stability in modern steelmaking production. In the model design, the mechanism model was based on thermodynamic principles and constructed a theoretical framework for the change of molten steel temperature. Meanwhile, the linear regression model made full use of historical operation data to extract the linear relationship between key operation parameters and molten steel temperature. The research results showed that this composite model could predict the changes in molten steel temperature in real time and adjust the operation parameters dynamically according to the prediction results, thereby achieving precise temperature control. In actual production tests, when the operating conditions of the model were met and the production process was stable, the hit rate of the end-point temperature prediction error within ±5 ℃ exceeded 95%. Moreover, the model had been successfully integrated into the automatic control system of LF furnace, achieving the automatic regulation and closed-loop control of temperature. Combined with modern control technology, this system could automatically optimize operation parameters based on real-time data, reducing the uncertainty and hysteretic nature of manual intervention. Practical applications had shown that the model not only improved the stability of temperature control, but also reduced energy consumption and production costs, providing strong support for the intelligent production of LF furnaces. In the future, the model was expected to be further promoted to other types of refining furnaces, providing technical references for the intelligent transformation of steel industry.

To promote the digital transformation of enterprises and realize the whole-process dynamic management of laboratory equipment, this paper aims to solve the pain points existing in traditional equipment management, such as inadequate overall coordination, low utilization rate, insufficient information sharing, and incomplete process monitoring. With Web technology as the core architecture, combined with rule engines, multi-type databases, 3D rendering engines and other technical means, an information management system for laboratory equipment is constructed. The system realizes functions including integrated equipment scheduling, information sharing and query, real-time data collection and storage, remote monitoring, and digital twin visualization. It has significantly improved equipment utilization and management efficiency, achieved 24 h full monitoring of the test process, effectively reduced safety and quality risks in testing, and provided a feasible technical solution for the digital transformation of laboratories and the high-quality development of enterprises.

The results of pendulum impact test of 700L steel at -40 ℃ show a high degree of dispersion. Usually, the arithmetic mean of impact energy is used to characterize the impact test results of materials. However, the test influencing factors in low-temperature environment are complex and diverse, which makes the measured values often difficult to accurately reflect the impact resistance performance of materials. To obtain more reliable impact energy test results of materials, -40 ℃ low temperature Charpy V-notch impact tests on longitudinal and transverse samples were conducted by pendulum impact testing machine. During the test, the distribution characteristics of the impact energy test results of V-notch specimens with 2 mm pendulum blade were mainly discussed. The influence of the two sampling methods of longitudinal and transverse sampling on the dispersion of impact energy values of 700L steel was systematically investigated, and the corresponding safe impact energy with 90% confidence level was obtained to evaluate the corresponding impact resistance performance of materials. The results showed that the impact energies of both sampling methods conformed to the normal distribution characteristics. At the corresponding 90% confidence level, the safe impact energies of longitudinal and transverse specimens were 31.58 J and 38.83 J, respectively. This analysis result provides theoretical and practical guidance for the application of Charpy impact test of 700L steel and the accurate acquisition of results.