Through the discussion of the traditional caliber and the analysis of simulation result, a new groove design method for bar rolling of uniform severe strain was proposed based on the principle of severe plastic deformation to manufacture ultra-fine grain(UFG),and flat-oval groove type with the characteristic of multidirectional severe deformation was developed. The warm rolling numerical model of bar was established and analyzed by nonlinear finite element method. The laws of plastic strain distribution in cross-section of bar were analyzed between the new caliber and traditional caliber. The simulated results indicated that the new flat-oval caliber can be better to introduce the plastic strain to the center of cross section and get uniform severe strain under the condition of qualified size. The largest strain was more than 5.0 at the center of cross section, which meets the severe deformation condition to produce ultra-fine grain.

The pock flaws on the surface of the hot-dip galvanized coating will not only affect its appearance, but also the employing properties of the hot-dip zinc-coated sheets and coils, the pock flaws were observed and analyzed by SEM and energy spectroscopy; meanwhile the surface roughness of the entry loop rolls and delivery loop rolls were measured. Results indicated that the pock flaws were caused by the excessive surface roughness of the rolls which injured the coating. And the zinc particle will cause the pock flaws. These defects could be decreased by polishing and cleaning the rolls surface.

The service life of roll surfacing layer is closely related to the surface hardness and quality of surfacing alloy, while the surface hardness is closely related to the microstructure of the surfacing alloy. The surfacing alloy was prepared on 45 # steel substrate by the submerged arc surfacing technology using high-chromium molybdenum flux cored wire as the surfacing welding material. The alloy layer deposited by 420L welding wire had the dendritic structure composed of Fe-Cr solid solution and carbide, while the alloy layer deposited by YD255Mo-S welding wire was mainly composed of the mixture of black acicular martensite and residual austenite. The average microhardness HV0.2 of alloy layers deposited by two kinds of welding wires was 620 and 634.6, respectively. The maximum error was 11.9% and 9.1%, respectively. The overall average hardness value of alloy layer welded with YD255Mo-S wire was high with little fluctuation. The relationship between the microstructure characteristics of surfacing alloy formed under two grades of welding wire and the surface hardness of the alloy was studied.

GB/T 228.1-2021 Metallic Materials-Tensile Testing-Part 1: Method of Test at Room Temperature was officially implemented on July 1^st, 2022. The main changes between GB/T 228.1-2021 and GB/T 228.1-2010 were compared, and the main differences between GB/T 228.1-2021 and ASTM E8/E8M-21 were summarized. The technical differences of the above standards were compared and analyzed in terms of the scope, nouns and terms, symbols, samples, and size measurement, testing equipment and accuracy, testing requirements and performance measurement, result rounding off and uncertainty in measurement. The results showed that the technical contents of GB/T 228.1-2021 had changed greatly compared with GB/T 228.1-2010, for example, adding two different types of strain rate control modes and the method for measuring the elastic modulus of metal materials by uniaxial tensile test, changing the estimation method of displacement rate of deformation compensation beam of testing machine system, etc. Compared with the above national standards, there were great technical differences between GB/T 228.1-2021 and ASTM E8/E8M-21, so we should be familiar with the relevant provisions during the test. Through the comparison of above standards, it was helpful for standard users to have a deeper understanding and use of relevant standards in actual production, teaching and scientific research.

Low-chromium ultrapure ferritic stainless steel is one of the main products of flange steel.Some irregular crack defects were observed in the end of the stamped flange during inspection. The cracks occurred at the end face or single face in the thickness direction. A sample with dimension of 20 mm×20 mm was sampled from the cracking part of flange, and the chemical composition was determined by X-ray fluorescence spectrometer. The section perpendicular to the rolling direction of the sample was polished and etched by FeCl₃+HCl mixed acid solution. The microstructure and morphology were observed by optical microscope (OM), and the precipitated phases of sample were analyzed by scanning electron microscope (SEM). The analysis showed that the annealing time at high temperature was too long, resulting in the precipitation of a large number of hard and brittle granular intermetallic compounds (Fe₂Ti and Fe₃P) in the crystal and grain boundary of the low-chromium ultrapure ferritic stainless-steel matrix. These precipitated phases were irregularly distributed in the form of strips along the thickness direction. The precipitation of these intermetallic compounds, especially the cold brittleness effect of P element, caused the increase of local stress concentration, leading to local cracking during cold working of flanges.

Two kinds of thermal simulation methods, i.e., stress relaxation method and double-pass compression method, as well as their specific research methods and application examples in the study of the second phase precipitation kinetics curve in steel were systematically introduced. The stress relaxation method used the stress relaxation process of the material to obtain the kinetics curve of the second phase precipitation in the steel at different temperatures. The double-pass compression method was used to study the kinetics of second phase precipitation at different temperatures by double-pass compression of samples in steel. Through practical application, it was found that the stress relaxation method had the advantages of short time and less sample demand, while the double-pass compression method could calculate the starting and ending points of precipitation more accurately, and obtain more accurate data, which was suitable for high-precision research. The application of two methods had achieved good results, which provided a reliable experimental method for the study of the second phase precipitation kinetics curve in steel. Moreover, they provided an important reference for the R&D and engineering design in metallurgical process of steel.

The microstructure and corrosion resistance of ultra-pure ferritic stainless steel 445J2 and austenitic stainless steel 316L were studied by means of microstructure analysis, tensile test, salt spray corrosion test, electrochemical test, and stress corrosion test. The results showed that 445J2 stainless steel had low work hardening orientation and good deep drawing formability. Compared with 316L, the 445J2 stainless steel had lower density, better thermal conductivity, smaller coefficient of thermal expansion, less thermal deformation, better salt spray corrosion resistance and pitting corrosion resistance. Moreover, it had no intergranular corrosion sensitivity and stress corrosion tendency. The 445J2 stainless steel could replace 316L austenitic stainless steel for the application in water system, building roof, curtain wall and many other fields with high corrosion resistance requirements.

Vickers hardness test is the most accurate test method in static hardness test. However, in the actual operation of Vickers hardness test, it will be interfered by many factors, thus affecting the experimental results. Several groups of parallel tests for Vickers hardness test on multiple standard plates were conducted using automatic Vickers hardness test equipment. The influence of indentation spacing on the measurement results was analyzed. The uncertainty of tested results was calculated according to GB/T 4340.1-2009. It was found that the larger the indentation spacing was, the smaller the uncertainty was, and more accurate the test result was. Some testing materials were selected to verify the above conclusions. At present, there was a lack of research on the influence of indentation spacing on hardness value.

The fracture of stop valves was observed in batches after use for one year. The fractured stop valves were comprehensively analyzed by means of chemical composition, hardness, microstructure and fracture appearance. The results showed that the chemical composition of the stop valves could meet the requirements of national standards (the mass fraction of Zn exceeds 38% of the total mass fraction). There was no abnormality for the hardness and microstructure. The fracture appearance indicated that the stress corrosion was the main reason to cause the failure of stop valves. The combined effect of three factors, i.e., no stress relief annealing was conducted for this batch of stop valves, the tightening force was larger, and the environment humidity was high, caused stress corrosion of stop valves which had strong tendency to stress corrosion. As a result, the early fracture occurred.

During the production of 9Ni steel medium-thick plates 06Ni9DR, many batches were unqualified in ultrasonic flaw detection. The defective parts of the samples were inspected and analyzed using the metallographic microscope and scanning electron microscope. The results showed that there were a large number of CaO-Al₂O₃ inclusions (in length of 61-167 μm) accompanied by a small amount of MgO and sulfide in the steel, which was main reason for the unqualified flaw detection. Due to insufficient addition of aluminum in LF deoxidation, the burning loss of aluminum during refining led to further reduction of aluminum content. Aluminum was added in the later stage of LF treatment or in the process of RH treatment, thus a large number of such inclusions were generated. After taking some measures such as controlling the end-point carbon and oxygen content of the converter, extending the RH vacuum treatment time and soft blowing time, and ensuring sufficient liquid steel sedation time, the quantity of inclusions in the steel plate had been significantly reduced. Meanwhile, the proportion of unqualified ultrasonic flaw detection decreased from 8.11% to 0.2%.

The production process of 55SiCr spring steel wire rod for oil quenched and tempered steel wire was introduced. The hot-rolled spring steel coils for high-strength oil quenched and tempered steel wires were successfully trial-produced through the reasonable composition design and control, the use of low alkalinity refining slag smelting process, the optimization of high-wire heating process system and the appropriate controlled rolling and controlled cooling process. The results showed that the chemical composition, non-metallic inclusions, metallographic structure, grain size, decarburization layer and mechanical properties of 55SiCr steel for oil quenched and tempered steel wire could meet the customer's requirements. The tensile strength of steel wire rod after oil quenched and tempered could achieve 2 000 MPa grade, and the section shrinkage rate was higher than 40%. The oil quenched and tempered steel wire was cold rolled to produce the automobile suspension springs, and the fatigue life of springs could meet the customer's requirements.

In order to investigate the distribution situation of rare earth elements in steel, the contents of rare earth sulfide inclusions and sulfur-oxygen complex inclusions in rare earth weathering steel were accurately determined. Two kinds of weathering steels, i.e., Q235RE and Q335RE, were studied. The inclusions in steels were extracted by non-aqueous electrolytic process. Moreover, the types of inclusions, the separation methods and the contents of rare earths were investigated by X-ray diffractometer (XRD) and inductively coupled plasma emission spectrometer (ICP). The results showed that the inclusions in Q235RE and Q335RE were mainly manganese sulfide (Ce₂S₃) and sulfur-oxygen complex inclusions (RE)₂O₂S. Three separation methods, i.e., 1%-2% hydrochloric acid, 1%-2% nitric acid and 2%-3% EDTA, were used for the separation of inclusions in rare earth weathering resistant steel Q235RE. Only when EDTA was used for separation, the cementite and unstable rare earth sulfide inclusions could be dissolved, while the sulfur-oxygen complex inclusions were retained. Therefore, EDTA separation technology could be used to accurately determine the contents of rare earth elements in rare earth sulfide and rare earth sulfur oxide inclusions.

The performance of drop hammer tear test and pendulum impact test of pipeline steel are two important parameters of materials, which can help determine the safety and reliability of materials or products. Two pipeline steel samples with different specifications and different properties were used to perform drop hammer tear test and Shaabi pendulum impact test at different temperatures. The impact shear section rate and the drop hammer shear area fraction in two test methods were compared. The difference and relationship were studied based on the test results. The results showed that the change laws of impact shear section rate and the drop hammer shear area fraction were basically consistent during the temperature variation for two pipeline steel samples with different specifications and different properties in drop hammer tear test and pendulum impact test.

The causes for circumferential cracking of stainless-steel heat exchange tube in the vertical heat exchanger were analyzed by the means of macroscopic observation of crack morphology and corrosion morphology of adjacent carbon steel tube, physical and chemical analysis of material, metallographic examination, fracture observation by SEM and X-ray energy dispersive spectrometer, corrosive anion analysis of cooling water, etc. The results showed that the crack originated from the outer wall of the heat exchange tube. The crack morphology and fracture morphology showed the characteristics of stress corrosion, while the cooling water outside the pipe had high concentration of chloride ion and sulfate. Moreover, the local oxygen content in cracking area was relatively high. The analysis indicated that the stress corrosion was the cause for cracking of the heat exchange tube.

The largescale production and heat treatment of 4Cr16MoN steel are provided by the equilibrium phase diagram and CCT curve of steel. The equilibrium phase diagram of 4Cr16MoN and 4Cr16Mo steel are calculated By JMatpro simulation software. Then the CCT curves are measured by DIL805A phase change thermal expansion. Here are the test conditions:1 050 ℃/s austenite, holding 5 min,cooling based on 10、3、12、1、05、01、008、005、003 ℃/s. The results showed that: in calculated equilibrium phase diagram of the two test steels, over a wide high temperature range the steel was maintained to be singlephase austenite, not δ ferrite; Two experimental CCT curves of the steels have independent pearlite and bainite regions; The critical cooling rate of P and B of 4Cr16MoN steel is 01 ℃/s and 12 ℃/s respectively, while the critical cooling rate of P and B of 4Cr16Mo steel is less than 003 ℃/s and 3 ℃/s.

The elastic modulus of metal materials was measured by the static method and the resonance method, respectively. In the static method, an electronic universal testing machine and extensometer were used for the tensile test of dumbbell-shaped bar samples, and the slope of the elastic section of the engineering stress-engineering strain curve was used to calculate the elastic modulus. In the resonance method, the bending resonance test of rectangular free beam sample was carried out by using dynamic elastic modulus and damping analyzer, and the elastic modulus was indirectly measured according to the relationship between the elastic modulus and the fundamental bending frequency. According to the standard for evaluation and expression of uncertainty in measurement, the measurement uncertainty of elastic modulus by static method and resonance method was compared using 7075 aviation aluminum alloy as an example. The results showed that the maximum uncertainty of static method was the deformation error measured by extensometer, and the maximum uncertainty of resonance method was the thickness measurement error. The measurement results by resonance method were better than those by static method. The measurement uncertainty analysis could provide reference for the selection of measurement methods and evaluation of results of elastic modulus.

The heat treatment process of improving the toughness was brought forward by studying the effect of heat treatment on the microstructure of the 3Cr13 which is the matrix of the metal based TiC ceramic cutter. This heat treatment process could eliminate the brittle carbides distributed along the prior grain boundaries like a net and bring in refined martensite. Hence, the heat treatment greatly improved the toughness of the cutter’s matrix and effectively enhanced the fracture resistance of the cutter, resulting in a lower cutter fracture ratio.

In the process of Gleeble3500 cylinder one-way compression, the increasing of temperature at the moment of compression was caused by multiple reasons. By means of different test cases of compressing the cylinder with Gleeble3500, the effects of larger space between the thermocouples and the decreasing of the workpiece resistance on the temperature detection were analyzed.

In order to obtain an EBSD sample preparation method suitable for oxide scale on the surface of hot-rolled steel strips, the oxide scale generated on the surface of 22MnB5 hot-rolled sheet was selected as the research object. The surface EBSD scanning effects of hot-rolled sheet strip under three sample fixture methods (i.e., cold mounting, hot mounting and clamp clamping) and two sample preparation methods (i.e., vibration polishing and manual sample preparation) were compared. The results showed that the hot mounting method was the most suitable fixing method for polishing the surface of hot-rolled strip steel with oxide scale. Both vibration polishing and manual sample preparation methods could characterize the microstructures (such as morphology, phase composition and grain size) of oxide scale on the surface of hot-rolled steel strip. The manual sample preparation method proposed could shorten the sample preparation time and cost while ensuring the sample preparation effect.

The chemical composition, gas content, hardness and non-metallic inclusions of 18CrNiMo7-6 wind power planet wheel forgings were tested to find out the reasons for the abnormal etching test. The results showed that 18CrNiMo7-6 molten steel was not completely deoxidized or it contacted with the air due to the imperfect protective measures during pouring. Al in the steel was oxidized to Al₂O₃, which was eventually remained and dispersed in the wind power planet wheel forgings, resulting in unqualified forgings etching detection. The forging samples were reanalyzed by etching test. The macroscopic examination on any cross section showed that the same black etching points could be found, which verified the analysis conclusion.

Experiment of eccentric tension is one of teaching content of material mechanics experiment. The experiment of eccentric tension can not be conducted directly on the universal material testing machine. One simple eccentric tension mechanism, which is fixed on the universal material testing machine, can test the strain of deformation under load of tension and bending so as to compute the maximum stress of material. And the function of universal material testing machine is expanded as well.

The relationship between the reliable detection length of artificial groove damage on the surface of round rod and the width of magnetic flux leakage detection channel was analyzed. Moreover, the detection and determination of the defect signal under the condition of defect signal length suppression was also investigated. The formation of the detection signal caused by the depth variation of the natural defect and the application conditions of the length suppression of the defect signal were analyzed. The "uncertainty principle" of magnetic flux leakage detection of round rod was obtained, and the detection of natural defects on round rod was a probability event. Finally, the empirical measures to improve the reliability of magnetic flux leakage for surface defects of round rods were proposed.

It was found that the hardness exceeded the standard when producing ø110 mm high wear-resistant alloy steel in the new medium-sized workshop of Special Steel Group. The CCT curve of the steel was measured through the thermal simulation test. The influence law of different cooling rate on phase transformation and microstructure hardness was obtained. The results showed that when the cooling rate was not higher than 0.2 ℃/s, the ferrite and pearlite transformation mainly occurred, and the hardness was not higher than 20.5HRC. When the cooling rate was in range of 0.5-2 ℃/s, the bainite and martensite transformation mainly occurred, and the hardness was in range of 40-51.7HRC. When the cooling rate was not less than 4 ℃/s, the martensitic transformation mainly occurred, and the hardness was less than or equal to 54.4HRC. According to the CCT curve, the round steel with hardness less than or equal to 21HRC could be obtained only when the cooling rate was controlled below 0.2 ℃/s in the rolling process in the workshop.

Hotcold fatigue performances of the same kind of steel at different temperatures in different ways were studied. One way is via controlling the test temperature strictly, and another is through test standard. The results showed that all the cracks were initiated from the notch. The fatigue crack based on the experimental is larger. When the controlled temperature is closer to the room temperature, the two sets of test data are closer as well.

Effect on the microstructure and mechanical properties of austenite stainless steel 022Cr17Ni12Mo2 of different heat treatment processes were investigated. Results show that as the heating temperature is increased from 950 ℃ to 1 250 ℃, the grain size becomes coarse, the α phase content drops at first then rises and arrives the lowest point at 1 150 ℃; the strength Rm、Rp02 and Rp10 decrease a little at different extents and the plasticity improves evidently. The cool manners have little impact on the grain size、strength Rm and elongation ratio, while comparing to air cooling，water cooling would be propitious to reduce the content of α phase, furthermore the strength Rp02 and Rp10 increase by 30-40 MPa.

The method C in ASTM A923-2014 for the detection of harmful intermetallic phases in dual phase steel (Standard Test Methods for Detecting Detrimental Intermetallic Phase in Duplex Austenitic/Ferritic Stainless Steels) does not clearly specify the sampling location and size of welding materials. Through the discussion of sampling method, sample preparation method, composition gradient rule at different positions from the fusion line and measurement factors affected by different weld bead heat, the influence of the above factors on harmful intermetallic phases of deposited metal in 2209 automatic TIG welding was investigated by optical microscope (OM), spark discharge atomic emission spectrometry and energy disperse spectroscopy (EDS). The results showed that the nitrogen element value and ferrite content were the important factors influencing the harmful intermetallic phase. After wet grinding using abrasive paper (>6.5 μm) and alcohol. The sampling in a single pass and more than 7 mm away from the fusion line could fairly and objectively evaluate the harmful intermetallic phase in dual-phase steel 2209.

Based on the Hollomon relation, the corresponding relationship between the n value and the yield ratio was deduced. According to this formula, the value of n of one material with certain thickness was firstly measured, which was then substituted to obtain the value of material constant C. For the materials of this type of steel with other thicknesses, the measurement of yield strength R_p0.2 and tensile strength R_m was only required to calculate the value of n according to the formula. The calculation values and measurement values of n of typical material were compared. The results showed that the proposed method for the calculation of n was accurate and simple to use, which greatly simplified the work of determining the n value of the same steel type. This method was especially applicable for the estimation of n value of ultra-thin materials or ultra-thick materials, which was difficulty measured in the laboratory.

In the process of metallographic analysis, the insetting of needle-like sample in micro-nano scale will easily cause the capillary phenomenon, which leads to the limited resolution of metallographic structure. As a result, it is difficult to accurately evaluate the micro structure. The needle-like sample in micro-nano scale were treated by grinding and polishing, and then eroded with the chemical reagents. After that, the sample was placed in ethanol and acetone solution for ultrasonic treatment followed by drying with a hair dryer. The results showed that due to the low melting point and high volatility of acetone solution, the addition of ultrasonic treatment in acetone solution in the process of conventional micro-nano metallographic sample could effectively remove the residual solution between the mosaic material and the sample. The occurrence of capillary phenomenon was reduced, which could ensure the clear observation of metallographic sample as well as the effective characterization of microstructure.

The leakage of pipe head (at the weld of tube sheet welded joint) occurred in the vulcanization process of diesel hydrotreating air cooler during running. The failure mode and reason were found through the microscopical examination, composition and microstructure analysis, and corrosion characteristic analysis of the pipe head of air cooler. It was found that the failure mode was sulfide stress corrosion. There were two reasons. One reason is the improper control of welding process. The welding cooling speed was fast, resulting in the formation of hardened structure. Another reason is the post weld heat treatment (PWHT) was also insufficient and the hardened structure was not improved.

The ductile iron planet carrier fractured in the process of use, the location of the fracture is between two planet holes. Through the comprehensive analysis of the planet carrier by means of macro analysis, micro analysis, mechanical properties and other analysis, it is determined that the fracture mode of the planet carrier is fatigue fracture, the fatigue expansion is sufficient, no phenomenon of excessive local force was found, and there are shrinkage porosity defects at the cracking position. The existence of shrinkage defects cut off the internal continuity of the material, resulting in the reduction of the strength of the fracture site, make the parts crack before reaching the fatigue strength of the material, especially the parts subjected to periodic alternating load. The shrinkage is serious and produce prematurely extending to the surface of the parts, so that the stress concentration coefficient at the defect on the surface of the part increases sharply, fatigue cracks resulting in early fatigue failure of parts.

By using of the super element model in association with the LFG model, the equilibrium concentration of xγ/αC, driving force for proeutectioid ferrite and pearlite transformation, ΔGγ→α+γ1 and ΔGγ→α+cem, and thermodynamic equilibrium temperature of Ae3 and Ae1 were calculated for TRIP steel, in addition, the influence on TRIP steel of different chemical composition and hot deformation conditions was discussed. The predicted and measured Ae3 and Ae1 for undeformed TRIP steel have good agreement, which shows that the calculations on phase equilibrium temperature in the paper is sufficiently accurate and reliable.

A special four-position clamp was designed to replace the single-position clamp. The whole-process numerical control macro program and directional precision compensation numerical control macro program were developed for continuous processing of tensile specimen of plate with different specifications. A new processing method and flow were formed. Through practical application, it could effectively save the non-maneuvering time of machine tool in machining process and maximize the efficiency, which solved the problems of precision error caused by tool wear and material cutting performance, and the deviation of the axis between the two heads of sample and the parallel part. The operation in the proposed method was simple and the continuous machining process was stable. This method had important practical significance in reducing labor intensity, shortening process, reducing tool consumption and realizing unattended machining.

The influence of surface pollution and discoloration after stable heat treatment on the properties of high temperature alloy products prepared from FGH4097 powders was studied. The results showed that the surface contamination discoloration of FGH4097 powder superalloy parts after stable heat treatment was due to the surface oxidation of the parts. The discoloration layer was a thin oxide film. The performance test indicated that the surface pollution and discoloration had little influence on the performance of parts, which could meet the use requirements.

The probe rotary ultrasonic testing can achieve rapid and automatic detection, and has been widely used by various steel mills. During flaw detection, a water ring is filled between the probe and the workpiece for inspection, and water serves as the coupling medium. It is necessary to solve the problem of rapid stability. The water flow and bubbles can affect the emission and reception signals of ultrasonic waves, leading to a decrease in detection sensitivity, and resulting in defect misdetection and missed detection. In order to improve this phenomenon, an automatic water flow regulation system was designed, which consisted of a programmable logic controller (PLC), an actuator, a flow regulation device, and a flow measurement device. In order to meet the precise regulation of water flow, the system adopted closed-loop control. The control quantity was obtained by inputting the given flow setting value and the deviation value after flow measurement through proportional, integral, and differential (PID) algorithm calculation. It acted on the water flow adjustment device and automatically adjusted the valve opening size, thereby achieving continuous and stable operation of the water supply system, which improved the detection efficiency of the flaw detection equipment and reduced the labor intensity.

The macroscopic examination, chemical composition and micro failure analysis were conducted for the cracking defect of the end of 42CrMoA roller shaft. The failure analysis showed that the cracking source of the roller shaft was the original end crack of the raw material. The process investigation and discussion analysis confirmed that the original end crack of raw materials was the sawing crack formed in the cold cutting process of grinding wheel saw. The main cause of sawing cracks was the combined effect of steel cooling stress and sawing thermal stress. The occurrence of sawing cracks could be prevented by annealing the steel and cooling slowly in pits.

The surface micromorphology of cold rolled automobile steel has an important influence on its properties such as stamping, coating, oil storage and corrosion resistance. The surface morphologies of DC04 produced by three different steel plants were characterized by OLS5100 laser confocal microscope, which were also compared with the images collected by scanning electron microscope. Meanwhile, the non-uniformity, height distribution and finish of surface micromorphology were evaluated by parameter characterization of laser confocal microscope. The test results showed that the surface topography images collected by laser confocal microscope had clear three-dimensional appearance and strong stereoscopic sense. The surface pits of DC04 produced by plant A were large and unevenly distributed, and the rolling marks at the bulge were significant. The surface pits of DC04 produced by plant B and C were many, and the surface micro-geometric morphology had a higher degree of regularization. The surface of the bulge was smooth, and the transition with the pit was smooth. The order of surface micromorphology non-uniformity of DC04 in the three steel plants was plant A > plant B > plant C, while the order of height distribution and finish was plant A < plant B < plant C.

SiCr spring steel heat-treated wire was used as the sample. The austenite grain size was tested by direct hardening method and oxidation method. In the direct hardening method for the test of austenite grain size of SiCr spring steel heat-treated wire, the sample was etched with 4% nitric acid alcohol solution. The results showed that the appearance of martensite could not be restrained, leading to the unclear austenite grain boundary when observed under a microscope. As a result, the grade of austenite grain size could not be accurately determined. For the oxidation method, the austenite grain boundary of spring steel heat-treated wire was clear under the microscope. The heating temperature was adjusted by measuring the phase transition temperature and phase transition kinetic curve. The holding time of temperature was determined according to the sample size. The optimal heat treatment process for SiCr spring steel was heating at 810 ℃ for 30 min, and it could be close to the austenitic grain size in real spring steel heat-treated wire. This study could guide the technological breakthrough of heat treatment in spring wire drawing plant to improve the performance of spring steel wire.

It pointed out that the reason for flaw detection unqualified of 4130X steel pipe was the nonmetallic inclusions caused by secondary oxidation of open cast furnace. Take ø500 mm continuous casting blank as the object, several samples were taken from different positions of the casting blank. It was found that the oxygen content, nitrogen content, Al loss and nonmetallic inclusions in the steel in the open casting part were higher than those in other parts, which implied that the secondary oxidation in the open casting part was more serious. In addition, the nearlier to open casting part the quantity and distribution density of inclusions with length more than 5 μm. It is indicated that the effect of secondary oxidation on inclusions more then 5 μm is obviously when open casting.

During the inspection of 2219 ring forgings, it was found that there were defects inside, which were about 5 mm from the inner diameter and 80 mm from the end face. The flaw detection showed that the defects were long strips with the length of about 30 mm, and the direction was parallel to the diameter direction of the forgings. In order to analyze the causes of the defects, the macrostructure, microstructure, scanning electron microscopy and energy spectrum analysis of the defective samples were studied in the laboratory. The results showed that the defects of 2219 aluminum alloy ring forging were hole defects, which were caused by the low AlZr input temperature during smelting. It reduced the diffusion rate of elements and increased the segregation of AlZr alloy phase, leading to the formation of hole defects.

The block peeling from the flange of rear wheel occurred when the subway wheel was used for a period of time. In order to find out the cause, some methods including chemical composition inspection, mechanical analysis, macroscopic observation of fracture and metallographic structure analysis were employed. The results showed that the block peeling from the flange of wheel was the typical characteristic of peeling caused by multisource high stress fatigue fracture. High hardness white layer martensite and the composite structure with depth up to 7 mm were the main reasons for block peeling from the flange. The composite structure on deep surface should be caused by the unreasonable quenching process. It was suggested to develop the reasonable quenching process for the flange of wheel to avoid formation of defect structures.