The Nb micro-alloyed X32 steel strip， used as the backing material for bimetallic band saw blades， is based on a medium-carbon Cr-Mo-Ni-V high-alloy composition system with the addition of 0.05% w［Nb］. The manufacturing route involves hot rolling and annealing at 750 ℃ carried out by TISCO， followed by multi-pass cold rolling， quenching at 1 050 ℃， and tempering at 500 ℃ performed by the users. The mechanical properties of the Nb micro-alloyed X32 steel used as backing material for bimetallic band saw are analyzed under different processing states， and the microstructure and carbide precipitates of the experimental steel are characterized by optical microscopy （OM） and transmission electron microscopy （TEM）. The results show that the microstructure of X32 steel strip in the annealed state is mainly granular pearlite， with a large number of M23C6 spherical carbides approximately 30 nm-100 nm dispersed in the fine ferrite matrix； the microstructure of the finished product is mainly tempered troostite， with a small amount of undissolved （Nb，M）C carbides and fine needle-like alloy segregation zones （primarily composed of Cr and Fe） distributed within the laths. The Nb micro-alloyed X32-Nb experimental steel used as backing material for bimetallic band saw exhibits higher hardness and strength at the hot-rolled and annealed， cold-rolled semi-finished， and finished processes compared to X32 steel， without obvious deterioration in elongation. Moreover， the finished saw blade demonstrates a longer service life in the idling test..The finished X32-Nb experimental steel saw blade exhibited a hardness of 50.5HRC， a tensile strength of 1 548 MPa， an elongation of 14.5%， and an idling-test service life of 70.5 h， thereby meeting the application requirements of users.
The cold crucible levitation melting （CCLM） technology uses a water-cooled copper crucible instead of a refractory crucible as the melting container， which can effectively solve the problem of corrosion of the crucible by the high temperature melt， and is suitable for the preparation of ultra-high purity metal materials. In this work， the K465 nickel-based cast superalloy is prepared by CCLM technology. When the vacuum level in the melting chamber is lower than 0.01 Pa， high-purity argon gas is introduced to start smelting. After the metal raw materials are completely melted， refining is performed for 10 minutes. The results of the chemical composition test indicate that the contents of the main elements in the alloy fully meet the standard compositional requirements and the compositional uniformity is excellent. The impurity contents of oxygen w［O］ and nitrogen w［N］ in the alloy are both controlled at 0.000 3%， while the sulfur w［S］ content is as low as 0.000 049%. The microstructure of the as-cast alloy primarily consists of γ matrix phase， γ ′ strengthening phase， （γ + γ ′） eutectic phase， as well as bulk and strip-shaped carbides enriched in titanium （Ti）， tungsten （W）， niobium （Nb）， and molybdenum （Mo）， which is consistent with the microstructural characteristics of the alloy prepared by vacuum induction melting （VIM）. Mechanical property tests demonstrate that the K465 superalloy prepared by CCLM exhibits a room-temperature tensile strength exceeding 1 000 MPa and an elongation above 5%. Moreover， the high temperature rupture life of alloy achieves more than 45 h under the service condition of 975 ℃ and 225 MPa. The research results show that the cold crucible levitation melting technology can prepare high-purity K465 nickel-based cast superalloy， which has excellent mechanical properties. This study provides an innovative technical approach for the melting of ultra-high purity superalloys.
To investigate the fracture of ER70S-6 wire rod during drawing， the microstructure of the fractured wire rod was examined by optical microscopy and scanning electron microscopy. A hard abnormal constituent was identified as bainite based on its hardness and morphology. Bainite impedes coordinated deformation of the microstructure and is the primary cause of wire-rod fracture during drawing. The tensile strength of the fractured wire rod was 1.07 times that of the normal wire rod， while its reduction of area was 95% of that of the normal wire rod； these differences in mechanical properties further increased its susceptibility to drawing fracture. To improve wire rod quality， the carbon mass fraction was controlled at approximately 0.070%. After rolling， the laying temperature was reduced from 880 °C to 850 °C， the roller conveyor speed was reduced from 0.15 m/s to 0.13 m/s， and the average cooling rate in the transformation region was reduced from 1.2 °C/s to 0.8 °C/s. The optimized wire rod consisted mainly of ferrite and pearlite， with no obvious bainite morphology observed. These composition and cooling-process parameters promote ferrite and pearlite transformation， suppress bainite formation， and thereby improve the drawability of the wire rod.
To investigate the effect of Ta addition on the evolution of MC carbides in the Ni16Co10W8Cr5Al alloy during homogenization at 1 200 ℃ and to elucidate the role of Ta in the stability of MC carbides， thermodynamic calculations， microstructural observations， image statistical analysis， and energy-dispersive spectroscopy （EDS） were used. The results revealed the effect of Ta on the compositional changes and coarsening of MC carbides after homogenization at 1 200 ℃ for 10 h. Thermodynamic calculations indicated that the addition of Ta enhanced the stability of MC carbides and increased their complete dissolution temperature. Statistical results showed that， after heat treatment at 1 200 ℃ for 10 h， both the area fraction and size of MC carbides increased； however， the changes in MC carbides in the 0Ta alloy were significantly greater than those in the 2Ta alloy. EDS elemental mapping revealed that the distribution of C was essentially consistent between the core and shell regions of the MC carbides， indicating that the core-shell structure mainly originated from the different distributions of metallic elements， including Ti， Nb， Ta， W， and Mo， between the core and shell regions. After Ta addition， Ta was evidently enriched in the MC-carbide regions and altered the distribution of Ti， Nb， W， and Mo， giving the particles a Ti-Nb-Ta multicomponent enrichment characteristic， thereby enhancing their stability and suppressing their coarsening during homogenization. Overall， Ta addition improved the stability of the MC carbides and retarded elemental redistribution and carbide coarsening during homogenization.
Post-rolling cooling control is a critical step in regulating the microstructure and properties of hot-rolled steel. Traditional physical models and data-driven models， constrained by simplified mechanistic assumptions， low learning efficiency， and difficulties in dynamic parameter adaptation， fail to accurately address the complex， time-varying conditions during rolling processes. Propose a post-rolling cooling control model based on Intelligent Augmentation （IA）， achieving deep integration of algorithmic and empirical knowledge. Its core principle combines "mechanistic constraints， data correction， and dynamic feedback." Practical applications demonstrate that this model effectively overcomes the limitations of traditional models—poor robustness and slow learning—with cooling control errors maintained within ±20 °C and a learning adjustment rate over 30% faster than conventional approaches. This advancement holds significant importance for improving the quality of hot-rolled steel products and advancing the intelligent transformation of the steel industry.
