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doi: 10.1007/BF00776897pmid: N/A
The fixed growth of the austenite-carbide colonies during carbonization of chromium alloys is prevented close to the grain boundaries of the initial ferrite. Restructuring of the colonies under various conditions is associated with diffusion of carbon and chromium in the ferrite and the creation of a thermodynamically unstable martensitic phase ahead of the recrystallization front, which is supersaturated with chromium and carbon. Thus, in the initial stages of growth, as the degree of supersaturation in the ferrite increases, lamellar rod-shaped colonies grow whose main growth direction is along the carbon concentration gradient. A decrease in the supersaturation of carbon in the ferrite as one moves away from the advancing front toward the center of the grain makes the isolated growth of the coarsely agglomerated phase along the boundaries of the initial ferritic grains possible. The less the amount of defects in the grain boundaries, the more the body of the ferritic grains becomes supersaturated. This leads to the simultaneous growth of the new phase at some distance from the general growth front of the colonies.
Karpman, M.; Sokolova, N.; Dmitrieva, E.; Andryushechkin, S.; Savkov, S.
doi: 10.1007/BF00776898pmid: N/A
1. For punching and coining die parts the optimum combination of properties (high hardness of the base and wear resistance of the surface and sufficient core toughness) is obtained with a combination of chemicothermal and heat treatments (with water quenching of the container) only for Kh12M and KhVG steels (and primarily with use of carbide coatings). 2. The following processes are recommended: for Kh12M steel chemicothermal treatment in a container with a fusible seal at 1050°C for 5 h, water quenching of the container with the parts; for KhVG steel chemicothermal treatment in a container with a fusible seal at 1000°C for 5 h, furnace cooling of the container, austenitizing in the same sealed container at 850°C for 2 h, water quenching of the container with the parts. 3. For punching and coining dies (taking into consideration the proposed chemicothermal and heat treatment process) use of high-chromium type Kh12M steel is most desirable.
Botvina, L.; Tetyueva, T.; Geikhman, T.; Kagan, L.; Artamoshkin, S.
doi: 10.1007/BF00776899pmid: N/A
1. Use of the relative length of a stable crackl c/b, where b is specimen width, is proposed for evaluation of the fracture resistance of a steel and determination of the critical defect size. 2. 09G2S steel has higher impact strength and crack resistance and a lower ductile-to-brittle transition temperature but a greater anisotropy of properties than 20 steel. 3. In fractures of specimens of 20 and 09G2S steels at temperatures of the ductile-to-brittle transition in impact bend and static tensile tests zones of drawing out (Θ 1) and of shear (Θ 2) and separation (Θ 3) fracture were observed. Their total is the zone of stable crack growth (l c). The ductile-to-brittle transition temperature of 20 steel determined from the fibrous constituent in the fracture (F=50%) is practically independent of notch sharpness of the specimens used.
Goritskii, V.; Shneiderov, G.; Aksenova, E.; Lipilina, Zh.
doi: 10.1007/BF00776902pmid: N/A
1. The metal of welded joints of thick steel sheet 10Kh25NM, which after normalization has a ferritic-bainitic structure, is prone to hot embrittlement. The base metal is pronest to hot embrittlement; after 2500 h holding at 450°C the rise of T50 amounts to 60°C. 2. The degree of hot embrittlement of steel 10Kh2GNM subjected to lengthy holding at 450°C decreases after shortterm (24 h) holding at 550°C, which indicates that heating a hydrocracking reactor vessel to such a temperature is permissible for the purpose of regeneration of the catalyst. 3. A correlation of T50 with the proportion of intercrystalline failure fIF was established in the form of a dependence of the type T50∼(1−fIF)/(1+fIF).
Malinov, L.; Cheilyakh, A.; Malinov, V.; Gogol, A.; Arkhipova, T.
doi: 10.1007/BF00776903pmid: N/A
1. Austenite forming during the isothermal quenching of high strength cast iron VCh50 is metastable and transforms to martensite in the course of mechanical testing. 2. The highest level of these or other properties of high strength cast iron is obtained at an optimal amount and stability of the austenite, which must be controlled by varying the isothermal quenching regimen.
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