Metal Science and Heat Treatment

Surovtsev, A.; Yarovoi, V.

doi: 10.1007/BF00712549pmid: N/A

1. On heating low-carbon steels containing 0.025–0.35% C at rates of 7.5–200 deg/min in the intercritical temperature range Ac1–Ac3 it is possible to isolate three basic temperature ranges: transformation of pearlite into austenite Ac3 S–Ac3 f, absence of transformation, and transformation of ferrite into austenite Ac3 S–Ac3 f. 2. The range for absence of transformations between temperatures for the finish of P→A-transformation and the start of F→A-transformation is greater as carbon content in the steel decreases. With a carbon content in the steel of 0.35% or more Ac1 f and Ac3 S almost coincide.

Nizhnikovskaya, P.

doi: 10.1007/BF00712550pmid: N/A

The ductility of iron-carbon alloys of the eutectic type is governed by the structure of eutectic carbides and it may be increased by two methods. The first envisages formation during prior heat treatment of dislocations in eutectic carbides and creation of subgrain boundaries along which during deformation there is carbide fragmentation. This method, as a result of the specific effect of the metal base on formation of dislocations in carbides and prevention of carbide failure under the action of compressive stresses from the surrounding solid solution, may only be used for alloys in which the carbide phase reinforces a metal matrix. The second method involves a marked increase in carbide ductility as a result of transformation occurring in them under the action of deformation [10]. This method may be used to increase the ductility of cast irons around the eutectic composition with eutectics whose matrix phase is carbide. In this way forming may be accomplished by rolling in the range of rates used in metallurgical production practice.

Yatsenko, A.; Repina, N.; Doronkin, K.

doi: 10.1007/BF00712551pmid: N/A

1. The primary structure of Fe-C-Al alloys based on α- and γ-solid solutions forms by dendrite crystallization. 2. Formation of peritectic γ- and ɛ-phases occurs on the basis of primary dendrites by rim growth. 3. Intracrystalline liquation of aluminum depending on alloy composition may be direct or inverse.

Toropov, V.; Bondarenko, Yu.

doi: 10.1007/BF00712552pmid: N/A

1. The possibility of using alloys with a unidirectional eutectic structure from the Ni-Al-Nb system as high-temperature materials has been demonstrated. Alloys containing 21–23% Nb and 2.0–2.5% Al after directional crystallization under thermal gradient conditions of 70–80 deg/cm and a crystallization rate of 0.3–0.4 mm/min have a unidirectional (composite) structure consisting of alternating parallel plates of γ- and δ-phases. 2. Time to failure for alloys of the Ni-Al-Nb system with a unidirectional structure in stress-rupture tests in a vacuum at 1100°C and a stress of σ=120 MPa is 14–24 h, and σ f 20 =910–950 MPa. 3. As an example of alloying with chromium it has been demonstrated that on making additions to eutectic alloys it is necessary to evaluate the tendency of the alloy towards orientated phase growth. Addition of 2–4% Cr to alloy with 23% Nb and 2–2.5% Al increases its time to failure to 69–81 h with the same test conditions.

Zaslavskii, A.

doi: 10.1007/BF00712553pmid: N/A

1. When different additives (S, Se, Pb, Ca, etc.) are added to steel, its machinability improves on account of the active participation of the forming inclusions in the processes occurring in the cutting zone. 2. When high-speed steel tools are used on automatic lathes, it is most expedient to machine lead-containing and sulfur-lead-containing steels. 3. In machining at cutting speeds above 70 m/min with sintered alloy tools it is recommended to use steels with additions of selenium or first-generation calcium steels. 4. At even higher cutting speeds and machining with sintered alloy tools it is most expedient to use second-generation calcium steel. The range of effective application of steels with improved machinability can be extended by complex alloying.

Velikikh, V.; Goncharenko, V.; Zverev, A.; Rudychev, V.

doi: 10.1007/BF00712554pmid: N/A

D'yachenko, V.; Tverdokhlebov, G.; Korosteleva, A.

doi: 10.1007/BF00712555pmid: N/A

1. The life of high-speed steel tools may be increased significantly as the result of laser treatment. 2. Positive results are obtained only after treatment of tools with certain pulse power densities, the values of which must be determined in each specific case. 3. The optimum values of laser radiation pulse power density must be selected on the basis of the structure of the steel in the irradiated zone, which must be a martensite-carbide mixture formed as the result of secondary hardening occurring under the action of the laser pulse. 4. Deviations from the optimum conditions of laser heat treatment lead to loss of strength of the cutting edge and poorer tool service properties.

Gusev, O.; Lazarenko, A.; Ivanov, B.; Markov, V.; Pecherskii, O.; Chebukov, E.

doi: 10.1007/BF00712556pmid: N/A

Ol'shanskii, N.; Mikhailov, A.; Krivonogov, V.; Trusova, I.

doi: 10.1007/BF00712557pmid: N/A

1. After electron-beam treatment a uniform finely dispersed structure with cellular distribution of the carbide phase is formed in the fused zone. The sizes of the cells and the carbides depend upon the electron-beam fusion conditions. 2. Electron-beam fusion of the working surface of the experimental lot of R6M5 steel punches made it possible to increase their life by 2.5–3 times.

Kalimullin, R.; Kozhevnikov, Yu.; Faizullin, I.; Valuev, V.

doi: 10.1007/BF00712558pmid: N/A

1. Laser treatment provides hardening of MA21 magnesium-lithium alloy but there is a reduction in its plastic properties. 2. The structure of the surface layer of MA21 alloy samples after laser treatment is characterized by significant refinement and uniformity in distribution of the phases across the volume.