The effect of prior heat treatments on the structure and properties of warm-rolled AlSl 52100 steel

Isothermal rolling of AISI 52100 steel at 923 K (650 °C) has been used to produce very fine spheroidized carbide particles 0.1 to 0.2 μm in size in a submicron grain size ferrite matrix. Pearlitic starting structures are not completely spheroidized by such warm rolling and some isolated pearlite colonies remain after rolling. Tempered martensitic starting structures result in more uniform structures after rolling. The effect of varying the austenitizing time and temperature and of two cycle austenitizing treatments before rolling of tempered martensite were studied. After rolling, the room temperature yield strength was raised, a result of the finer dispersion of carbides and the associated reduction in ferrite grain size. The presence of isolated pearlite colonies in rolled material reduces the room temperature ductility. Formerly Graduate Student, Department of Mechanical Engineering, United States Naval Postgraduate School     

Effect of rolling temperature on the deformation and recrystallization textures of warm-rolled steels

Warm-rolling trials were carried out on three interstitial-free (IF) steels (stabilized with either niobium or titanium), an extralow-carbon (ELC) steel, and an experimental low-carbon chromium (LC Cr) material at temperatures between 440 °C and 850 °C. The influence of rolling temperature on their as-rolled microstructures and deformation and recrystallization textures was investigated. Also, the effect of coiling simulation and degree of rolling reduction on the r values of some of these materials was examined. In-grain shear bands were evident in all as-rolled microstructures, but their sensitivity to deformation temperature varied between steels. Shear bands of moderate intensity were formed in the IF steels across all temperatures. In the ELC material, intense shear bands were formed at low rolling temperatures, but at higher temperatures, this intensity was drastically reduced. The development of shear bands at the higher rolling temperatures was significantly enhanced by alloying with chromium. The deformation textures produced were typical of rolled ferrite materials. The intensity of this texture increased markedly with temperature for the ELC grade. Conversely, the intensity of the recrystallization texture decreased with increasing temperature. The addition of chromium was found to strengthen the {111} component and, hence, the formability. The sharpness of both the deformation and recrystallization textures of the IF steels was relatively unaffected by rolling temperature. These differences are attributed to the intensity and frequency of shear-band formation and the dynamic strain-aging (DSA) behaviors of the various materials.     

On the structure and properties of high-nitrogen low-carbon non-austenitic steels

Phase transformations, when cooling and heating non-austenitic high-nitrogen low-carbon steels containing chromium and other alloying elements, as well as structure and mechanical properties of these steels were analyzed. It was confirmed that these steels have high temperature chromium diffusion controlled pearlitic type transformation and martensitic type transformation. Experimental high nitrogen steels after quenching and tempering provide mechanical properties of about the same level as high strength commercial alloyed steels. Features of nitrogen as an alloying element in steels discussed allow the supposition of a possible reduction of the consumption of nickel, manganese, molybdenum or tungsten in high strength alloyed steels.     

Effect of grinding on the structure and properties of roll steels

A thermal model for the grinding of quenched alloy roll steels has been developed. The temperatures in the cutting area are calculated by this model, and the effect of grinding conditions on the structure and hardness of the surface layers of a roll steel quenched for martensite is studied.     

The effect of heat treatment on the properties and structure of molybdenum and vanadium dual-phase steels

A systematic study was made of the effect of the heat treating parameters,(i.e., temperature, time, and cooling rate) on the properties and structure of molybdenum and vanadium bearing dual-phase steels. The volume percent martensite was found to be the major structural factor that controls the strength and ductility of these steels. The relationship between strength and ductility was independent of alloy addition for the alloys studied. Annealing temperature was shown to be very important in these alloys, especially at high quench rates. The molybdenum alloy exhibited better hardenability than the vanadium alloy for equivalent heat treating conditions. Therefore, for a given set of annealing conditions the molybdenum alloy generally had the highest tensile strength and lowest total elongation. A minimum in the 0.2 pct yield strength was found at a specific volume fraction martensite. The increase in yield strength at the lowest volume fraction studied can be related to a jog or discontinuity in the stress-strain curve during tensile testing. This jog was found to be the result of the lack of a sufficient amount of free dislocations. The causes of this deficiency of the dislocations may be: 1) an insufficient amount of transformed martensite, 2) a large martensite interparticle spacing, 3) dynamic recovery of dislocations during cooling, and 4) pinning of dislocations by precipitates during cooling.     

Effect of thermomechanical processing on structure and properties of low carbon steels

The microstructure of one plain carbon and two microalloyed steels has been refined by two different thermomechanical processing schedules in a laboratory rolling mill. The factors controlling the structural refinement have been investigated. The results indicate that a combination of single/two stage rolling prior to reaustenitization treatment and finish rolling in the (α + γ) region followed by controlled cooling improves the mechanical properties by refining the ferrite grain size.     

Effect of cryogenic deformation on the structure and properties of chromium-nickel steels

The effect of rolling at a temperature of 77 K and subsequent tempering on the structure and properties of chromium-nickel 05Kh14N14T2 and 15Kh14N14Yu1 steels is investigated. The formation of a nanocrystalline martensite phase in an austenitic matrix has been established. It is shown that additional hardening of the metal occurs due to the precipitation of intermetallic phases during heat treatment. The steels under study are high-strength and hard-magnetic after cryogenic deformation and heat treatment.     

Mechanical and tribological properties of wear-resistant hot-compacted steels with a heterogeneous structure

Institute of Materials Science Problems, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, No. 3(363), pp. 42–46, March, 1993.     

Effect of fine structure on mechanical properties of hot-forged powder steels

Comparative analysis of the substructural parameters and mechanical properties of hot-forged steels reveals regular changes in the mechanical characteristics depending on the degree of imperfection. It is shown that higher imperfection at lower forging temperatures of porous billets can increase the strain hardening of particles. The maximum strain hardening of carbon steels is revealed at the maximal structural imperfection and a density of 7.77 g/cm³ after forging a billet heated to 1100°C. The high strain hardening of chromium steel results from high dispersion of coherent scattering regions. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 7–8 (456), pp. 91–99, 2007.     

带状组织对低碳微合金钢性能的影响及控制

研究了两种不同规格、不同成分的低碳微合金钢,通过分析它们的力学性能及对应的铁素体-珠光体(F-P)带状组织情况,讨论了F-P带状组织对塑性和韧性的影响,并从连铸板坯的冶炼过程中的成分优化、降低中心偏析,降低板坯的终轧温度、以及提高冷却速率等多方面提出了相应的带状组织的控制措施.     

High-strength carbon steels with hereditary fine crystal structure. III. Effect of the structure on the mechanical properties of powdered carbon steels

Conclusions By using powdered metals with the corresponding substructure forming in vibration grinding, and by locking the polygonized substructure in the compacts on dislocations of carbon atoms, it is possible by the method of powder metallurgy to put into effect the idea of thermomechanical strengthening of the alloy Fe + C, greatly to increase its strength and ductility.The pure high carbon steels with hereditary finely crystalline structure thus obtained are in regard to structural strength (the combination of the characteristics k_1c and _y) on the level of some steels subjected to thermomechanical treatment and of high alloy steels. This may make it possible to increase considerably the load-bearing capacity of industrial carbon steels, to ensure their reliability and durability. The principal factor responsible for the low brittle strength of hypereutectoid low tempered carbon martensite is insufficient purity as regards admixtures in the initial material.Translated from Poroshkovaya Metallurgiya, No. 1(289), pp. 91–95, January, 1987.     

Effect of heat treatment on mechanical properties and structure of high-strength pipe steels with a ferrite-bainite structure*

The effect of heat treatment on mechanical properties and microstructure of high-strength low-alloy ferrite-bainite pipe steels is studied. Specimens are heated in a laboratory furnace up to a temperature in the range 100?C850°C. Dependences for the change in mechanical properties on heating temperature and the main features of steel structure are determined. TEM is used to study excess phase precipitation, including Nb and V carbonitrides, during heating. Unfavorable temperature ranges are determined for heating pipe steels with a ferrite-bainite structure. The results obtained may be used in industrial production and during development of new technology for thermomechanical treatment.     

Influence of Mn and Si contents on structure and mechanical properties of ferritic-pearlitic HSLA steels

Laboratory melts of microalloyed low carbon steels with an increased silicon content of about 1 % and manganese contents between 0.3 and 1.3 % were thermomechanically rolled in a laboratory two-high rolling stand to plates of about 10 mm in thickness. The influence of chemical composition and finish rolling temperature (FRT) on the ferrite-pearlite structure of the plates (tensile and Charpy impact tests) was investigated. The choice of the temperature range of finish rolling with respect to the γ/α transformation start temperature strongly influences the ferrite-pearlite structure and the mechanical properties. The most fine-grained and homogeneous ferrite-pearlite structure and the best combination of strength and toughness have been obtained with steels containing about 1 % Mn and 1 % Si rolled with a finish rolling temperature of about 850°C.     

Influence of dispersed microadditives on the structure and properties of powder carbon and high-chromium steels

The influence of dispersed different nature microadditives on structure formation and volume changes during sintering, and strength of powder carbon and high-chromium steel is investigated. Mechanisms of the effect of additives on the formation of their structure are described. It is shown that the introduction of sodium bicarbonate provides the largest strengthening of carbon steel, while the introduction of boron nitride provides that of high-chromium steel. The level of increasing the strength depends on the sintering temperature and amount of additive.     

Effect of temperature sequence during hot strip rolling on structure and properties of mild steels

Reduced temperatures can be applied for rolling of mild steels in wide hot strip mills. This has been investigated by laboratory and production trials with unalloyed and microalloyed deep drawing grades. A reduced slab reheating temperature leads to a grain refinement prior to rolling and to incomplete dissolution of precipitates. Decreased rolling temperature results in partial deformation in the ferrite region. The flow curves of mild steels show a relative minimum below γ/α transformation temperature, thus only low deformation forces are necessary. Ferrite rolling can develop coarse or partly recrystallized microstructures, depending on amount of strain and on coiling temperature. The yield strength, as a measure of cold formability, can be lowered compared to conventional rolling in the austenite region.