Showing papers on "Tempering published in 2005"

Steels: Processing, Structure, And Performance

Abstract: In this Second Edition, new information and references are integrated into chapters. Emphasis is still on processing, alloying, microstructure, deformation, fracture and properties of major steel types ranging from low-carbon sheet steels, pearlitic rail and wire steels, to quench and tempered medium- and high-carbon martensitic steels. Microstructural aspects of steelmaking, hardenability, tempering, surface hardening, and embrittlement phenomena are updated, and chapters on stainless and tool steels remain in the Second edition. The work is intended to be tutorial and is an essential state-of-the-art reference for anyone that makes, uses, studies and designs with steel.

Steel Heat Treatment Handbook

Abstract: Fundamental concepts in steel heat treatment the effects of alloying elements on the heat treatment of steel hardenability quenching and quenching technology distortion of heat-treated components heat treatment equipment vacuum heat treatment steel heat treatment heat treatment with gaseous atmospheres nitriding techniques and methods induction heat treatment - basic principles, computation, coil construction, and design consideration induction heat treatment - modern power supplies, load matching, process control, and monitoring heat treatment of powder metallurgy steel components metallurgical property testing mechanical property testing methods steel nomenclature environmental and safety regulations affecting heat treaters. Appendices: common conversion constants temperature conversion table volume conversion table hardness conversion tables - hardened steel and hard alloys recommended Mil 6875 specification steel heat treatment conditions colours of hardening and tempering heats weight tables for steel bars.

Pre-aging to improve bake hardening in a twin-roll cast Al–Mg–Si alloy

Abstract: Heat-treatable Al–Mg–Si aluminum alloys are increasingly used for automotive body panel applications. They are shipped and formed in T4 temper while still formable and are subsequently given a bake cycle to increase strength by age hardening while the paint is cured. The industrial paint-bake treatment, however, is too short to fully exploit the age hardening potential of these alloys. Hence, the microstructure in the conventional T4 temper must be modified by creating clusters that grow and readily transform into coherent precipitates upon paint baking. The present work was undertaken to improve the paint-bake response of a twin-roll cast 6016 sheet by employing artificial aging between the solution treatment and the paint-bake cycle. Pre-aging in a wide temperature range (60–200 °C) was effective in improving the bake hardening response of the twin-roll cast 6016 sheet which, when processed without any pre-aging, failed to meet in-service strength requirements with a rather poor bake hardening response of 35 MPa.

Effect of fine precipitation and subsequent coarsening of Fe2W laves phase on the creep deformation behavior of tempered martensitic 9Cr-W steels

Abstract: The effect of fine precipitation and subsequent coarsening of Fe2W Laves phase on the creep deformation behavior was investigated for simple 9Cr-W steels containing 0, 1, 2, and 4 wt pct W. After tempering, the specimens were subjected to creep tests at 823, 873, and 923 K for up to 15,000 hours. The precipitation of Fe2W Laves phase takes place during creep at boundaries from the supersaturated solid solution of the high-W steels, the 9Cr-2W and 9Cr-4W steels, but not in the low-W steels, the 9Cr-0W and 9Cr-1W steels. The fine precipitation of Fe2W Laves phase decreases the creep rate in the primary or transient creep region, while the subsequent large coarsening of Fe2W Laves phase reduces the precipitation strengthening and promotes the acceleration of creep rate in the tertiary or acceleration creep region after reaching a minimum creep rate. The change in shape of creep rate curves with stress and temperature is explained by taking fine precipitation and subsequent coarsening of Fe2W Laves phase into account.

Influence of silicon content on the precipitation of secondary carbides and fatigue properties of a 5%Cr tempered martensitic steel

Abstract: In comparison with the conventional AISI H11 tool steel, which contains approximately 1 wt.% silicon, the modified steel AISI H11 (∼0.35 wt.% silicon) exhibits improved tensile and fatigue properties at 550 °C – the estimated tool surface temperature during the high-pressure injection of aluminium alloys. The effect of silicon on the stability of secondary carbides was studied using transmission electron microscopy and small-angle neutron scattering. Silicon has a considerable influence on the precipitation of secondary carbides. A higher volume fraction and density of small particles were observed in the low-silicon-grade steel, both after heat treatment and after fatigue testing. The final discussion focuses on the influence of silicon in the precipitation sequence. It is concluded that silicon has a detrimental effect as it shifts the secondary hardening peak towards lower tempering temperatures.

Direct additive laser manufacturing using gas- and water-atomised H13 tool steel powders

Abstract: To date only gas-atomised tool steel powders have been used for direct laser additive manufacturing and the potential benefits of using water-atomised powders have not been explored. As the use of the process in the rapid tooling field is growing, there is a need to explore if the less expensive water-atomised materials can be realistically utilised. A comparative investigation is described, using gas- and water-atomised H13 powder deposited with a CO2 laser and coaxial powder feed nozzle. Multiple layer wall dimensions, composition, microstructure, surface finish and hardness are related to process conditions and the causes of the observed phenomena are discussed. An energy-balance method is used to model the temperature of the powders and the results used to explain some of the effects. Results indicate that using the lower cost water-atomised powder still allows a metallurgically sound component to be built and does not significantly affect surface finish. The build rate is, however, lower and the water-atomised powder tends to produce slightly softer walls, attributable to a higher temperature during tempering of deposited material by subsequent laser passes.

Low temperature tempering of a medium carbon steel in high magnetic field

Abstract: The effect of low temperature magnetic tempering on carbide precipitation in a medium carbon steel, 42CrMo, has been investigated. As-quenched steel specimens were tempered at 200°C for 60 min without and with a 14-T magnetic field. Results show that under the magnetic field processing there forms the relatively high-temperature monoclinic χ-Fe5C2 carbide with a denser distribution and smaller sizes, as compared to the usual orthorhombic η-Fe2C carbide obtained without the magnetic field. The impact of the external magnetic field refers to a change in the precipitation sequence of the transition carbides by effectively lowering the Gibbs free energy of the high magnetization phases. The denser distribution and smaller size of χ-Fe5C2 precipitates are attributed to the increased nucleation rate and the weaker diffusion capacity required for growth as the formation temperature is lower. This offers additional dispersion strengthening to compensate for the decrease in strength and hardness due to the loss of supersaturation of carbon atoms in the matrix and raises the toughness of the steel.

Modifying Cast Tungsten-Molybdenum High-Speed Steels with Niobium, Zirconium, and Titanium

Abstract: The influence of modifying additives of niobium, zirconium, and titanium on the structure and properties of cast tungsten-molybdenum high-speed steels R6M5 and R6M5K5 is studied. Results of metallographic and x-ray diffraction analyses and of studies of fracture surfaces of the steels after casting, annealing, hardening, and tempering are discussed. The relationship between structural parameters, the degree of contamination of the metal by nonmetallic inclusions, and mechanical properties is established. It is shown that modifying with the mentioned elements in optimum amounts primarily promotes an increase in the impact toughness and wear resistance of the metal.

Heat treatment of multi-element low alloy wear-resistant steel

Abstract: The effect of heat treatment on the performances of multi-element low alloy wear-resistant steel (MLAWS), which is used to make the rolling mill torii liner, was investigated. The results show that the hardness and tensile strength increase as the quenching temperature is increased from 840 to 900 °C. However, the hardness decreases rapidly as the quenching temperature is increased beyond 900 °C, while the temperature has little influence on the tensile strength when it exceeds 900 °C. No clear influence on the impact toughness has been observed unless the quenching temperature is beyond 920 °C. As the tempering temperature exceeds 300 °C, tiny ɛ carbides separate out from martensite and bainite complex structures and cause the carbon content in the complex structures to decrease. This results in the toughness to increase significantly. The best wear resistance can be obtained by tempering at 350 °C. The optimum heat treatment of MLAWS comprises quenching at 900–920 °C and tempering at 350–370 °C.

High strength cold rolled steel sheet reduced in dispersion in mechanical characteristic, and its manufacturing method

Abstract: PROBLEM TO BE SOLVED: To provide a high strength cold rolled steel sheet reduced in dispersion in mechanical properties and its manufacturing method. SOLUTION: The high strength cold rolled steel sheet has a composition which consists of 0.06 to 0.15% C, 0.5 to 1.5% Si, 1.5 to 3.0% Mn, ≤0.05% P, ≤0.01% S, 0.5 to 1.5% Al and the balance Fe with inevitable impurities and in which the value of A, defined by A=Si+9×Al, satisfies 6.0≤A≤20.0. Moreover, the steel sheet has a structure which is composed of a dual-phase structure of ferrite and martensite and in which the area ratio of the ferrite is 40 to 90%. When manufacturing this steel sheet, recrystallization annealing/tempering treatment is carried out by carrying out: holding at a temperature ranging from the Ac 1 point and the Ac 3 point for ≥10 sec; cooling down to 500 to 750°C at ≤20°C/sec cooling rate; rapid cooling down to ≤100°C at ≥100°C/sec cooling rate; and tempering at 300 to 500°C. COPYRIGHT: (C)2007,JPO&INPIT

Contribution of Microstructural Factors to Hardness Change during Creep Exposure in Mod.9Cr-1Mo Steel

Abstract: The effect of microstructural factors on hardness was investigated in normalized, tempered, aged and crept materials for Mod. 9Cr-1Mo steel, using nanoindentation and microhardness tests. Nanohardness and microhardness decreased during tempering, aging and creep exposure. Dislocation spacing, lath width, high angle boundary (block and packet boundary) spacing and inter-particle spacing increased during tempering, aging and creep exposure. A converted Vickers hardness was introduced to compare directly nanohardness and microhardness to Vickers hardness. The converted Vickers hardness increased with indent size in all the materials tested. Hardness at an indent size less than 1μm mainly consists of dislocations inside lath grains. Hardness at an indent size larger than 1μm originates from not only dislocation but precipitates and high angle boundaries such as block and packet boundaries. Comparing the converted Vickers hardness with lath width and high angle boundary spacing in normalized material with no precipitates, it was found that the lath boundary does not contribute to hardness. The difference in converted Vickers hardness between tempered and aged material was obviously large at the indent size, greater than inter-particle spacing. The decrease in hardness during aging is caused by increase in inter-particle spacing due to coarsening and coalescence of precipitates. On the other hand, not only changes in precipitates but also increase in high angle boundary spacing and dislocation spacing contribute to decrease in hardness during creep exposure.

Structure and mechanical behavior of heavily drawn pearlite and martensite in a high carbon steel

Abstract: Neutron diffraction measurements have revealed that cementite peaks disappear in a pearlite steel with drawing and that the residual intergranular stresses are generated. The diffraction profiles in a heavily drawn specimen suggest the tetoragonality with a small c/a in the ferrite matrix. Although cementite was hardly observed in the heavily drawn specimen, its c/a value determined by neutron diffraction and mechanical behavior are quite different from those of as-quenched martensite. The changes in hardness and c/a with annealing or tempering were also different between heavily drawn pearlite and marteniste. Hence, most of carbon atoms do not exist inside the ferrite lattice in the drawn pearlite and multi-scaled heterogeneous plastic deformation in pearlite seems to affect the asymmetry in the diffraction profile. Fracture behavior and hardness change with tempering is different in the two microstructures.

Influence of martensite volume fraction and tempering time on tensile properties of partially austenitized in the (α + γ) temperature range and quenched + tempered ferritic ductile iron

Abstract: In the present study, the effect of martensite volume fraction and tempering time on the tensile properties of ferritic ductile iron with dual matrix structure was investigated. For this purpose, specimens were intercritically annealed (partially austenitized) in the two phase region (α + γ) at various temperatures of 795 and 815° C for 20 min and then quenched into oil held at 100° C to obtain different martensite volume fractions. Some specimens were also conventionally heat treated (austenitized at 900° C and then quenched + tempered) for a comparison reason. The results showed that a structure having proeutectoid ferrite plus martensite has been developed and volume fraction of proeutectoid ferrite and martensite can be controlled to influence the strength and ductility. Specimens quenched from the (α + γ) temperature range exhibited much greater ductility than conventionally heat treated specimens. The tensile strength increased and ductility decreased with increasing martensite content. By increasing the tempering time, the yield and UTS decreased and ductility increased. The specimens tempered for 3 h and having 62% martensite volume fraction (MVF) exhibited the best combination of high strength and ductility. The tensile and proof stress of this material is much higher than pearlitic grades and ductility is lower than ferritic grades. The specimen tempered for 3 h and having ∼ 25% MVF exhibited the best combination of high strength and ductility compared to ferritic grades. However its strength is slightly lower but the ductility is almost three times higher than pearlitic grades.

Method for producing high tensile steel sheet

Abstract: A method for producing a high tensile steel sheet, which comprises casting a steel having a chemical composition, in mass %, that C: 0.02 to 0.18%, Si: 0.05 to 0.5 %, Mn: 0.5 to 2.0 %, Al: 0.005 to 0.1 %, N: 0.0005 to 0.008 %, P: 0.03 % or less, S: 0.03 % or less, P: 0.03 % or less, and the balance: Fe and inevitable impurities, subjecting the resultant steel to hot rolling so as for the sheet to have a prescribed sheet thickness, without cooling it to its Ar3 transformation point or lower or after re-heating it to its Ac3 transformation point or higher, subsequently subjecting the rolled sheet to the direct quenching or accelerated cooling from its Ar3 transformation point or higher, to cool it to 400˚C or lower, and then tempering the cooled sheet to such a degree that a portion of the sheet being central in the thickness direction has a highest temperature of 520˚C or higher, with an average rate of the temperature rise in the above portion of the sheet of 1˚C/s or higher for the range from 460˚C to a prescribed tempering temperature being its Ac1 transformation point or lower, by the use of a heating apparatus provided being directly connected to the same production line as that for a roller and an apparatus for direct quenching or accelerated cooling. The above method allows the production of a high tensile strength sheet which is superior to a conventional sheet in the balance between tensile strength and toughness before PWHT and after PWHT and has a tensile strength of 570 MPa (N/mm2) or more, by adopting, in the tempering treatment for a quenched and tempered steel sheet, a specific value as the rate of temperature rise in a portion of the steel sheet being central in the thickness direction.

Effect of microstructure on elastic property at high temperatures in ferritic heat resistant steels

Abstract: Elastic moduli were evaluated by tensile and abrupt stress loading tests at high temperatures in the JIS STBA24, ASTM A542 and ASME T91 steels to clarify the influence of microstructure on estimation of the elastic modulus. In the JIS STBA24 steel of ferrite-pearlite structure, the elastic moduli evaluated from conventional tensile tests are in good agreement with that obtained from ultrasonic pulse method over a wide temperature range. On the other hand, in the ASTM A542 and ASME T91 steels of tempered martensitic lath structure, the elastic moduli evaluated from conventional tensile tests abruptly decreases at temperatures higher than 773 K, in contrast with the elastic moduli obtained by ultrasonic pulse method. Anelastic deformation occurs at high temperatures under applied stress in the ASTM A542 and ASME T91 steels due to elastic bending of the lath boundary. In the steels of martensite, elastic moduli estimated by instantaneous strain, which contains no anelastic deformation upon abrupt stress loading agree with those obtained by ultrasonic pulse method. The elastic modulus does not depend on the strain rate at 873 K in the JIS STBA24 steel. On the other hand, the elastic modulus decreases with decreasing strain rate at 873 K in the ASME T91 steel due to the anelastic deformation during tensile tests.

Analysis of the precipitation behaviour in a high-speed steel by means of small-angle neutron scattering

Abstract: Small-angle neutron scattering (SANS) and energy-filtered transmission electron microscopy (EFTEM) were employed to characterise the precipitation behaviour in the high-speed steel HS6-5-2 during tempering. With SANS the evolution of the size distribution of precipitates during isothermal tempering at 590 °C was investigated. The SANS results are discussed assuming that three populations of precipitates can be distinguished during tempering at 590 °C. The smallest population with sizes around 1 nm is supposed to be carbon-rich clusters. Intermediate-sized particles between approximately 1 and 10 nm might be either MC and/or M 2 C carbides, which cannot be distinguished by SANS. In addition, the ratio A of magnetic and nuclear scattering intensity was used to gain information on the composition of the precipitates. The A -ratio is discussed assuming a substitution of iron in the precipitates by carbide forming elements with increasing tempering time. Finally, the correlation of the results obtained by SANS with those achieved by EFTEM is presented.

Systems for tempering components of a printing machine

Abstract: A system is provided for tempering, or controlling the temperature of a printing machine to maintain a desired temperature by the use of a cooling device. The cooling device prepares, on a first output, a tempering medium having at least one first desired temperature level, for a first supply current of the tempering medium for the components whose temperatures are to be controlled. The cooling device provides a first cooling process which can be carried out by a first fluid circuit. Tempering medium, which is to be cooled to a tempering temperature that is below the ambient, or an external temperature, are provided. A second cooling process is carried out by a device for cooling a second fluid circuit which is different from the first fluid circuit, by the use of outside air. The supply circuit, that is used to convey the tempering medium of the desired temperature, to the component whose temperature is to be controlled, can be coupled, in a thermal manner, to both of the cooling processes by the use of at least one heat exchanger.

Phosphorus segregation in 2.25Cr-1Mo steel

Abstract: Phosphorus segregation to grain boundaries in a commercial grade 2.25Cr–1Mo steel subjected to a variety of heat treatments has been examined using X-ray spectroscopy in a field emission gun scanning transmission electron microscope. A number of points have been established. Segregation of phosphorus to grain boundaries is present after austenitising and quenching. Tempering for 2 h at 650°C enhances phosphorus segregation during the following aging processes at 520°C. A higher austenitisation temperature (larger grain size) makes subsequent segregation more intense. For specimens austenitised at 1100°C, the concentration of phosphorus segregated to grain boundaries steadily increases with aging time after tempering (from 0 to 210 h). For specimens austenitised at 900°C, the phosphorus concentration at grain boundaries first increases, reaches a maximum at an aging time of ∼ 210 h and then decreases with aging time (480 h).

Effect of microstructure on static and dynamic mechanical property of a dual phase steel studied by shear punch testing

Abstract: The high-speed deformation behavior of a dual phase steel was studied by means of dynamic Hopkinson bar shear punch testing, with an emphasis on the influence of microstructure. Dual phase microstructures with different fractions of martensite were obtained by changing heat treatment parameters during intercritical annealing. The effects of low temperature tempering (170°C, 235°C, and 300°C) and bake hardening treatment (5% pre-strain followed by holding at 170°C for 20min) were also investigated for two selected microstructures containing 22% and 61% martensite, respectively. Quasi-static shear punch property was also measured by a MTS hydraulic machine and compared with dynamic results. Additionally, quasi-static tensile tests for some specimens were also conducted for validating the shear punch data.

The effect of alloying on the resistance of carbon steel for oilfield applications to CO2 corrosion

Abstract: A systematic study has been conducted to investigate the influence of a wide range of alloying elements and different processing conditions on the resistance of low-carbon steels to CO2 corrosion. Strong carbide-forming microalloying elements such as Ti, Nb and V, along with Cr additions, and different levels of Mn, Si, Cu, Mo and Ni, have been explored, along with treatments simulating different processing conditions, for example, controlled rolling, and quenching and tempering. Corrosion testing, including flow loop tests, has been carried out, along with evaluation of mechanical properties, weldability and hot ductility. The programme has developed steels with improved CO2 corrosion resistance and hence identified a potential route for producing more economical carbon steels for oilfield applications. The work has been carried out as part of the UK- Brazil Corrosion Network.

Anticorrosion and antiwear martensitic stainless steel and its production method and use

Abstract: The invention relates to a sort of martensitic stainless steel which resists the corrosion and abrasion, in addition to the method of making it and its usage. The chemical composition of the steel is (wt %): Cu‘0.45i½0.60u¼Cru‘16.00i½19.00u¼Niu‘2.50i½4.00u¼Mou‘2.50i½4.00u¼Siiœ1.00u¼Mniœ2.00u¼Piœ0.03u¼Siœ0.03, the rest is Fe. The technical steps of making the steel comprise smelting, forging, annealing, quenching, tempering and so on. Said steel has high mechanical property and resistance to corrosion, and its hardness can reach HRC46~54, which can be used for manufacturing elements adapted in the seawater and the agent containing chloride.