Showing papers on "Tempering published in 1987"

The measurement of stress in steels of varying microstructure by magnetoacoustic and Barkhausen emission

Abstract: Magnetoacoustic emission (MAE) and Barkhausen emission (BE) have been measured as a function of applied magnetic field and tensile stress from mild-steel samples in a wide range of heat treatments, to develop a technique to measure stress without prior knowledge of the microstructure. The results are supplemented by measurements of magnetic coercivity and mechanical hardness. MAE is found to decrease with increasing applied stress, whereas the variation of BE is more complicated. The amplitudes of both MAE and BE, as well as the coercivity and hardness are also found to depend on the microstructure to varying degrees. Thus in ferritic-pearlitic and ferritic-pearlitic-martensitic steel MAE is much more sensitive to stress than to changes in microstructure, whereas the sensitivity of BE to stress and microstructure is similar. Above 50 MPa MAE is also more sensitive to stress in ferrite containing cementite, whereas BE both lacks a monotonic dependence upon stress and is sensitive to microstructure. In martensite, however, there is no MAE, the BE increasing monotonically with stress. Tempered martensitic structures give a weak MAE signal that is more sensitive to tempering temperature than applied stress, whereas the BE increases with stress for tempers below 500°C and decreases above. The dependence of MAE and BE on magnetic field are discussed in terms of domain-wall nucleation and irreversible motion in ferrite at higher fields, and irreversible wall motion through martensite or pearlite at lower fields. The results imply that MAE can be used alone to measure stress provided the general form of the microstructure is known; otherwise BE can be used as an additional technique to resolve any ambiguity.

Effect of boron additions on the toughness of heat-treated low-alloy steels

Abstract: Despite the widespread commercial use and acceptance of boron-containing heat treated steels for many engineering applications, some controversy persists about the toughness characteristics of these steels in comparison with boron-free grades. Therefore, the present investigation was conducted to compare the heat treating response and toughness properties of three boron-containing steels, namely 10B30, 50B35, and 94B30, with those of 8637 steel without boron. The boron additions in the range 0.0012% to 0.0018% significantly increased the hardenability of the boron steels, but did not influence their tempering behavior, as expected. Charpy V-notch impact transition curves were determined for the steels after quenching to fully martensitic structure and tempering to hardness levels of 35 and 40 HRC. Allowing for the slight differences in hardness among the steels, and a slightly coarser grain size in one of the steels, the toughness characteristics of the boron and boron-free steels were essentially similar.

Effect of overlap pass tempering on hardness and fatigue behaviour in laser heat treatment of carbon steel

Abstract: Etude experimentale sur un acier 0,51C-0,71Mn-0,29Si soumis a un traitement laser simple ou double. Determination sur les echantillons ainsi traite de la durete Vickers, la resistance a la fatigue et le comportement a la rupture

Process for producing nickel steels with high crack-arresting capability

Abstract: A process for producing a Ni-steel with high crack-arresting capability is disclosed. The process comprises the steps of: heating a steel material containing 2.0-10% of Ni to a temperature between 900 and 1,000° C.; hot rolling the steel material to provide a cummulative reduction of 40-70% at 850° C. or below, and finishing the rolling operation at 700°-800° C.; immediately after completion of the rolling step, quenching the steel material to a temperature not higher than 300° C.; and subsequently tempering the quenched slab at a temperture not higher than the Ac1 point.

Microstructure, phase equilibria, and transformations in corrosion resistant dual phase steel designated 3CR12

Abstract: To optimize the properties of the new corrosion resisting steel 3CR12 the microstructure has been studied as a function heat treatment. The kinetics of both the decomposition of austenite and the reaustenization reactions have been investigated using a series of isothermal anneals. The steel has a dual phase ferrite–austenite structure between 800 and 1350°C and the amount of austenite is maximum at about 1050°C. At this temperature a higher nickel version of the alloy is fully austenite. On cooling to ambient temperature, the austenite transforms to a lath-type martensite. Heat treatments at temperatures up to 800°C cause the slow tempering of the martensite, the recovery and recrystallization of original ferrite regions, and the nucleation and growth of newly formed ferrite. The growth of ferrite requires the concomitant precipitation of carbides and nitride particles from the austenite or martensite and these particles mark the stepwise movement of the interface. In contrast the reaustenization...

Microstructure and mechanical properties of a 3Cr-1.5Mo steel

Abstract: Tensile and impact properties were determined for a steel (3 wt pct Cr-1.5 wt pct Mo-0.1 wt pct V-0.1 wt pct C) considered a candidate for elevated-temperature pressure-vessel applications. The steel was tested in two heat-treated conditions: normalized and tempered and quenched and tempered for various tempering conditions. Similar tempering treatments for the quenched and the normalized steels led to similar strengths. However, for the lowest tempering parameter used, the impact properties for the quenched-and-tempered steel exceeded those for the normalized-and-tempered steel, resulting in an excellent ductile-brittle transition temperature (-70 °C) and upper-shelf energy (225 J) for the quenched-and-tempered steel at a high strength (770 MPa ultimate tensile strength). Further tempering reduced the strength for the steel in both heat-treated conditions. The impact properties of the quenched steel were only slightly changed by further tempering, but those for the normalized steel improved, eventually equaling those for the quenched-and-tempered steel. The difference in impact properties after the two heat treatments was attributed to a difference in bainite microstructures.

High-strength spring steel

Abstract: A high-strength spring steel which produces retained austenite less than 10 % in content by weight after quenching in steps of quenching tempering, and has high fatigue strength and relaxation resistance. The steel contains 0.30 to 0.75 % carbon, 1.0 to 4.0 % silicon, 0.5 to 1.5 % manganese, 0.1 to 2.0 % chromium, and 2.0 % or less nickel, all by weight, and iron and unavoidable impurities for the remainder. The steel further contains 0.05 to 0.5 % vanadium and/or 0.05 to 2.0 % molybdenum, as required. Preferably, the retained-austenite content is set to less than 10 % by restricting the carbon, silicon, and nickel contents as follows: 35 × C (%) + 2 × Si (%) + Ni (%) < 23 %. Preferably, moreover, the oxygen and nitrogen contents of the steel are restricted to 0.0010 % or less and 0.005 % or less, respectively. By doing this, the fatigue strength of the steel can be further improved.

Process for producing high toughness, high strength steel having excellent resistance to stress corrosion cracking

Abstract: A process for producing a high toughness, high strength steel having excellent resistance to stress corrosion cracking including the steps of: preparing a steel slab including 0.02 to 0.10 wt % of C, 0.50 wt % or less Si, 0.4 to 1.5 wt % Mn, 1.0 to 7.5 wt % Ni, more than 1.0 wt % up to 1.5 wt % Mo, 0.80 wt % or less Cr, 0.01 to 0.08 wt % sol. Al, and the balance of Fe and unavoidable impurities; heating the steel slab to a temperature of from 1000° C. to 1250° C.; hot rolling the heated steel slab at a finishing nip temperature of from 700° C. to 880° C., at a total reduction rate of 40% or more effected at the finishing nip temperature or lower, and at a finishing temperature of 650° C. or higher, to provide a steel plate; then quenching the steel plate by initiating water cooling at a temperature of the Ar3 point thereof or higher and by terminating the water cooling at a temperature of 150° C. or lower; and tempering the quenched steel plate at a temperature of the Ac1 point thereof or lower.

Nondestructive measurement of stress in ferromagnetic steels using harmonic analysis of induced voltage

Abstract: A method for nondestructively measuring mechanical stresses in ferromagnetic steels was explored by applying a sinusoidal magnetic field to the materials and analysing the harmonic content of the resulting voltage induced in a sensing coil. The uniaxial stress dependence of the third harmonic amplitude was investigated along with the feasibility of separating stress effects from the effects of variations in material properties such as hardness, grain size and tempering temperature. The results obtained from SAE 4340 steel and AISI 410 stainless steel with various grain sizes, hardnesses and yield strengths showed that it is feasible to reduce the effects of material property variations by using the anisotropy in the harmonic amplitude as a stress indicator and thus to measure stresses in components made of ferromagnetic steels.

Influence of silicon on strength and toughness of 5 wt-%Cr secondary hardening steel

Abstract: The effects of manganese and silicon on the mechanical properties of the 5 wt-%Cr secondary hardening steel H-11 have been investigated. This steel normally contains about 0·5 wt-%Mn and 1wt-%Si. Two other steels were also considered, both identical to H-11, except that one contained no manganese and the other neither manganese nor silicon. The room temperature hardness and impact toughness were determined for the three steels for tempering temperatures ranging from 200 to 600°C. The results indicate that manganese has no influence on the tempering response or toughness of H-11, but that silicon significantly influences both.MST/506

TEM investigation of the tempering behaviour of the maraging PH 17.4 Mo stainless steel

Abstract: The PH 17-4 Mo steel (Z6 CND 17.04.02), used in the steam generator of nuclear reactors, was investigated in order to determine the structural evolution occurring during tempering carried out under various conditions of duration and temperature. The formation and growth of different types of carbides such as Mo2C, M23C6 and M7C3 and of Fe2Mo intermetallic compound were studied and also of reversed austenite. A small secondary hardening peak was observed for tempering close to 400' C which is related to the Mo2C carbide precipitation; beyond this temperature, softening occurs.

Microstructure of as‐quenched 3.5NiCrMoV rotor steel. Part I. General structure and retained austenite

Abstract: The microstructural features have been examined for 3.5NiCrMoV steam turbine rotor steel, in the as‐quenched state and tempered at 500 °C. Quenching produces lath martensite, with bands of retained austenite at the lath boundaries and, to a lesser extent, at prior austenite grain‐boundaries. Autotempering occurs during the quench, resulting in loss of tetragonality of the martensite and extensive carbide precipitation in the matrix and to a lesser degree at prior austenite grain boundaries, but not at lath boundaries. Tempering at 500 °C leaves the lath structure largely intact, but causes retained austenite to transform to bands of ferrite and cementite. This transformation does not correlate with the reduction in stress corrosion crack velocity which occurs on tempering. The strength of 3.5NiCrMoV steel in the as‐quenched and 500 °C tempered conditions is most probably due to the combination of carbide precipitation strengthening and substructure strengthening. Copyright

Metallic traveler for spinning machine

Abstract: PURPOSE:To produce a metallic traveler for a spinning machine having excellent toughness, wear resistance and heat resistance by subjecting pulverized powder of a high-speed tool steel to sintering, compacting, drawing and heat treatment. CONSTITUTION:The pulverized powder of the nitrogenous high-speed tool steel contg. 3.0-5.0% Cr, 3.0-10.0% Mo, 1.5-11.0% W, 0.8-5.3% V, and <1.3% C, and contg. C+N in a 0.7-2.0% range is subjected to sintering, compacting, hot rolling, warm drawing, cold drawing and cold rolling to produce a wire having a prescribed sectional shape. Such wire is worked to the metallic traveler for the spinning machine to be used for a yarn twister, etc., by a forming machine and thereafter the traveler is subjected to hardening and tempering treatments. Fine and hard metallic carbide 5 and carbonitride 6 are uniformly dispersed into a martensite base 4. The metallic traveler for the spinning machine which has excellent wear resistance, heat resistance and toughness, decreases the burn of the traveler and is usable for a long period of time is thus obtd.

Manufacture of high-tensile steel with low yielding ratio

Abstract: PURPOSE: To manufacture a steel combining low yielding ratio with high tensile strength, by hot-rolling a steel having a specific composition containing Mn and Al under specific conditions, by air-cooling the hot-rolled plate until a temp. where proper amounts of ferrite are precipitated is reached, and by successively applying quench-and-temper treatment to the above. CONSTITUTION: A steel slab consisting of, by weight, 0.01W0.20% C, ≤0.6% Si, 0.5W2.2% Mn, 0.001W0.1% Al, ≤0.006% N, and the balance Fe with inevitable impurities is heated to 900W1,200°C. Subsequently, rolling is applied so that cumulative draft at ≤900°C and finishing temp. are regulated to ≥30% and Ar 3 +80°CWAr 3 -20°C, respectively, and austenite grains are refined. Successively, air cooling is applied until a temp. of Ar 3 -20°CWAr 3 -100°C is reached, followed by cooling down to ≤300°C at ≥2°C/sec cooling rate. Then, tempering treatment is applied at a temp. of the Ac 1 point or above to form the structure into ferrite=bainite=martensite. Moreover, Ni, Mo, Cu, Cr, V, Nb, Ti, B, Ca, and REM are incorporated by specific amounts or below to the above steel composition, if necessary. COPYRIGHT: (C)1988,JPO&Japio

Mining/construction tool bit having bit body fabricated from Mn-B steel alloy composition

Abstract: A mining and construction bit body is composed of a Mn-B steel alloy composition. The alloy content of the composition in percents by weight includes: carbon, 0.33-0.38; manganese, 1.10-1.35; boron, 0.0005 minimum; silicon 0.15-0.30; sulfur, 0.045 maximum; and phosphorus, 0.035 maximum. The composition has a minimum hardenability of 47 Rockwell C at the Jominy 6/16 position and a maximum as-rolled hardness of 22 Rockwell C such that without anneal the composition meets hardenability and machinability requirements that make it useful for fabricating mining and construction bit bodies of all sizes. The mining and construction bit body is made by a process which includes the steps of, first, providing a rod in an as-rolled condition and being composed of the Mn-B steel alloy composition having the above-defined alloy content, then, machining the rod in its as-rolled condition without an anneal to the desired size and shape of the bit body, and, finally, heat treating the bit body to obtain the desired mechanical properties of hardness and toughness. The heat treating step includes heating the bit body to a temperature above 1550 degrees F., subjecting the bit body to quenching at a severity of approximately 0.7 H value to cool and harden it, and tempering it to improve its toughness. The quenching can occur in one of of oil, water or a polymer-water mixture.

Manufacture of high-tensile steel plate with low yield ratio by accelerated cooling method

Abstract: PURPOSE: To provide the desired low yield ratio, high strength, and high toughness by hot-rolling an Nb-containing steel with a specific composition under specific conditions and subjecting the resulting hot-rolled steel plate to accelerated cooling and then to tempering treatment. CONSTITUTION: A steel having a composition consisting of, by weight, 0.03W0.2% C, 0.03W0.5% Si, 0.4W2.3% Mn, 0.01W0.1% Al, 0.1W0.5% Mo, 0.01W0.05% Nb, 0.3W1.5% Ni, and the balance Fe with inevitable impurities is cast. This steel is hot-rolled so that draft in an uncrystallized austenite region and finish rolling-finishing temp. are regulated to ≥30% and ≥Ar 3 point, respectively. Directly after rolling, accelerated cooling is applied from ≥Ar 3 point down to ≤750°C at 2W40°C/sec cooling rate. Then, tempering treatment is applied at 300W700°C. If necessary, one or more kinds among 0.02W0.15% V, 0.3W0.05% Cr, 0.2W1.3% Cu, 0.0003W0.003% B, and 0.005W0.03% Ti are incorporated to the above steel. By using this high-tensile steel plate with low yield ratio, the safety of welding construction can be improved. COPYRIGHT: (C)1989,JPO&Japio

Belt type continuously variable transmission

Abstract: PURPOSE:To improve abrasion resistance of pulleys and a block and improve the durability of the transmission by using the pulleys applied with induction hardening and tempering through the high concentration carburization onto chrome-molybdednum steel and the block applied with carburization, hardening and tempering onto chrome-molybdenum steel. CONSTITUTION:Pulleys 10 and 20 are made of the material which is applied with the induction hardening and tempering up to the depth of 0.1 mm or more through the high concentration carburization onto chrome-molybdenum block, and a block 50 is made of the material applied with the carburization, hardening and tempering onto chrome-molybdenum steel, and the surface hardness is made to HV 750 or more. Then, the fine high carbon martensite structure is generated on the pulleys 10 and 20, and the surface hardness or the hardness in the vicinity of surface is increased, and the high pressure compression residual stress is generated, and a proper quantity of residual austenite can be secured. While, in the block 50, fine chrome and molybdenum are dissolved into the martensite matrix having the superior uniformity, and the hardness and toughness can be improved. Therefore, abrasion resistance is improved, and the durability of the transmission can be improved markedly.

Structural characterization of Fe-Al-C permanent magnetic alloys

Abstract: The Fe-7.91wt.%Al-1.98wt.%C permanent magnetic alloy is reported. The alloy reaches the optimum magnetic properties after quenching from 1200 °C in oil to room temperature, followed by tempering at 300 °C for 240 min. The microstructure of the alloy with the optimum magnetic properties has been characterized using transmission electron microscopy. The existence of rectangular precipitates of the Fe3AlC phase generating along the 〈100〉 directions was observed. The alloy examined is very hard (60–65 HRC) and brittle both after quenching and tempering and exhibits the transcrystalline cleavage fracture.

Production of seamless steel pipe of martensitic stainless steel having excellent low-temperature toughness and stress corrosion cracking resistance

Abstract: PURPOSE:To obtain the titled seamless steel pipe having excellent low-temp. toughness and stress corrosion cracking resistance by working a seamless steel pipe having a prescribed component compsn. at and in a specified temp. range and reduction of area then cooling the steel pipe down to a room temp. to form martensitic structure and subjecting the steel pipe to a tempering treatment in a prescribed parameter range. CONSTITUTION:The seamless steel pipe of the martensitic stainless steel contg., by weight % 0.15-0.25% C, 0.20-1.00% Si, 0.20-1.00% Mn, <=0.030% P, <=0.0030% S, and 11.0-14.0% Cr is produced by a Mannesmann mandrel mill system. The steel pipe is then worked at 13-90% reduction of area in a 1,000-650 deg.C range in the final hot finishing stage at the time of the above-mentioned production. The steel pipe after said working is cooled down to the room temp. to form the martensitic structure and is then subjected to the tempering treatment to bring the tempering parameter defined by T(20+logt) (T; deg.K, t; time) in a 20,500-21,600 range. The seamless steel pipe of the martensitic stainless steel having the excellent low-temp. toughness and stress corrosion cracking resistance is thus obtd.

Production of high-strength spur gear

Abstract: PURPOSE:To produce a high-accuracy high-strength spur gear having excellent dedendum bending strength by subjecting a round bar consisting of a grain coarsening-resistant low N-Nb steel having a specific compsn. and having a required length to preliminary upsetting then to warm precision die forging and further to a grain refinement carburization treatment. CONSTITUTION:The round bar consisting of the case hardening steel for warm forging contg. 0.07-0.25% C, =1 kinds among 0.4-3% Ni, 0.4-1.5% Cr, 0.15-0.5% Mo, consisting of the balance Fe and unavoidable impurities, having the excellent resistance to grain coarsening and having a prescribed length is subjected to preliminary upsetting at >=20% total upsetting ratio after descaling. The bar is then heated to 100-200 deg.C and is immersed in a water soluble lubricating agent soln. to form the lubricating film thereon. Such bar is subjected to high-frequency heating to 650-900 deg.C then to precision die forging to the spur gear. The spur gear is subjected to sizing, etc. then to the carburization treatment, followed by cooling down to the Ar1 transformation temp., and hardening and tempering by reheating, by which the dedendum crystal grain size is fined to ASTM No.10 or above.