Showing papers on "Tempering published in 1996"

Nitrogen in Iron and Steel

Abstract: A short review of beneficial effects of nitrogen in steel is given including mechanical and corrosion properties, and the data of interatomic interactions and distribution of solute atoms in solid solutions are discussed with the aim of explanation of the physical nature of nitrogen steels. The concept is presented according to which aloying by nitrogen enhances the metallic component of interatomic bonds and provides more homogeneous distribution of substitutional solutes through short range ordering of nitrogen atoms and strong chemical interaction between nitrogen and alloying elements, which results in the high thermodynamical stability of nitrogen austenitic steels. The opposite tendency to clustering and concentration inhomogeneity of austenitic steels due to carbon is shown. Inheritance of the atomic distribution by martensite is discussed in terms of short range atomic order and data on crystal structure of precipitations during tempering of nitrogen martensite are presented as compared to carbon and carbon+nitrogen martensites.

Principles of the heat treatment of plain carbon and low alloy steels

Abstract: This invaluable resource book will help you immeasurably in determining which steel and heat treatment process will best meet your needs. It reviews current methods, both quantitative and correlative, in determining hardness or strength. You get a brief review of the concepts behind the common method of graphically depicting decomposition of austenite, the time-temperature transformation (TTT) diagram. It's followed by the ways of calculating hardenability from chemical composition and austenite grain size. Heat transfer during quenching is also discussed, including temperature-time curves for various shapes like bars and plates. Subsequent tempering is analyzed for you in great detail along with austentizing, annealing, normalizing, martempering, austempering and intercritical heat treatment. Thoroughly up-to-date, this book also covers computer modeling of heat treatment processes.

Process for producing high-strength seamless steel pipe having excellent sulfide stress cracking resistance

Abstract: A process for producing seamless steel pipes having performances at least equivalent to those of conventional seamless steel pipes produced by off-line heat treatment, which process permits pipe production and heat treatment to be conducted on one and the same production line The process is characterized by using a billet of a low-alloy steel containing 015-050 % C, 01-15 % Cr, 01-15 % Mo, 0005-050 % Al, 0005-050 % Ti and 0003-050 % Nb and also by comprising the following steps (1) to (5): (1) hot rolling the billet at a draft of 40 % or above in terms of cross-sectional compressibility, (2) finishing the hot rolling at 800-1,100 °C, (3) concurrently heating the rolled pipe immediately after the finishing under the temperature and time conditions satisfying the following relationship (a) in a concurrent heating unit: 23500 « (T+273) x (21+log t) « 26000(a), wherein T represents a temperature (°C) of 850 °C or above, and t represents a time (hr), (4) quenching the pipe immediately after being taken out of the concurrent heating unit, and (5) subjecting the quenched pipe to final tempering at a temperature of the Ac1 transformation point or below It is acceptable to conduct intermediate heat treatment (quenching or a combination of quenching with tempering) between the steps (4 and 5)

Microstructural basis for the effect of chromium on the strength and toughness of AF1410-based high performance steels

Abstract: The variation in strength and Charpy impact toughness as a function of tempering temperature in the range of 200 ‡C to 650 ‡C was investigated in AF 1410 and AF 1410 + 1 pct Cr steels produced in a laboratory-scale, and a commercially produced AerMet 100 steel. The tensile test results showed that AF 1410 + 1 pct Cr had lower strength compared to AF 1410, while AerMet 100 had the highest strength of the three steels examined. Transmission electron microscopy (TEM) studies demonstrated that the strength variations among the steels can be attributed to differences in the matrix/carbide coherency strain and the volume fraction of the strengthening M2C carbides. The toughness values of the three steels were comparable when tempered up to 424 ‡C. Tempering at and above 454 ‡C resulted in a relative enhancement of toughness in AF 1410 + 1 pct Cr steel compared to AF 1410. This toughening was attributed to the destabilization of cementite at lath and prior austenite boundaries and the formation of reverted austenite.

Kinetics of precipitation in power plant steels

Abstract: The ability of steels to resist creep deformation depends on the presence in the microstructure of carbide and intermetallic compounds which precipitate during tempering or during elevated temperature service. The precipitation occurs in a sequence which leads towards thermodynamic equilibrium. Kinetic theory has recently been developed which enables such sequences to be modelled using an adaptation of the classical Johnson-Mehl-Avrami equations. Our modification permits the treatment of more than one precipitation reaction occurring simultaneously, a feature which is essential for the reactions observed experimentally in a wide range of secondary hardening steels. In this paper, the model is applied to a series of power plant steels. It is possible to explain some interesting differences between the steels as a function of the chemical composition.

M2C precipitates in isothermal tempering of high Co-Ni secondary hardening steel

Abstract: The effects of isothermal tempering on the coarsening behavior of hexagonal M2C precipitates and the secondary hardening reaction in ultrahigh-strength AerMet 100 steel were investigated. The tempering temperatures were 468 °C, 482 °C, and 510 °C, and the tempering time spanned the range from 1 to 400 hours. Experimental studies of the coarsening behavior of the carbides were made by utilizing transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffractometry (XRD). The hardness at the secondary hardening peak was about HRc 55. The average length and diameter of M2C carbides were 4 to 8 nm and 1.5 to 2.5 nm, respectively, at all three tempering temperatures; hence, the aspect ratio was almost 3, an equilibrium value in this case. The size of the M2C carbides increased monotonically with time, but the growth kinetics did not exactly follow the classical coarsening behavior. The amount of precipitated austenite increased with tempering time and temperature. M2C precipitates were still relatively fine even after 200 hours of tempering. This feature seemed to be closely related to the high hardness maintained after prolonged tempering.

Influence of Matrix Structure on the Abrasion Wear Resistance and Toughness of a Hot Isostatic Pressed White Iron Matrix Composite

Abstract: The influence of the matrix structure on the mechanical properties of a hot isostatic pressed (hipped) white iron matrix composite containing 10 vol pct TiC is investigated. The matrix structure was systematically varied by heat treating at different austenitizing temperatures. Various subsequent treatments were also employed. It was found that an austenitizing treatment at higher temperatures increases the hardness, wear resistance, and impact toughness of the composite. Although after every different heat treatment procedure the matrix structure of the composite was predominantly martensitic, with very low contents of retained austenite, some other microstructural features affected the mechanical properties to a great extent. Abrasion resistance and hardness increased with the austenitizing temperature because of the higher carbon content in martensite in the structure of the composite. Optimum impact energy values were obtained with structures containing a low amount of M (M7C3+M23C6) carbides in combination with a decreased carbon content martensite. Structure austenitized at higher temperatures showed the best tempering response. A refrigerating treatment was proven beneficial after austenitizing the composite at the lower temperature. The greatest portion in the increased martensitic transformation in comparison to the unreinforced alloy, which was observed particularly after austenitizing the composite at higher temperatures,[1] was confirmed to be mechanically induced. The tempering cycle might have caused some additional chemically induced transformation. The newly examined iron-based composite was found to have higher wear resistance than the most abrasion-resistant ferroalloy material (white cast iron).

Characterization of plasma sprayed Fe-17Cr-38Mo-4C amorphous coatings crystallizing at extremely high temperature

Abstract: A Fe-17Cr-38Mo-4C alloy powder was plasma sprayed by three processes: an 80 kW low-pressure plasma spray (LPPS), a 250 kW high-energy plasma spray (HPS), and a 40 kW conventional plasma spray (APS) The as-sprayed coating obtained by the LPPS process is composed of only amorphous phase As-sprayed coatings obtained by the HPS and APS processes are a mixture of amorphous and crystalline phases The three as-sprayed coatings exhibit a high hardness of 1000 to 1100 DPN The amorphous phase in these coatings crystallizes at a high temperature of about 920 K A very fine structure composed of hard ϰ-phase and carbides is formed after crystallization The hardness of the coating obtained by LPPS reaches a maximum of 1450 DPN just after crystallization on tempering and retains a high hardness more than 1300 DPN after tempering at high temperatures of 1173 or 1273 K The corrosion potential of the amorphous coating is the highest among the three coatings and higher than that of a SUS316L stainless steel coating The anodic polarization measurements infer that the corrosion resistance of the amorphous coating is superior or comparable to SUS316L stainless steel coating in H2SO4 solution

Analysis of Tempering Stresses in Metal-Ceramic Disks:

Abstract: Previous studies showed that residual compressive stresses induced by thermal tempering retarded the growth of surface cracks in bilayered porcelain disks. The objectives of the present study were: (1) to determine whether thermal tempering by air blasting reduces the length of cracks induced by microhardness indentation in metal-ceramic disks, and (2) to use visco-elastic finite element analyses to calculate transient and residual stresses in metal-ceramic disks. Ni-Cr-Be disks, 16 mm in diameter and 0.3 mm in thickness, were prepared with a 0.5-mm-thick layer of opaque porcelain and a 1.5-mm-thick layer of body porcelain. Metal-porcelain combinations were selected to provide a range of thermal contraction mismatch values. The disks were fired to the maturing temperature of body porcelain and then were subjected to three cooling procedures: (1) slow cooling in a furnace (SC), (2) cooling in air (FC), and (3) air tempering (T) by blasting the surface of the body porcelain with compressed air. The lengths of cracks induced in the surface of the body porcelain by a microhardness indenter were measured immediately after indentation at 20 points along diametral lines. The results of Tukey's multiple-contrast analyses indicated that the mean crack lengths of air-tempered specimens were significantly smaller (p < or = 0.05) than the crack lengths of the fast-cooled and slow-cooled groups. Except for one case, there were no statistically significant differences in the mean crack lengths between FC and SC specimens independent of thermal contraction mismatch. Residual tensile stresses were calculated for SC and FC specimens for all thermal contraction mismatch cases, with the largest values being associated with combinations containing the body porcelain with the smaller contraction coefficient. Calculations by use of the model confirmed that tempering induces large residual compressive stresses in the surface of body porcelain for all of the thermal contraction mismatch cases included in this study.

Numerical Simulation of Soda-Lime Silicate Glass Tempering

Abstract: The paper deals with the computation of residual and transient stresses in a tempered glass plate. The modelling takes into account the viscoelastic behavior and the structural relaxation of glass. The evolution of stresses with time during the rapid cooling is computed. Simulation results are compared with experimental ones from the literature available. Levels of transient tensile stress in the surface are analysed.

Laser surface treatment of tool steels

Abstract: Laser surface treatment (LST) is a promising technique to improve the wear and corrosion resistance of materials. In die case of tool steels, laser surface treatment is carried out preferably in the liquid state to allow for complete dissolution of alloy carbides. In this paper, the main requirements for materials used in different types of tools and the advantages of using surface engineered materials for these applications are presented. The application of laser melting to the treatment of tool steels is exemplified for AISI 420 and 440C Cr steels and sintered AISI T15 HSS. Usually, the laser melted layers contain martensite, retained austenite and carbides. In steels containing large proportions of ferrite-forming alloying elements δ-ferrite may also be observed. The laser treatment of sintered steel leads to the elimination of residual porosity. The proportion of retained austenite in laser surface melted steels is much higher than in conventionally treated steels. However, the hardness of the steel is high because the austenite is strengthened by solid solution, dislocations and the small grain size. The high volume fraction of retained austenite usually prohibits the application of tool steels in the laser treated condition. Austenite may be eliminated by double or triple tempering treatments at temperatures in the range 550 to 650 °C. During tempering, carbides precipitate within austenite and martensite, and austenite transforms to martensite. Strong secondary hardening is often observed and the temperature of the secondary hardening peak of laser surface melted (LSM) steels is higher than after conventional heat treatment.

Effect of Holding Time in the (α + γ) Temperature Range on Toughness of Specially Austempered Ductile Iron

Abstract: Austempered ductile iron (ADI) finds wide application in the industry because of its high strength and toughness. The QB' process has been developed to produce a fine microstructure with high fracture toughness in ADI. This process involves reaustenitizing a prequenched ductile iron in the (α + γ) temperature range followed by an isothermal treatment in the bainitic transformation tem-perature range. In the present work, the effect of holding time in the (α + γ) temperature range on the structure and un-notched toughness of ADI has been studied. Prior to the austempering treatment, the as-cast ductile iron was heat treated to obtain martensitic, ferritic, and pearlitic matrix structures. In the case of prequenched material (martensitic matrix), the un-notched impact toughness increased as a function of holding time in the (α + γ) temperature range. The reaustenitization heat treatment also resulted in the precipitation of fine carbide particles, identified as (Fe,Cr,Mn)3C. It was shown that the increase in holding time in the (α + γ) temperature range leads to a reduction in the number of carbide particles. In the case of a ferritic prior structure, a long duration hold in the (α + γ) temperature range resulted in the coarsening of the structure with a marginal increase in the tough-ness. In the case of a pearlitic prior structure, the toughness increased with holding time. This was attributed to the decomposition of the relatively stable carbide around the eutectic cell boundary with longer holding times.

Heat treatment response of sintered M3/2 high speed steel composites containing additions of manganese sulphide, niobium carbide, and titanium carbide

Abstract: Metal matrix composites based on a sintered M3/2 high speed steel (HSS) and containing either single additions of TiC, NbC, or MnS particles or combined additions of MnS + TiC or MnS + NbC were sintered to full density and subjected to a conventional hardening heat treatment cycle of austenitisation, quenching, and double tempering. Relatively poor hardnesses and strengths were obtained in any composites that contained MnS particles, principally because of the weakening effects of MnS particles in the structure but also as a result of decarburisation of the steel matrix when oxygen introduced by the MnS particles reacted with carbon. Composites that contained TiC were changed in structure so that matrix M6C carbides were replaced by the less soluble MC carbide. They consequently showed slightly reduced hardening response compared to the baseline M3/2 HSS after heat treatment. Ball milling was necessary in powder mixtures that contained NbC to break up particle agglomerates. The resultant fine gra...

Combined quenching and tempering induced phosphorus segregation to grain boundaries in 2·25Cr–1 Mo steel

Abstract: Combined quenching and tempering induced phosphorus segregation to prior austenite grain boundaries in α 0·077 wt-%P doped 2·25Cr–1Mo steel was examined using field emission gun scanning transmission electron microscopy. The results indicate that combined equilibrium and non-equilibrium phosphorus segregation may play an important part in temper embrittlement of the steel caused by direct tempering after quenching. Non-equilibrium segregation requires the formation of sufficient quantities of vacancy–impurity complexes and their migration to grain boundaries is of great importance in the segregation. For this reason, the mechanism for migration of the complexes is discussed in detail.MST/3419

Process for austempering ductile iron

Abstract: A process for austempering ductile iron includes austenitizing a ductile iron casting of low alloy content followed by quenching the workpiece for a controlled period of time in a quench medium such as water, an aqueous polymer solution or a medium speed quench oil. The workpiece is then austempered in an air tempering furnace, resulting in a ausferrite microstructure essentially free of pearlite and martensite, and with mechanical properties meeting ASTM designation A897-90 "Standard Specification for Austempered Ductile Iron Castings." The process eliminates the need for a molten salt bath for quenching and tempering.

Mössbauer spectroscopy study of the aging and tempering of high nitrogen quenched Fe-N alloys: Kinetics of formation of Fe16N2 nitride by interstitial ordering in martensite

Abstract: The distribution of nitrogen atoms in austenite and during the different stages of aging and tempering of martensite is studied by Mossbauer spectroscopy, X-ray diffraction, and transmission electron microscopy (TEM). Transmission Mossbauer spectroscopy (TMS) and conversion electron Mossbauer spectroscopy (CEMS) are used for studying the austenite phase where the distribution of nitrogen atoms is found to depend on the nitriding method, gas nitriding in our case, or ion implantation. Conversion electron Mossbauer spectroscopy, which concerns a depth predominantly less than 200 nm, reveals a nitrogen atom distribution different from that found in the bulk by TMS. The identification and kinetics of the stages of aging and tempering of martensite are followed by TMS measurements, and the phase characterization is confirmed by X-ray diffraction and TEM. The major stages are the early ordering of nitrogen atoms, which leads to small coherent precipitates of α-Fe16N2; the passage by thickening to semicoherent precipitates of α-Fe16N2; the dissolution of α-Fe16N2 with the concomitant formation of /gg’-Fe4N; and the decomposition of retained austenite by tempering. The three first stages correspond to activation energies of 95, 126, and 94 kJ/mole, respectively, consistent with the nitrogen diffusion for the first and third stages and the dislocation pipe diffusion of iron for the second.

High hardness martensitic stainless steel with good pitting corrosion resistance

Abstract: An inexpensive martensitic stainless steel which has good hot workability, can be subjected to cold forming with no need of complicated annealing treatment, and exhibits both good pitting corrosion resistance and high hardness after quenching and tempering. The high hardness martensitic stainless steel consists essentially, by weight, of more than 0.15 % but not more than 0.40 % C, not more than 2.0 % Si, not more than 2.0 % Mn, not less than 11.0 % but less than 15.0 % Cr, 1.0 to 3.0 % Mo or Mo and W in terms of Mo + 1/2 W, 0.02 to 0.15 % N, 0.1 to 1.5 % Ni, 0.1 to 2.0 % Cu, and the balance iron, Ni and Cu being contained in ranges meeting a relationship of Ni/Cu > 0.2, the Cr equivalent being not more than 10, a value of the pitting corrosion resistance index being not less than 20.

High strength steel material excellent in sulfide stress cracking resistance and its production

Abstract: PROBLEM TO BE SOLVED: To provide a steel material (particularly a seamless steel tube) com posed of inexpensive low alloy steel and having high strength and excellent sulfide stress cracking resistance and its production. SOLUTION: The high strength steel material excellent in sulfide stress cracking resistance is composed of a low alloy steel of 0.20-0.60% C (carbon) content and has a metallic structure consisting of 1-10% volume fraction of retained austenite and the balance essentially martensite. Particularly, proof stress in this steel material is ≥77.3kgf/mm 2 , and further, the cracking critical stress (σ th) in the NACE TM 0177 bath is regulated to a value not lower than actual yield stress. As to the method of manufacturing this steel material, a low alloy steel of 0.20-0.60% C (carbon) content is hot-worked, hardened, and then tempered at a temp. exceeding the Ac 1 transformation point. In this method, it is preferable that hardening is carried out by means of direct hardening from hot working and tempering is performed at a temp. in the region between a temp. higher than the Ac 1 transformation point and (Ac 1 transformation point + 30°C). COPYRIGHT: (C)1997,JPO

Carbon or nitrogen alloyed quenched and tempered stainless steels : a comparative study

Abstract: Some conventional stainless quenched and tempered steel grades were modified by substituting nitrogen for carbon and by variing the contents of chromium, molybdenum and nickel. Results of a comparative study of carbon and nitrogen steels are presented in a wide range of tempering temperatures. In nickelmartensitic steels nickel can be partially substituted by nitrogen without harming the properties. Due to their finer microstructure nitrogen steels with 15-17 %Cr, 2 %Ni and 0.2 %N, at the same strength level, offer higher toughness and better corrosion resistance than the respective conventional steel X20 CrNi 17 2.

Non-tempering type hard butter

Abstract: PROBLEM TO BE SOLVED: To obtain the subject butter not requiring a tempering process although the butter is a non-lauric acid and a non-trans fatty acid, excellent in heat resistance, snap properties and bloom resistance, having a specific solid fat number, containing prescribed different trilglycerides in a specified ratio. SOLUTION: This hard butter has >=50% solid fat number at 20 deg.C and >=20% at 30 deg.C and the ratio of St/P of >=1 and comprises (A) 30-60% of an SOS type triglyceride (e.g. the one in which S in the compound contains St and P in the ratio of St/P of =2) when a 14-24C saturated fatty acid, stearic acid, palmitic acid and oleic acid are shown by S, St, P and O, respectively.

Precipitation Behaviour and Stability of Nitrides in High Nitrogen Martensitic 9% and 12% Chromium Steels

Abstract: Precipitation behaviour and stability of nitrides has been investigated in two high nitrogen, high vanadium containing martensitic 9-12% chromium steels under different heat treatment conditions. Microstructural evolution during the heat treatments was studied by hardness measurements, optical microscopy, transmission electron microscopy and energy dispersive X-ray analysis. Nitrides with f.c.c. structure were found to precipitate very uniformly and densely during aging in the austenite (ausaging) as well as during aging in the ferrite (tempering) at temperatures between 823 and 973 K. Microstructural evolution during tempering was influenced by pre-precipitation of the nitrides in the austenite prior to the martensitic transformation. It is shown that the hardness of martensite and tempered martensite depend strongly on the size and distribution of nitrides. Niobium is dissolved in primary vanadium nitrides. Dissolution and reprecipitation of these nitrides in the austenite was found to be influenced by the presence of niobium. Ausaging treatment of a niobium containing alloy at 898 K has a more significant effect on the martensite hardness than a niobium free alloy. The stability of dense precipitation states produced in the austenite prior to the martensitic transformation is discussed in terms of the development of non uniform precipitation states during tempering of the martensite. The uniformity of the precipitation states is stabilized by a pre-overaging treatment in the austenite. It is shown for a martensitic 12% chromium alloy, that a pre-ausaging treatment retards the formation of the rapid coarsening hexagonal chromium nitride which dissolves a high amont of vanadium during tempering at 973 K. As a result the tempering resistance becomes improved by maintaining an increased density of face centered cubic nitrides precipitated in the austenite.

High toughness high-speed steel member and manufacturing method

Abstract: Disclosed is a high-speed steel member and manufacturing method thereof. The member has Nb content of 0(incl.) to 2.0 (excl.) % in the hard state after hardening and tempering and in its micro-structure, contains either or both of M 6 C and M 2 C type carbides representing a rate of 0 to 2% to the total area, and the remainder substantially consisting of MC type carbide. The difference of crystallization temperatures is 30° C. or more between MC type carbide and M 6 C or M 2 C type eutectic carbide. The high-speed steel member exhibits a high toughness and a small anisotropy of the mechanical property namely, a hardness of HRC 60 or more and a Charpy impact value ratio between the longitudinal direction and the direction perpendicular thereto in a forged material is 0.7 or more and are quite useful for plastic working.

The effects of microstructure, strength level, and crack propagation mode on stress corrosion cracking behavior of 4135 steel

Abstract: The stress corrosion cracking (SCC) susceptibility of 4135 steel in a simulated sea water solution has been analyzed in an attempt to understand the effect that microstructural changes associated with the corresponding changes in strength level have on both intergranular (IG) and transgranular (TG) crack propagation modes. After a selection of heat treatments, the following different microstructural variables were studied: the effect of grain size on IG fracture processes; the influence of the grade of tempering on the SCC resistance and crack propagation mode; and the effect of type and content of bainite and the effect of ferrite in mixed microstructures. A global analysis shows that the typical SCC resistance-strength level inverse relationship can only be applied when the microstructure re-mains invariable. An important microstructural control of SCC behavior was found for TG processes at moderate and low strength levels. The data analysis showed the following: a beneficial effect of increasing the grain size when crack propagates at grain boundaries without precipitates; the existence of a critical tempering temperature so that a sudden IG-TG change happens without any apparent relation to microstructural changes; the beneficial effect of bainite presence as a substitute for mar-tensite and high SCC resistance of structures containing over 50 pct ferrite, associated with their low strength levels.

Laser cladding of iron-base alloy on Al-Si alloy and its relation to cracking at the interface

Abstract: The present study established the basic operating range and diagram for cladding, by means of a laser, a cast Al-Si alloy substrate with an iron-base material. Considering that the main difficulty was interface cracking during this processing, the factors affecting the interface cracking ratio (ICR) were investigated from two aspects: the laser processing parameters (e.g., laser power, traverse speed, powder-feed rate, preheating temperature of the substrate, tempering temperature) and the material factor, including the composition of clad. The substrate temperature and the tempering temperature were found to be important for controlling ICR, and the content of Al and Ni in the clads also had significant influence on ICR. The intermetallic compounds formed in the interface region were analyzed to understand the effect of Ni content on ICR. Clads of thickness from 1.2 to 1.5 mm that were crack free and had good fusion were achieved by controlling the substrate temperature or adjusting the Al content in the clads.

Effect of postweld treatment on the fatigue crack growth rate of electron-beam-welded AISI 4130 steel

Abstract: This article studies the effect ofin-chamber electron beam and ex-chamber furnace postweld treatments on the fatigue crack growth rate of electron-beam-welded AISI 4130 steel. Mechanical properties of the weldment are evaluated by tensile testing, while the fatigue properties are investigated by a fatigue crack propagation method. Microstructural examination shows that both postweld treatments temper the weldment by the appropriate control of beam pattern width, input beam energy, and furnace temperature. In addition, the ductility, strength, and microhardness of the weldment also reflect this tempering effect. The fatigue crack growth rate is decreased after both postweld treatments. This is mainly caused by the existence of a toughened microstructure and relief of the residual stress due to the fact that (1) the residual stress becomes more compressive as more beam energy is delivered into the samples and (2) postweld furnace tempering effectively releases the tensile stress into a compressive stress state.