Effect of lead on the properties of structural steel

Conclusions The effect of lead on the fatigue strength of structural steels and their susceptibility to embrittlement during heating is due to the difference in the coefficient of thermal expansion of lead particles and iron with heating of lead-containing steels and to the mosaic stresses resulting from this, which induce fracture and prefracture, and also the influence of liquid lead as a surface-active substance with regard to the steel. These characteristics of the behavior of lead particles in steel in the cutting zone at high strain rates are accompanied by an increase of temperature and promote better machinability of the steel in comparison with the steel without lead. On the basis of the results we do not recommend lead-containing steel for parts subject to fatigue and having high strength _b<1200–1400MPa) or for parts heated to 200–500° in the course of operation.Scientific-Research Institute of Metallurgy, Chelyabinsk. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 6–8, November, 1980.     

Hot Ductility and Deformation Behavior of C-Mn/Nb-Microalloyed Steel Related to Cracking During Continuous Casting

Hot ductility studies have been performed on C-Mn and C-Mn-Nb steels with an approach to simulate the effect of cooling conditions experienced by steel in secondary cooling zone during continuous casting. Thermal oscillations prior to tensile straining deteriorate hot ductility of steel by deepening and widening the hot ductility trough. C-Mn steels are found to exhibit ductility troughs in three distinct zones whereas C-Mn-Nb steel shows drop in ductility only at low temperature in the vicinity of ferrite transformation temperatures. Start of ferrite transformation in steels causes yield ratio to increase while work hardening rates and strength coefficient decrease with decrease in test temperature in presence of thermal oscillation prior to tensile testing. Inhibition of recrystallization due to build-up of AlN particles along with the presence of MnS particles in structure and low work hardening rates causes embrittlement of steel in austenitic range. Alloying elements enhancing work hardening rates in austenitic range can be promoted to improve hot ductility. The presence of low melting phase saturated with impurities along the austenitic grain boundaries causes intergranular fracture at high temperature in C-Mn steels.     

A Comparison of the High-Temperature Oxidation of 17Cr-2Ni and 18Cr-8Ni Austenitic Stainless Steels at 973 K

The oxidation behavior in air at 973 K of theaustenitic stainless steels 18Cr8Ni and17Cr-2.5Ni-10.5Mn-2Cu-0.17N (low-nickel content), wasstudied in a thermobalance. The steels were heated fromroom temperature up to 973K at 10 K min^-1, oxidizedfor 80 hr and then cooled to room temperature at 80 Kmin^-1. The two steels had the same weightgains, 0.18 mg cm^-2, which is equivalent tooxidation layers about 1.15 m theoretical thickness. In both cases, thegeneral shapes of the WS^-1 (mgcm^-2) curves vs. t (hours) were parabolic,but X-ray diffraction of the oxidized surfaces, surfaceand crosssection optical microscopy and SEM observations and EDSmicroanalysis show important differences betweenthem.     

Structural materials for atomic reactors with liquid metal heat-transfer agents in the form of lead or lead—Bismuth alloy

Natural safety nuclear reactors operate at a working temperature of the liquid-metal lead heat-transfer agent equal to 550°C, which intensifies the metal corrosion and is fraught with the danger of thermal embrittlement. It is shown that long-term operation of the equipment requires inhibition of the heat-transfer agent by oxygen and the use of silicon steels. However, alloying with silicon increases the susceptibility of the steel to thermal and radiative embrittlement. This makes it necessary to create new steels with a stable structure. The suggested composition of austenitic steel 04Kh15N11S3MT is designed for shell and internal structures, and steel 10Kh9NSMF is designed for the pipe system of the steam generator. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 20–24, September, 1999.     

Steels with controlled hardenability for induction hardening

Conclusions Steels of the CH and LH type developed in the Soviet Union permit the use of a new method of induction hardening — bulk-surface hardening — and efficient utilization of the high-strength conditions (_b = 230–250 kgf/mm²). These steels make it possible to improve the structural strength, operating characteristics, service life, and reliability of critical heavily loaded machine parts.At the same time, CH steels make it possible to reduce by a factor of 2–3 the quantity of alloying elements, reduce the electrical energy for heat treatment, and completely exclude the cost of quenching oil for heat treatment in automatic equipment with high labor productivity, while retaining good working conditions. All this leads to substantial savings in production and operation. For example, when transmission gears (cylindrical and conical) are manufactured from LH steels the annual savings amount to more than 700,000 rubles at two automobile plants. Machine parts of CH steels — half axles and bearings in railway cars —have saved respectively six and four million rubles annually. The introduction of controlled-hardenability steels for induction hardening is a necessary condition for technological progress in machine construction and metallurgy.Moscow Evening Metallurgical Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 18–23, July, 1980.     

微Ti钢焊接热循环过程中的第二相粒子

采用“Ｓｐｅｅｄ”法电解萃取复型技术,用透射电子显微镜,研究了分别含有Ｔｉ－Ｎ和Ｔｉ－Ｎｂ－Ｎ的两种微合金钢焊接热模拟后,第二相粒子的溶解析出行为及对焊接热循环的响应。系统测定了不同热模拟工艺下第二相粒子的尺寸、数目及分布特征;分析了热模拟工艺参数（峰值温度Ｔｐ,保温时间ｔｐ,冷却时间ｔｍａｘ／８）对析出颗粒尺寸分布特征的影响,探讨了钢中第二相颗粒的长大、溶解行为对高温奥氏体晶粒度的影响以及微量Ｎｂ与Ｔｉ复合添加的作用。结果表明,微量Ｔｉ－Ｎｂ复合合金化对高温奥氏体晶粒的细化经仅用微Ｔｉ合金化的钢更强烈,钢中微细第二相粒子对细化高温奥氏体晶粒具有主要作用。     

An evaluation procedure for hot‐spot tensions in welded plates

Summary

This paper describes an investigation of the correlation between HAZ microstructures amd mechanical properties in the post‐weld heat treatment (PWHT) of two types of thermomechanical control process steels (TMCP steels), especially the relationship between the stress relaxation behaviour and high‐temperature deformability. Simulated weld heat treatment was performed with a welding thermal cycle simulator at a maximum temperature of 1623 K. PWHT was performed at a heating rate of 55.6 K/ksec. The mechanical properties in the PWHT process were evaluated by rising‐temperature constant‐strain rate tests and rising‐temperature constant‐load tests. The effect of PWHT in reducing ductility is discussed from the perspective of the precipitation behaviour of intergranular and transgranular carbides and the associated deformability of the matrix in each HAZ structure. The results obtained may be summarised as follows:

1. The results obtained during measurement of the stress relaxation behaviour in the rising‐temperature constant‐strain rate tests suggest that the bainite structures of both steels clearly show more stagnation or delay in their stress relaxation behaviour than the other HAZ structures at a PWHT temperature above 600 K. This implies that the matrix is resistant to softening. The non‐AcC type steel also exhibits more stagnation in the higher temperature range under the effect of alloy carbide precipitation at the grain boundaries than the AcC type steel.

2. The results obtained in the rising‐temperature constant‐load tests run to determine the high‐temperature strength and inherent deformability of the HAZ structure suggest that the bainite structures of both steels tend to lose more ductility than the other HAZ structures, having a reduction of area of 35% at a fracture temperature of 850–900 K. The non‐AcC type steel also exhibits a greater loss of ductility in all HAZ structures than the AcC type steel.

3. The results of the TEM observations made to determine the causes of this ductility loss suggest that a difference in the carbide precipitation behaviour near the grain boundaries in each HAZ structure in the PWHT process affects the plastic deformability of the matrix, and that the trend of reducing plasticity differs in each HAZ structure. These trends are more pronounced in the non‐AcC type steel containing alloying elements with a strong carbide‐producing tendency, such as e.g. Nb, Ti, etc.

4. All HAZ structures of the AcC type steel show a trend of reducing ductility at a fracture temperature of 850–900 K. This feature is not found in conventional carbon steels with an identical composition and may well be due to the fact that this temperature range corresponds to the ductile‐brittle transition range. It is necessary to resort to a method of fabrication able to reduce the hardened structures as far as possible during welding, i.e. to ductility reducing counter‐measures in the PWHT process, such as e.g. welding heat input control, preheating, etc.

5. To evaluate the ductility and brittleness of steels, it is important to gain a good understanding of their plastic deformability, and the paper proposes a method for evaluation of the ductility of the TMCP steels on the basis of the relationship between the amount of displacement produced in the rising‐temperature constant‐strain rate tests and the plastic deformability of each HAZ structure in the PWHT process as obtained in the rising‐temperature constant‐load tests. This method enables the risk of cracking and degree of embrittlement to be identified and proves effective in practical applications.

     

Thermal cycling treatment of low-carbon steels with hardening from the intercritical temperature range

Conclusions Thermal cycling treatment of 08Kh2G2F and 30KhGSN2A steels with intermediate hardening from intercritical range temperatures (Ac₁+20–40°C) provides an ultrafine austenitic grain size of 2.5–3.5 m. The obtaining of a finer and more uniform structure of these steels in comparison with thermal cycling treatment consisting of three hardenings from the area of the stable state of austenite provides a 1.2–1.4 times higher impact strength at low temperatures.Institute of the Physics of Solids, Academy of Sciences of the USSR. I. P. Bardin Central Scientific-Research Institute for Ferrous Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 47–49, August, 1988.     

Effect of carbon,chromium, and nickel on the α ⇄ γ transformation and properties of Cr - Ni - Mo - V steels

The aim of the present investigation is to determine some regular features of alloying Cr - Ni - Mo - V steels for critical parts with allowance for the structure, hardenability, level of properties, and semibrittleness temperature. For this purpose the concentration of carbon in Cr - Ni - Mo - V steels was varied from 0.03 to 0.47%, chromium from 0 to 4%, and nickel from 0 to 5% at a constant concentration of the other elements (0.5% Mo, 0.6% Mn, 0.25% Si, -0. 1% V, 0.015% S, 0.012% P), and the cooling rate from the austenitization temperature was varied from 25 to 1000°C/h.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 7 – 9, March, 1996.     

IFKhAN-54, a New Inhibitor of Acid Corrosion of Steels

Corrosion and electrochemical behavior of low- and high-carbon steels (steel 20 and 7) in aqueous solutions of sulfuric acid and that of Armco iron in aqueous solutions of hydrochloric acid at 80 and 20°C were studied in the presence of a new effective inhibitor, IFKhAN-54, which is a technical product of condensation of aldehydes with nitrogen-containing oligomers. IFKhAN-54 was found to retard anodic iron dissolution, functioning mainly as a blocking inhibitor in hydrochloric acid (for the acid composition studied). In sulfuric acid, its effectiveness is enhanced in the presence of chloride ions. New inhibitive formulations based on IFKhAN-54 suppress acid corrosion of steels very effectively, including corrosion in chloride-free sulfuric acid.     

Effect of niobium on recrystallization of ultralowcarbon cold-rolled automobile sheet steel

Conclusions  

Über das Verhalten einiger CrNiMo-Stähle beim Einsatz im chemischen Betrieb

The behaviour of some CrNiMo steels in use at chemical plants A report is given about the behaviour of some highly alloyed CrNiMo steels in use in inorganic-chemical plants. The observations are supported and supplemented by results of potentiostatic tests. In the presence of mixed acids, the corrosion resistance of the steels greatly depends, e.g., on the SO: Cl^? ion ratio. In the presence of Cl^? ions and at higher temperatures, exceeding about 70°C, the resistance is largely influenced by the specifically orientated analytical and structural pattern of the steels. Attention is drawn to the detrimental influence, especially in cast metals and welds, of the concomitant element, silicon, which — if encountered in increasing quantitities — favours the segregation of several corrosion-promoting phases. Examinations of case of damage in practical operation, supported by potentiostatic tests with CrNiMo steels, with and without copper contents, have shown that the presence of copper is apt to reduce the corrosion resistance in media containing hydrochloric acid or chlorine ions. On the other hand, a copper content may be beneficial in sulphate solutions free from chlorine ions.     

Structure and properties of Fe−Cr−Mn steels after quenching with preheating in the intercritical temperature interval

Conclusions The quenching of high-alloy chromium-manganese steels, which includes preheating in the intercritical (+) temperature interval and subsequent short-term austenitizing, the latter eliminating homogenization of the -solid solution, increases the dispersity of the martensite and stabilizes the austenite.In this case, the strength and plastic properties of the steels are improved as compared with normal quenching.Mariupol' Metallurgical Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 45–47, June, 1990.     

Optically Scanning the Morphology of Protective Layers and Forecasting the Corrosion Resistance of Thermally Oxidized Steel

The results of investigating the morphology and protective properties of surface layers obtained on chromium steel 1810 by oxidizing in air at a temperature of 140 to 950°C are considered. After a special digital treatment, the scanned optical images of a small surface area probed allow one to introduce and determine those parameters of the morphological nonuniformity of the thermal oxide layer which affect its protective ability. Corrosion tests of oxidized specimens confirmed the applicability of the scanner morphological control to predicting the protective properties of thermal coatings against pit corrosion in chloride-containing electrolyte solutions.     

Process of vacuum hardening of cutting and sharpening tools of high-speed steels in belt furnaces

The technical possibilities of vacuum elevator and bell furnaces commonly used for brazing and annealing precision parts in instrument-making and electronics can be widened. Small thin-blade tools of powder steels R6M5-P, 10R6M5-MP and silver steels R6M5, R6M5K5 with a minimum tolerance for sizing after hardening at a low cooling rate have high operational properties. The present paper is devoted to the process of heat treatment of special tools of the listed steels used to cut and shape ribbons, rods, and foils of alloys 36NKhTYu, 29NK, BrB2 in vacuum bcil furnaces under conditions of batch and small-batch production in electrical-engineering enterprises.     

High strength austenitic steels

Conclusions Transitional steels have an unusual combination of mechanical properties. They may have a low yield stress (20–40 kg/sq. mm=28, 400–56, 900 psi) and a high tensile strength (100–200 kg/sq mm=142, 000–284, 000 psi). The mechanical properties of these steels depend mainly on the extent to which austenite decomposes into martensite in deformation, and on the fracture strength [resistance to failure under the action of normal stresses], of the martensite formed. When martensite produced by quenching is present in the initial steel, its rupture resistance also determines the mechanical properties of the steel.In tensile tests on transitional nickel steels containing 0. 26% carbon, initially purely austenitic, there was a considerable plastic deformation (elongation up to 60%); fracture occurs without necking, and the elongation exceeds the reduction of area. In spite of considerable preliminary plastic deformation, the failure is of the brittle type.3. It has been confirmed that in steels containing unstable austenite, a combination of strength and ductility can be achieved, unattainable in steels of other structural categories.     

Thermophysical property measurements on low alloy high strength carbon steels

The solidus/liquidus temperatures, heat of fusion, specific heat capacity, and thermal expansion for AISI 43 10 and 4320 steels were measured in this study. Both steels have similar heat of fusion values and solidification temperature ranges but differ in the absolute solidus/liquidus temperatures. The specific heat capacity vs. temperature curves for both steels show similar trends with difference in the peak value at austenite phase transformation temperatures.

Both steels demonstrate similar thermal expansion trends and absolute values. The thermal expansion vs. temperature curve shows considerable difference between the heating part and the subsequent cooling part which reflects the different solid state phase changes experienced during the heating and cooling of these two heat-treatable steels. This phenomenon should be taken into account during the modeling of welding, casting and other processing of these steels. The relative density as a function of temperature for these steels can be estimated based on the thermal expansion values.     

Effect of nitrogen and stacking-fault energy on twinning in [ \bar 1 11] single crystals of austenitic stainless steels

The dependence of critical shear stresses for twinning τ _cr ^tw on the stacking-fault energy γ₀, the nitrogen concentration C _N (wt %), and the test temperature has been studied for [ $ \bar 1 $ 11] single crystals of austenitic stainless steels upon tensile deformation. It is shown that τ _cr ^tw ～ γ₀/b ₁ in nitrogen-free steels, while it exhibits a nonmonotonic dependence on the nitrogen concentration C _N in nitrogen-alloyed steels. An increase in τ _cr ^tw at C _N = 0.3 wt % and its decrease at C _N ≥ 0.5–0.7 wt % are determined by the competition of two contributions to τ _cr ^tw , namely, a decrease in γ₀ and a solid-solution hardening with increasing nitrogen concentration.