This coincides with the observations in the dilatometer experiments. by 2027 from US$ 277.9 Bn. It improves machinability and resistance to corrosion and it intensifies the effects of other alloying elements. It can be seen that except in the oxidizing medium HNO3, the role of molybdenum is positive. After this double or even triple tempering in the range 510 to 610 deg C is carried out. pointed out that VN precipitates can lead to a significant decrease in the grain size in a high nitrogen content vanadium micro-alloyed steel [23]. The parameters about the degree of deformation during hot rolling. In austenitic stainless steels between two and seven percent are added, in duplex stainless steels, between three and five percent. Mo containing as-rolled DP steels does not require the post rolling inter critical heat treatments. The chemical composition of precipitates changed from Nb(C, N) to (Nb, Mo)(C, N) because of the addition of Mo. However, the heat-affected zone (HAZ) of the steel plate must be subjected to a higher temperature thermal cycle and longer residence at high temperature during high heat input welding [10]. For HSLA steel grades containing Mo, Mn (manganese) and Nb (niobium), rolling in roughing mill should begin around 1200 deg C. This results into the finest austenite grain size going into the finishing train of rolling mill. It can make the internal structure of steel dense, refine grain power, reduce aging sensitivity and cold brittleness, as well as improve welding performance. Moreover, it still remains unclear the precise role of Mo in the precipitation behavior of pinning particles. Figure 1 presents the schematic diagram of the machining locations of Charpy V-notch impact samples. Size distribution of the precipitates in the four kinds of steel. The microstructure was refined and the toughness was enhanced after the addition of 0.07% Mo in steel. doi: 10.1016/j.jmst.2017.11.020. Study of the mechanical properties, including creep, and of the welding and fabrication characteristics of steel containing 0.5 per cent chromium and 0.5 per cent molybdenum, designed for elevated-temperature service, has shown this grade to be essentially similar to 0.5 per cent molybdenum steel without chromium. Respectively, the influence of molybdenum on the corrosion resistance of chromium-nickel austenitic stainless steel in nitric acid, sulfuric acid, acetic acid, phosphoric acid, urea, and other media. Shao Y., Liu C., Yan Z., Li H., Liu Y. Therefore, in the production, equipment manufacturing, and application of molybdenum-containing austenitic stainless steel, attention should be paid to prevent the formation of intermetallic phases in the steel. The experimental evidence on the effects of Mo on precipitates and toughness of steel should be explored further. The refinement of grains by the pinning effect of fine precipitates has been acknowledged as an effective way to improve the toughness and strength of steel [13,14,15]. The size distribution of ferrite grains in the four kinds of rolled steel sheet is shown in Figure 5. heat-affected zone; high-strength low-alloy steel; impact toughness; microstructural evolution; molybdenum; precipitates. The temperature of the ingots taken out of the heating furnace was 1180 C, the starting rolling temperature was 1160 C, and the finishing rolling temperature was 830 C. Case hardened steels Mo content ranges from 0.15 % to 0.5 %. Compared with the stretch zone in Figure 7a, the area of the stretch zone in Figure 7b was reduced. The addition of Mo can suppress the Widmansttten ferrite (WF) formation and promote the transformation of acicular ferrite (AF), leading to the fine transformed products in the heat-affected zone (HAZ). The average size of austenite grain in N1, N2, N3, and N4 steel. Adjusting the carbon content is the simplest way to change the mechanical properties of steel. Effect of molybdenum in stainless steel Doctor Mathews, referring to the effect of molybdenum, states that a tendency is indicated to keep the carbon in the combined or martensitic form, and when the carbon is in that condition, molybdenum retards its passage to the sorbitic or troostitic state. EAF use of MoO3 needs some care to minimize losses due to volatilization and other reasons. The studies were conducted under nonconformal contact conditions on En-31 steel and conformal contact conditions on piston ring and liner materials . Figure 8 shows the micromorphological characteristics of the fracture in N1, N2, N3, and N4 steel. The test results of impact toughness in Table 3 were in good agreement with the analysis results of fracture morphology in Figure 7 and Figure 8. 2. ); moc.621@75955235631 (X.M. It has . The size distribution of precipitates in the four kinds of steel is shown in Figure 12. With the increase of Mo content, the volume fraction of precipitates tended to increase. government site. Prikryl M., Kroupa A., Weatherly G.C., Subramanian S.V. Mo when added to austenitic and duplex stainless steels improves resistance to pitting corrosion especially by chlorides and sulphur chemicals and also their weldability. As a large atom, Mo increases the elevated temperature strength of stainless steels through solid solution hardening. 1.Molybdenum can inhibit the formation of carbonation and promote the formation of pearlite. The precipitates turned out to be a square shape, when Nb(C, N) or (Nb, Mo)(C, N) was present in the core, and Ti (C, N) was distributed at the Nb(C, N) or (Nb, Mo)(C, N) periphery (Figure 14). Melting point of Mo is 2610 deg C and boiling point is 5560 deg C. The phase diagram of the iron molybdenum (Fe-Mo) binary system is at Fig 1. sharing sensitive information, make sure youre on a federal Moreover, molybdenum has a stronger impact on properties when upper bainite is formed during cooling. It provides customers with high-quality refractory metals & alloys such as tungsten, molybdenum,tantalum,rhenium,titanium,andzirconiumat a very competitive price. They are used in applications that are more corrosive, such as chemical processing plants or in marine applications. The features of Vanadium in steel. Size distribution of ferrite grains in the four kinds of rolled steel sheet. Fifty images showing the distribution of the precipitates in each steel were obtained by TEM, which allowed us to count the number of precipitates per area. Figure 14 shows the morphology and elemental distribution of the typical precipitates in N4 steel with 0.07% Mo. The welding test was carried out with the American Lincoln three-wire submerged arc welding machine (Lincoln Electric, Cleveland, OH, USA). It was obviously observed that the number density of precipitates showed a continuous increasing trend with the increase of Mo content. Size distribution of the precipitates in the four kinds of steel. Jun H.J., Kang K.B., Park C.G. http://creativecommons.org/licenses/by/4.0/. 2017;705:8997. The samples were chemically etched in a 3% nitric acid solution (3 mL HNO3 + 97 mL C2H5OH) for 25 s after mechanical polishing. It was sup-posed that molybdenum decreases the activating effect of sulfur species [15] conceivably by decreasing the surface coverage of adsorbed sulfur on a corroding sur-face, i.e. Molybdenum. The basis of this section is to cover some of the different alloying elements added to the basic system of iron and . Stainless steels In austenitic stainless steels Mo is in the range of 2 % to 7 % while in duplex stainless steels it is in the range of 3 % to 5 %. The addition of 1 % to 2 % of Mo to ferritic stainless steels also significantly increases the corrosion resistance and the elevated temperature strength. Reliability. After rough machining, steel articles are normally given a subcritical annealing treatment at 680 to700 deg C and slowly cooled to relieve machining stresses. The parameters about the degree of deformation during hot rolling are shown in Table 2. Though not very well documented, other possible symptoms of molybdenum toxicity involve joint and muscle pain, weakness, fatigue, loose stool and weight loss. 2001;32:16351647. Molybdenum in stainless steel welded . . behavior of aluminum alloy against steel This study aims to understand the impact of various lubri-cant additives on the friction- and wear behavior of alumi-num alloys against steel. Some common steel chemical elements like C, P, S, Si, Mn, Cr, Ni, Co, Mo etc . When Mo was not added into the steel, the stretch zone occupied a large area and the impact toughness was low (Figure 7). The width of GBF in CGHAZ of N1, N2, and N3 steel was approximately 18.72, 10.71, and 8.24 m, respectively, which indicated that it decreased with the increase of Mo content. Mandal G.K., Das S.S., Kumar T., Kamaraj A., Mondal K., Srivastava V.C. Jang J.H., Lee C.H., Heo Y.U., Suh D.W. Silicon (Si) and copper (Cu) may be present in quantities up to 1 % each. Molybdenum is a ferrite former. This prevents the formation of harmful coarse ferrite grains. There were a few river patterns on the cleavage facets (Figure 8b). Thus, Equation (4) indicated that the finer size and higher volume fraction of precipitates had a more positive pinning effect on the grain, which was consistent with the change trend obtained from the experimental results. Enter your e-mail address and your password. They are used in applications that are more corrosive, such as chemical processing plants or in marine applications. The microstructure in N2 steel containing 0.04% Mo consisted of GBF, WF and upper bainite (Figure 6b), and the size of GBF and austenite were finer than those in N1 steel. When the content of chromium in stainless steel is sufficient, molybdenum has an obvious effect on improving the corrosion resistance of stainless steel. Effect of Molybdenum on the Impact Toughness of Heat-Affected Zone in High-Strength Low-Alloy Steel, Multidisciplinary Digital Publishing Institute (MDPI). The stretch zone covered a large proportion of the total area of the fracture. Therefore, how to improve the toughness of HAZ has become an important research topic as the strength, plate thickness, and welding heat input continue to increase. In the range of 00.07%, the impact energy of HAZ increased with the increase of Mo content, which indicated that the addition of an appropriate amount of Mo was beneficial to improve the impact toughness of HAZ in steel. In small quantities in stainless steel, molybdenum increases hardenability and strength, particularly at high temperatures. The microstructure of coarse-grained heat-affected zone (CGHAZ) in steels, (a) N1 steel, (b) N2 steel, (c) N3 steel, and (d) N4 steel. Mo is used efficiently and economically in iron and steels for the following. Figure 4 shows the microstructure characteristics of hot rolled steel sheets. Effect of Alloying elements in Steel and Phase diagram Alloying elements are added in interstitial position, and creates strain field around it. FOIA When added to Cr steels it greatly diminishes the tendency of steels to decay in service or in heat treatment. Adding molybdenum to tool steel can improve red hardness. These results suggested that the addition of Mo can strongly influence the microstructure in CGHAZ, thereby affecting the impact toughness of HAZ. The addition of Mo can suppress the Widmansttten ferrite (WF) formation and promote the transformation of acicular ferrite (AF), leading to the fine transformed products in the heat-affected zone (HAZ). This allows for normal uncertainties in scrap composition and permits closer control of final Mo content. In the EAF production of HSLA steel, alloy steel, and heat resisting grades, where Mo content is normally less than 1 %, MoO3 is added to the liquid steel bath after meltdown is complete and after initial sample for chemical analysis has been taken. Certain constituents may also be harmful if swallowed. . Disclaimer, National Library of Medicine In cattle, molybdenum has also been linked to fertility problems. Additionally, a few hot compression tests were carried out to simulate the press hardening process of these experimental steels. The microstructure in CGHAZ was mainly comprised of AF when 0.07% Mo was added in steel (Figure 6d). Molybdenum does not occur naturally as a free metal on Earth; it is found only in . The effect of strain aging on mechanical properties and the CTOD parameter value has been examined. A. All Rights Reserved 2019, Design & Developed By: Star Web Maker. This distortion in crystal structure and presence of strain field prevents dislocation movement making steel stronger and harder. Molybdenum containing grades of stainless steels are generally more corrosion resistant than molybdenum-free grades. The other families, martensitic, duplex and precipitation hardenable stainless steels each represent less than 1% of the total market. In the N1 steel without Mo and N2 steel with 0.04% Mo, the microstructures of cast ingots were composed of polygonal ferrite (PF) and pearlite (Figure 2a,b). With the enhancement of the impact toughness in HAZ, the area of fibrous crack zone increased gradually, and the area of the stretch zone was correspondingly reduced. Molybdenum is a silver-white refractory metal with a melting point of 2615 and a density of 10.2g/cm3. The changes of austenite size in the four kinds of steel were in situ observed and recorded by LSCM to evaluate the role of Mo in the refinement of microstructure. doi: 10.1007/s11661-001-0142-6. The microstructure was refined and the toughness was enhanced after the addition of 0.07% Mo in steel. Addition of Mo to boron-alloyed steel improves the hardenability by suppressing the precipitation of Fe 23 (C, B) 6; this is known as the combined Mo-B effect.However, the maximum Mo content for the combined effect to occur is still unclear because previous studies on this effect mainly investigated steels with a Mo content of less than 0.80%. Mos important alloying properties have given it a significant role in modern industrial technology, which increasingly requires materials that are functional under high stress, expanded temperature ranges, and highly corrosive environments. Google Analytics generates statistical and other information about our websites use. This is especially important in the case of as-rolled HSLA strips and plates, and for high speed tool steels containing Mo. Answer: As you most likely know, carbon, and to a lesser extent manganese, have the greatest effect on hardenability in steels. . Rev. As shown in Figure 7d, the area of the fibrous crack zone and tip blunting zone increased significantly, and the fracture surface was dark and had no metallic luster. As of the end of 2014, the United States had 2.7 million tons of molybdenum reserves, and 5.4 million tons of identified molybdenum resource. Overheating is to be avoided, and the precautions regarding surface protection are necessary. . Steels containing chromium and nickel suffer from temper brittleness i.e. For the range of 00.07%, the addition of Mo gave a reduction in the size of grains. This is the normal practice in EAF and BOF steelmaking. As shown in Figure 6c, although a small amount of upper bainite was observed, the size of GBF and austenite were further refined in the N3 steel containing 0.06% Mo. With the addition of Mo, the height of cleavage steps increased (Figure 8e). Meanwhile, the addition of Mo retarded the transformation of WF in CGHAZ and promoted AF formation. These characteristics have significant effects on CNWs and can be adjusted as a growth interlayer. Effects of Zr-Ti on the microstructure and properties of flux aided backing submerged arc weld metals. Influence of Molybdenum on the Performance of Stainless Steel. and X.M. Technol. The functionality is limited to basic scrolling. The authors declare no conflict of interest. official website and that any information you provide is encrypted The synergistic effect of alloying elements and heat treatment produces various microstructures and properties. The chemical composition, size distribution, and number density of precipitates in steel were investigated by TEM. Vanadium is added for strength and toughness via grain refinement in as-rolled (control) as well as normalized steels. The morphology of the tip blunting zone in N1, N2, N3, and N4 steel was shown in Figure 8c,f,i,l, respectively. All authors have read and agreed to the published version of the manuscript. Materials (Basel). (This transformation is also called the Ar 1 transformation, r standing for . A total of five samples were prepared for testing the impact toughness in each of the studied steel. The microstructure of cast ingots, (a) N1, (b) N2, (c) N3, and (d) N4 steel. Abstract. The difference between the families is fundamental on an atomic level. Therefore, due to the addition of Mo, the average size of precipitates was reduced significantly, and the number density of precipitates was increased substantially. Mater. The samples prepared for LSCM observation were austenitized at 1100 C for 300 s. Typical results reflecting austenite grain size characteristics in N1, N2, N3, and N4 steel are shown in Figure 9ad, respectively. Chen C.Y., Chen C.C., Yang J.R. Microstructure characterization of nanometer carbides heterogeneous precipitation in TiNb and TiNbMo steel. An overview of the specialty steel raw materials markets in europe and their latest price moves. Size distribution of ferrite grains in the four kinds of cast ingot. HHS Vulnerability Disclosure, Help Journal of Materials in Civil Engineering, Volume 35, Issue 2, February 1, 2023. Han G., Xie Z.J., Xiong L., Shang C.J., Misra R.D.K. In the austenitic stainless steels the atoms, here iron, chromium and nickel, are arranged on the corners of the cube and in the center of each of the faces of the cube. It has been pointed out in the literature that the longer the fibrous crack zone extends, the better the toughness of the material [26]. Second holding at 1100 deg C is helpful. 2012;57:187207. For example, austenitic stainless steels are non-magnetic, while ferritic and duplex stainless steels are magnetic. The authors declare no conflict of interest. Molybdenum containing grades of stainless steels are generally more corrosion resistant than molybdenum-free grades. Medina S.F., Gmez M., Rancel L. Grain refinement by intragranular nucleation of ferrite in a high nitrogen content vanadium microalloyed steel. The model can be used to predict in detail the flows of ferrous materials in various phases, including the recycling phase by extending steel, alloying element . This also improves dimensional stability during hardening. In the existence of ammonia and hydrogen sulfide after hydrogen refined desulfurization reactions and its fluid pipes, it can form ammonium hydrogen sulfide(NH4HS), the nitrogen in the raw material is transformed into NH3 in the reactor, and in the outflow heat exchanger, ammonia and hydrogen . Mater. (a) STEM BF image of the typical precipitate, (b) STEM DF image of the typical precipitate, (cg) EDS mapping of the precipitate in the N4 steel with 0.07% Mo addition. Federal government websites often end in .gov or .mil. The number density of the precipitates in N1, N2, N3, and N4 steel was 5 106/mm2, 1.2 107/mm2, 1.8 107/mm2, and 3.5 107/mm2, respectively. The introduction of molybdenum to 304L steel resulted in an . Owing to the superior comprehensive properties, including excellent low-temperature impact toughness, high tensile strength, and good weldability, high-strength low-alloy (HSLA) steels have been widely applied in various fields, such as ship construction, offshore engineering, navy vessels, and even nuclear fission power plant components [1,2,3,4,5,6,7,8,9]. Molybdenum is mainly used in iron and steel industry, generally more than 80% is added to the molybdenum in steel, only about 20% to produce metal molybdenum, molybdenum alloy, super alloy and special chemical products, they are mainly used in petroleum chemical industry, light industry, electronics and other high-tech fields. Pu J., Yu S.F., Li Y.Y. Mo is normally referred in short as moly. V (Vanadium ) Supplements of molybdenum come in many different forms and dosages. In view of a= 0.287 nm [31], the lattice misfit () between ferrite and Nb(C, N) was approximately 11.39%, while the between ferrite and (Nb, Mo)(C, N) was approximately 5.40% calculated by Equation (1). The value of f can be calculated by the following equation [34]: where N is the quantity of particles per area, and S0 is the specific area for estimation. The grain refinement is known to be conducive to the improvement of toughness. Master curve characterization of the fracture toughness behavior in SA508 Gr.4N low alloy steels. In Figure 8k, the cleavage facets were smaller, more white tearing edges were observed, and the cleavage surface was further uneven, which indicated that the steel possessed the ability of a certain resistance to crack propagation. The addition of Mo can suppress the Widmansttten ferrite (WF) formation and promote the transformation of acicular ferrite (AF), leading to the fine transformed products in the heat-affected zone (HAZ). The metal was first isolated in 1781 by Peter Jacob Hjelm. Finally, the surface was scored to 3 mm squares and the sample etched first with 10% nitric acid solution (10 mL HNO3 + 90 mL C2H5OH) and then soaked with alcohol. The addition of Mo can suppress the Widmansttten ferrite (WF) formation and promote the transformation of acicular ferrite (AF), leading to the fine transformed products in the heat-affected zone (HAZ). Its melting point is 2620, and it has the advantages of strong interatomic bonding, a small expansion coefficient, high electrical conductivity, and good thermal conductivity. Available forms Mo is supplied as ferro-molybdenum (Fe-Mo) and as molybdic oxide (MoO3). Molybdenum (0.2-5.0%): Found in small quantities in stainless steels, molybdenum increases hardenability and strength, particularly at high temperatures. After taking 300-800 micrograms of molybdenum supplements each day for 18 days (for a total dose of 13.5 mg), a man developed hallucinations and seizures, eventually resulting in permanent brain damage [ 13 ]. 2) The low content of Mo formed the cementite with iron and carbon, and the special carbide of molybdenum can be formed when the content is high. The microstructure of coarse-grained heat-affected, The microstructure of coarse-grained heat-affected zone (CGHAZ) in steels, ( a ) N1, The macroscopic morphology of fracture after impact test at the distance of 2, The micromorphology of the fibrous crack zone ( a , d , g, In situ observation of austenite grain size in N1 ( a ), N2. In order to improve your experience on our website, we use functionally necessary session cookies, but no advertising or social media cookies. The lattice misfit between ferrite and carbonitride can be calculated by the following equation [29]: where is the lattice misfit between ferrite and carbonitride, acarbonitride is the lattice parameter of carbonitride, and a is the lattice parameter of ferrite. Molybdenum can also increase the hardenability, toughness, and tensile strength of steel. It has been demonstrated that a relatively small change in the number density and size distribution of the precipitates can strongly influence the size of ferrite and prior austenite grain [27]. Does chrome molybdenum steel rust? and molybdenum) that occur in steel materials and that result from mixing during end-of-life (EOL) processes. The rates of interim dumping duty for exporters from South Africa are set at 25.3%, and took effect from 19 December, 2022. The samples obtained from the base material after rolling were austenitized at 1100 C for 300 s and then used for TEM observation by the carbon extraction replica technique. This fact, plus Mos ability to strengthen ferrite even at elevated temperatures, has led to the development of a series of heat-resisting steels. The analysis of fracture micromorphology further showed that the micromorphology of fracture changed greatly with the increase of Mo content, which suggested that the morphology characteristics of fracture may be closely related to the toughness of the steel. We list 21 chemical elements and effects on mechanical properties of steel. SiO2is the main impurity, but it may also contain small amounts of Cu, sulfur (S), and phosphorus (P). Molybdenum, often nicknamed as "Moly", has many important metallurgical effects in HSLA and alloy steels: Moly is a potent hardenability agent and, thus, a standard constituent in heat-treatable steels. Dietary Sources of Molybdenum A substantial number of measurements were conducted to determine the average size of the precipitates. Figure 2ad shows the microstructure of the cast ingots of N1, N2, N3, and N4 steel, respectively. Sci. Effect of titanium in steel Titanium is a strong deoxidizer in steel. For this the specific temperatures are chosen depending upon the composition of the steel. The effect of molybdenum on interphase precipitation and microstructures in microalloyed steels containing titanium and vanadium. Cast irons Mo content ranges from 1.0 % to 3.0 %. Based on their microstructure, stainless steels are divided into the following families: The division based on microstructure is useful because the members within one family tend to have similar physical and mechanical properties. Mo dissolves in both alpha and gamma iron and in the presence of C forms complex carbides (FeMo)6C, Fe21Mo2C6, and Mo2C. Gong P., Liu X.G., Rijkenberg A., Rainforth W.M. It can also improve the strength and creep resistance at high temperatures. It is not suitable for use in induction melting furnaces, vacuum practices, or as a ladle addition. The addition of one or two percent molybdenum to ferritic stainless steels also significantly increases the corrosion resistance and the elevated temperature strength of these stainless steels. Yu H, Wu K, Dong B, Yu L, Liu J, Liu Z, Xiao D, Jing X, Liu H. Materials (Basel). We use the Google Analytics service to analyse website use and visitor numbers as part of a continual improvement process. Effect of microstructure and heat treatment of steel 1) Mo can be solidity dissolved in Ferrite, Austenite and Carbide, and is an element to reduce Austenite phase zone. It is believed that the increase in the number density and decrease in the size of precipitates caused by the addition of Mo can refine the size of grains. they become brittle if held at a temperature between 250500C and as such their shock resistance becomes poor at these temperatures. Wang Q., Zhang C., Li R., Gao J., Wang M., Zhang F. Characterization of the microstructures and mechanical properties of 25CrMo48V martensitic steel tempered at different times. As a contrast, with 0.07% Mo, the size of ferrite grain was uniform and further refined (Figure 2d). Materials (Basel). Both ferritic and austenitic stainless steels contain about 1 % Si for oxidation resistance. Maraging steels Mo content ranges from 4.0 % to 5.0 %. When the deviation of test value was large, the alternative samples were used for testing. In this study, four kinds of steel with different Mo content were designed to systematically investigate the effect of Mo on the toughness of steel. The main role of molybdenum in stainless steel is to improve the corrosion resistance of steel and the resistance to pitting corrosion and crevice corrosion. 2018;34:737744. The precipitates consisted of Nb, Mo, C, Ti, and N elements. In hot-work steels and high speed steels, it increases red-hardness properties. Mo is used extensively because its inclusion (alone or with other alloying metals) results in a more economical way of getting improved properties in steels. Size distribution of ferrite grains in the four kinds of rolled steel sheet. Tungsten Copper Alloy for Electronic Packaging Materials. Thank you for reading our article and we hope it can help you to have a better understanding of theinfluence of molybdenum on the performance of stainless steel. The microstructure of cast ingots, ( a ) N1, ( b ) N2,. Thus, the increase in the number density of precipitates was attributed to the decrease of lattice parameter caused by the addition of Mo. Heavy section forgings, which could be vulnerable to embrittlement because they can cool slowly through the known embrittling temperature range, are normally made from Mo containing steels. The effect of chlorine containing chlorine in the raw material on the hydrogenation process 1. When the content of Mo was 0.06%, the size of ferrite grain was significantly refined, and a small amount of fine acicular ferrite (AF) was observed (Figure 2c). All data generated or analyzed during this study are included in this article. It means that with the increase of Mo content in the range of 00.07%, the size of ferrite grain has a tendency to decrease. After this, heating to the austenitizing range, 1170 to 1240 deg C (depending on grade) is to be rapid to minimize grain growth. The high melting point of molybdenum makes it important for giving strength to steel and other . Thus, it can be inferred that with the addition of Mo to the steel, the complex precipitate phase (Nb, Mo)(C, N) was formed by the partial replacement of Nb by Mo in the Nb(C, N). Mo acts by increasing lattice strain, thus increasing the energy required to dissolve out iron atoms from the surface. In other words, further improvement of the impact toughness of HAZ in steel may be achieved by the addition of Mo. Moreover, the size distributions of N1, N2, N3, and N4 steel follow the log-normal form, with average sizes of 169.8, 145.0, 122.8, and 93.0 m, respectively. Molybdenum primarily increases the corrosion resistance of stainless steels (see Grades and Properties ). Formation mechanism and control methods of acicular ferrite in HSLA steels: A review. 2021 Aug 7;14(16):4424. doi: 10.3390/ma14164424. It improves machinability and resistance to corrosion and it intensifies the effects of other alloying elements. ; writingoriginal draft preparation, X.W. The chemical composition of precipitates changed from Nb(C, N) to (Nb, Mo)(C, N) because of the addition of Mo. The effect of molybdenum on steel includes the following: Tensile strength, heat resistance and weldability of steel is increased by the molybdenum, but as soon as the content is too high the forgeability is negatively influenced. It has been reported that the carbonitride was believed to hold a BakerNutting orientation relationship with the ferrite matrix [30]. A detailed analysis of the precipitates focusing on the chemical composition, size, and number density has been undertaken to understand the contribution of Mo on the improvement of steel toughness. An official website of the United States government. Often used in chromium-nickel austenitic steels, molybdenum protects against pitting corrosion caused by chlorides and sulfur chemicals. Sintered Mo-containing 304L steel is less prone to pitting corrosion in environment containing chlorides than 316L with Mo addition. Mo improves the corrosion resistance of stainless steels. Your email address will not be published. Figure 7c shows the fracture surface of the sample with 0.06% Mo addition. This result further supported that the addition of Mo can refine the grain, which may be associated with the pinning effect of the precipitates located in the grain boundaries [27,28]. To investigate the effect of Mo content on the microstructure, the microstructure of the cast ingots was observed by OM. The microstructure, precipitates, and austenite grain in high-strength low-alloy steel were characterized by optical microscope, transmission electron microscope, and laser scanning confocal microscopy to investigate the effect of Mo on the toughness of steel. However, with the increase of molybdenum content, the high-temperature strength of steel is improved, such as durability, creep, and other properties are greatly improved. The four kinds of studied steels containing no Mo (N1), 0.04% Mo (N2), 0.06% Mo (N3), and 0.07% Mo (N4) were smelted in a 100 kg vacuum induction furnace and cast into ingots. Adding molybdenum in structural steel can improve mechanical properties. When the volume fraction f and diameter d of precipitates was substituted into Equation (3), the size of grain (Dc) in N1, N2, N3, and N4 steel can be calculated as follows: 2759.40 (1.52/Z), 1745.17 (1.52/Z), 1351.21 (1.52/Z), and 922.11 (1.52/Z), respectively. 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