Abstract: Manganese is an important industrial raw material and widely used in powder metallurgy materials. This article provides an overview of the application of manganese in materials such as sintered steel, damping alloys, aluminum alloys, titanium aluminum alloys, tungsten based heavy alloys, and hard alloys. It can be expected that manganese will have broad application prospects in improving the performance of powder metallurgy materials and developing new powder metallurgy materials.
Keywords: manganese; Powder metallurgy; application prospect
Introduction: The element manganese was discovered as early as 1774, but its important role in the steel industry was not recognized until the invention of the bottom blown acidic converter in 1856 and the open hearth steelmaking method in 1864. Nowadays, manganese, as an effective and inexpensive alloying element, has become an indispensable and important raw material in the steel industry. About 90% of manganese is consumed in the steel industry, second only to iron in terms of usage, while the remaining 10% is consumed in sectors such as non-ferrous metallurgy, chemical industry, electronics, batteries, and agriculture.
Manganese and its compounds are commonly used raw materials for the production of powder metallurgy materials. The importance of manganese in powder metallurgy materials has been recognized by people since 1950. Subsequently, the application of manganese in the powder metallurgy industry gradually expanded. High strength sintered steel containing manganese series has been developed through the development of mother alloy technology and pre alloy technology. Moreover, it plays an important role as the main component or additive component in other powder metallurgy materials. This article provides an overview of the application of manganese in powder metallurgy materials.
1. The role of manganese in high-strength sintered steel
Low alloy sintered steel with the simultaneous addition of manganese and silicon as alloying elements exhibits good strengthening effect and sintering size stability, is inexpensive, and has a strong competitive advantage. According to relevant reports, the Fe-3.2% Mn-1.4% Si-0.4% C alloy sintered at 1250 ℃ for 60 minutes has a tensile strength of 800-1000MPa. Sintered iron and sintered steel are mainly used for manufacturing mechanical parts, and when selecting alloy elements, attention must be paid to their impact on dimensional stability. In general, the addition of silicon causes shrinkage of the compact during sintering, while the addition of manganese causes expansion of the compact. Simultaneously adding manganese and silicon can effectively control the appearance and size of the sintered body. Size changes in the 5 component samples measured Δ In L/L0, it was found that Fe-2.0% Si-2.0% Mn and Fe-2.0% Si-4.0% Mn were basically the same as pure iron, with a size change of 1.2% to 1.4%; And Fe-4.0% Mn is relatively high, about 1.7%; Fe-2.0% Si is relatively low, about 0.7%. The mechanical properties of several sintered steels containing nickel, molybdenum, copper, manganese, and silicon are listed in Table 1. It can be seen that sintered steel with the addition of both manganese and silicon alloy elements has high performance.
Meanwhile, during sintering, manganese sublimates and forms vapor. Figure 1 shows the manganese vapor pressure of Fe-45% Mn-20% Si alloy at 600-1200 ℃. When sufficient manganese is added, manganese vapor is filled into the voids of the compact to effectively prevent oxidation of other elements and deposition on the surface of iron particles. Through surface diffusion, volume diffusion, etc., it uniformly infiltrates the iron particles, even the particle center, accelerating the alloying rate. Observing the Fe-2.0% Si-4.0% Mn sample, it was found that there was instantaneous liquid phase formation. The liquid phase promotes the rapid diffusion of alloy elements and may overcome the inhibitory effect of the oxide layer on the surface of the parent alloy particles, achieving high uniformity of alloy elements.
2. Improving the cutting performance of iron-based sintered materials
Adding manganese sulfide (MnS) to sintered steel can effectively reduce cutting force and improve its cutting performance. In iron-based materials, manganese sulfide is a brittle and lubricating metal inclusion with much lower strength than the iron matrix. The role of manganese sulfide in materials is equivalent to that of pores, which disrupts the continuity of the iron matrix, reduces strength, and thus reduces cutting force. Han Yunqiu et al. found that the cutting performance of sintered steel was effectively improved after containing manganese and sulfur elements. For 600MS grade iron powder with manganese and sulfur content of 0.318% and 0.21%, the average cutting force of the sintered sample was only 295MPa, far lower than the 688MPa of grade SC-100.26 with lower manganese and sulfur content. The experimental results of Yin Pingyu et al. show that adding manganese sulfide powder to the Fe-2% Cu-0.5% Mo-0.6% C sintering system greatly improves the cutting performance of the material. Moreover, additives have no significant impact on the sintering temperature, hardness, and dimensional accuracy of the material.
Experiments have shown that the formability and sintering performance of steel powder in 304L austenitic stainless steel have undergone significant changes after the addition of manganese sulfide. The addition of manganese sulfide powder reduces the compact density. When the manganese sulfide content is below 0.6%, the compact shrinkage ratio and sintered density decrease with the increase of additive content; But after exceeding 0.6%, it rises. After adding manganese sulfide powder, the corrosion resistance of sintered steel deteriorates. After soaking in a 10% concentration of FeCl3 corrosion solution, the loss of sample quality increases with the increase of manganese sulfide addition. Manganese sulfide has a significant impact on the fatigue fracture of powder metallurgy sintered steel. Cracks originate from voids on the surface or lower layer of the sample and propagate in various modes. However, the addition of manganese sulfide does not change the fatigue mechanism of sintered steel. At the same time, it was found that the flexural strength, fracture toughness and other properties of sintered steel are not only affected by the amount of manganese sulfide added, but also have a clear relationship with the particle size of additives. Manganese sulfide phase is mainly distributed between matrix particles or pores, while there are few particles inside, so the grain size of manganese sulfide has a direct impact on the above properties.
Manganese infiltration on the surface of sintered steel
Sintered steel often requires wear protection and heat treatment, including surface quenching, carbon nitrogen co infiltration, soft nitriding, boron infiltration, etc. By using these methods, a hardened surface can be obtained, but to some extent, it can increase the size of the part. It is not advisable to perform finishing treatment on hardened parts, and only size correction can be done through grinding. Manganese infiltration treatment can be used to manufacture sintered wear-resistant parts and ensure that the dimensional accuracy of the parts remains unchanged, avoiding the aforementioned drawbacks. Alloying the surface of manganese can be carried out during the sintering process, thereby eliminating additional processes such as carburization, hardening, and grinding. Manganese infiltration generates a surface hardening layer of austenitic manganese steel, which has properties similar to high manganese steel.
The characteristics of parts with manganese diffusion treatment on the surface have special value for applications in wear and high temperature conditions. Pohl measured the hardness and strength of surface manganese infiltrated samples (the samples were tempered at 450 ℃ for 1 hour). According to the author's results, at a testing temperature of 450 ℃, the hardness of surface manganese infiltrated parts is higher than that of carbon nitrogen co infiltrated parts, with values of approximately 400HV0.05 and 350HV0.05, respectively; Moreover, compared to the hardness value at room temperature, the surface manganese infiltrated parts have not decreased much, still accounting for 80% of room temperature, but the carbon nitrogen co infiltrated parts only have 50%. The fatigue strength of surface manganese infiltrated parts is higher than that of carbon nitrogen co infiltrated parts, and it increases linearly with the increase of tempering temperature. The value at 450 ℃ is 8% higher than that at room temperature.
4. Manganese based damping materials
According to relevant reports in 1976, Mn Cu damping alloys have been successfully developed through powder metallurgy methods. Sintering is carried out in hydrogen gas with a lower dew point, and the final sintering temperature of Z depends on the manganese content. The alloy containing 55% Mn is about 900 ℃, while the alloy containing 75% Mn is raised to 1075 ℃. When the particle size of manganese powder decreases from -100 mesh to -325 mesh, the sintering density and tensile strength slightly increase. 60Mn-40Cu alloy is sintered in vacuum, and if the sintering temperature is not lower than that in hydrogen, manganese will significantly evaporate. During the heating process, the compact first expands by a few percent, and only contracts when the temperature approaches the final sintering temperature of Z. Table 2 presents the tensile strength and hardness data of 60% to 75% Mn alloy (containing 1% binder). The sample is heated in hydrogen gas and kept at 760 ℃ for 0.5 hours, 860 ℃ for 1 hour, and the final sintering temperature of Z is kept for 1 hour to obtain Z high tensile strength. Pores and other organizational characteristics reduce mechanical properties but increase relative damping performance. After sintering, the material can achieve good damping performance, which is desirable from the perspective of simplifying the process and reducing costs.
Damping materials based on manganese include Mn Cu, Mn Fe, and Mn Ni alloys. During the sintering process of the Mn Cu system, it exhibits a unidirectional diffusion mechanism of manganese entering copper, resulting in the formation of a single-phase solid solution. Mn Cu alloy is a good damping material. The attenuation ability of Mn Cu (70% Mn) alloy during tempering was studied, and it was found that during the tempering process, the pre quenched sintered sample had γ Solid solution has a very similar attenuation mode to ordinary cast alloys; However, the difference is that even if the tempering temperature reaches 460 ℃, the attenuation strength of the sintered alloy is relatively low. They believe that the reason for this phenomenon is related to the excellent chemical uniformity of the alloy. Increasing the copper content in the alloy leads to an increase in density, hardness, sound wave propagation rate, and Poisson's ratio, but the ratio of Young's modulus to bulk elastic modulus (E/K) decreases. When the E/K is in the range of 2.0~2.4, alloys with high manganese content corresponding to high E/K values have better damping properties. Sintered Mn Cu alloy containing α- Mn and γ- MnCu phase has a damping constant in the range of 10-1 and is insensitive to temperature and frequency. After quenching of Mn Cu alloy at 1123K, only γ- MnCu single-phase composition. There are two peaks on the logarithmic decay rate temperature relationship curve of single-phase alloys, located at positions 223K and 460K, respectively. The intensity of these two peaks is higher than that of M2052 alloy produced by casting. The author believes that the main peak located at 223K is caused by the twin interface in the microstructure, while the other peak originates from the face centered orthogonal structure (fct) γ- The transition of MnCu to face centered cubic structure (fcc). In addition, manganese alloys containing copper and nickel components have a high coefficient of thermal expansion and have application prospects in various fields, such as as using bimetallic sheets in thermal response controller devices.
5. The application of manganese in aluminum alloys
The addition of manganese element to aluminum alloy is usually completed by powder metallurgy process after melting and crushing. During melting and cooling, a high cooling rate is adopted to avoid the formation of coarse Al6Mn phase. Therefore, two methods of adding MnAl flakes or manganese powder injection to the aluminum alloy matrix were attempted. The results indicate that the former method relies on the heat released by the reactions between components, allowing the solid solution process of manganese to be maintained without the need for additional equipment, resulting in a lower temperature required for the entire process; Moreover, the material properties are less dependent on the size of manganese particles. When using the latter method, additional equipment is required due to the loading of manganese metal powder through high-speed airflow. In addition, using this method has a long process cycle and significantly higher operating temperature than other methods. Meanwhile, it was found that the particle size of manganese powder, whether larger or smaller than the Z-optimal size, is not conducive to material performance.
Al Mn alloy is a common aluminum alloy, which is composed of α The solid solution and Al6Mn intermetallic compound are composed of two phases. Intermetallic compounds have a significant impact on the mechanical properties of alloys. With the increase of compound content, the yield stress and fatigue strength of the alloy significantly increase, while the elongation decreases (especially in lower temperature working environments). After adding a small amount of chromium to Al Mn alloy, the properties of the alloy changed significantly. After studying the relationship between the mechanical properties and composition of Al - (6-8)% Mn - (1-3)% Cr alloy. The results showed that after the Mn+Cr content was higher than 8.8%, the strengthening degree of the alloy significantly increased due to precipitation. Al-7Mn-3Cr alloy has excellent strengthening effect, with a tensile strength of 480MPa and an elongation of 7%. When the amount of chromium added is low, the second phase of Al6Mn precipitates in the alloy; When the amount of chromium added is high, Al7Cr phase is formed. After heat treatment of the hot extruded alloy sample, G phase, i.e. (Mn, Cr) Al12 phase, is generated in the system. The formation of the second phase has a significant impact on the microstructure and mechanical properties of the alloy. The addition of silicon element to Al Mn alloy also achieved good results. Hawk et al. prepared Al-12.6Mn-4.8Si alloy using rapid solidification technology. After annealing at 350 ℃ for 100 hours, the microstructure of the sample was very stable, and there was no decrease in strength and elongation. In the range of room temperature to 380 ℃, the tensile strength decreased from 465MPa to 115MPa, and the elongation increased from 6% to 12%; When the temperature rises to 425 ℃, the elongation rate further increases to 30%. At the same time, the strength and plasticity of alloys depend on the strain rate, and both strength and plasticity are improved at high strain rates. The creep test results show that within the testing temperature range, the creep activation energy of the alloy is between 100 and 230 kJ/mol, and the stress index is between 3 and 5. The high-strength AlMnCe alloy prepared by powder metallurgy process has higher wear resistance than traditional alloys. The Al90Mn8Ce2 alloy exhibits Z-best compressive strength and hardness, reaching 900MPa and 26HRC, respectively, after isostatic pressing under conditions of 753-793K and 1.2GPa. The improvement in strength is attributed to the fine grains and second phase strengthening of the alloy [44]; Research has found that Al90Mn8Ce2 alloy has excellent wear resistance. For example, under the condition of 773K, the wear resistance of this alloy is three times that of ordinary A355 aluminum alloy. It was also found that the second phase hard particles such as Al6Mn, Al4Ce, and Al2O3 in the material are beneficial for improving the wear resistance of the alloy.
6. Conclusion
Manganese, as the main component or additive of powder metallurgy materials, plays an important role in improving material properties and developing new materials; Moreover, manganese has abundant resources and low prices. The research and development of manganese applications are of great significance both in scientific theory and production practice. With the expansion of market demand and the development of materials science and technology, the application prospects of manganese will undoubtedly be even broader.
However, the expanded application of manganese has encountered obstacles from itself, which are that manganese is easily oxidized and oxides are difficult to reduce. In the process of powder metallurgy production, the oxidation of manganese has always been a very challenging problem. With the development of powder making technology and sintering technology, the problem of preventing manganese oxidation has been alleviated, but it has not been completely solved. While advocating for the expansion of the application of manganese, it is also necessary to strengthen research in this area and find reasonable measures.
2024 January 4th Week Marginal Product Recommendation:
Material Specification Sheet–MG-6:
Material specification sheet – MG-6 is Ball and roller bearing steel according to EN ISO 683-17. Ball and roller bearing steel for balls and rollers of any dimension,rings and discs up to 30mm effective thickness.
