hardness sharply increased

molybdenum alloy welding characteristics of molybdenum and molybdenum alloy steel welded structure, used more often in the actual production, but because of molybdenum and molybdenum alloy and steel physical properties of a larger difference in welding process, a lot of problems. Analysis of the problem from the welding concluded, molybdenum and steel welding performance depends primarily on molybdenum and molybdenum alloy composition and performance. Iron - molybdenum alloy state diagram in Figure 1. Fe from the state diagram shows the various concentrations of Mo to form α-Fe and α-Mo solid solution. In addition you can also form two intermetallic brittle phase ε-Fe3 No2 and η-FeMo. Fe3 No2 until 1450 ℃ temperature range are relatively stable. State diagram of η-phase, there is a temperature range of its 1180 ~ 1540 ℃, when the cooling time, η-phase decomposition of ε-phase and α-phase solid solution. Molybdenum and steel welding has the following main features. ① molybdenum steels mainly depends on molybdenum and molybdenum alloy composition and performance. Molybdenum and molybdenum alloy and steel welding, when heated to 400 ℃, minor oxidation. Above 600 ℃, the rapidly oxidized to MoO3 compounds. The solubility of oxygen in the molybdenum is small, when the oxygen content increases, the formation of oxides along the grain boundaries, compounds of other impurities are also brittle phase in the grain boundary precipitates, the welding difficult. ② welding molybdenum steel, molybdenum base metal close to the side, prone to high hardness and brittleness zone, the width of up to 0.5 ~ 3μm. Here are the main component of intermetallic compounds Fe3 Mo2 and FeMo. Close to the steel base metal side than on the molybdenum base metal brittleness orientation small, but fast cooling rate after welding, the side of the base metal molybdenum appears martensite, resulting in the weld heat affected zone and the splice area embrittlement in the weld stress under the effect of severely increase the tendency to crack joint. Therefore, molybdenum and steel is a relatively poor weldability. ③ molybdenum and steel welding dissimilar weld metal consists of three parts, components and solder joints uniform. Close to the steel base metal side is made of steel and composed of an intermetallic compound phase organization, its hardness is increased dramatically; near molybdenum base metal side is made of an intermetallic compound consisting way, hardness sharply increased; weld intermediate is made between molybdenum and steel consisting of an intermetallic compound, the hardness is high. Molybdenum steel welded joint tissue components with uneven great influence on hardness, shown in Figure 2. 2, (1) is composed of an intermetallic compound of steel and the duplex structure; (2) between the steel and the intermetallic compound of molybdenum plating; (3) is a molybdenum compound and a metal phase composed of tissue. (2) molybdenum and steel welding a) molybdenum and steel welding - brazing molybdenum and steel (carbon steel, stainless steel) using welding, electron beam welding and gas welding and other welding methods, welding can be achieved - brazed joints. This welding process is the essence of the steel side of the molten metal more, and molybdenum increase the side just heating without melting or melting little liquid metal is steel formed by infiltration brazed seam. This avoids the formation of iron and molybdenum compounds Fe3 Mo2 and FeMo, the joint area embrittlement problem is solved. Molybdenum steel electron beam butt welding directly, the weld metal composition mainly 20Mo-80Fe in the Mo base material is displayed on the side of the boundary eutectic α + ε, and the formation of large intermetallic Fe3 Mo2 and FeMo. Since the presence of intermetallic compounds, the weld metal brittle and easily cracks increases, reducing the performance of the joint, its poor weldability. Therefore, molybdenum and steel fusion welding, the joint strength is not high, you should avoid direct welding, it is generally used welding - brazing.

its high temperature resistance, low temperature resistance

Chromium-molybdenum alloy chromium-molybdenum alloy pipe tube 15 is a seamless, its performance is much higher than the average of seamless steel tubes, because the steel contains Cr more inside, its high temperature resistance, low tungsten carbide plate resistance, corrosion resistance seamless smaller than the other, so the alloy tube in the petroleum, chemical, electric power, boiler and other industries use more widely. 15 Cr-Mo alloy pipe principle of purified hydrogen at 300-500 ℃, the purification of the hydrogen to be introduced into chrome molybdenum alloy tube 15 side, the hydrogen is adsorbed on the wall 15 chromium-molybdenum alloy, the palladium 4d lack of two electron shells, which can generate instability in the hydrogen bond (palladium and hydrogen this reaction is reversible), the role of the palladium, hydrogen is ionized proton radius of 1.5 × 1015m, while palladium the lattice constant of 3.88 × 10-10m (20 ℃), the so by 15 Cr-Mo alloy pipe, under the action of the palladium and proton and electron binding and re-form hydrogen molecules from the 15 Cr-Mo alloy tube to another side to escape. In the 15 chromium-molybdenum alloy tube surface, not dissociated gas is impermeable, it can take advantage of 15 chromium-molybdenum alloy tube to obtain high purity hydrogen. Although palladium to hydrogen permeability has a unique, 15 Cr-Mo alloy pipe pure palladium but poor mechanical properties, high temperature oxidation, the recrystallization temperature is low, easy to make the 15 Cr-Mo alloy pipe] deformation and brittle, and therefore can not be used pure palladium as through the membrane. Add the proper amount of palladium and Ⅷ Group IB elements, made ??of palladium alloy, palladium can improve the mechanical properties of 11 automobile axle casing seamless pipe (GB3088-82) is manufactured automobile axle casing and the drive axle axle shaft tubes of high-quality carbon structural steel and alloy steel seamless hot-rolled palladium alloys, silver accounting for 20-30%, other ingredients (such as gold, etc.) content of <5%

improve its strength and improve the low temperature ductility.

Molybdenum alloy, are molybdenum matrix by adding other elements consisting of non-ferrous alloys. Major alloying elements are titanium, zirconium, hafnium, tungsten carbide inserts, and rare earth elements. Titanium, zirconium, hafnium, molybdenum alloy element not only from solid solution strengthening effect, maintaining low alloy ductility, but also form a stable carbide dispersed phase, increase the tensile strength and the recrystallization temperature. Molybdenum alloy has good heat conductivity, and low coefficient of expansion at high temperature (1100 ~ 1650 ℃) has a high strength, easy processing than tungsten. Can be used as a gate and anode tube, electric light support material, as well as for the production of die-casting and extrusion dies, spacecraft parts. Because molybdenum alloy welding low temperature brittleness and fragility, and the high-temperature oxidation, so their development is restricted. Industrial production of molybdenum alloys, molybdenum and titanium zirconium, molybdenum, tungsten and molybdenum, rare earth alloy, used more often is the first class. Molybdenum alloy is the main way to strengthen the solid solution strengthening, precipitation strengthening and work hardening. Can be obtained through the plastic processing molybdenum alloy sheet, strip, foil, tubes, rods, wire and profiles, but also improve its strength and improve the low temperature ductility.
(Figure) molybdenum alloy head (press tool)
Molybdenum-based alloy by adding other elements. The refractory metals, molybdenum and alloys have good thermal conductivity, electrical conductivity and a low coefficient of expansion (similar glass with electron tubes), at high temperature (1100 ~ 1650 ℃) has a high strength, compared with tungsten, easy processing, and thus in the tube (grid and anode), electric light source (supporting material), metal processing tools (die casting and extrusion dies and piercing plug) manufacturing and aerospace industries in the applications. Molybdenum molten glass etching ability, it does not contaminate the glass oxides. Since 1943, molybdenum material has been used in the glass industry for heating electrodes. Mo-30W alloy has excellent anti-corrosion properties of molten zinc, has been successfully applied zinc industry. Molybdenum is also used in the manufacture of sulfuric acid in the production of heat exchangers and valves and other components.

but at present, with a protective coating to improve this performance

Industrial production can be divided Molybdenum crucible alloy Mo-Ti-Zr-based, Mo-W series and Mo-Re alloys, and hafnium carbide particles in the precipitation strengthening Mo-Hf-C based alloy. TZM alloy has excellent performance, is the most widely used molybdenum alloy. TZC (Mo-1.25 Ti-0.15 Zr-0.15C) TZM alloy has a higher temperature than the strength and the recrystallization temperature, but the processing difficulties, application is limited.
Molybdenum alloys and solder brittleness and low temperature brittleness temperature oxidation and other shortcomings, so the development is restricted. Alloying method using molybdenum alloy is difficult to improve the high temperature oxidation resistance, but at present, with a protective coating to improve this performance. Molybdenum alloys in the study of the problem is to improve the high temperature strength and the recrystallization temperature, to improve the low-temperature plastic material. Pure molybdenum material in the study of the problem is to improve the low-temperature ductility, i.e. reduce its plasticity - brittle transition temperature.
Molybdenum alloy is the main way to strengthen the solid solution strengthening, precipitation strengthening and hardening (see metal reinforced). Titanium, molybdenum, zirconium, and hafnium is the main alloying elements. Molybdenum alloying elements on the hardness of the rolling bar chart next page. Titanium, zirconium and hafnium can not only solid solution strengthening and maintaining the low-temperature plastic material, and can form a stable, dispersed carbide phase, to improve the strength and recrystallization temperature.

but to quickly appropriate

Molybdenum alloy plastic processing is not only forming means, but also can improve the strength and molybdenum alloy to improve its low temperature ductility. Molybdenum and its alloys produced by conventional plastic processing methods sheet, strip, foil, tubes, rods, wire and profiles. Molybdenum alloy materials processing is characterized by hot deformation processing operations for each channel on the performance of the final product has a significant impact. Molybdenum tube oxidized rapidly above 600 ℃, at about 725 ℃ volatile oxidation products and the liquid phase appears, so molybdenum and alloys are commonly used for heating the hydrogen or other reducing atmosphere protection. Since thin layer of molybdenum contamination, use caustic to melt, the thermal processing may be carried out under atmospheric conditions, but to quickly appropriate. Molybdenum and alloys should be cold plastic - brittle transition temperature or higher.
Molybdenum and its alloys ingots produced mainly by powder metallurgy process can also be used smelting production process. Generally small size of the blank to use more powder metallurgy process, large-sized billets both can be used. Taken processes depend on the performance requirements of the final product. Suitable powder density of the blank of the theoretical density is about 93 to 96%. Industrial molybdenum and alloys used mainly vacuum consumable arc melting and electron beam melting. Coarse grains subject extrusion ingot blooming only after processing

China's tungsten mining production

After several years of development, China's tungsten mining expanding production scale, technology development capability, market competitiveness has reached a certain level, to the needs of users at home and abroad the production of various tungsten minerals, has made great achievements. In 2006, China's tungsten industry sales income 311 million yuan, sales profit of 6.4 billion yuan, an increase of 7% over 2005. 91 major companies nationwide sales of tungsten carbide plate industry accounted for 63.0%, compared with 2005 growth of 20 percent, including mining, smelting, tungsten carbide, tungsten metal and tungsten iron enterprise sales revenue increased by 22.4%, 20.5%, 16.5 %, 11.7% and 7.4%. 2006 Chinese exports of tungsten 31,710.45 tons, only a 1.8% increase over 2005, an increase of 10.7 percentage points mitigation; exports of 1.09 billion U.S. dollars, an increase of 36.3% over 2005. Imports 7,890.9 tons, an increase of 71.5% over 2005; imports amounted to $ 202 million, an increase of 108.2% over 2005. Net export volume of 23,819.6 tons, 10.3 percent less than in 2005; net exports of $ 888 million, up 26% over 2005. 2006 exports of tungsten equivalent to one ton in 2002, 2003, 4 tons in 2004, 3 tons, 1.3 tons in 2005. First half of 2007, China's tungsten industry production and operation showing a steady and rapid development momentum. 2007 1-6 months, the national output of 40,309 tons of tungsten concentrate (equivalent WO365% volume, the same below), an increase of 18.65% over the previous year. January to June 2007, total export volume of 15,343.8 tons of tungsten metal products, compared with 2006 growth of 8% over the same period, exports 535 million U.S. dollars, an increase of 91.7%. Total imports of tungsten products (including concentrates) metal content of 3430.2 tons, and imports $ 85,335,000, respectively, over the same period in 2006, an increase of 87.5% and 121.9%. Export Carbide 1245.6 tons, a growth of 17.06 percent over the same period, exports $ 479,747,700, down 4.52%, the average export price of $ 385,153.9 / ton, down 18.4%. Chinese tungsten ore resources are monopolized, but did not get monopoly profits. The reason is that Chinese exports of tungsten product structure is irrational, excessive exports, low prices. Primary products with low added value export-oriented, is currently China Tungsten Industry Foreign Trade fatal weakness. With the development of the market, China's tungsten industry gradually complete product varieties, the market structure and the industrial layout slowly norms, tungsten products prices also rose more than two years after the basic stabilized. After 2008, industry consolidation may be accelerated, and this process also pregnant with greater investment opportunities.

Tungsten-copper composite material

1, high-performance materials for aerospace materials with high density tungsten copper, transpiration cooling performance, high temperature strength and resistance to erosion ablation performance in the aerospace industry as a missile, rocket nozzle throat insert, gas rudder assembly, air rudder, hoods and weight and so on. 2, the vacuum contact material contact material must have very good machining properties and thermal shock resistance, when breaking the contact and arcing, contact material in a few tenths of time temperatures thousands of degrees Celsius. I produced the W-Cu contact material due to its excellent physical properties and is widely used. Advantages: High ablation resistance, high toughness, good electrical conductivity, thermal conductivity. Good machining performance. 3, EDM electrode EDM carbide products in use, due to the particularity makes WC copper or graphite electrode wear quite fast, for this material EDM, the company's production of W-Cu electrodes are most suitable. Product properties: corrosion, high speed, low loss rate, the exact shape of the electrode, excellent processing performance, WC workpiece surface quality. 4, electronic packaging materials W-Cu electronic packaging materials, with both tungsten low expansion properties, but also with copper's high thermal conductivity, it is particularly valuable is that its thermal expansion coefficient and thermal conductivity can be adjusted by the material composition and be designed, thus giving the application of the material brought great convenience. We use high-quality high-purity raw materials, molding, high temperature sintering and infiltration, got excellent performance of the W-Cu electronic packaging materials and heat sink material. For materials with high-power device package, such as a substrate, a lower electrode and the like; performance of the lead frame; military and civilian thermal control device such as thermal control board and the heatsink. Advantages: a matrix that matches the type of thermal expansion coefficient and the high thermal conductivity; excellent high temperature stability and uniformity; excellent processing properties;