2018年2月23日星期五

TZM Alloy Manufacturing - Raw Materials Preparation

In TZM alloy manufacturing, to prepare high quality raw materials has great significance for obtaining high-strength sintered alloy blank. Fine powder particles can reduce the sintering temperature, but also easy reunion, is not conducive to mix powder. At the same time, the powder impurities as low as possible, which can improve the density and strength of the alloy, to ensure that composition of the alloy is not out of control. Thus, molybdenum powder particle size is about 2.0 ~ 3.5um and purity is 99.95%, which is most conducive to producing high strength TZM alloy.

TZM alloy plate picture

Heating TiH2 and ZrH2 powder, Ti and Zr will break down form TiH2 and ZrH2 and add to Mo powder. Some Ti, Zr will react with matrix to form solid solution strengthening. Another Ti, Zr, will react with O, C to form carbide which is second phase and to produce second phase strengthening. Ti, Zr added by chemical reaction, so the size of Ti and Zr has reached the atomic or molecular level. The minimum fee's size of TiH2, ZrH2 can be purchased on the market is smaller than 10um and purity is about 96%.

During mixing powder, the lanthanum nitrate solution and stearic acid solution was added into mixed powder, instead of La2O3 and graphite powder, because solution can make powder mixed evenly. On the other hand, lanthanum nitrate can produce La2O3 during the sintering process, and stearic (C18H36O2) acid can be decomposed into C elements. These elements are produced by reaction, so that more uniform mixed in powder and finer, which is conducive to form solid solution strengthening and second phase strengthening. Further, stearic acid can act as a lubricant and release agent during pressing.

During mixing, using ethanol as a solid - liquid mixed media, can prevent and reduce powder oxidation. What’s more, stearic acid is insoluble in water, but it is soluble in alcohol.

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TZM Alloy Boat

TZM alloy has many good properties, such as high temperature resistance, high strength, high melting point, high elastic modulus, low linear expansion coefficient, good corrosion resistance and good thermal conductivity, so it is widely used in various fields. TZM alloy is also often prepared to a boat for molybdenum powder production. As we knew, molybdenum powder should produce at high temperature environment, which is at least 1000 ℃. The boat used for containing molybdenum powder should have good high temperature resistance, not easily deformed, and at high temperature there is not oxidation reaction to produce impurities.

TZM alloy boat picture

TZM alloy not only meet the above requirements, and using TZM alloy to make bout for molybdenum powder production can improvement the strength of powder, and also does not increase the impurity content of molybdenum powder. Titanium zirconium molybdenum alloy is made in a boat usually using a combination method, which is to mix stamping method with welding method. TZM alloy boat production processes are as following:

1. To obtain TZM alloy plates by vacuum furnace melting method or a powder metallurgy method.  The alloy boat molding temperature is about 600 ℃ and heating type is isothermal heating.
2. Select the GTAW welding process to weld TZM alloy. When the welding current at 210A, welding speed is 4mm/s and the argon gas flow rate is 8-12L / min, the weld of TZM is the best;

3. TZM alloy will oxidation at high temperatures, so during process, should do some oxidation resistance treatment. At 0 ~ 400 ℃, the oxidation rate of the alloy is slow and the surface will generate volatile MoO2. At 400 ~ 750 ℃, the alloy is rapidly oxidized and the surface will generate volatile MoO3. At 800-1000 ℃, alloy quality significantly fewer, because MnO3 is  evaporation.

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2018年2月11日星期日

TZM Alloy Mechanical Property Influence Factors

There are many influence factors affecting TZM alloy's mechanical property, including production method, deformation processing, annealing temperature and neutron radiation treatment.

Using different production method to produce TZM alloy the mechanical property of alloy is vary. Using arc melting method and powder metallurgy method to produce TZM alloy the high temperature property and mechanical property has great improved, which is better than pure molybdenum’s. When the temperature is lower than 1000 ℃, the performance of the two methods obtained TZM sheet is considerably, but using arc melting method obtained TZM bars strength is better than powder metallurgy obtained. When the temperature is higher than 1200 ℃, powder metallurgy method produced TZM plates and bars performance is equivalent, but they poorer than using arc melting method produced.

TZM alloy picture

TZM alloy after hot-forging and extrusion process, the elongation at room temperature up to 33%. Compared with the un-deformation TZM alloy the elongation has been greatly improved, indicating that proper treatment can improve the plastic deformation of the alloy. In addition, the annealing process can also affect the mechanical property and structure of the alloy. As the annealing temperature increase, TZM alloy’s hardness and tensile strength decreased, plastic increased. TZM alloy after neutron irradiation, strength and hardness significantly increased, while the elongation decreased sharply, but fracture toughness decreases to a lesser extent.

In addition, the strain rate has a greater influence on the TZM alloy’s mechanical property. At 400 ℃, the tensile strength of the alloy substantially does not vary with strain rate changes. At room temperature and 1000 ℃, the strength of the alloy with the change of strain rate were increased 30% and 20% separately. At 1200 ℃, the strain rate increases, the intensity of TZM alloy is increased 80%. At 1400 ℃, the strength of the alloy increased from 20MPa to 135MPa. It is shows that when the temperature is below 1000 ℃, strain rate has little effect on the alloy ‘s strength. When the temperature is higher than 1200 ℃, with temperature increasing, strain rate influence on the strength is more obvious.

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2018年2月9日星期五

TZM Alloy Deoxidation Mechanism Analysis during Vacuum Sintering

The experiment found that TZM alloy during powder metallurgy sintering process mainly has two kinds of deoxidation mechanism: the first one, metal oxide of carbon reduction system to form metal carbides and CO; the second one, MoO2 happening disproportionation reaction at vacuum high temperature to form metal Mo and MoO3 gas, where the MoO3 gas will be discharged by vacuum system.

Firstly, analysis the influence of carbon content on TZM alloy deoxidation during vacuum sintering. Experiment arrangement as follows: adding 0.5% TiHx and 0.09% ZrHx into molybdenum powder, and then dividing the sample into three parts, in the sample were added 0.04%, 0.07%, 0.10% different proportions of carbon, and finally made TZM alloy rods. Tested oxygen content and the carbon content of TZM alloy bar found C element content and TZM alloy deoxidation effect is proportional to, but excess carbon can cause alloy component failure.

molybdenum alloy picture

In addition, the oxygenium of molybdenum mixed powder mainly decisions by oxygen content of molybdenum powder. Molybdenum powder after the reduction reaction, the mainly existing way of oxygen is molybdenum oxide, which the most stable is MoO3 and MoO2, and MoO3 in a vacuum and high temperature will volatilize into a gas, so at high temperature molybdenum oxide mainly exists by MoO2 form. The experiment found that in the case of high temperatures and the absence of air, MoO2 happen disproportionation reaction to produce metal Mo and gaseous MoO3, and gaseous MoO3 will be discharged by vacuum system.

TZM alloy deoxygenation process mainly achieved by carbon reaction and disproportionation reaction of MoO2 which occurs in high-temperature vacuum sintering process. The reaction temperature and air pressure of product in vacuum furnace will have great impact on the quality of these two reactions. Reducing the partial pressure of product and improving vacuum degree can reduce the deoxygenation reaction temperature of the beginning which is good for reducing oxygen content of TZM alloy.

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2018年2月4日星期日

TZM Alloy TIG Welding

TZM alloy because of its good high-temperature properties are widely used in high temperature mold industry, aerospace, industrial machinery and other industries. TZM alloy as a structural material used in these areas typically require the desired shape and configuration which can achieved by welding skills. The experiment found that, in order to prevent TZM oxidation or inhaled nitrogen and other impurities in the welding process, a better method is TIG welding. Using TIG welding, it can make TZM alloy during welding process protect by inert gas (argon) to cut off the air and to prevent oxidation or nitrogen elements intrusion. The experiment found that the optimum welding parameters are as follows: welding speed 4mm / s; argon gas flow: 10L / min; welding current: 210A.

TZM alloy after TIG welding to do seam X-ray inspection found that when the welding current is 210A, the weld is flat and there is no holes and cracks on TZM surface, smooth appearance on the alloy. Observing the microstructure of welded joint found, the weld zone has coarse grains and there are some small holes, but weld microstructure is dense and no cracks. On the other hand, TZM alloy coarse grained zone and the transition zone affected by the heat of the welding process to virtually eliminate the original structure and to formed a relatively coarse equiaxed crystalline, while the original base material still maintaining crystalline sheet organizational structure.

TZM TIG welding photo

Observing its tensile strength found that the average tensile strength of welding is significantly less than the original base material. The increase of the elongation of the alloy is due to the thermal effect of the welding process to eliminate the portion of fiber texture which is formed by rolling, so that the edge of the weld is "softening." Observing the tensile fracture of TZM alloy after welding found the welding coarse grained area is not lamellar crystals, but still showing intergranular brittle fracture morphology. Coarse equiaxed grain replaced lamellar crystals, thus the weak strength of the material, but at some certain extent, improving the plastic of material can basically meet the requirements of ordinary structural.

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2018年2月1日星期四

Ferro Molybdenum Price in China - Feb. 02, 2018

Trading in the international molybdenum market is thin owing to the weak demand and the price of ferro molybdenum and molybdenum oxide rises slightly. In China, the whole market is quiet and price maintains weak adjustment.

For molybdenum concentrate, with the coming of Chinese Spring Festival, miners not only reduce the production, but also are reluctant to sell, which support the high price of raw materials. Most miners are mainly producing according to previous orders.

The price and quantity of steel biddings fail to meet the market expectations, and thus ferro molybdenum price shows signs of decline. Steel mills’ plans for stocking up are almost completed, so manufacturers remain low willingness in purchasing, the market trading tends to be quiet.

Supported by high raw material price, molybdenum chemical and manufacturing enterprises raise product quotations and have not any plan to sell. Terminal customers are hard to buy low-price products, so the enquiry becomes less.

Prices of molybdenum products on Feb. 02, 2018

ferro molybdenum price picture

Picture of ferro molybdenum
ferro molybdenum picture
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2018年1月24日星期三

Titanium Zirconium Molybdenum Cube

Titanium zirconium molybdenum cube is kind of hard and tough metal which has silver-grey or gray gloss surface. TZM cubes have lots of advantages such as high strength, high toughness, high temperature resistance and corrosion resistance which are widely used as semiconductor components, holder, lead frame and high temperature furnace exothermic material and so on. On the other hand, at present, TZM cube and molybdenum rod are usually used for trim the grinding wheel which are the best raw materials for trim the grinding wheel.

titanium zirconium molybdenum cube picture

Although, TZM cube and molybdenum rod are all can trim the grinding wheel, but the cubes are more suit for trim large grinding wheel which usually called the millwrights. And molybdenum rods are more suit for small grinding wheel. Because using TZM cube to trim can get better result than using other material, what’s more, the high quality and efficiency of TZM cube can improve the production efficiency and quality.

Chinatungsten Online not only produce TZM cube with various size, we also produce molybdenum cube, TZM sheet, TZM plate, TZM tube and other related products. There are Impurity element content table.

impurity element content table

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