How to Choose Sintering Methods for Titanium-Zirconium-Molybdenum (TZM) Alloy?

The earliest produced in the industry is titanium-zirconium-molybdenum (TZM) alloy, which is a molybdenum alloy containing 0.4%-0.55% titanium, 0.06%-0.12% zirconium and 0.01%-0.04% carbon. The total amount of alloying element does not exceed 1%. 

There are two main sintering methods for titanium-zirconium-molybdenum alloy: hydrogen protection sintering and vacuum sintering as following: 

1.Hydrogen protection sintering: the product is sintered under the protection of hydrogen. 

During the process, due to the reduction effect of hydrogen, the oxides in the molybdenum powder will be replaced by hydrogen, reducing the oxygen content in the material to below tens of ug/g. For molybdenum alloys with active elements such as titanium and zirconium, due to the high activity of alloying elements, they will react with impurity gases in hydrogen to form oxides, nitrides, hydrides, etc., resulting in high impurity content in TZM alloy. It seriously affected its mechanical properties. Therefore, vacuum sintering is more popular with most factories.

In the process, generally a slight excess of carbon element (relative to the predetermined composition) is added to deoxidize the metal oxide through the reduction of carbon element. Among them, there are two main types of deoxidation mechanisms: metal oxides in the carbon reduction system produce metal carbides and CO, and MoO2 undergo disproportionation reactions under vacuum and high temperature to produce metal Mo and MoO3 gases which are extracted.

In the disproportionation reaction of metal oxides and MoO2 in the carbon reduction system, the temperature at which the two reactions start is related to the partial pressure of the product gas in the furnace. As the partial pressure of the product in the furnace decreases, the reaction start temperature gradually decreases. Therefore, increasing the vacuum degree in the furnace and reducing the partial pressure of the product gas can lower the temperature at which the deoxygenation reaction proceeds, which is beneficial to the deoxygenation.

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What Are Strengthening Mechanisms of TZM Alloy

TZM is molybdenum’s prime alloy and is an alloy of titanium, zirconium and carbon. This alloy is the most popular materials among various kinds of molybdenum metal and molybdenum alloys. 

With better high temperature resistance, greater strength, it can be used as a mold for high-temperature heat processing of metals. In addition, to be applied in the hot runner system as nuzzle tip, it can maintain the plastic melting state and helps the formation of plastic products. 

For the strengthening mechanisms of TZM alloy, the types are as following: 

1. Solid solution strengthening

The solid solution strengthening of TZM is to add Ti, Zr and other alloying elements to dissolve in the Mo matrix. Among them, the strengthening effect of Zr is the most obvious, followed by Hf. This is because the base lattice of Mo is distorted. The larger the difference in the size of the solute and solvent atoms during solid solution, the better. The effect of solid solution strengthening is relatively stable above 1000 ℃, but it is not as good as deformation strengthening, but in practice, due to the limitation of solubility, the addition amount is not very large.

2. Second phase strengthening

When the second phase is uniformly distributed in the matrix phase with fine dispersed particles, it will have a significant strengthening effect, which is called the second phase strengthening. The strengthening of the second phase in TZM is due to the addition of Ti, Zr and C in Mo to form fine carbide particles. Their existence can effectively hinder the movement of dislocations and produce the strengthening of the second phase.

3. Deformation strengthening

TZM alloy is required to be below the recrystallization temperature, and the effect of deformation strengthening increases as the amount of deformation increases. In the process of deformation, the crystal grains of the alloy elongated along the processing direction, the crystal lattice is raised, the dislocation density increases, and the grains are produced, which increases the strength of the alloy. The strength of the annealed alloy can be significantly reduced. If the alloy is nitridated while annealing, nitriding points are generated in the matrix after nitriding, and the hardness and tensile strength of the alloy can be further improved.

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What Are the Benefits of Metal Plating on Molybdenum Copper Alloy

Molybdenum is a non-ferrous metal with high melting point, high strength, high hardness, wear resistance, and good thermal and electrical conductivity, while molybdenum copper alloy (Cu-Mo alloy) is a pseudo-alloy made by copper and molybdenum that does not solidify with each other.

This alloy contains less copper, so it basically possesses most of the physical and chemical properties of molybdenum, and also has the characteristics of copper at the same time, that is, it has high electrical conductivity, high thermal conductivity, small expansion coefficient, good corrosion resistance, non-magnetic and good processing properties, etc.

Given the broad application prospects., the material is widely used in many fields such as metallurgy, machinery, petroleum, chemical industry, national defense, aerospace, electronics, nuclear industry and so on. There are mainly: vacuum contacts, conductive heat dissipation components, instrumentation components, rockets that are used at a slightly lower temperature, high-temperature components of missiles, and components in other weapons, such as range extenders. At the same time, it is also used for solid sealing, sliding friction reinforcing ribs, water-cooled electrode heads in high-temperature furnaces, and electro-machined electrodes.

In actual use, molybdenum-copper alloys are often subjected to surface modification treatments such as electroplating and coating to meet specific functional requirements on their surfaces, such as high-temperature brazing and reducing contact resistance. However, the surface of Cu-Mo alloy is very easy to oxidize, and the chemical properties of the oxide film are very stable, the surface wettability is poor, and it is very difficult to perform surface treatment. Therefore, the gold plating can greatly improve its conductivity and brazing performance. It meets the application requirements in military electronics and aerospace products.

For regular metal plating, Ni, NiAu, NiAg, or Au plating are the most common. The thickness of plating is about 3~5 microns and gold plating is about 1 micron. Sometimes, AuSn plating is required. 

Chinatungsten Online can provide customized molybdenum copper alloy with effective thermal conductivity and good high-temperature tolerance.

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Cu/Mo/Cu Heat Sink (CMC) for Radio Frequency and Lead Frames

High power electronics and circuits generate a lot of heat during operation. The heat sink materials help to eliminate the heat of the chip, transfer it to other media, and maintain the stable operation of the chip.

Tungsten-copper and molybdenum-copper alloy are the most common heat sink materials, which are a kind of heat sink substrate commonly used for high airtight packaging such as CPU, IC, solid microwave tube. This material has a thermal expansion coefficient and high thermal conductivity that match different substrates; excellent high temperature stability and uniformity; excellent processing performance.

Cu/Mo/Cu heat sink (CMC) is a composite material with a similar sandwich structure, the core material is molybdenum, and both sides are covered with copper. The basic concept of the design is to use the high thermal conductivity of copper and the low thermal expansion characteristics of molybdenum. By adjusting the thickness ratio of copper, molybdenum and copper, it can achieve a thermal expansion coefficient matching ceramic materials and semiconductor materials, and a higher thermal conductivity. The expansion coefficient and thermal conductivity are designable. 

At present, the CMC products are mainly used in radio frequency, microwave and semiconductor high-power devices, heat sinks, lead frames, low-expansion layers and heat conduction channels of multilayer printed circuit boards (PCBs).

As the thermal conductivity of molybdenum is unsatisfactory, so people strive to improve it. In order to improve its thermal conductivity and heat dissipation performance, it is usually used to increase the copper content. However, the increase in copper content can improve the thermal conductivity, but as another performance requirement, the linear expansion coefficient CTE is required to match the chip as much as possible. However, excessively increasing the copper content will result in a mismatch between the linear expansion coefficient and the chip. The long-term thermal expansion and contraction process will easily cause the chip to be damaged and invalid due to inconsistent thermal expansion. 

The ideal heat sink material should have a linear expansion coefficient CTE, which is basically matched with the chip, and has the highest possible thermal conductivity, especially the Z-direction (thickness) thermal conductivity, so that the heat of the packaged chip and other electronic devices can be quickly discharged. In order to increase its power density, achieve high power, reduce the volume and realize the miniaturization of the device. CMC material is now the one of the materials to meet above requirements.  

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What Do You Know About the Disadvantages of TZM Plate or Sheet?

TZM alloy is an attractive molybdenum-based alloy (0.4-0.54% Ti, 0.06-0.12 %Zr, 0.01-0.04% C, balance Mo) utilized in industries with high strength, high temperature and vacuum requirements, including aerospace, electronics and heat treatment. TZM alloy plate can perfectly server these areas when the working temperature ranges from 700 ℃ to 1400 ℃。

Compared with pure molybdenum plate, TZM plate has a more stable crystal structure and a higher recrystallization temperature. This is due to the small amount of zirconium and titanium doped in the molybdenum substrate. In addition, the extremely fine-sized composite carbides Mo2C, TiC and ZrC refine and suppress the molybdenum grains, so that alloy plate has better weldability and creep resistance than the pure molybdenum plate.

However, there are still many disadvantages for this material. 

1. Oxidation. Although the material can be used in the temperature above 2000℃,the premise is that its working environment is vacuumed or under the protection of nitrogen, cracked ammonia or other atmosphere. Molybdenum alloy plates will start to oxide at about 400 ℃ and become to fast at about 700 ℃. If they work at above 2000 ℃, they will oxide immediately. 

2, Welding. Molybdenum or tungsten products can be welded, but require certain equipment and technology. Normally, the technology includes cooling welding and vacuum welding with pointed welding wire. Silver, stainless steel or structural alloy steel can not be the material of wire. It must be with very high melting point and strength, such as TZM. 

3, Form. The form of TZM alloy products is limited as they can not be bent even with small angles. If a product requires to be bent into certain shapes, it should be through riveting or welding together two parts. 

Apart with plates, TZM mill products available from either process include forging billets, bar, rod, sheet and foil. All forms in basically the same size range as pure molybdenum with the exception of thin foil. 

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Advantages of Heat Sinks and Semiconductor Base Plates Made from Molybdenum Copper Alloy

Thermal management and packaging components, such as heat spreaders and semiconductor base plates, are used to regulate the temperature of electronic systems and help to control operating temperatures of high-power semiconductor devices. Effective thermal management components use cost-effective, composite materials that possess high thermal conductivity and low thermal expansion.

Molybdenum copper high performance composites are fabricated from carefully controlled molybdenum that is vacuum infiltrated with molten copper. This results in a MoCu composite that has high conductivity and a matched low thermal expansion for heat sinks.

Molybdenum copper composites to be used extensively in thermal mounting plates, chip carriers, flanges, and frames for high-powered electronic devices. With the thermal advantages of copper with the very low expansion characteristics of molybdenum, molybdenum copper has properties similar to those of silicone carbide, aluminum oxide, and beryllium oxide. The thermal conductivity and low expansion also make molybdenum copper alloy an excellent choice even for extremely dense circuits.

It is a composite of molybdenum and copper. By controlling the content of molybdenum, we can design its coefficient of thermal expansion (CTE), matching that of the materials, such as Ceramics (Al2O3, BeO), Semiconductors (Si), Kovar, etc.

The advantages of heat sinks provided by Chinatungsten, heat spreaders, semiconductor base plates, and substrates lie in the thermal material properties. Their controlled CTE (coefficient of thermal expansion) perfectly matches with semiconductor and ceramic packaging materials. When used in combination with high TC (thermal conductivity), thermal management and packaging components remove heat rapidly from high powered electronic devices.

The CTE of our materials is adjustable whilst also maintaining high thermal conductivity, which makes our engineered thermal materials ideal for high-reliability electronics that generate considerable amounts of heat.

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Molybdenum Pin for Sapphire Growth Furnace and Electric Light Source Parts

How do you describe molybdenum pin? 

Molybdenum rods are rods with a diameter larger than 0.020 inch, according to standards such as ASTM B387 and ASTM F289, while in China, they feature straight lines and diameters above 0.4mm. Some rods can be able to be machined into pins, but not all rods can be called pins. For straight molybdenum wires with diameters above 0.05mm and are cut into certain lengths, they are also called pins or needles. 

Molybdenum pins are made of pure molybdenum material with good performance at high temperature because of high melting point, high strength, high hardness, low resistivity, small expansion coefficient and corrosion resistance. As the material is easy to oxide when the temperature is higher than 400 ℃, the product should be stored in a dry, ventilated, acid-alkali-free atmosphere to prevent oxidation. If they are kept in store for a very long time, its package should be in vacuum.  

In addition to the straight moly pins, one of their ends can be machined into tips with specific dimensions with tolerance. which type to be chosen depends on the applications of users. In that case, drawings should be provided for evaluation. 

Thanks to the advantages of the material, moly pins now are widely used as vacuum devices, high-temperature furnace heating devices, sapphire growth furnace, vacuum furnace, rare earth smelting furnace, glass smelting furnace, quartz smelting furnace, and electric light source parts, etc., and their applications in lighting, new energy, metallurgy, machinery, electronics, military industry and other fields have been rapidly expanded.

Molybdenum pins are generally immediately available in most volumes, including bulk quantities. Chinatungsten Online can produce materials to custom specifications by request, in addition to custom compositions for commercial and research applications and new proprietary technologies. Kindly feel free to contact us if you have got the inquiry. 

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Molybdenum Disulfide Is Used in Machinery Equipment as Lubricants

When machinery equipment is in motion, friction and wear are almost inevitable on the surfaces between relatively moving parts. The use of lubricants is an effective technical measure to control friction, reduce wear, and maintain the original accuracy of machinery and equipment.

Reasonable selection of lubricating materials can control the friction of the two moving surfaces, slow down the wear and protect them from damage. The surface film formed by the solid lubricant of molybdenum disulfide (MoS2) has this function. 

MoS2 is the main component of molybdenite, which is a black solid powder with metallic luster. It is a very important solid lubricant, especially suitable for high temperature and high pressure. The powder has the advantages of good dispersibility and non-sticking. It can be added to various greases to form a non-sticky colloidal state, which can increase the lubricity and extreme pressure of the grease. It is also suitable for high-temperature, high-pressure, high-speed and high-load mechanical working conditions to extend the life of the equipment.

Place the solid lubrication on the surfaces of the two friction pairs of machinery equipment, and rely on the mechanical action between their friction surfaces to form a layer of molybdenum disulfide surface film with a high degree of adhesion attached to the solid surface, which can reduce or eliminate the direct contact between the two surfaces, reduce the friction and wear of the moving pair surface in the mechanical equipment, and extend the service life of the equipment.

The special MoS2 for coatings provided by Chinatungsten Online has a finer particle size, reaching sub-micron level, more uniform distribution, more concentrated particle size, and has good dispersibility and surface activity, which is suitable for uniform coverage on the surface of the grinding wheel.

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Molybdenum Alloy Piercing Plug Is Used for Piercing Seamless Steel Tubes

Molybdenum alloy piercing plug is produced by high-quality molybdenum powder mixing with titanium, zirconium and carbon powders, and processed by mixing, forming, sintering, and machining. The density of finished products is ≥9.4g/cm3. 

As molybdenum metal has many characteristics, such as high temperature resistance, oxidation resistance, high hardness, it is usually used to be the raw material for piercing plug to be used for piercing seamless steel tubes, such as stainless steel, brazing steel, high temperature alloy steel, molybdenum and other special parts.

The plug is actually a vulnerable part in the steel industry. With the increasing scarcity of molybdenum resources and the continuous rise of molybdenum prices, improving its service life and the comprehensive yield in the production process are the main subject of researchers. Fortunately, after 40 years of development, China has made many revisions and optimizations in terms of raw material formula, production technology and cost control. 

Initially, the plus is made of pure molybdenum powder, but its service life is short and people has to make further research. After adding some rare earth elements, the plug can obtain longer service life. The elements include Ti, Zr, C and so on. 

The addition of titanium powder can activate the surface of the molybdenum particles during the sintering process, and can improve the alloying degree and uniformity of finished plug during the sintering process. The effect of adding zirconium powder is similar to that of titanium powder, and the activity strengthening effect of zirconium is greater than that of titanium.

The addition of carbon is very important. Most of carbon forms hydrocarbons with hydrogen in the hydride during the sintering process, and removes the hydrogen in the hydride to the limit, so as to achieve the effect of activation and combustion. Meanwhile, it can interact with titanium and zirconium at high temperatures. Forming two-phase refractory metal carbides TC and ZC can strengthen molybdenum. 

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Molybdenum Crucible for Sapphire Growth Furnaces Improves Quality of Sapphire

Crystal growth is the basis of many cutting edge technologies, such as sapphire touch screens, LED lighting components, solar cells, and high-power lasers. Only when the manufacturing and material processes are continuously improved, from raw materials to finished products, the changing requirements of the industry can only be met.

Corrosion resistance, creep resistance and high temperature performance make molybdenum made crucibles very suitable for high temperature crystal growth processes. When sapphire is easy to extract, higher sapphire yield and quality can be achieved. The molybdenum-based crucible has heat resistance and a smooth surface, making it durable and cost-effective.

The surface roughness of the molybdenum crucible needs to be higher than 1.6 µm. When the surface of the crucible is rough, the sapphire is not easy to take out and it is easy to damage the crystal. In addition, the crucible will be damaged in the process. Chinatungsten Online's ultra-smooth crucible eliminates these problems. Sapphire manufacturers can benefit from this product because it eliminates complex and expensive processes. In addition, the smooth surface is resistant to corrosion caused by aggressively molten sapphire. This function can extend the service life of reusable crucibles.

Molybdenum crucibles for sapphire growth furnaces are available with a variety of dimensions including round, in numerous standard diameters and wall thicknesses. Custom configurations are available. In addition, many other components for these furnaces are also customized. 

Molybdenum crucibles are in great demand. The reason for this demand is that the development of molybdenum is very complex and involves comprehensive knowledge of handling materials and setting up machines. Chinatungste’s integrated manufacturing process, quality system and metallurgical expertise ensure that we provide high-quality components for the crystal growth industry. if you have got any purchasing plan for them, please feel free to contact us. 

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How to Improve the Quality of Molybdenum Plate in the Rolling Process

Molybdenum plate is made from pure molybdenum material with excellent mechanical and physical properties such as high temperature resistance, good thermal and electrical conductivity, and low thermal expansion coefficient. Nowadays, it is widely used in the construction of furnace tooling and parts and as a feedstock for the fabrication of parts for the electronics and semiconductor industries.

To ensure good quality, the manufacturing process is important, especially the rolling process. Starting from the plate blank, and going through the steps of forging-cogging, hot rolling, warm rolling, cold rolling, annealing, and surface cleaning, etc., until the required size is obtained. Compared with vacuum smelting billets, powder metallurgy sintered billets have advantages of few procedures, good mixing, less impurities and qualitied slab, etc.

In the rolling process, the rolled piece undergoes plastic deformation under the action of the rolling force, resulting in work hardening. In the subsequent hot rolling and warm rolling, usually one heating is accompanied by multiple passes, so that the two opposite processes of hardening and softening of recovery and recrystallization exist at the same time, that is, dynamic recovery and dynamic recrystallization occur. 

The recovery and recrystallization that occur in the annealing, holding process and subsequent cooling after the deformation is interrupted or terminated are static recovery and static recrystallization, which are mainly reflected in the cold rolling stage. For rolled products or as raw materials for subsequent drawing, stamping and other processes, the process parameters in the rolling determine the quality, performance and application of the plate itself.

After rolling with a deformation of more than 60%, the density of the molybdenum plate is basically close to the theoretical density of molybdenum, which enables it to be widely used in many fields. After cleaning, the plate’s surface will become silver-gray metallic luster. The finished product has a flat, smooth surface, no heavy skin.

Chinatungsten Online is one of the leading molybdenum plate/sheet suppliers with more than twenty years’ experience. Please contact us if you have got any purchasing plan. 

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How to Extend the Service Life of Molybdenum Wires

Molybdenum wires are pressed and sintered from our high purity molybdenum powders to compact ingots by powder metallurgy and then drawing. As a leading molybdenum manufacturer, we are capable of providing wires with a range of diameter from 20 microns to 2mm. 

Many end-users would require a good quality of products. How to extend the service life of these wires? Here are some tips: 

1.Installation 

Wires made of molybdenum are easily deformed and broken. Therefore, they can not be bended during installation. If bended, cut it off to avoid wire breakage during operation. The cutting fluid should also be replaced in time during use because it will turn black after a long time of use, which will directly affect the performance of products.

2.Operation 

When the wire is discharged during operation, it will also be damaged. However, due to the good mechanical properties of molybdenum, the damage is small. Therefore, it would be better to using low-energy processing parameters to reduce the damage. After running for a period of time when the color of wire becomes write, workpieces can be cut with normal high current. In addition, after replacing the wire, running new wire for 5-10 minutes before cutting the workpiece, so that the internal stress of the molybdenum wires can be released. 

When the moly wire breaks during the operation of the cutting machine, most of the broken ends are within a dozen to dozens of turns after the reversing of the wire barrel. It can be seen that the metal wire at both ends of the head and tail is easier to be broken. Therefore, in the cutting process, the wire barrel is reversed to form a switch control block and move a little outward or inward at regular intervals.

3. Maintenance

Routine maintenance of molybdenum wire can also improve the service life, such as: daily storage, placement and time. It should be stored in a ventilated and cool place with low humidity, and the temperature is 20℃~25℃ to avoid oxidation. In addition, it should not be placed for more than 6 months. While using it, check whether the packaging is damaged or deformed.

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Types of Silicon Carbide Heating Elements for Producing Lithium Ion Battery Components

Silicon carbide (SiC) heating elements are non-metal high temperature heating element made from high-quality green silicon carbide. Compared with metal electric heating elements, this element has the advantages of high temperature, oxidation resistance, corrosion resistance, long life, and convenient installation and maintenance. 

The operating temperature of the silicon carbide heating elements can go up to 1550°C in an oxidizing atmosphere, or inert gas atmospheres of argon or helium. in a reducing atmosphere, the maximum obtainable operating temperature is 1350°C. Nowadays, they are widely used in various high-temperature electric furnaces and electric heating equipment in magnetic materials, powder metallurgy, lithium ion battery components, ceramics, glass, metallurgy and machinery industries.

Our silicon carbide electric heating elements adopt a new production process for the availability of an excellent heat and cold resistance ratio, energy saving and long life. Meanwhile, they can avoid the damage to the furnace body caused by the excessive temperature of the cold zone. Chinatungsten Online manufactures the following types of SiC heaters. 

1.Equal-diameter Silicon Carbide Rod

It has the advantages of low resistance, long service life, and energy saving, which is commonly used in rare earth phosphors, electronics, magnetic materials, powder metallurgy, precision casting and other industries, as heating elements for pusher furnaces, mesh belt furnaces, trolley furnaces, and box furnaces.

2. Thick-end SiC Rod

It is an electric heating element composed of a hollow tubular heating part and a thickened end. Meanwhile, it is hard and brittle, resistant to rapid cold and heat, and will not deform under high temperature. Mostly used in test furnaces. 

3. U-Shaped Alpha Silicon Carbide Rods

The rod is composed of two equal diameter silicon carbide rods sharing a cold end, and can be connected to the power cord at one end of the kiln. Its surface can be used in the temperature of about 1500 ℃. Given that, it is mostly applied in kilns with high furnace temperature and high furnace temperature uniformity requirements.

4. Gun-shaped SiC Rod

This shape of element is improved from the U-shaped rod by extending 40mm to 60mm length at the U-shaped end to support the rod body. It is matched with double heating element rod to be used in the glass bottle industry to produce soda-lime flat glass. 

5. W-shaped Silicon Carbide Rod

The special rod is composed of a common silicon carbide rod connected to one end of three high-purity silicon carbide rods. The joint is also made of the same material, and the structure of the rod is exactly the same so that it can be used for horizontal installation in a float glass cell. Besides that, it can be directly connected to the three-phase power supply and the furnace top can be connected in one direction.

6. H-shaped Silicon Carbide Heating Elements

This heating element is commonly used for heating and heat preservation of forehearths and pot sections in the glass industry. As a non-linear resistor, its resistor has a large dispersion at room temperature.

7. Reaction Bonded Single Spiraled Heating Elements

Single spiraled element is an electronic component specially processed by precise calculation and design on the basis of equal diameter SiC rod. Its using temperature can reach 1500 ℃, used for heating of kilns with special needs. Its characteristics are: more power saving, simple operation, high temperature and long life.

8. Reaction Bonded Double Spiraled Heating Elements

The double spiraled element is an electronic component specially processed by precise calculation and design on the basis of the U-shaped heater. It is designed to meet the small space in the furnace and the normal U-shaped rod cannot be installed in the electric furnace. It is mainly used for the heating of kilns with special needs. Its characteristics are: power saving, simple operation, high temperature and long life. 

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Why Should We Do a Protective Coating for Molybdenum-copper Alloy (MoCu alloy)?

Molybdenum-copper alloy (MoCu alloy) is a pseudo-alloy composed of two insoluble metals molybdenum and copper. As a result, it gains characteristics both of these two metals, such as high thermal conductivity, low thermal expansion coefficient, non-magnetic, low gas content, good machining performance and special high temperature performance.

What is the protective coating?

In order to improve the high temperature resistance and welding performance of finished products, there can be a layer of coating on the surface, usually nickel or gold. Displacement plating, chemical roughening, chemical nickel plating, or cyanide gold plating are the most common used methods. 

We use scanning electron microscope and EDS to analyze its morphology and composition of the coating, and test welding and high temperature resistance by gold-tin welding according to GJB1941-94. The results show that the displacement plating method achieves the uniformity of the chemical properties of element Mo and element Cu at the interface of the Mo-Cu alloy substrate, and avoids the problem of excessive internal stress in the deposited crystal due to different chemical activities; chemical roughening increases the specific surface area at the interface of the substrate, increases the number of "mechanical bites" at the interface of the coating and the substrate, and improves the bonding strength of the coating and the substrate.

The high temperature resistance of the gold plating layer obtained on the surface of the MoCu substrate is ≥350℃, and the void ratio after welding is ≤30%, which meets the requirements of welding technical indicators. 

Molybdenum-copper alloy has high thermal conductivity, up to about 200W/m·K, and has the advantages of small thermal expansion coefficient and easy machining. It is used in spacecraft phased array antenna T/R module bottom plate and high-power microwave shell and power device carriers and other fields that have good application prospects. However, its surface wettability is poor and cannot meet the soldering functional requirements of solders such as PbSnAg, SnAgCu and AuSn.

In order to improve the weldability, it is necessary to coat a gold plating layer with excellent welding performance on the surface. however, as the surface composition of the molybdenum-copper alloy is composed of two metal elements with relatively different chemical properties, and the content of chemically inert Mo element is as high as 85%, it is difficult to coat the gold coating on the surface.

In aerospace products, the solders used in the early days were mainly low melting point solders such as PbSnAg and InSn. The peak temperature during the soldering process was all below 230°C, so the high temperature resistance of the gold coating is relatively low. With the development of T/R module housing and chip packaging technologies, high melting point solders represented by AnSn have been widely used. The peak soldering temperature is as high as 300℃. 

During the high-temperature soldering process, the gold plating layer and the molybdenum copper alloy substrate will expand due to thermal expansion. The thermal stress caused by the coefficient mismatch increases, resulting in quality problems such as skinning and blistering of the gold coating. Therefore, in order to meet the welding requirements of spacecraft stand-alone load products, higher requirements are put forward for the preparation and high temperature resistance of the gold coating on the surface of the MoCu alloy.

There are many grades for moly copper alloy, such as Mo85Cu15, Mo80Cu20, Mo70Cu30, Mo60Cu40, Mo50Cu50, Mo40Cu60. Different grades match different densities, thermal conductivities and coefficients of thermal expansion. Other customized grades also can be customized.

Chinatungsten is a professional manufacturer of molybdenum for more than two decades, if you have got any purchasing plan for related products, please feel free to contact us, we will offer you our most favorable prices and qualitied products. 

If you have any inquiry of MoCu plates, please feel free to contact us:

Email: sales@chinatungsten.com/sales@xiamentungsten.com

Tel.: +86 592 5129696/+86 592 5129595

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How to Avoid TZM Rods from Splitting During Processing Nuzzle Tips for Hot Runner System?

Pure molybdenum has very high melting point, which makes it useable in most high temperature applications. However, with the development of molybdenum alloy, titanium-zirconium-molybdenum (TZM) alloy has become a good all-round candidate no matter in vacuum furnace industry, medical diagnostic equipment industry or other industries. 

Although TZM alloy products are expensive than pure molybdenum, in certain applications the additional cost is offset by its increased strength at elevated temperatures. 

People add trace elements such as titanium and zirconium to molybdenum to remove the grain boundary embrittlement phase through solid solution strengthening of trace elements, and its reactant acts as a dispersed phase to strengthen the alloy to improve its performance. 

The suggested applied temperature is between 700 and 1400 degrees Celsius. Like pure molybdenum, it starts to oxide at 400 degrees Celsius, and rapidly oxides at above 500 degrees Celsius. However, at operating temperatures exceeding the recrystallization temperature of pure molybdenum (900 to 1,100 degrees Celsius), TZM is much stronger. And in load-bearing applications exceeding 1300 degrees Celsius, TZM is twice as strong as pure molybdenum.

In the vacuum furnace industry, TZM is the material of choice for load-bearing hearths and horizontal posts; in the medical diagnostic equipment industry, it is used as the material of choice in rotating anodes in X-ray tubes; in hot runner system, it can be machined into nuzzle tips and keep plastic in melt status. 

However, when applied in hot runner systems, TZM rods will be machined into nuzzle tips, and during this process, some problems may occur, such as split, cracking, unmachinable, tools easy to be damaged, or debris easy to stick on tools. 

Reasons for these problems are complex, for example, when tools are easy to be damaged during processing, it probably shows signs that TZM rods has high hardness. However, it cannot be assured it is the problem of hardness, the selected tools may also cause this problem. If you require lower hardness, debris are easy to stick on the surface of tool. Therefore, there should be a comprehensive solution for these problems. 

Chinatungsten is a professional manufacturer of molybdenum. Our knowledgeable and experienced refractory metal sales engineers are standing by to help you select the best metal for your application and solve whatever problems you meet. 

If you have any inquiry of TZM rods, please feel free to contact us:
Email: sales@chinatungsten.com/sales@xiamentungsten.com
Tel.: +86 592 5129696/+86 592 5129595

Fax: +86 592 5129797

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How to Select Tin Oxide Electrodes or Molybdenum Electrodes Based on the Glass to Be Produced

There are many kinds of glass melts with different melting temperature and raw material components, which have different requirements for the electrode during melting. Therefore, special materials of electrode will be customized for this process. 

The melting point of most glass lies around 1,400~1600℃, depending on its composition. As a result, glass production requires a great deal of heat energy. Regenerative glass furnaces, recuperative glass furnaces, oxygen-fuelled glass furnaces as well as all-electric glass furnaces are the most popular furnaces. Usually, electrodes made of molybdenum metal and tin oxide are enough for these furnaces. 

Tin oxide electrodes can be used to melt almost all different glass at temperatures below 1450°C. Due to the demand for special glass production, they can also be used in glass melting furnaces above 1650°C. While molybdenum electrodes are commonly used for melting soda-lime glass and high borosilicate glass, with a higher applying temperature and surface current intensity. Their operating temperatures can be as high as 2000 ℃.

Molybdenum electrode is made of pure molybdenum material. Its surface temperature is generally higher than the temperature of the molten glass by 200°C in the glass furnace. If the surface temperature reaches 2000℃, the loss of the electrode is also greater. Generally speaking, surface temperature is related to the current density. The greater the surface current density, the faster the loss. The most suitable surface current density should be 1.0～0.7A/cm2. When the furnace requires higher glass quality and longer serving life, lower surface current density should be required. The maximum surface current density of the electrode should not be greater than 2A/cm2. Usually, the consumption of electrode is relatively small in glass or E glass with higher iron content.

Tin oxide is a high-quality refractory material and is non-conductive. Various conductive additives are added to the tin oxide powder to become a tin oxide electrode after sintering, which has good conductivity after the temperature is higher than 1000 ℃. Tin oxide electrodes are generally recommended to be used in glass furnaces at a temperature not higher than 1450 ℃. When the rare earth glass is melted higher than 1650℃, it can still maintain very good performance, but the service life will be shortened accordingly.

The correct use of molybdenum electrode and tin oxide electrode is critical to furnace design and manufacturing engineers. The value of the electrode is often only 10% to 15% of the value of the furnace, but for glass furnaces of different glasses and designs, the correct application of the electrode is the decisive factor for the success of the furnace.

If you have any inquiry of molybdenum electrodes, please feel free to contact us:
Email: sales@chinatungsten.com/sales@xiamentungsten.com
Tel.: +86 592 5129696/+86 592 5129595

Fax: +86 592 5129797

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