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GH3600(ASTM/ASME UNS N06600) is a high temperature and oxidation resistant nickel based alloy. It is widely used in petrochemical processing, nuclear power and aerospace industry. Aerospace GH3600 alloy tubes are mainly used for hydrogen and oxygen rocket engines of upper stage power devices of carrier rockets. At present, the United States is planning on the basis of hydrogen and oxygen rocket engine’s orbit transfer vehicle and single stage to orbit of the space shuttle, developed for landing on the moon of Saturn rocket, second, third class, the J – 2 lox/lh2 engine developed by France and other European countries Ariane rocket and Japan is developing, the carrier rocket level above all use hydrogen engine as their main power devices.

At present, forging and drilling or cross-rolling piercing technology is mainly used in the billet of Nickel-based pipes in China. Due to the limitation of forging ratio, the uneven grain size of tube billet and a waste of raw materials in the drilling process, forging and drilling process are generally only suitable for thick wall, a short length and difficult to prepare hot-processed tube billet. Although the cross-rolling piercing process has high efficiency and high yield, due to its own structural constraints, whether it is two-roll or three-roll cross-rolling piercing, the material is not subjected to three-dimensional compressive stress, which results in circular micro-cracks on the cross-section of the billet and affects the possibility of subsequent processing. GH3600 alloy pipes for aerospace use are extruded to avoid the above situation.  Operations details including:

The equipment of extrusion blank is 2.5MN horizontal extrusion press. The blank size is 125 mm x 37 mm x L. The extrusion force is 1.6-1.8MN. The extrusion parameters are heating temperature 960-980 C, holding time 90-120 min, preheating temperature 500-600 C, extrusion speed 80-100mm?S-1 and extrusion ratio 10.1.

Two different rate distribution methods were used for cold rolling of finished products. The effects of different cold rolling processes on mechanical properties of products were compared for different cold rolling processes from 15mm *1.75mm to 5.8mm *0.4mm. The annealing pass processing rate of process 1 ranges from 68.9% to 70%, and that of process 2 ranges from 51.5% to 56.9%. The results are as follows:

• GH3600 alloy tube can be extruded to refine the microstructure obviously and improve the microstructure uniformity.
• The cold processing rate of finished products is controlled within the range of 51% to 57%, which can not only obtain good finished product structure, but also improve the room temperature elongation and yield strength at high temperature, and obtain better performance of finished products. Elongation of 39.8% at room temperature and 900 ℃ under the Rm of 124 Mpa, Rp0.2 is 82 Mpa.

The key point of tube extrusion is the matching of extrusion ratio and extrusion temperature. High extrusion ratio is beneficial to obtain the more uniform structure, but it will increase the extrusion pressure at the same time. While high extrusion temperature reduces the extrusion pressure, it also reduces the surface quality and dimensional accuracy of the product. At the same time, the sheath and lubrication mode of the high temperature alloy extrusion also play a crucial role.

Titanium is silver colored and one of the most corrosion-resistant structural metals. It took 120 years from the first titanium discovery in the late 18th century to the production of pure titanium and then the metallurgist spent nearly 40 years put the pure titanium obtained in the laboratory into the industrial production. Many researchers have done plenty of experiments. In 1948, Dupont company finally successfully produced tonnage porous and irregular shape titanium, that is, sponge titanium.

The production principle of sponge titanium is to reduce TiCl4 by Mg and generate Ti and MgCl and then vacuum distillation to remove the residual Mg and MgCl2 to obtain a pure, spongy, multi-empty titanium lump. The titanium lump is taken out, peeled, cut, and crushed to make sponge titanium.

During the reduction, distillation process, influenced by the complex factors such as temperature, pressure, furnace condition and segregation, there exist some impurities in titanium sponge lump. According to Chinese standard GB/T 2524, titanium sponge can be classified 0-5 levels, a total of six grades, namely the MHT 100, MHT 110, MHT120, MHT140, MHT160, MHT200 (The number refers to Brinell hardness maximum values), purity (%) quality generally is 99.1 ~ 99.7, total impurity elements (%) of 0.3 ~ 0.9, impurity element oxygen quality (%) of 0.06 ~ 0.30, hardness (HB) is 100 ~ 200.

How was the titanium sponge packaged?

Accoding to Chinese national standard: sponge titanium is packed according to the net weight of 70kg ~ 250kg per barrel (piece), the packing barrel is galvanized iron barrel lined with polyvinyl chloride film bag, sealed with open cover, the junction of the barrel cover and the barrel body should be able to identify whether the package is intact. It’s usually 200 kilograms a barrel now for titanium sponge manufacturer. After packaging, the barrel is pumped out and filled with argon and should be stored in a dry warehouse, not piled up in the open air or mixed with acid, alkali and other corrosive items. The sponge titanium should be handled with care during transportation to prevent dampness and damage of seal.

How to maintain and storage titanium sponge?

Titanium sponge oxidizes easily. Its large exposed area can absorb a lot of oxygen, the oxidized sponge titanium is impossible to remove oxygen elements in the casting of titanium ingots unlike steel making and only be discarded.

Long-term storage of titanium sponge is costly and dangerous. It’s said that sponge titanium can be stored for three years with argon gas filled in PVC film bags, but it was denied by titanium processing plant. Generally speaking, the longest period of one year is appropriate. Besides, the storage of sponge titanium must require regular rotation, generally one-year rotation, so that the storage cost of sponge titanium will be very high.

Spongy titanium Storage is dangerous. The titanium sponge allows 5% powder, so that in the processing and treatment of titanium sponge if dust clouds produced, it is easy to cause combustion when met open fire or electrostatic fire.

In conclusion, sponge titanium is not suitable for long-term storage. The porous “sponge titanium” cannot be used directly and must be melted into liquid in an electric furnace before it can be cast into ingots. Titanium ingots are in a dense state, which is a necessary process in the titanium production and is convenient for loading, unloading and handling. Therefore, in terms of the advantages like the low cost of maintenance, fire and shock resistant, recyclable, economy and convenience, it is quite appropriate to store titanium ingots.

Sponge titanium production is the basis of titanium industry and titanium sponge is an intermediate product in its purest form and material for titanium alloy. It is mainly used to produce titanium ingot, which in turn is used to make slab, billet, pipe, bar, plate, sheet, and other titanium mill products such as titanium alloys, billets, ingots etc.

Titanium and titanium alloys is a silver colored and highly active metal. It’s characterized by its high strength, high corrosion resistance, low weight ratio, low thermal conductivity and no magnetism. Titanium is widely used for a wide variety of applications where demand high levels of reliable performance. There are a number of important factors should consider when choosing titanium products for buyers. When tackling shipping jobs, knowing the material weight is essential.

The commercial pure titanium metal and its allot has relatively low density, are less than 5.0 g/cm3 at room temperature. First of all, the most important thing to know, all of the titanium products like titanium plate, bar, tube and other shapes, the density is all the same. Following chart shows density values for various titanium alloys at room temperature.

Density values for the most commonly used titanium alloys at room temperature :

Knowing its density is not enough, other factors like size, section area and tolerable are also indispensable when calculating the weight of titanium material. Calculation formula including:

• Titanium and titanium alloy plate weight(kg)= Length(mm)*Width(mm)*Thickness(mm) *Density(g/cm3) ÷1000000
• Titanium and titanium alloy round bar weight(kg)= Diameter*Diameter *Length* Density(g/cm3)* 0.7854÷1000000
• Titanium and titanium alloy tubing weight(kg)= (Outside diameter — wall thickness) * wall thickness(mm)*Length(mm)*Density(g/cm3)*π÷1000000

The weight of titanium material calculated according to the above formula is called theoretical weight. In the actual processing, there will be some tolerances in size and precision accuracy, which will affect the actual weight of the product. The theoretical weight can be known as a reference, the actual weight is a more important and practical factor that can be ignored, especially in the process of shipping and installation, the difference between these two weights will greatly affect the cost and design and installation.

Hot work tool steel is the high alloyed Cr-Mo-V tool steel which used for the non-cutting forming of workpieces made of iron and alloys at high temperatures. They are applied in processing such as hot forging dies, extrusion, drop forging as well as tube and glass products manufacturing. In recent years, in order to meet the large and complex shape of hot processed workpieces, there produce higher requirements for the mold load and tool steel performance. Therefore, many countries and tool steel mills continue to develop standards for mold steel and tool steel themselves.

Due to the different environment(application, temperature, pressure, atmosphere) of hot working tool steel, the mold bears a variety of pressure. In order to reduce the melting loss of casting dies, it is not enough only to improve the performance of tool steel, but also the surface treatment technology. In order to improve the service life of die, tool steel should be selected according to the service environment, tech design and other aspects such as:

1.High-temperature strength

The hot forging die and casting die contact directly with the processed material at high temperature, making the surface of the die soften and the surface strength of the die decrease. In addition, under the action of forming pressure and thermal stress, the surface of the mold is prone to crack and bond, which affects the appearance of processed workpieces. Therefore, the requirement of tool steel is to restrain high temperature softening and keep the strength (softening resistance) of steel. The secondary carbides in hot working tool steels after quenching and tempering play an important role in improving the softening resistance of steels. The addition of Mo, W, V and other alloying elements has a good effect on improving the softening resistance. However, excessive alloying elements will lead to component segregation and the increase of carbides, resulting in a decrease in toughness. Thus hot work tool steel must have both softening resistance and toughness.

2.The toughness

Mold cracks occur in the corner of the mold, machining defects and hot cracks and other stress concentration parts. But the toughness of steel will affect the crack resistance of die steel. Charpy impact value and fracture toughness value are the most commonly used toughness evaluation indexes. Cr, Mo, W and V carbides in hot working tool steel play a great role in improving the softening resistance and hardening hardness. However, the excess carbides are the main reason for the decrease of toughness of tool steels. Therefore, according to the need of strength – toughness balance, the composition of hot work tool steel should be designed reasonably. Ni is an element that does not form carbides, but the solid solution in tool steel matrix can improve its toughness.

The toughness of steel is closely related to the cooling speed of steel. During the quenching process of large molds, the cooling speed of the center is lower than the cooling speed of the surface, the normal and uniform quenching structure in the center is often not obtained, resulting in a decrease in toughness. Therefore, the hardenability of steel should be improved. Cr, Mn, Mo and V are effective elements to improve the hardenability. The evaluation methods of quenchability include continuous cooling transition curve (CCT) and Charpy impact value of slow cooling quenching in semi-cooling time. The semi-cooling time is the time when the temperature of steel decreases from quenching temperature to 1/2 quenching temperature. The operation of setting various semi-cooling time can simulate the cooling speed of the large mold center.

3.The thermal cracking resistance

Hot working tool steel mold, especially casting mold which requires workpiece with a flawless appearance, often occurs hot – cracking. These tortoiseshell cracks in the mold use process expansion, growth, resulting in cracking. The causes of hot cracks are that the surface of the mold is softened by the heat of the processed workpiece, the internal oxidation of the existing cracks caused by the contact between the mold and the atmosphere, and the local expansion and contraction caused by repeated heating and cooling heat cycle promote the crack expansion. In order to restrain the occurrence of hot cracks, the high temperature strength (softening resistance) and toughness of tool steel should be improved.

4.Melting resistance

Melting loss is a special damage form of casting die. The aluminum and magnesium ejected react with the mold material to alloying the surface of the mold, resulting in mold wear and thermal bonding. This phenomenon is called melting loss. The effective method to prevent melting loss is to avoid contact between liquid aluminum and liquid magnesium and Fe, the main component of mold material. Diffusion treatment including sulfur nitriding and coating treatment (PVD, CVD) surface treatment are the most effective methods.

Lkalloy Steel is a leading exporter and supplier of H13 hot work steel in plates, blocks and flat /square /round bars, we provide AISI H13 tool and die steel in all sizes as your requirements. Consult our team for h13 steel projects.

In the last article, we discussed “what’s the admiralty brass”, today let us take the “brass” on the table. As the two of frequently used of copper alloy, they indeed have various of similarities more than the literalness, sometimes brass and bronze are a source of confusion and people often mix them up, Can you tell the difference between them? If you are facing the same confusion, this article will be a timely help.

Alloying difference

Both brass and bronze include a small range of other elements including arsenic, lead, phosphorus, aluminum, manganese, and silicon. Brass is an alloy of copper and zinc, in proportions which can be varied to achieve varying mechanical and electrical properties. In contrast, bronze is an alloy of copper and tin. There are many different bronze alloys, but typically modern bronze is 88% copper and 12% tin.

Surface difference

The most intuitive and visual difference is the color of the metal surface. Bronze is characterized by its reddish brown color (depending on the bronze alloys) while brass has a dull-gold surface. Brass can range in color from red to yellow depending on the amount of zinc added to the alloy. You can also tell the difference between brass and bronze from its surface.

Property difference

Brass has higher malleability than bronze. The relatively low melting point of brass various from 900 to 940℃, depending on composition. Its flow characteristics make it a relatively easy material to cast. By varying the proportions of copper and zinc, the properties of the brass can be changed, allowing hard and soft brasses.

Compared with brass, bronze is hard and brittle. It has a higher melting point and melts at 950℃, that also depends on the amount of tin percent. Bronze resists seawater corrosion and metal fatigue more than steel and is also a better conductor of heat and electricity than most steels.

Application difference

The different property leads to the difference of application. Brass is commonly used in the production of some complex shaped stamping products, such as condensing pipe, drainage pipe, shell and so on, or some small hardware, mechanical parts. Brass is also used for decoration for its bright gold-like appearance or where need low friction such as locks, gears, bearings, doorknobs, musical instruments and even zippers.

Because of its good performance of resistance to corrosion and hardness, Bronze is used in some elastic elements, cables or conductive materials even sculptures, musical instruments and medals, and in industrial and nautical applications such as bushings and bearings.

Price difference

The price varies depending on which grades you are comparing and alloying elements mixed in. There are over 40 standard grades of brass with a zinc content varying from around 36-42%, while bronze with about 6- 12% tin. The price of zinc is lower than copper while the tin is high than copper, sometimes due to the manufacturing processes, for casting or forging. In general, bronze is usually more expensive than brass.

While these two “red metals” may look similar, they are actually quite different. Visit our other copper metals, click here

References:

http://en.wikipedia.org/wiki/Brass