Color codes of commonly used tool steel

Color code refers to the identification marked with paint on the steel cross-section or body to identify different steel grades and materials. Color coding is necessary to ensure that steel is correctly identified, used and stored. Tool steel has a wide range of application in many industry sectors known for their exceptional combination of hardness and toughness. We understand how difficult it can be identifying the materials from the steel appearance. That’s why we need color code on the end of flats and round bars. The color codes of commonly used tool steel are shown below:

 

LKALLOY is a leading supplier of Tool steel. We mainly stock and produces tool steel bar, tool steel flats, tool steel plates and other forms in various size and specifications. Call me now to fulfill your steel needs!

What is titanium sponge?

 

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.

 

 

 

 

Why titanium is popular in bicycle manufacturing?

Titanium is a silver colored and highly active light metal. Its density is 4.51g/cm3, which is only 57% of iron but three times in the term of the strength. Designs made using the properties provided by titanium often result in reliable, economic and more durable systems and components that exceed service life expectations at a lower overall cost in the long run.

In recent years, titanium and its alloy has a very wide range of applications in the bicycle manufacturing, not only the frame, we can say that almost every part of the bicycle can basically have the parts made of titanium alloy material, such as titanium alloy vertical, titanium alloy horizontal and other parts, even including screws. Titanium alloy can be said to belong to the super-high-end metal materials, and the processing process is extremely complex.

Compared with other metals used in bicycle frames, titanium has a higher ability to cope with road surface defects and deformation. This means that carefully designed titanium frames can better handle bumpy surface surfaces and thus provide a more comfortable driving experience. Titanium frames are usually paired with carbon forks to enhance road comfort. Road bike frames are made of titanium in different proportions from other metals (usually aluminum and vanadium), depending on the required physical properties, which improve the durability and physical properties of the pure metal. Another advantage of titanium frames is that they do not corrode like steel. So in general, titanium frames often exhibit a distinctive metallic gray sheen.

Similar as aluminum, titanium pipe kits can be cold drawn and hydraulically formed, so while the titanium frame may have a circular main pipe with external cable wiring, the pipe suite may have other shapes and also allow for internal wiring. An extreme example is Lynskey’s Helix framework suite, which uses spirally twisted tubes to help resist twisting forces.

As with any metal frame, the length and inclination of the frame pipe are cut before welding. Because the reactions with oxygen, welding titanium casings are more complex than making alloy frames, and it can take up to five hours of labor to complete the weld. The fitting must then be tapped to fit the parts bolted to the frame, and final finishes and markings added. Although most titanium frames are welded, there are other options. Caminade, a French maker of bespoke car frames, has just launched its Allroad frame component, which uses titanium tubes attached to carbon lugs to make it cheaper than an all-titanium welded frame.

 

Titanium is almost ideal for bike manufacturing. It’s light, tough, comfortable, and if designed right, it gives you incredible responsiveness and propulsion. The increasing complexity of the pipe suites now available means that the stroke can be adjusted to provide the qualities needed to handle terrain types. In so many bicycle material such as steel, aluminum alloy, carbon fiber, and so on, only titanium alloy with high strength, low density, low elastic modulus, good fatigue resistance and corrosion resistance, it is much better than carbon fiber material of bicycle, carbon fiber material parts are also expensive, but have a fatal weakness is beyond repair.

It can be said that titanium alloy has inherent advantages in the term of repair, the damage of carbon fiber is irreparable, although sometimes just a little crack, but titanium alloy don’t act like this, the damage of titanium alloy will only appear in the welding joints, at this time as long as the re-welding implements, they can continue to use. So the titanium frame and components have unique competitiveness and advantages

Titanium material weight calculation formula

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 :

MaterialCP TitaniumTi-5Al-2.5SnTi-6Al-7NbTi – 6Al – 4VTi – 15Mo
Density g/cm34.514.484.524.434.96
Density

lbm / in3

0.1630.1620.1630.1600.179

 

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.

Tool Steel Grades Definition System

According to the different chemical composition, tool steels can be divided into carbon tool steels, alloy tool steels and high speed steels (high alloy tool steels). Alloy Tool steel (here referred tool steel) is a type of carbon and alloy steel that is well-matched for tool manufacturing because of its hardness, resistance to abrasion and ability to withstand high pressures. American Iron and Steel Institute (AISI) and the Society of automotive engineer system(SAE) uses a basic alphabet-digit system to designate the carbon and alloy tool steels. Some tool steel series have additional resistance to corrosion due to added chemical properties such as vanadium, some series are restricted in order to minimize the potential of cracking while water quenching with the manganese content and other series offer various methods other than water to quench the material, such as oil. The main alloy tool steel series including:

 

S series: Shock resisting types

Shock resisting tool steel has been designed to resist shock at low or high temperatures. Its low carbon content is required to achieve the necessary toughness. This group of metals has high impact toughness, but a low abrasion resistance. Typical applications of S-Grade tool steel include Battering Tools, Boiler-Shop Tools, Chisel Cold Working, Swaging, Chipper Knives. Shock resisting steel grades including S1(T41901), S2(T41902), S4(T41904), S5(T41905), S6(T41906), S7(T41907).

A series: Air hardening, medium alloy cold working tool steel

A series tool steel is a very versatile, all-purpose tool steel that is characterized by low distortion factor during heat treatment, due to the increased chromium content. This tool steel has good machinability and a balance of wear resistance and toughness. Typical applications of A-Grade tool steel include Arbors, Cams, Die Bending, Blanking, Coining, Embossing, Cold Forming, Lamination. Air hardening steel grades including A2(T30102), A3(T30103), A4(T30104), A5(T30105), A6(T30106), A7(T30107), A8(T30108), A9(T30109), A10(T30110), A11(T30111).

 

D series: High carbon, high chromium cold working tool steel

High carbon and chromium cold working tool(Air hardening steel ) was formulated to combine both the abrasion resistance and air-hardening characteristics. Common applications for these tool steels include forging dies, die-casting die blocks, and drawing dies. AISI D2(T30402) is the commonly used D series tool steel. Other types including D3(T30403), D4(T30404), D5(T30405),D6(T30406), D7(T30407).

 

O series: Oil Hardening cold working tool steel

O series tool steel has good abrasion resistance and toughness for a wide range of applications. Typical applications of O-Grade tool steel include Arbors, Bushing, Chasers (Thread Cutting), Die Blanking, Cold Forming, Cold Trimming, Knurling Tools. O series types including O1(T31501), O2(T31502), O6(T31506), O7(T31507)H series: Hot-Working tool steel

hot work tool steel is used to cut material at high temperatures. The H-Group has added strength and hardness for prolonged exposure to elevated temperatures. They are low in carbon and moderately high in additional alloys. AISI H1-H19 are 5% chromium based, H20-H39 are tungsten based and H40-59 are molybdenum based. H13(T20813) is the most widely used industrial hot working tool steel.

 

Besides the series mentioned above, there also cover several series below:

T series: Tungsten base high speed steel

M series: Molybdenum base high speed steel

W series: Water-hardening tool steel

P series: Plastic mold

L series: Low alloy special purpose tool steel

F series: Carbon tungsten special purpose tool steel

 

The choice of Tool Steel series depends on a number of factors likes sharp cutting required, impact loading, abrasion resistance and heat treating. Lkalloy is a leading AISI tool steels and high speed steel suppliers with a wide variety of tool steel grades, shapes and sizes. Contact us to inquire about tool steel.

 

References

https://en.wikipedia.org/wiki/Tool_steel

What’re the main properties of hot work tool steel?

 

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.

Corrosion resistance analysis of duplex stainless steel S32205 plate

 

Duplex stainless steel S32205 combines the advantages of Ferrite and Austenite steel. It characterized good corrosion performance excellent welding performance, is widely used in industry and components like chemical processing, paper manufacturing, desalination equipment, firewalls, bridges, pressure vessels, heat exchangers, turbine blades and transmission shafts of offshore systems.

The higher content of chromium, molybdenum and nitrogen alloying makes the duplex stainless steel S32205 have good corrosion resistance. If the duplex stainless steel contains at least 30% ferrite in the microstructure structure, its corrosion resistance is much better than that of the austenitic stainless steel 304 or 316. However, ferrite is sensitive to hydrogen embrittlement, so in environments or applications where hydrogen may enter the metal and lead to hydrogen embrittlement, duplex stainless steel 2205 does not have high corrosion resistance at this time. Corrosion of duplex stainless steel 2205 including: pitting corrosion (critical pitting corrosion temperature CPT, pitting corrosion weightlessness, pitting corrosion potential); Intergranular corrosion (critical crack corrosion temperature CCT, crack corrosion weightlessness); Stress corrosion test (boiling magnesium chloride, hydrogen sulfide stress corrosion). This article is to analyze the corrosion resistance of 2205 steel plate from the test results.

 

Pitting corrosion resistance

For a specific chloride environment, each grade of stainless steel can be described by the critical point corrosion temperature (CPT), above which the pitting corrosion begins to occur and can develop to the extent visible to the naked eye within 24 hours.No pitting occurs below this temperature. It is a representation of a particular stainless steel grade and environment. The table below showed pitting corrosion rate of S32205 according to ASTM A923 06C:

TestTesting temperature,℃Testing time, hCorrosion rate,mg/d㎡.h
S3220525±1241.21

 

Intergranular corrosion resistance

Intergranular corrosion often appears at joint gaskets, sediment bottoms, and bolt joints. There is a similar critical temperature for intergranular corrosion, that is the critical crevice corrosion temperature (CCT), which depends on the stainless steel specimen, the chloride environment, and the characteristics of the crevice (compactness, length, etc.). Because of the geometry of the gap and the fact that it is difficult to present the same gap size in practice, the CCT measurement data are more dispersed than the critical point corrosion temperature (CPT). For the same grade of steel and the corrosion environment, CCTS tend to 15 ~ 20 ℃ lower than the CPT. The table below showed intergranular corrosion resistance of S32205 measured according to ASTM A923:

S32205Time(hour)Corrosion
Corrosion rate48h96h144hNo
0.3850.1240.120

 

Stress corrosion resistance

Like many materials, duplex stainless steel is prone to stress corrosion fracture under certain conditions. This may occur at high temperatures, in environments containing chlorides or in media that are prone to hydrogen cracking. Environmental conditions in which stress corrosion cracking may occur in duplex stainless steel such as a 42% boiling magnesium chloride solution test, a droplet evaporation test in which the metal is exposed to a pressurized aqueous chloride system at a high temperature (the temperature in the system may be higher than that at normal pressure). Table 3 showed stress corrosion resistance of S32205 below:

Testing standardStressTimeCracking or notEvaluation
ASTM A9230.8 Rp0.2720hoursNoQualified

 

Tests have proved that compared with austenitic stainless steel and ferrite stainless steel, duplex stainless steel has better corrosion resistance. The 2205 stainless steel plate sample used in the test is according ASTM A240 and with a size of 1600*2500*10mm, We also supply a wide range of metals for a variety of applications. Our stock including stainless steel, tool steel, titanium, brass and copper. Any metal projects, call us now!

 

 

What’s the difference between brass and bronze?

 

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

 

What’s admiralty brass?

 

Brass is a Copper-zinc alloy with the addition of alloying elements such as Tin, Arsenic, Manganese, Aluminum, Silicon and Lead, which are usually less than 5 %. Theses addition elements enhance the whole alloy properties, making the material is ideal for specific application areas.

There are over 40 standard grades of brass with zinc content varying from around 5-40%. Admiralty brass is a version of Brass that contains 70% copper, 29% zinc and 1% tin. The solubility of tin in brass varies greatly. When the solubility of zinc in copper increases from zero to about 38%, the solubility of tin in alpha phase decreases from 15% to 0.7%. Tin is very insoluble in a Zn-saturated alpha solid solution, but when the zinc concentration increases to beta phase appearance, the tin solubility increases. A small amount of tin solid solution in brass can improve the strength and hardness of the alloy, but when the amount is more than 1-5%, the plasticity reduced. That is the addition of tin that makes it the distinction from other Brass Alloys.

The reason for the addition of tin is because of the added corrosion resistance in saltwater. Admiralty Brass has good corrosion resistance and is specially used for fresh, salt or brackish water application, and for that reason, it is also called the “admiralty bras”.

Admiralty brass is available in forms of sheet and tubing. Admiralty Brass tubes have good corrosion resistance and are specially used for steam condensers cooled with fresh, salt or brackish water. They are usually used as condenser tubes, Evaporator and Heat Exchanger tubes, Distiller tubing in oil refineries, heater equipment as well as other industrial processes.

There are three types of admiralty brass in American Society for Testing Material, that’s UNS C44300, C44400, C44500(previously used destination are type B, type C, type D in turn). Copper alloy UNS C44300, C44400, C44500 tubes shall be furnished in the annealed O61 temper unless otherwise specified on the purchase order. The copper elements of them various from 70% to-73%, while exist a tiny difference in the content of arsenic, antimony and phosphorus.

 

Copper alloy Tin Lead Iron maxZincArsenicAntimonyPhosphorus
C443000.9-1.20.070.06remainder0.02-0.06//
C444000.9-1.20.070.06remainder/0.02-0.1/
C445000.9-1.20.070.06remainder//0.02-0.1

 

Admiralty Brass is one of the most frequently used brass alloy in their family, mainly used in condenser and heat exchanger applications by the petrochemical industry, ship-building, power plants and desalination plants etc. More details about size, dimension and price, Contact us now.

 

 

4 commonly used welding methods for titanium alloy

 

Titanium offers an amazing corrosion resistance but is two times lighter than steel. Titanium also has a very high tendency to oxidize at higher temperatures. It extremely important to keep the molten metal away from atmospheric air while welding because even very little contamination of oxygen will lead to porosity. With the wide application of titanium and titanium alloy, the progress of welding technology gives us more choices. It not only saves the material, but also reduces the quality of the whole workpiece. Here we will introduce the 4 kinds of commonly used welding methods: Tungsten Inert Gas arc welding, metal inert gas welding, laser braze welding, vacuum electron beam welding and so on.

 

Tungsten Inert Gas arc welding(TIG)

 

TIG is the best-welded process for titanium alloy plate and tube with a thickness below 3mm. Tig welding can be divided into open welding and pool welding or manual welding and automatic welding according to the methods.

gas tungsten arc welding in the atmospheric environment is using the shielding and purge gas to welding nozzle, drag cover and backside protective device to separate the welding high-temperature area from the air, so as to prevent the air from invading and contaminating the metal in the welding area. This is a type of local gas protection welding method. When the welded parts are complex in structure and difficult to finish the protective cover or back side, the welding inside the weld pool should be adopted. The pool body should be vacuumed before welding and then filled with argon or argon helium mixture. then welding inside the pool conducted under an inert atmosphere, which is a welding method of overall gas protection. Often Titanium is welded in a gas chamber with pure argon gas to make sure that the weld pool gets proper protection.

 

Metal inert-gas welding

MIG works by using a continuously feeding of welding wire that burns, melts and fuses both the base and parent metals together. You can weld a variety of materials such as mild steel, stainless steel and titanium, obviously. In this process for welding titanium and titanium alloy, the welding material and its thickness needs to be selected strictly. Generally, thin titanium plate adopts the technology of droplet transition welding, while thick plate adopts the droplet spray transition method. The effect of melting argon arc welding is excellent compared with other welding methods, mainly used for welding thick titanium alloy plate. Protective gas content and pre-welding cleaning are key factors to MIG processing.

 

Laser braze welding

Laser braze welding has incomparable advantages to other welding methods, it’s stability and automation, not affected by the magnetic field, especially suitable for precise titanium and titanium alloy pipe. As a non-uniform body, The structure and properties of welding joint are greatly changed, and the plastic damage behavior of joint is quite different from that of homogeneous material. The results show that the fatigue life of titanium alloy thin plate laser welding and active laser welding head is lower than that of base metal. The defocusing of the laser beam is also the key factor to affect the weld-forming quality.

 

Electron beam welding

From the early 1960s, as an advanced high-energy beam processing method, electron beam welding began to be applied to the welding of precious metals in the atomic energy industry, aircraft manufacturing and aerospace industry. Titanium absorbs O2 and N2 at high temperature rapidly, making the welding seam brittle, while vacuum electron beam can obtain high-quality welding joint, which is a unique advantage of vacuum electron beam welding. With the rapid development of the application of cutting-edge technologies such as aerospace, the uniqueness of materials used for aerospace parts and the particularity of welding requirements make electron beam welding quickly become a necessary process for the processing of these important parts, which is widely used in the welding of aircraft important bearing parts and engine rotor parts.

The electron beam welding of titanium alloy plate can be realized by adopting reasonable welding process. Obtaining a reliable joint is the key for electron beam when welding titanium alloy, because the reliability of joint performance will directly affect the safety of titanium alloy structure. Saresh of the National Institute of Technology Calicut in India performed single-channel electron beam welding on the 17.5mm thick titanium alloy plate, but the weld head failed to realize full penetration welding. When double-channel double-side electron beam welding is adopted, the total penetration welding of titanium alloy plate with a thickness of 17.5mm can be achieved, but the backside welding shall be followed as far as possible after the front welding is completed to avoid the fusion zone hole caused by welding joint pollution.

 

Even the mature welding technical, there are many basic factors make titanium difficult welding from other metals: a higher melting point and layers of shielding to prevent oxidation. In spite of the precautions that need to be taken, many engineers are more routinely and economically welding titanium.