Order of ASTM B111 Aluminum Bronze Tubes

Through a couple of weeks of effort, we are ready to deliver the ASTM B111 UNS C61300 Aluminum Bronze Tubes to our Italian Customer.

They will be used for heat exchangers, the dimension is: OD 10MM x WT 0.89MM x Length 1,500MM.

We also can produce UNS C11000, UNS C44300, UNS C68700, UNS C70600, UNS C71500.

If you have such RFQs, welcome to contact us via [email protected] or WhatsApp:+86 177 7897 6690

Order of ASME SB265 Gr.2 Titanium Plate

Finally, we successfully delivered the precious metal sheet to our Saudi Arabia customer. They will be used for manufacturing the Pressure Vessels for the Petrochemical plant.

Standard: ASME SB265, ASME SECTION II Part B

Grade: 2






Why ammonia corrosion are common for copper and its alloys?

Ammonia is an important raw material for the manufacture of nitric acid, ammonium salt and amine. Ammonia is gas at room temperature and can be liquefied under pressure. Most metals such as stainless steel, aluminum, magnesium, titanium, etc. have excellent corrosion resistance to ammonia gas, liquid ammonia and ammonia water, except copper and other copper alloys.

Copper – Zinc alloys including navy brass and aluminum brass are copper alloys that most susceptible to ammonia-induced stress corrosion cracking (NH3SCC). Ammonia stress corrosion cracking in copper alloy heat exchanger tubes is characterized by surface cracking, green/light blue Cu-Ammonia-corrosion complexes (compounds) and the formation of a single or highly branched crack on the tube surface, which can be transgranular or intergranular, which depending on the environment and stress levels. Liquid ammonia stress corrosion is formed when the medium simultaneously meets the following conditions:

  1. Occasions where liquid ammonia (water content no more than 0.2%) is likely to be polluted by air (oxygen or carbon dioxide);
  2. The operating temperature is higher than -5℃.

In fact, oxygen and other oxidants such as water are important conditions for stress corrosion of copper. There is a lot of potential corrosion in petroleum refining due to impurities in the original and additives in the process of processing. The types of ammonia-induced cracking corrosion including:


H2S-NH3-H2O corrosion

This is mainly determined by the concentration, flow rate and properties of the medium. The higher the concentration of NH3 and H2S, the more serious the corrosion; The higher the flow rate of the fluid in the tube, the stronger the corrosion. The low flow rate leads to ammonium salt deposition and local corrosion; Some media, such as cyanide, aggravate the corrosion, and oxygen (which enters with the injected water) accelerates the corrosion.

Ammonia corrosion of sulfuric acid alkylation tower top

In order to control the excessive corrosion of the column top system in the fractionation section, alkaline washing and washing reactor products are very important to remove acidic impurities. Precedents of neutralizing and film-forming amine inhibitors have sometimes been used in tower top systems. To reduce the corrosion rate and minimize the amount of inhibitor used, neutralizing amines or NH3 can neutralize the tower topwater condensate to a pH of 6 to 7. However, in some cases, NH3 can cause stress corrosion cracking of navy brass tubes in overhead condensers.

Ammonia corrosion of catalytic reforming

There are several types of stress corrosion cracking in catalytic reforming units, one of which is ammonia-induced stress corrosion cracking. NH3 exists in the effluent of the pretreatment reactor and reforming reactor and is dissolved in water to form ammonia, causing rapid stress-corrosion cracking of the copper-based alloy.

Ammonia  corrosion of delayed coking unit

The equipment of the delayed coking unit is susceptible to low-temperature corrosion mechanisms, including ammonia-induced stress cracking of copper-based alloy. These corrosion mechanisms play a role in the process of water quenching, steam coke cleaning and air venting. But since all coking towers usually have vent pipes and blowdown tanks, they are almost continuously exposed to wet vent steam and liquid.

Quench and vent vapors and liquids usually contain large amounts of H2S, NH3, NH4Cl, NH4HS, and cyanide, which are released from the thermal cracking reaction of the feed to the coking plant. Due to the presence of NH3 in the coking unit, ammonia-induced stress corrosion cracking occurs in copper alloy tubes at a high pH value.

Ammonia corrosion of sulfur recovery unit

Gas feeds are usually rich in H2S and saturated water vapor, and may also be mixed with hydrocarbons and amines, which can cause H to permeate the metal, so consider the risks of hydrogen-induced cracking (including hydrogen bulging) and sulfide stress cracking (SSC) in gas feeds. In addition, there may be NH3 in the gas feed, which can cause nh3-induced stress corrosion cracking, and cyanide can also accelerate the corrosion rate.


When the mass fraction of Zn is reduced to less than 15%, the corrosion resistance of Cu – Zn alloy is improved. The SCC in the steam environment can sometimes be controlled by means of preventing air from entering. The sensitivity of copper alloys is generally assessed by examining and monitoring the PH value of water samples and NH3. Eddy’s current inspection or visual inspection can be used to judge the cracking of the heat exchanger bundle. In short, copper and its alloys should be avoided in production processes involving ammonia and liquid ammonia.

Heat treatment of Beryllium Copper C17200

The heat treatment of Cu-Be alloy is mainly solid solution annealing and aging hardening. Unlike other copper alloys whose strength is obtained only by cold machining, wrought copper beryllium is obtained by cold machining and hot aging hardening processes up to 1250-1500 Mpa. Aging hardening is often referred to as precipitation hardening or heat treatment. The ability of beryllium copper alloy to accept this heat treatment is superior to other alloys in terms of forming and mechanical properties. For example, complex shapes can be achieved at the highest strength and hardness levels of any other copper-base alloy, that is, in the rolling and subsequent aging state of the material. The following text describes in detail the aging hardening process of high strength Cu-Be alloy C17200, as well as the specific heat treatment of forging and casting alloys, recommended heat treatment equipment, surface oxidation and general solution annealing methods.

During aging hardening, microscopic beryllium-rich particles are formed in the metal matrix, a diffusion-controlled reaction whose strength varies with aging time and temperature. The recommended standard time and temperature allow the parts to reach their peak strength within two to three hours without compromising strength due to prolonged exposure to temperature. For example, the C17200 alloy response curve in the figure shows how low temperature, standard temperature, and high aging temperature affect the peak performance of the alloy and the time required to reach peak strength.

As can be seen from the figure, at low temperatures of 550°F(290°C), the strength of C17200 increases slowly and does not peak until about 30 hours later. At a standard temperature of 600°F(315°C) for 3 hours, the strength of C17200 changed little. At 700°F(370°C), the intensity peaks within 30 minutes and drops almost immediately. In short, as the aging temperature increases, both the time required to reach the peak intensity and the maximum intensity available decrease.

C17200 Copper Beryllium can be aged at different strengths. Aging peak refers to aging to the maximum intensity. The alloys that have not aged to their maximum strength are unaged, and alloys that have exceeded their maximum strength are over-aged. Under-aging Cu-Beryllium increases toughness, uniform elongation and fatigue strength, while over-aging increases conductivity, thermal conductivity and dimensional stability. Copper beryllium doesn’t age at room temperature even if it’s stored for a long time.

The allowable deviation of aging hardening time depends on furnace temperature and final performance requirements. In order to reach the optimum age at standard temperature, the furnace time is generally controlled within ±30 minutes. For high-temperature aging, however, more precise timing is needed to avoid averaging. For example, the aging time of C17200 at 700°F(370°C) must be controlled within ±3 minutes to maintain peak performance. Similarly, due to the sharp increase of aging response curve at the initial stage, insufficient aging also requires strict control of process variables. In a standard aging hardening cycle, heating and cooling rates are not important. However, to ensure that parts do not start to age before they reach temperature, thermocouples can be placed to determine when the desired temperature has been reached.


Aging Hardening Equipment

Recirculating air furnace. The temperature of the recirculated air furnace is controlled at ±15°F(±10°C). It is recommended for the standard aging hardening of copper-beryllium parts. These furnaces are designed to accommodate large and small volumes of parts and are ideal for drum stamping parts on the carrier of aging. However, due to its pure thermal quality, it is necessary to avoid insufficient aging or too short the aging cycle of mass parts.

Chain Aging Furnace. Steel strand aging furnace with a protective atmosphere as a heating medium is suitable for processing large quantities of beryllium copper coil, usually in a long furnace, so that the material can be expanded or curled. This allows for better control of time and temperature, avoiding partial uniformity and the ability to control special periods of insufficient or high temperature/short time aging and selective hardening.

Salt Bath. We also recommend the use of salt baths to age harden beryllium copper alloys. Salt baths provide quick and even heating and are recommended in any temperature hardening range, especially for short periods of high-temperature aging.

Vacuum Furnace. Vacuum aging of copper-beryllium parts can be accomplished successfully but care must be taken. Because vacuum furnace heating only relies on radiation, it is difficult to heat parts with large loads uniformly. The parts outside the load are exposed to more direct radiation than the parts inside, so the temperature gradient after heat treatment will change the performance. To ensure uniform heating, the load should be limited and the parts must be isolated from the heating coil. Vacuum furnaces can also be used to backfill inert gases such as argon or nitrogen. Similarly, unless the furnace is equipped with a recirculating fan, the parts must be protected.


Can copper and steel be welded together?

As we all know, copper and steel (iron) are two different metals. The thermal conductivity of copper is 7-11 times greater than that of ordinary carbon steel, and it is difficult to reach the melting temperature. When copper is melted, its surface tension is 1/3 less than that of iron, and its fluidity is 1-1.5 times greater than that of iron. Iron and copper are infinitely soluble in a liquid state and finite in solid-state and do not form intermetallic compounds. For the solid solution of iron and copper, the solubility of iron in copper at 650℃ is only 0.2%, and that of copper at 1094℃ is only 4%. In addition, the linear expansion coefficient of copper is about 40% larger than that of iron. The crystallization temperature range of iron-copper alloy is about 300-400℃, and it is also easy to form (Cu+Cu2O), (Fe+FeS), (Ni+Ni3S2) and another low-melting eutectic. The liquid copper or copper alloy has a strong permeability to the grain boundary of the steel near the crack zone. The characteristics of copper determine that the welding of steel and copper is often difficult.

  1. Welding heat crack.
  2. Intergranular penetration and penetration crack.

This generally occurs in the near-weld zone of the steel side matrix. The data show that the addition of Mn, Ti, V and other elements to the copper alloy or welding seam containing Ni, Al and Si can effectively reduce the tendency of penetration crack. For example, when the content of Ni is higher than 16% (mass fraction), no penetration crack will occur, while serious penetration will occur to the bronze containing tin. In addition, the microstructure of steel also affects, such as liquid copper can infiltrate austenite but not ferrite, so single-phase austenitic steel is prone to osmotic cracks, but not for Austenitic – Ferrite dual-phase steel.

  1. The weld overcast

It is generally believed that the overcast in welds is caused by the high content of Fe in welds. When the liquid metal of infinite solution solidifies from high temperature to solid, the solubility of Fe decreases greatly, forming overcast in the weld, which will affect the performance of welding seams.


But because steel and copper have similar lattice types, lattice constants, and atomic radii at high temperatures, special welding techniques allow them to be welded together. It is generally believed that when Fe is 0.2%-1.1% in the weld, the weld structure is large α-phase, with poor crack resistance. With the increase of iron content, the weld was α+ε biphasic structure with the best crack resistance, especially when the Fe mass fraction was 10%-43%. Do you know how to weld stainless steel and copper?


Manual arc welding, argon arc welding and gas shielded welding can weld steel and copper and their alloys. It is recommended to use pure nickel or a nickel-based alloy containing copper to deposit the transition layer because of the strong crack resistance of nickel-based welds. Nickel element can greatly reduce or eliminate the copper and copper alloy permeable steel, which is helpful to eliminate the permeable crack in the heat-affected zone. In this experiment, pure copper 300mm×150mm×5mm C11700 copper plate and steel A 106 were taken as examples. After surfacing the transition layer, silicomanganese bronze wire 201 and wire 202 could be used as filler metal materials to strengthen the deoxidation of the melting pool.

Step 1. The oxidation film and oil stains on the surface of copper and steel metal base metal were cleaned up and polished, and then the copper side groove was processed to a side of 40° and the surface roughness Ra was 0.8m ~ 1.0m.

Step 2. The copper and steel metal base materials are heated in a box furnace. The heating temperature was 400℃ ~ 500℃ and kept for 30min ~ 45min.

Step 3. The copper plate and the carbon steel plate base material are filled with S201 red copper wire by tungsten argon arc welding (TIG) and fixed by spot welding. Then, the copper plate is connected by fusing and brazing, and the arc is shifted to the base material on the copper side (arc deviation is 10° ~ 25°). Parameters: current 140A ~ 160A, voltage 8V ~ 10V, protective gas He ~ Ar mixed gas, gas flow rate 15L/min; The volume ratio of He and Ar in the mixture of He ~ Ar is 8:2.

Step 4. Clean the welded joints with a wire brush until it has a metallic sheen and the welding is finished.


This welding method of copper and steel adopts He ~ Ar high energy protection gas to concentrate the line energy, which can shorten the residence time of high temperature in the melting pool and prevent the excessive melting of the substrate to make the copper and steel completely mix, spread and increase the copper content at the interface, resulting in the continuous infiltration of the steel side and the formation of low-melting eutectic heat cracks.

At the same time, He ~ Ar mixture of high-energy protective gas can also inhibit the combination of oxygen and copper, thus inhibiting the formation of oxide particles at the copper interface and preventing the formation of cracks. In addition, in the welding process, the arc is inclined to the copper side to ensure that the steel side is not melted, and the fusion and brazing joint are formed to avoid the excessive penetration of molten copper into the steel side and the formation of penetration crack, so as to reduce the high-temperature action time of the heat-affected zone and improve the plasticity and toughness of the welded joint.


The bright annealing process of copper alloy strip and wire

The common heat treatment methods of copper alloy are homogeneous annealing, stress – free annealing, recrystallization annealing, solid solution and aging treatment. In order to prevent oxidation during processing, save the cost of pickling and obtain a bright surface, it is allowed to anneal copper alloy strip, wire and coil tube in a protective atmosphere or vacuum furnace, that is, bright annealing.

A large amount of O2, CO2 and H2O in the air will oxidize the surface of the copper alloy, which must be pickled before further processing. Heating in a protective atmosphere can reduce the oxygen content in the furnace and greatly improve the surface quality of the annealed copper alloy. Bright annealing process does not need pickling equipment, no environmental pollution, will not harm the health of personnel, reduce the metal loss and save costs, and greatly extend the service life of copper alloy strip, wire and coil.

Protective gas

Common protective gases are O₂, CO₂, CO, H₂, H₂ O and N₂. Among them, N₂ can be considered as an inert gas in the heat treatment temperature and does not participate in chemical reactions, while O₂, CO₂ and H₂ O are oxidizing gases, and CO and H₂ are reducing gases. the main components of surface oxidation of copper in the reaction are O₂ and H₂ O. Oxygen reacts with copper and zinc to form metal oxides. The equation is 4Cu + O₂ ==== 2Cu₂O.

Very small amounts of oxygen in the protective atmosphere are enough to oxidize copper and zinc. The oxygen content in the furnace must be less than 1ppm for the bright treatment of copper alloy, otherwise the alloy surface will oxidize. Because water vapor can oxidize copper alloys containing zinc, aluminum, lead, tin, beryllium and so on in heating, and the lower the temperature, the more obvious the oxidation. Therefore, the atmosphere in the furnace must be kept below -60 ℃.

The main protective atmosphere used in heat treatment of copper alloy is: high purity nitrogen, purifying exothermic atmosphere, nitrogen, ammonia decomposition gas; Pure hydrogen and so on. Among them, the high purity nitrogen itself has no reduction ability, the reducing atmosphere in the purification exothermic atmosphere and the nitrogen-based atmosphere has less CO and H2, and the reduction potential is low, so they are not suitable for the bright treatment of copper alloy. At present, the protective atmosphere is mainly ammonia decomposition gas and pure H2. 75% of ammonia decomposition gas is H2, and the remaining 25% is N2. This is because H2 has a good reduction and excellent heat transfer performance than nitrogen, high-speed temperature consistency and rapid cooling also increase the productivity correspondingly; With the change of the heat transfer effect, the temperature difference in the charge decreases, and the phenomenon of adhesion decreases. The density of hydrogen is very low, which can greatly reduce the energy consumption per unit and the resistance of hot air circulation, and reduce the noise of the furnace platform strong circulation motor, keeping it below 85dBA.



Lubricants also play an important role in achieving a good bright annealing effect. First, it must completely evaporate, without removing oxygen from the process of spotless heating, or the oxygen will react with the hydrogen in the protective gas to form steam, reducing the reduction potential. Secondly, mineral oil and emulsion are used as a lubricant in cold rolling of copper strip. The characteristics of the emulsion are good cooling effect, can obtain a large number of trace pressure, and make high-speed rolling possible, improve the productivity, but the emulsion has the defects of impurities and easy to be eroded, so the emulsion rolling strip must be annealed in a short time, otherwise, it will be corroded. At present, low viscosity mineral oil has been known as the main lubricant due to less impurities and volatile after heating, can achieve a good bright annealing effect.


Bright annealing equipment

The bright annealing processing equipment of copper alloy strip, wire and coil are mainly bell type annealing furnace. The process is not only to get a smooth surface and suitable mechanical properties, and without phenomenon of glue, which have a higher requirements for the performance and structure of annealing equipment.

  • Good furnace temperature uniformity

Annealing equipment must have very good furnace temperature uniformity so that the annealing temperature of copper alloy is accurately controlled. Hooded annealing furnace has strong convection circulation system, effective recirculating fan, large air volume, high wind pressure, fast wind speed, excellent heat exchange effect, the furnace temperature uniformity is less than ±5 ℃, so that all the furnace charge can get uniform mechanical value and process value. At the same time, the annealing time is shortened and the productivity is improved.

  • Good sealing

The workload space is an all-metal enclosure. With the aid of a water-cooled rubber seal between the hearth flange and the inner cover flange, the circulating fan device achieves an absolute vacuum sealing space. There is no mechanical seal at the fan shaft and there is no possibility of leakage. Therefore, the dew point of the protective atmosphere can be maintained at -60 ℃ during the whole annealing process, which makes it possible for the bright annealed copper alloy.

First of all, the vacuum should be pumped and then the nitrogen should be sent to purge so that the atmosphere in the working space is as pure as possible, that is, it contains as low oxygen as possible. Test the tightness of the working space to find the leakage point so that there is no chance of mixing air and hydrogen. This vacuum process is essential for copper alloy wires and tubes. In the annealing process, the whole heating stage is cleaned by a protective atmosphere instead of a vacuum. Because the protective atmosphere can remove the evaporating lubricant more effectively than a vacuum to ensure the surface of the annealed workpiece is bright and clean.

  • Unique combination cooling system

In general, each set of hood-type furnace is equipped with two hearth, a heating hood and a cooling hood. For optimum benefit, the furnace cooling time must be shorter than the heating time to allow sufficient time for vacuum displacement at the end of cooling, unloading, loading, and annealing in the next cycle.

Equipped with high efficient strong convection circulating fan, the heat transfer rate of convection is greatly increased, and the time of the furnace is greatly shortened during the annealing process of heating, heat preservation and cooling. In addition, the combined air/water cooling system, not only at the beginning of cooling, cooling hood blower suction air sprayed on the surface of the inner hood, has been cooling the inner hood to below 200 ℃, and then the water spraying device began to work, spraying water on the inner hood until the end of cooling. It not only prolongs the service life of the inner cover but also greatly shortens the cooling time.


What’s beryllium copper used for?

In last article, we discussed the question”What’s Beryllium Copper”, as well as we know, Beryllium Copper is also known as beryllium bronze, is a type of precipitated hardened copper alloy with beryllium as the main alloying element. Its density is 8.3g/cm³, 0.2~2.75% beryllium making its strength is twice that of other copper alloys. Beryllium copper alloy is a nearly perfect alloy with similar strength limit, elastic limit, yield limit and fatigue limit as special steel in mechanical, physical, chemical and mechanical properties and corrosion resistance. At the same time, it has high thermal conductivity, electric conductivity, hardness, abrasion resistance, temperature stability and creeps resistance. It also has the advantages of good casting performance, non – magnetic and no spark during impact.

There are different forms of classification for Beryllium copper alloy. It can be divided into deformable beryllium copper alloy and cast beryllium copper alloy according to the processing form of the final shape. It also can be divided into high strength and high elasticity beryllium copper alloy (C17000, C17200, C17300) and high conductivity copper-beryllium alloy (C17500, C17510) according to beryllium content and its characteristics. Beryllium copper provides a good processing performance, hardness after solid solution aging treatment can reach HRC38 ~ 43, a wide range of uses and more than 70% consumption of beryllium in the world is used for the production of beryllium copper. It is mainly used in mold industry, automobile industry, nuclear power industry, computer industry, electronic industry, temperature controller, cell phone battery, computer, automobile parts, micromotor, brush needle, advanced bearing, contact parts, gear, punch, all kinds of a non-spark switch, all kinds of welding electrodes and precision casting mold:

High strength beryllium copperReliable connectorTelecommunication, medical, computer, military, aviation, computer, connector
Durable switchAutomobiles, household appliances, telecommunications
High sensitivity sensorBellows, reeds
Highly elastic nodeBattery contacts, wireless appliances, electromagnetic shielding
High strength springFixing clip, pressing ring, gasket
High conductivity beryllium copperHigh-temperature connectorsautomotive, electrical, power distribution, fuse ends
High current relayAutomobile, electric appliance, electric motor
Casting Beryllium copperToolsSafety and explosion-proof tools
MouldsChildren’s toys, plastic moulds, casting moulds, die casting moulds
DevicesSubmarine cable repeater, oil and gas
High-temperature componentsWelding electrode, rolling welding, generator shaft, steelmaking crystallizer


Appendix table: 1. The common standards for Beryllium Copper

ASTM B194Copper beryllium plate, sheet, strip and rolled bar
ASTM B196Copper beryllium bars and rods
ASTM B197Copper beryllium wire
ASTM B643Copper beryllium seamless tube
ASTM B441Copper – cobalt – beryllium and copper-nickel – beryllium bar/rod
ASTM B534Copper-cobalt-beryllium and copper-nickel-beryllium plates, sheets, strips and rolled bars

2. The common material for Beryllium Copper



Carbide VS HSS drill bit

A drill bit is a cutting tool with circular cross-section that create holes in an alloy materials. The commonly used drill bits mainly include spiral bit, flat bit, center bit, deep hole bit and bush bit. Reaming and countersink drill bits may not be used to drill holes in solid material, but they are traditionally considered drills. High-quality drill bits are generally made of carbide and high-speed tool steel while the former can cut two to three times faster than the latter.

The carbide drill bit is made tungsten carbide powder as matrix and cobalt powder by pressing and sintering as its binder. It usually contains 94% tungsten carbide, 6% cobalt and 1% other metals, also known as tungsten steel. Tungsten carbide, cobalt carbide, niobium carbide, titanium carbide and tantalum carbide are the common components of tungsten steel. The grain size of carbide component (or phase) is usually between 0.2 to 10 microns and the bonding metal is generally iron group metal, commonly used is cobalt, nickel, so there are tungsten cobalt alloy, tungsten nickel alloy and tungsten titanium cobalt alloy. Tungsten steel bit material sintering molding is to press the powder into a blank, and then into the sintering furnace heating to a certain temperature (sintering temperature), and keep a certain time (insulation time) and then cooling to get the desired performance of tungsten steel.

The hardness and strength of carbide drill bit are not only related to the content of tungsten carbide and cobalt, but also to the powder particles. The average grain size of tungsten carbide phase is less than 1 micron. This drill has not only high hardness but also excellent compressive and flexural strength. The carbide bit can be divided into solid carbide bit, carbide indexable bit, welded carbide bit and carbide crown bit according to the material how it’s made. Some bits are made entirely of carbide alloy, while others have a welded shank, that is, a drill shank made of stainless steel and each bit is suitable for specific machining.

High-speed steel (HSS) is a high carbon tool steel containing lots of tungsten and cobalt and is rich in molybdenum, tungsten and vanadium. HSS bit is a type of alloy bits made of HSS and offer combining properties such as excellent high hardness, wear resistance, good strength and toughness, heat resistance and corrosion resistance. These properties are possible to be attained due to a special microstructure, composed of a matrix around 65 HRC even in high-temperature in the case of high-speed cutting.

HSS drill is mainly used to manufacture complex thin blade and impact-resistant metal cutting tool, but also can manufacture high temperature bearing and cold extrusion die, such as turning tool, drill bit, hob, machine saw blade and high demand molds. But it also has poor toughness, brittle big shortcomings, in order to improve the hardness and wear resistance of drill bit, can be substrate chemical vapor deposition layer of 5 ~ 7 microns on the high speed steel hard titanium carbide (TiC) or titanium nitride (TiN), or inject titanium, nitrogen, and carbon ion implantation to a certain depth, the matrix or on top of the screw drill with physical method to generate a layer of film. Today here we are going to show you how to choose a high quality HSS drill bit. Firstly, how to judge the drill bit from its surface color?

High quality polished HSS bits are often white, and of course, rolled bits are also white to be fine ground. Generally speaking, the nitriding bit is black, which is a chemical method to increase the hardness of the tool by placing the finished tool in a mixture of ammonia and water vapor and holding it for 540~560 ° c. The Tan bit is generally cobalt bit. The cobalt bit, originally white, turned a tan after grinding and atomizing. The gold M42 (Co5%) Ti-plated bit has a hardness of HRC78, higher than that of cobalt-bearing bits (HRC54). Color is not the only factor to judge the quality of the drill, so how to choose the drill? Generally speaking, the white ones are generally fully polished HHSB drills, the gold ones are titanium nitride plated, and the black ones are either nitride alloy steels or carbon tool steels.

What is kovar alloy?

KOVAR alloy is an Iron-Nickel-Cobalt alloy with a density of 8.36g/cm3 and a linear expansion coefficient between 20 and 500℃ equal to that of glass and ceramics. Most metals cannot be sealed with glass because their thermal expansion rate is different from that of glass and the joints are liable to break when cooled. The nonlinear thermal expansion curve of KOVAR alloy can usually be matched with glass. It combines with glass through the intermediate oxide layer of nickel oxide and cobalt oxide, and the bonding strength depends on the thickness of the oxide layer. The reduction of cobalt makes the proportion of iron oxide lower and the oxide layer easier to melt and dissolve in the molten glass, allowing the joint to withstand a wide range of temperatures.

KOVAR alloy provides a tight mechanical connection between hard glass (e.g., borosilicate glass) and ceramics within a certain temperature range. Judging from the color of the interface, gray, gray-blue or grey-brown means a good seal, and black indicates that the alloy has been over-oxidized and weak bonding. Kovar alloy is suitable for glass/ceramic-metal seals in scientific equipment such as vacuum tubes (valves), microwave tubes, X-ray and microwave tubes, transistors, diode integrated circuits, etc.

Commercial brands for Invar alloy


Special MetalsNilo® K
FrenchAperam Alloys Imphy

(Imphy Alloys)

Dilver P1®
GermanVDM MetalsPernifer® 2918


Standards for Invar alloy


ASTM F15 K94610DIN 17745 Ni-Co 29 18


YB/T 5231 4J29


Perm invar alloy composition




Typical linear coefficient of expansion(4J29)

TemperatureAverage coefficient of linear expansionā,10-6/℃


More information about special alloys, contact LALLOY today!

What is invar alloy?

INVAR alloy, the abbreviation of Invariability, composed of64% Fe, 36% Ni and little other elements such as S, P, and C, has a very low linear expansion coefficient under 100 ℃, also known as low expansion steel, it’s firstly found by French physicist C.E.GuialmeI by 1896. The NVAR trademark was originally held by the French elfin alloy company and conformed to AFNOR NF A54, DIN 17745, ASTM F1684 and ASTM B753.

Most metals expand in volume when heated and contract when cooled, but for invar alloy, because of its ferromagnetism and the invar effect over a certain temperature range, has an extremely low coefficient of expansion, sometimes even zero or negative. Invar alloy is indispensable for manufacturing precision instrument due to the advantages of low expansion, has been widely used in the electronics industry and precision instrument industry and other areas where required special size like double metal materials, magnetic materials, such as measuring instruments with a fixture, astronomical telescope components, optical instruments, liquid, gas storage containers, antenna parts, FPD shielding frame, high precision printing with the framework, such as laser gyroscope.


Commercial brands for Invar alloy

FrenchAperam Alloys Imphy(Imphy Alloys)Invar®
AmericanCARPENTERInvar 36® Alloy
Special MetalsNILO alloy 36
GermanVDM MetalsPernifer® 36
ItalyValbruna AGSG5


Standards for Invar alloy

StandardsAFNOR NF A54-301, Fe-Ni36DIN 17745 Ni36,1.3912ASTM F1684 UNS K93603ASTM B753 T-36YB/T 5241 4J36


Perm invar alloy composition



Physical property

Density, g/cm3: 8.12

Hardness, HV: 140

Tensile strength, MPa: 500

Elongation, %: 30~45%

Modulus of elasticity, MPa: 134000

Cupping test value, mm: 9.8

Thermal conductivity, W·(m·K)-1:  0.109~0.134

Magnetoconductivity, mH·m-1: 2.04


Invar alloy coefficient of linear expansion(4J36)

The ratio of the length of metal at 0 ° c to its length at 1 ° c for each change in temperature is called the linear expansion coefficient.:

TemperatureThe average coefficient of linear expansion, ā,10-6/℃


More information about special alloys, contact LALLOY today!