Archive for category: company news

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.

 

Lubricant

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.

 

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.

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

French	Aperam Alloys Imphy(Imphy Alloys)	Invar®
American	CARPENTER	Invar 36® Alloy
	ATI	ATI 36™
	Special Metals	NILO alloy 36
German	VDM Metals	Pernifer® 36
	VAC	VACODIL 36
Japan	NIPPON YAKIN	NAS 36
Italy	Valbruna AG	SG5

 

Standards for Invar alloy

Country	French	German	American	China
Standards	AFNOR NF A54-301, Fe-Ni36	DIN 17745 Ni36，1.3912	ASTM F1684 UNS K93603ASTM B753 T-36	YB/T 5241 4J36

 

Perm invar alloy composition

Grades	Fe	Ni	C	Si	Mn	P,max	S,max	Cr	Co
1.3912	R	35.0~37.0	≤0.05	≤0.3	≤0.5	/	/	/	/
K93603	R	36.0	≤0.05	≤0.4	≤0.6	0.015b	0.015b	≤0.25	≤0.5
T-36	R	36.0	≤0.15	≤0.4	≤0.6	0.025	0.025	≤0.25	≤0.5
4J36	R	35.0~37.0	≤0.05	≤0.3	0.2~0.6	0.02	≤0.02	/	/

 

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.:

Temperature	The average coefficient of linear expansion, ā，10-6/℃
20℃~50℃	0.6
20℃~100℃	0.8
20℃~200℃	2.0
20℃~300℃	5.1
20℃~400℃	8.0
20℃~500℃	10.0

 

More information about special alloys, contact LALLOY today!

Rare Earth Elements (REE) is a group of metals for short, which including 17 kinds of Elements: 15 lanthanides, that is lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and two other Elements scandium (Sc) and yttrium (Y). Rare earth elements are almost insoluble in copper, but the addition of a little amount of rare earth elements, whether alone or mixed, is beneficial to the mechanical properties of copper and has little impact on the conductivity of copper. Such elements can form high melting point compounds with impurities such as lead and bismuth in copper and are distributed in grains as fine spherical particles to improve the high-temperature plasticity of copper alloys.

Experimental results show that adding 0.008% mixed rare earth or Y less than 0. L % to copper can significantly improve the mechanical and technological properties of copper. Copper alloys containing 0.01%~0.15% La have better mechanical properties, conductivity and softening resistance than Cu-0.15ag alloys, and have been widely used in electronics, petrochemical, metallurgy, machinery, energy, light industry, environmental protection, agriculture and other fields. Today here we will discuss the effect of rare earth elements on copper and its alloy.

 

Deoxidized and dehydrogenated

Strong affinity with oxygen, rare earth oxides offer good thermal stability, solid deoxidization products with copper in slag phase liquid surface is removed. Addition of rare earth metal an remove the small amount of oxygen in copper and its alloy obviously. Thermodynamic calculation show that the lanthanum, cerium, praseodymium, rubidium is more strong deoxidizer, their deoxidization ability at high temperature is significantly higher than aluminum and zirconium, also more than beryllium, magnesium, and calcium.

The copper solution is essentially insoluble in N2, CO2, and water vapor, but it’s opposite for O2, SO2, and H2. To hydrogen atoms dissolved in molten copper, rare earth elements are easy to react with hydrogen atomic state generated RH2 type RH3 and the stability of the hydride (R: rare earth element), which strongly exothermic reaction. Because of the small amount of hydrogen dissolved in copper, hydrogen absorbed by rare earth elements and the preference of R – H is a state of solid solution in copper and the alloy after adding rare earth elements, the hydrogen content will not reduce, but the rare earth has formed a stable solid solution, and hydrogen can be avoided under the condition of heating by hydrogen reduction of copper in copper oxide to produce steam to produce hydrogen embrittlement.

During copper processing, the addition of rare earth elements to the dissolved copper melt can quickly absorb and dissolve the hydrogen in the atomic state, and under certain conditions, the hydride with low density and easy to float on the surface of the copper solution can be generated, and under the action of high temperature, the hydrogen can be decomposed again, or it can be oxidized into the slag phase.

 

Removing impurities

Rare earth has strong chemical activity and can combine with many fusible components to form refractory binary or multiple compounds. They can interact with the low melting point elements sulfur, phosphorus, tin, and lead to combine into a variety of high melting point rare earth compounds or metallic compounds with various atomic ratios, such as Ce3Pb(1200℃) and BiCe3(1400℃), which will remain solid and slag together from the liquid copper, thus to achieve the purpose of removing impurities.

 

Structure refining

Rare earth elements can reduce or eliminate columnar crystals, refine grains and expand equiaxed crystal regions. The atomic radius of rare-earth elements (0.174nm-0.204nm) is 36% to 60% larger than that of copper (0.127nm). They react with some elements to form high-melting point compounds suspended in solution, which increase the number of grains, reduce the size and diffuse distribution, improve the plasticity and strength of the alloy, and reduce surface cracks and other defects.

For example, the addition of rare earth elements in C28000 copper alloy can refine the as-cast grains, which is conducive to the transition from neutral phase to carbon phase during recrystallization annealing, thus improving the mechanical properties of C28000 brass at room temperature.

 

Change the shape and distribution of impurities

Rare-earth elements can turn some of the strip, flake, or even block-shaped impurities in metals and alloys into punctate or spheres. For example, the inclusions of beryllium copper alloy are mostly irregular angular Cu2O and Cu2S. When the rare earth element increases to 0.05%, part of the inclusions are spheroidized; when it increases to 0.32%, all of the inclusions are spheroidized. Finally, it can make the impurities evenly distributed throughout the crystal and improve the comprehensive properties of the metal.

 

In summary, the addition of rare earth elements to copper and copper alloys can form high melting point compounds with oxygen, sulfur, lead, lead, etc. to remove impurities and purify; It can form a stable compound with hydrogen and dissolve in copper in the solid solution state, avoiding “hydrogen embrittlement”. The morphology and distribution of some impurities were changed to improve the metallographic structure, refine the grains, reduce or eliminate the columnar grains, and expand the equiaxed crystal region. These combined changes improve the property of casting, processing, mechanical, welding and corrosion resistance of copper and its alloys.