Smelting aluminum can be done by thermal reduction, but the cost is too high. Electrolysis method is used in industrial aluminum smelting. The main principle is Hall-Heru aluminum electrolysis method: Pure alumina as raw material using electrolytic aluminum, because pure alumina melting point high (about 2045℃), it is difficult [TJC STEEL]to melt, so industrial melting cryolite (Na3AlF6) as a flux, so that alumina at about 1000℃ dissolved in liquid cryolite, cryolite and alumina melting body, and then in the electrolytic cell, Use carbon block as Yin and Yang poles for electrolysis.
There are four links in the production process of aluminum forming a complete industrial chain: aluminum ore mining - alumina production - electrolytic aluminum smelting - aluminum processing and production.
In general, two tons of aluminum ore produce one ton of alumina; Two tons of alumina produce one ton of electrolytic aluminum.
To date, many methods have been proposed to extract alumina from aluminium ore or other aluminum-containing raw materials. Some[TJC STEEL] methods have been phased out for technical and economic reasons, while others are still in the experimental research stage. The proposed alumina production methods can be classified into four types, namely, alkali process, acid process, acid-base combined process and thermal process. At present, only the alkali process is used in large-scale industrial production.
Bauxite is one of the most important aluminum resources in the world, followed by alum, nepheline, clay and so on. At present, the [TJC STEEL]world alumina industry, with the exception of Russia, which uses nepheline to produce part of the alumina, almost all of the world's alumina is produced from bauxite as raw material.
Bauxite is an ore consisting mainly of diaspore, diaspore, or diaspore. Up to now, all the bauxite resources which can be used for alumina production in China are diaspore type bauxite.
The content of alumina in bauxite varies greatly, from about 30% to more than 70%. Bauxite contains chemical composition in addition to alumina, the main impurities are silicon oxide, iron oxide and titanium oxide. In addition, there are a small amount or trace of calcium and magnesium carbonate, potassium, sodium, vanadium, chromium, zinc, phosphorus, gallium, scandium, sulfur and other elements of the [TJC STEEL]compound and organic compounds. Gallium content in bauxite is small, but in the process of alumina production will gradually accumulate in the circulating mother liquor, so that it can be effectively recovered and become the main source of gallium production.
One of the main indicators to measure the [TJC STEEL]quality of bauxite is the ratio of alumina content and silica content in bauxite, commonly known as aluminum-silicon ratio.
In the production of alumina by the alkali process, aluminium ore is treated with a base (NaOH or Na2CO3) to convert the alumina in the ore into a solution of sodium aluminate. Impurities such as iron and titanium and most of the silicon in the ore become insoluble compounds. The insoluble residue (red mud) is separated from [TJC STEEL]the solution, then washed and discarded or treated comprehensively to recover the useful components. Pure sodium aluminate solution can be decomposed into aluminum hydroxide, after separation, washing and calcination, alumina products are obtained. The decomposing mother liquor is then recycled to treat another batch of ore. Alumina production by alkali process includes Bayer process, sintering process and Bayer - sintering combined process.
Bayer process is a method of extracting alumina from bauxite, which was invented by the Austrian chemist K. J. Bayer in 1889 ~ 1892. There have been many improvements in process technology for over a hundred years, but[TJC STEEL] the basic principles have not changed. In honor of Bayer's great contribution, the method has been using the name Bayer method.
The Bayer process consists of two main processes. The first is the dissolution of alumina from bauxite under certain conditions (the term used by the alumina industry is leaching). The following is the same) process, and then the process of water resolution in the solution of sodium aluminate supersaturated by aluminum hydroxide, which is the two patents filed by Bayer. The essence of Bayer process is to extract[TJC STEEL] alumina from bauxite by hydrometallurgy. In the Bayer process of alumina production, siliceous minerals can cause the loss of Al2O3 and Na2O.
In the Bayer process, bauxite is crushed and wet-milled along with lime and circulating mother liquor to make qualified pulp. After predesilication, the pulp is preheated to dissolution temperature for dissolution.
After the dissolution of the pulp after evaporation and cooling into the dilution and red mud (solid residue after dissolution) settlement separation process. The secondary steam produced by the self-evaporation process is used to preheat the pulp. After settlement and separation, the red mud is washed into the red mud yard, and the separated crude liquid (sodium aluminate solution containing solid floating matter, the same below) is sent to the leaf filter. Coarse liquid through the leaf filter to remove most of the floating matter is called semen. Semen enters the decomposition process to get aluminum [TJC STEEL]hydroxide by seed decomposition. After the decomposed alumina is graded and separated and washed, part of it is returned to the crystal seed decomposition process, and the other part is roasted to get alumina products. After the seed decomposition, the mother liquor is returned to the dissolution process through evaporation to form a closed cycle. Alumina is obtained by roasting aluminum hydroxide.
The dissolution conditions required for different types of bauxite vary greatly. The diaspore type bauxite can be well dissolved at 105℃, diaspore type bauxite can have a faster dissolution rate at 200℃, and diaspore type bauxite must [TJC STEEL]be dissolved at a temperature higher than 240℃, its typical industrial dissolution temperature is 260℃. Dissolution time is not less than 60 minutes.
The Bayer process is used to treat bauxite with high aluminum-Si ratio. The process is simple, the product quality is high, and the economic [TJC STEEL]effect is far better than other methods. The advantages are more outstanding when it is used to treat the easily dissolved bauxite. At present, more than 90 percent of the world's production of alumina and aluminum hydroxide is produced by the Bayer process. Due to the special nature of China's bauxite resources, about 50% of China's alumina is produced by Bayer process. The process combining Bayer process and sintering process is called combined process. The combined method can be divided into parallel combined method, series combined method and hybrid combined method. The method used to produce alumina is mainly determined by the grade of the bauxite (i.e. the aluminum-silicon ratio of the ore). From the general technical and [TJC STEEL]economic point of view, the sintering method is usually used when the ratio of aluminum to silicon of ore is about 3. The Bayer method can be used for ore with Al/Si ratio higher than 10. When the grade of bauxite is between the two, the combined method can be used to give full play to the advantages of Bayer method and sintering method, and achieve better technical and economic indicators. At present, the global annual alumina production is about 55 million tons, and China's alumina production is about 6.8 million tons.
Aluminum alloy smelting has the characteristics of heat consumption, easy oxidation, easy inspiration, easy absorption of impurities metal.
1) Burning More Calories:
Although the melting point of aluminum is low, the potential heat of melting is large, the specific heat is large, the blackness is small, the [TJC STEEL]reflection of heat is strong, and other commonly used metals such as iron, copper, when melting heat consumption.
2) Easily Oxidation:
Aluminum has a great affinity for oxygen and it can oxidize very quickly to form Al2O3. Although the alumina film formed on the melt surface has a protective effect, it is difficult to remove the oxide film once it is damaged and enters [TJC STEEL]the melt. Because one Al2O3 is not easy to reduce, the second is its density and melt similar. It is suspended in the melt, with the melt into the ingot, to the quality of processing materials will be adversely affected. What's more, aluminum oxide is a good carrier of various gases, and its presence will make aluminum melt absorb a lot of hydrogen. Therefore, reducing oxidation as much as possible is an important problem in aluminum alloy smelting.
3) Easy to Inhale:
Aluminum and aluminum alloys have a strong ability to inhale (mainly hydrogen), especially in the presence of water vapor or reducing atmosphere in the furnace gas. Although the absolute amount of hydrogen absorption of aluminum [TJC STEEL]and aluminum alloy is not large, but at the melting point, the solubility of hydrogen in the solid phase and the liquid phase is very different, the formation of porosity and porosity of the ingot crystallization tendency is very large. Therefore, reducing hydrogen absorption as much as possible is another important problem in aluminum and aluminum alloy smelting.
4) Easy to Absorb Metal Impurities:
Some of the alloyed elements in aluminium and aluminium alloys are highly chemically active. They not only absorb iron dissolved directly from iron crucible and tools, but also replace iron, silicon, zinc and other metallic impurities [TJC STEEL]from many oxides in furnace lining and many chlorine salts in fluxes. Once these metallic impurities enter the aluminum melt, they cannot be removed. And the more times of melting, the higher the impurity content, the greater the impact on the performance of the alloy, the serious grade degradation of pure aluminum, the alloy composition exceeds the standard and scrapped. [TJC STEEL]Therefore, to prevent the pollution of metal impurities is the third important problem in the smelting of aluminum and aluminum alloy.
65Mn spring steel, manganese to improve hardenability, φ12mm steel can be quenched in oil, surface decarburization tendency is smaller than silicon steel, after heat treatment of the comprehensive mechanical property is better[TJC STEEL] than carbon steel, but has overheating sensitivity and temper brittleness. It can be used as small size flat, round spring, cushion spring, spring spring, spring ring, valve spring, clutch spring, brake spring and cold drawn wire cold coil coil spring, etc.
Execution standard: GB/T 1222-2007
● Characteristics and scope of application:
65mn strength. Hardness, elasticity and hardenability are higher than No. 65 steel, with overheating sensitivity and tempering brittleness tendency, water quenching has the tendency to crack formation. Annealed state machinability [TJC STEEL]is acceptable, cold deformation plasticity is low, poor weldability. Plate springs under moderate load, helical springs and spring washers up to 7-20mm in diameter. Spring ring. High wear resistance parts, such as grinder spindle. Spring clamp. Precision machine tool screw. Cutting tools. Sleeve rings for spiral roller bearings. Railway rails, etc
● Chemical composition(%):
Carbon C: 0.62 ~ 0.70 Si: 0.17 ~ 0.37
Manganese Mn: 0.90 ~ 1.20[TJC STEEL]
Sulfur S: ≤0.035
Chromium Cr: ≤0.25
Nickel Ni: ≤0.30
Copper Cu: ≤0.25
● Mechanical Properties:
Tensile strength σb (MPa) : 825~925
Elongation δ10 (%) : 14~22.5
Reduction rate of cross-section (%) : no more than 10
Hardness: hot rolling,≤302HB; Hot rolling + heat treatment,≤321HB
● Heat Treatment Specification and Metallographic Structure:
Heat treatment specification: [TJC STEEL]quenching 830℃±20℃, oil cold; Temper 540℃±50℃(for special needs,±30℃).
Metallographic Structure: Tretinite.
● Critical point temperature (approximate value) Ac1=726℃, Ac3=765℃, Ar3=741℃, Ar1=689℃, Ms=270℃.
Normalizing specification: temperature 810±10℃, air cooling. 
● State of delivery: hot[TJC STEEL] rolled steel to heat treatment or no heat treatment of delivery, cold drawn steel to heat treatment of delivery.
● Supply specifications:
Disk circle: Φ5.5 ~ 16mm
Forging: Φ160 ~ 450mm
65Mn density ρ= 7.85g/cc, the steel can be cold rolled into steel plate, steel strip and steel wire, the production of spring. 65Mn can also be made into tools such as fitter's chisel, cutting needle, etc. 65Mn steel can be made of general section size of 8 ~ 15mm or so small spring, such as a variety of small size flat, round [TJC STEEL]spring, cushion spring, spring spring.
760℃×30min insulation, and then at 20℃/h cooling rate to 700℃×6h furnace cooling, to obtain a complete spheroidized structure, uniform size.
Argon arc welding butt welding process
In order to reduce the consumption of electrodes, DC positive connection is selected for wire butt welding test, that is, DC power supply is selected, the wire is connected to the positive pole of the power supply, and the tungsten pole is connected to the negative pole of the power supply.
The tungsten electrode containing 1% or 2% thorium oxide has high electron emission efficiency, good current carrying capacity, good anti-pollution performance, easy arc starting and stable arc. For ease of handling, a thinner thorium tungsten electrode with a diameter of 2 mm was selected and the front end of the electrode was sharpened.
Argon is chosen as the protective gas because of its low arc voltage characteristic, which is especially useful for manual arc welding of thin sheet and wire.
Dc manual argon arc welding machine was selected for the test. Before welding, the two ends of the wire were carefully smoothed.[TJC STEEL] In order to prevent the porosity of the welding spot, the oil at the end was cleaned with acetone. Place the polished wire at both ends on the flat and clean aligning plate (Figure 1), so that the two ends are aligning, leaving no gap at the joint, and press both sides of the joint with a pressing iron. Connect the wire to the positive electrode of the welder and the tungsten electrode to the negative electrode, and then switch the current to 20 A, 15 A, 10 A and 8 A respectively for welding. When welding, the ignition point arc next to the joint and make it burning stable, the arc moved to the joint to melt the joint metal and quickly extinguish the arc, at the same time,[TJC STEEL] slightly apply the top forging force, after cooling to complete the welding process, the welding process does not use filler wire.
It is found that when the welding current is 20 A, the arc combustion is intense, the metal spatter at the joint is serious, and the solder joint collapse is serious. When the current is adjusted to 15 A, the arc combustion is stable and the pool spatter is less, but the weld is still collapsed. However, when the current drops to 10 A, arc initiation is easy, arc combustion is stable, and there is no collapse phenomenon at the weld. Figure 2 shows the shape of the welded joint photographed with A digital camera under Leica MZ6 stereo microscope at a welding current of 10 A. It can be seen that the cylindricity of the joint is good, and it can meet the requirements of the line saw after grinding. When the current is adjusted below 8 A, it is difficult to start the arc and the arc is unstable, so it is difficult to complete the welding process.
Welded joint test
Due to the tendency of 65Mn steel to overheat, the welding heat affected zone has great influence on the mechanical properties of the joint. The joint of 65Mn steel wire with diameter of 0.7mm is very hard and brittle after argon arc welding. If the welding spot is gently bent, it will be brittle at the fusion line or weld, and the fracture shows obvious brittle fracture morphology. The obtained joint consists of a weld and a heat-affected zone, and the microhardness of each zone from the weld center to the base metal is tested along the joint axis. The measurement results show that from the base metal to the heat-affected zone and the middle of the weld, the microhardness increases sharply, and the hardness in the middle of the weld reaches HV 1 060, which indicates that hard and brittle structures are formed in the heat-affected zone and the middle of the weld. For this kind of joint with hard and brittle structure, in order to improve its toughness and plasticity, reduce its hardness, hardness, strength, plasticity and toughness of the appropriate match, must be the welding joint for appropriate tempering treatment. After heat treatment, the brittleness of the heat affected zone should be eliminated, while the base material should be able to maintain a certain strength and elasticity. Tempering is carried out in the box-type resistance furnace, and the tempering process is shown in Table 1. The tempered steel wire welding joint is carefully polished so that its diameter is roughly equal to that of the base material, and then the tensile test is carried out on the WE-50 tensile testing machine. Take three samples of each tempering treatment, and take the average value of their tension.
It can be seen from the test that after heat treatment above 330℃, the elasticity of the base material basically disappears, and the fractures all occur in the base material, rather than in the solder joint and its heat-affected zone, which indicates that although the brittleness of the heat-affected zone disappears completely after heat treatment, the strength of the base material is greatly reduced (the tensile strength of the base material used is 1 663 MPa after the test). At 260℃ for 10 min, although the elasticity of the material is basically unchanged, the brittleness of the heat affected zone cannot be eliminated. When the heating temperature is 280℃ and the heat is held for 10 min, the effect is the best. The tensile strength of the heat affected zone is only about 20% lower than that of the base material, and the elasticity of the base material is less disappeared. The microhardness of the welding head tempered at 280℃ was tested along the axis in each zone of the longitudinal profile. It was found that the maximum hardness value of the weld was reduced to about HV 500, which was about 1 times lower than that of the untreated one. Welded ring wire should not only meet the requirements of strength and elasticity, but also have a certain fatigue strength.
1RK91 is one kind of super martensitic stainless steel with high strength and toughness developed by Sandvik in Sweden in the early 1990s. The UNS number of [TJC STEEL]1RK91 is S46910, and according to the naming method in our country, it is 02Cr12Ni9Mo4Cu2TiAl.
Chemical Element Content of 1RK91 (%):
Si: 0.5 or less;
Mn: 0.5 or less;
P: 0.02 or less.
S: 0.005 or less;
Cr: 12 or less;
Ni: 9 or less;
Cu: 2 or less;[TJC STEEL]
Mo: 4 or less;
Ti: 0.9 or less;
Al: 0.4 or less.
Different from the traditional idea that alloy carbide or nitride is the main hardening phase to make the steel achieve high strength, 1RK91 steel uses Fe-Cr-Ni as matrix, Cu, Mo, Ti, Al as strengthening elements, controlling C to 0.02% or less. Firstly, the alloy elements were fully dissolved into the matrix by solution treatment, and then quickly cooled to [TJC STEEL]obtain the susaturated plate-strip martensite structure. After aging treatment, precipitation hardening phase mainly composed of intermetallic compounds was precipitated from martensite matrix, and part of martensite was reversed to form reversed austenite.
1RK91 steel uses intermetallic compounds as the strengthening phase and reversed austenite as the toughening phase to obtain the best strength and toughness coordination. As an element harmful to strength and toughness, C is [TJC STEEL]included in the control presence. Both theoretically and practically, the development of this kind of steel is regarded as a breakthrough in ultra-high strength steel.
① Excellent mechanical properties, can achieve very high tensile strength and hardness level.
② Corrosion resistance equivalent[TJC STEEL] to 304L or 316L under corresponding conditions.
③ Maintain mechanical properties at temperatures up to at least 400°C.
④ Very good relaxation property.
⑤ Good weldability.
1RK91 steel through 1000℃ after solid solution, can be cold processing into bars, plates, steel wire and steel strip and other metallurgical products, then after 450 ~ 475℃ aging treatment, in the high strength condition of 3000MPa still has good [TJC STEEL]plasticity and excellent fracture toughness; At the same time, it also has excellent cold working and welding properties, good corrosion resistance and over-aging resistance.
Sandvik also verifies that 1RK91 steel does not have any potential cytotoxicity through Vitro (cytotoxicity) test, so it can safely contact with human tissues, body fluids or blood, in accordance with the requirements of all relevant allergy [TJC STEEL]and skin irritation test standards.
1RK91 is used to manufacture parts and instruments for use in a variety of complex conditions, such as electric razor mesh blades, medical suture needles, surgical blades, drills, scissors, files, clamps, punches, guides and other surgical instruments.
253MA is a kind of heat-resistant austenitic stainless steel designed for applications requiring high creep strength and good [TJC STEEL]corrosion resistance.
The chemical composition of 253MA is balanced, so that the steel has the best comprehensive performance in the temperature range of 850℃-1100℃, extremely high oxidation resistance, oxidation skin temperature up to 1150℃; [TJC STEEL]Very high creep deformation resistance and creep fracture strength; In most gas medium has good resistance to high temperature corrosion and brush corrosion resistance; High yield strength and tensile strength at high temperature; Good formability and weldability, and adequate machinability.
In addition to the alloying elements chromium and nickel, the 253MA stainless steel also contains small amounts of Rare Earth Metals (REM), which significantly improves its oxidation resistance. Nitrogen was added to improve creep[TJC STEEL] properties and to make the steel complete austenite. Although the chromium and nickel content is relatively low, this stainless steel in many cases has the same high temperature characteristics as high-alloyed alloy steel and nickel-based alloys.
Application of 253MA Austenitic Stainless Steel:
253MA is widely used in sintering equipment, blast furnace equipment, steel melting, furnace and continuous casting equipment, [TJC STEEL]rolling machine (heating furnace), heat treatment furnace and accessories, mineral equipment and cement production equipment. 253MA steel can be used to 900 ℃ pressure occasions and working temperature up to 1150 ℃ non-pressure high temperature parts.
Chemical Composition of 253MA Austenitic Stainless Steel:
S 0.030 or less
Cr 20.00-22.00[TJC STEEL]
● Characteristics and Scope of Application:
CuZn20 common brass and [TJC STEEL]CuZn20 similar properties, high strength, plastic is also good, high corrosion resistance, used as thin wall pipe, corrugated pipe paper mesh and building supplies.
● Chemical Composition:
Copper Cu: 79.0 ~ 81.0
Zinc Zn: margin
Lead Pb: ≤0.03
P: ≤0.01[TJC STEEL]
Antimony Sb: ≤0.005
● Mechanical Properties:
Tensile Strength σb (MPa) : ≥265
Elongation δ10 (%) : ≥50[TJC STEEL]
Note: tensile Mechanical properties of sheet metal
Sample size: Thickness ≥0.5 heat treatment
● Heat Treatment specification:
Hot working temperature 820 ~ 870℃; Annealing temperature 600 ~ 700℃; The low temperature annealing temperature to eliminate internal [TJC STEEL]stress is 260℃.
An Alloy of Copper and Zinc is Named Brass:
Brass composed of copper and zinc is called plain brass.
If it is made up of more than two elements of multiple alloys is called special brass. Such as a copper alloy composed of lead, tin, manganese, nickel, iron, silicon. Brass has strong wear resistance. Special brass, also called special brass, has high strength, high hardness and strong chemical corrosion resistance. The mechanical properties of machining are also prominent. The seamless copper tube made of brass is soft and wear-resistant. Brass seamless pipe can be used in heat exchangers and condensers, cryogenic lines, submarine transport pipes. Manufacturing [TJC STEEL]sheet, bar, bar, pipe, casting parts, etc. Copper in 62% ~ 68%, strong plasticity, manufacturing pressure equipment. Shanghai Qianfu Metal Materials Co., Ltd. is a production and sales of non-ferrous metal materials enterprises, main: phosphorus copper wire, phosphorus copper rod, phosphorus copper pipe, phosphorus copper [TJC STEEL]flat wire; Red copper, brass. White copper, tin bronze, aluminum bronze, silicon bronze, beryllium bronze, lead material, the company has opened up the domestic and international markets, special specifications can be customized, timely delivery, quality assurance! In order to [TJC STEEL]meet the special needs of our customers, our company has introduced and imported copper materials: More than 50 series of anaerobic copper, red copper, red copper, brass, lead brass, tin brass, iron brass, aluminum brass, manganese brass, silicon brass, nickel brass, tin bronze, tin phosphor bronze, aluminum bronze, beryllium bronze, chromium bronze, zirconium bronze, chromium zirconium bronze, iron bronze, nickel silicon bronze, cadmium bronze, magnesium bronze, silicon bronze, zinc white copper, iron white copper, aluminum white copper, manganese white copper, etc. A variety of specifications: copper strip, copper pipe, copper bar, copper sheet, copper plate, copper plate.
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