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| What are the characteristics of aluminum alloy iron additive tablets? |
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Posted by: haomeialu - 02-25-2018, 07:14 AM - Forum: aluminium faq
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With the rapid development of social economy, especially in the industrial construction process, will use a variety of white powder or granular flux, of which aluminum alloy iron additive in the process of metal smelting plays an important role. You will find aluminum alloy additive product features more obvious, mainly by a variety of inorganic salt drying treatment in accordance with a certain proportion of mixed ratio made, then, you know the characteristics of aluminum alloy additive products?
[img=300x0]http://www.aluminiumstrip-hm.com/wp-content/uploads/2018/02/20170915102390549054-300x281.png[/img]![[Image: 20170915102390549054-300x281.png]](http://www.aluminiumstrip-hm.com/wp-content/uploads/2018/02/20170915102390549054-300x281.png)
What are the characteristics of aluminum alloy iron additive tablets?
First of all we have to know in the industrial production process which will use a variety of aluminum alloy iron additive tablets, and aluminum alloy iron additive product advantages of performance is more obvious, mainly used to clear the internal aluminum liquid and floating in the oxidation Slag, you can make aluminum liquid becomes more pure, with the role of slag agent. The aluminum alloy iron additive product is characterized by good stability, is easy to break down at high temperatures, the gas will produce hydrogen reaction, but also from the solution which overflow, in the aluminum smelting process which plays an important role.
You will find aluminum alloy iron additive products, the scope of application is still relatively wide, especially in the smelting of aluminum and aluminum smelting play an important role. At the same time, you have to understand its use, you can add the entire aluminum alloy iron additive products evenly into the aluminum liquid which quickly pressed into the aluminum liquid, fully stirred after standing, slag, and then you can also use inert gas Aluminum alloy iron additive tablets into the aluminum liquid effect is better.
What are the characteristics of aluminum alloy iron additive products, you should know clearly? In many large and small enterprises smelting aluminum products, you must actively understand their use, but also pay attention to its use, the entire amount of aluminum alloy additive products for the amount of aluminum liquid weight of about 0.3%, the higher the purity of aluminum The words can be appropriate to add some aluminum alloy iron tablets. In addition, in the packaging storage time, you should pay attention to dry storage.
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| Common problems with aluminum plates and causes |
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Posted by: haomeialu - 02-25-2018, 07:08 AM - Forum: Knowledge & Technique
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Common problems with aluminum plates and causes
1. The surface bubbles
2. The quality of the perforation is not good. The hydrogen content of the ingot is loose. The uneven surface of the ingot surface is dirty to the east and is not cleaned before the furnace. After the corrosion, the cast block and the coated aluminum plate surface have erosion residue traces; The heating time is too long or the temperature is too high. When the first weld is rolled, the emulsion is not closed, and the emulsion flows under the aluminum plate.
3. The cracking of the cast block is too large, and it is cracked from the end of the ingot. The heating temperature is too high or too low.
4. The mechanical property is not qualified and the heat treatment system or the heat treatment equipment is not normal. Quenching fashion material is large, salt bath tank temperature is not enough fashion furnace, thermal insulation time is not enough, did not reach the specified temperature is out; The heat treatment system or test method adopted in the laboratory is not correct; The sample size is incorrect and the sample surface is damaged.
5. The casting quality is not good, there are metal or non-metal residue in the aluminum plate.
6. The tear lubricant composition is not qualified or the emulsion is too strong, the plate and the roll can slide, the metal deformation is not uniform; The rolling rate is not controlled, and the pressure is too large. Excessive rolling speed; The tension of the drum is not correct and the tension is unstable. Poor annealing quality; Insufficient metal plasticity; The roller type control is not correct, the metal internal stress is too large; Edge of hot rolled drum; When rolling, the lubrication is not good. The coil is not positive, and the tension stress is generated on the side of the plate, and the pressure is produced. The edge is produced by a small tear. After repeated rolling, it continues to expand from the crack and even tear. In the finishing time, the clamping clamps are unevenly or unevenly, or the plates have split edges, which can cause tearing when stretching. When quenching, the hood is not good or too tight, so that the plate fracturing, stretching and straightening can cause tearing.
7. It is not correct to adjust the amount of overpressure. Failure or improper use of thickness gauge; Roller type control is not correct.
8. Pressing (folding) roller type is incorrect, for example, the bearing of the press light machine is hot, so that the roll end of the roll is swollen, and the result is thin on both sides of the plate. The front plate wave is too large, so that the pressure light is too large, and the pressure is broken. When the laminate is pressed light, it is easy to produce pressure. The plates are thick on both sides and easy to produce pressure.
9. Non - metal rolling mill roll, roller, scissoring machine and so on not clean, the processing of the dirt in the aluminum plate car, through rolling and forming; The parts of the roller, guide roller, three-roll straightener and coiler of cold rolling mill are not clean, and the dirt is pressed in. The rolling oil nozzle is blocked or the pressure is low. The emulsion replacement is not timely, the aluminum powder is not clean and the emulsion tank is not cleaned.
10. The high temperature instrument of overheat treatment equipment is not accurate; The temperature is not uniform in each area of the electric furnace; In the absence of proper heat treatment system, the metal heating temperature reaches or exceeds the metal overheat temperature; If the loading is not positive, the area near the heater may produce local overheat.
11. When the metal is pressed into the heating process, the metal debris falls on the plate and is formed after rolling. When hot rolled, the edge of the roll is less, and the metal on the crack is dropped on the belt plate. The cutting edge of the disc is not good, the edge of the belt is burr, and the compressed air does not blow the metal scraps on the surface of the belt plate. After the roll is glued, the aluminum plate is pressed onto the strip. The ruler was clamped tightly and the scraped crumbs fell on the board.
12. The wave roller type adjustment is not correct, the original roller type is not suitable; Failure or improper use of panel control system; The raw material of cold rolled raw material or the convex in the section; The selection of pressure rate, tension, speed and other technological parameters is improper. All kinds of straightening machine adjustment is not good, straightening roll gap is not consistent, make sheet thin side produce wave; For stretch straightening and bending straightening machine, the elongation rate is not chosen properly.
13. After hardening, washing and drying, the surface residual acid, alkali or nitrite traces will be corroded after a period of time. Improper storage of board, water drop on board; In the process of processing, the auxiliary materials of contact products, such as oil, rolling oil, emulsion, packaging oil, etc. contain water or alkaline, which may cause corrosion; Too high temperature or bad packaging during packing, damaged during transportation.
14. Cut hot rolling mill roll, guide plate to adhere to aluminum, make hot pressing plate with scratch; The guide plate of cold rolling mill, pinch roller, etc. The finishing line is cut by the guide road; When the finished product is packed, it is not properly carried.
15. When the element diffuses annealing and quenching, the heat treatment system is not properly implemented, and the heating time can be prolonged or the heat preservation temperature can be increased. Too many times of annealing and quenching; The tail of hot rolled or pre-cut machine is not required to cut the head in accordance with the process specification, causing the aluminum layer to be unqualified. The wrong use of aluminum plate, the use of aluminum plate is too thin.
16. Too thick for the same reason as 7 "too thin".
17. It is easy to cause chafing when it is not careful. The conveyor belt is not positive, and the slanting plate is brought forward when rolling, so that the belt plate and the roll can produce relative friction. The tension is not correct when the volume is rolled, the tension is small when the roll is taken, the tension is large when the roll is open, and the roll pulls the roll tightly to make the plate stagger. There is too much oil in the lubricating oil, which is different from the residual oil on the drum after rolling.
18. The disc shear spacing is adjusted too narrow after narrow shear; Insufficient spare capacity of hot coarse rolling; When the hot finishing mill is adjusted, it is not very good to consider the amount of cold shrinkage and shear allowance during shear.
19. In the short cut, the ruler or equipment malfunction.
20. The two ends of the roller are different at the end of the roller. The guide tape board is not positive, and the strip is extended on both sides. Hot mill roll preheating is not good, roll shape is not correct; The emulsion jet is uneven or the nozzle is blocked; When the press is rolled, the plate is not in alignment.
21. The heating temperature is too low, the crack edge produced when hot pressing is not cut off, and the edge is expanded after cold rolling. The edge of the hot roll is too small, which may cause the splitting edge; Too large or too small; The casting gate is not cut off, it will crack when hot rolling; Cut the sides unevenly, cutting too little, may produce a split edge; The annealing quality is not good, the metal plasticity is not enough; The aluminum sheet is not properly placed, so the side is not completely aluminum.
22. The crack or heating temperature is too high or too low; The rolling rate inappropriately causes compression.
23. Shrinkage hole casting quality is not good.
24. The emulsion is not clean, or the new emulsion is uneven.
25. When the emulsion mark is rolled, the emulsion is not blown clean, so that the emulsion is involved in the cylinder; The hot precision rolling temperature is too low, the emulsion concentration is too high; There is water in the duct, and it blows on the strap with the air.
26. The aluminum laminated aluminum sheet is not properly placed, and the metal clad aluminum plate and ingot are staggered when hot and rough rolling. In hot rough rolling, the cast block is not properly delivered; It is too small to weld when the welding is rolled. It is too large for the side aluminum casting roll. The cutting edge of finishing shear and hot finishing is not uniform, and too little is cut.
27. To be hit in the process of carrying or parking. When cold rolling or annealing, the card is not good, and the annealing material is not clean, there are metal objects or protrusions; Cold rolled into hard metal slag or other hard stuff.
28. In the cold rolling of the pine tree, the pressure is too large, and the metal is sliding due to the large friction force between the rolls. The concentration of rolling liquid is too large, and the fluidity is not good, and it cannot be distributed evenly on the plate surface, and the pine tree will be produced after rolling. The thickness display instrument fails; Cold rolling tension is too small.
29. The wave or sickle shape is produced by pressing the indentation hot rolling. When it is cut through the tail feeding roller, scissors, three rolls and so on, and the cutting of the guide plate of the rolling machine, it is crushed; The quantity of annealing charge or removal is more, so that the drum is loose; Hot rolled road aluminum scratch strip, after cold rolling production; The road of cold rolling mill, three rollers, five rollers appear to be viscous or roiling, scratches, abrasion aluminum plate, through rolling production; The tension of cold rolling and hot rolling is not stable, the tension size does not match, or the loading and unloading rolls are not careful, so as to make the laminates between the layers.
30. After the nitrite mark quenching, the washing is not clean, and the surface of the plate is not clean.
31. The roll of a cold rolling mill is coated with metal residue, or the roll is printed on the board. The straightening and rollers are sticky with metal scraps, not clear rollers or rollers. Before straightening, the metal residue falls on the plate and is caused by straightening.
32. The adhesive aluminum is caused by the uncleanliness of the straightener roller on the shearing machine. All multi-roll straightening machine is easy to stick to the plate surface; When hot rolling or cold rolling, the roll is sticky.
33. Break the sheet and handle with carelessness.
34. Kneading and quenching of the plate is too big and scratch each other; Careless loading and unloading, or loading too much, making the plates misbehave each other.
35. The tension control is improper when the horizontal wave cold rolled sheet, so that the inside turns in the drum make the nest. Stop in the middle of the rolling process.
36. The thickness of the aluminized layer is too high. The tail of hot rolled tail or preshear head is too small; Aluminum plate is used wrong; The alkaline wash time is too long.
37. Residual rolling oil on the plate after the oil trace.
38. Slip line plate during stretching for stretching quantity is too big a slip line (45 °) along the direction.
39. When the water mark is quenched, it is not cleaned and pressed to the plate.
40. The surface is not bright roller, roller, straightening roller is not enough, the lubrication performance is not good, too dirty.
41. Small black spots in the process of hot rolled plate, due to the high temperature emulsion decomposition, decomposition product and make the roll because of bad lubrication in the process of rolling friction and aluminum and the aluminum powder at high temperature interaction, produce "small black spots" in the emulsion, after rolling and pressure to the aluminum plate on the surface, form small black spots; Emulsion stability is bad, not clean, bad lubricity, prepared with hard water, uneven emulsion injection on the roll, and channel is not clean, roller, cooking, tubing, fuel tank is not clean and easy to produce "small black spots".
42. Due to the poor quality of the milling surface, the surface oxidation of the cast block is heated, and the quality of the cast block is not good enough to form a strip or block.
43. In the process of rolling, uneven deformation is produced in the end or side of plate, and it is spread when rolling.
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| What are the common quality problems of aluminum plates? |
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Posted by: aluhm - 02-25-2018, 07:02 AM - Forum: aluminium faq
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In aluminum plate with the production process, because the equipment or personnel error prone to quality problems such as reasons, aluminium is common quality problems summarized below here, hope the production department to attach importance to this problem.
Oil is a common quality problems: pollution is refers to the rolling aluminium tip surface with oil after the too much. And bring the excess oil, other than the rolling oil film in the process of cutting production and finished goods inspection visible surface with oil. These oil mainly by roll neck or mill on exports, bottom left, splash, dripping on the box, and the abnormal, rolling mill, rolling mill roller clearer thickness head drops of oil, and often complex than dirty.
This oil pollution will bring great harm to the surface of the aluminum coil: first, because most of the finished aluminum coil products are decorative or packaging materials, there must be a clean surface; Second, its thickness is thin, it is easy to form bubble in subsequent annealing, and it is affected by the excessive amount of oil in the area. The oil pollution defect is an important index to evaluate the quality of aluminum foil.
. Solution: strict inspection equipment before production, if once found in the device too much oil to wash and timely find the reasons, at the same time to board face cleaning products processing, if wash not to drop products do scrap processing, oil product storage and flow into the market is prohibited.
Scratches are frequent customers of quality problems: scratches, bruises, and bruises are intermittent or continuous on the surface of the aluminum sheet. It is usually produced when the sharp object is sliding relative to the surface of the foil.
The main reasons are: there are pointed defects on the surface of roller and guide roller. Shear, coiling, cutting mechanical guide roller, guide road with pointed defect or dry debris. Bruise: a scar on the surface of a box that is caused by a relative slip or dislocation due to the surface or surface of an object, or by the relative slip or dislocation after contact with the surface.
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| Common problems and elimination methods of aluminum processing |
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Posted by: aluhm - 02-25-2018, 07:00 AM - Forum: Knowledge & Technique
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Professional knowledge of aluminum processing and production:
1. Causes and elimination methods of extruded product bubbles and peeling defects?
Bubble or peeling: a convex bubble on the surface of the product, usually seen in the head and tail, complete with a bubble, and a broken bark.
(1) extruded product bubbles and the causes of peeling.
extrusion cylinder, pressure pad wear out-of-tolerance, extrusion cylinder and the pressure pad size mismatch, and at the same time using two diameter difference exceeds allowable values of gasket;
The extrusion cylinder and the extrusion pad are too dirty, with oil, water, graphite, etc.
The lubricating oil contains water;
There is too much spatula on the surface, too deep; The surface of cast ingots has pores, sand holes, loose tissue and oil, etc.
... When replacing the alloy, the tube is not cleaned;
The temperature of the extruded cylinder and the temperature of the extruded ingot are too high;
‡ ingot casting temperature, size more than allow the negative deviation;
ˆ ingot is too long, fill quickly, ingot casting temperature, cause the drum fills, and so are not entirely within the cylinder exhaust, or improper operation, not execute exhaust process;
The design of the die is not reasonable, or the residual material is improper. The residual material in the shunt hole and the guide hole is partially brought out.
(2) the method of eliminating bubble and peeling of products.
container and dummy blocks with the size of the reasonable design; Check the size of the tool regularly to ensure that it meets the requirements. The extruded cylinder should be repaired in time, and the extrusion pad should not be too poor.
The surface of the caster is clean, smooth and dry.
When the alloy is replaced, the cylinder is completely cleaned;
... frequently check equipment and equipment to prevent excessive temperature and speed;
... Strict implementation of technical procedures and systems;
† reasonable design, manufacturing mold, diversion hole and diversion hole design into 1 ° ~ 3 ° slope;
‡ operation strictly, shearing residual material correctly and completely exhaust.
2. Causes and elimination methods of extrusion crack defects of extruded products?
Crush crack: the jagged (periodic), cracking or tearing of the edge of the extruded material or the thickness difference. Macroscopic and microscopic observation shows that there are more cracks at regular intervals, and the high strength aluminum alloy is prone to this cracking. When the extrusion temperature or extrusion speed is high, the extrusion material is embrittled at high temperature, and the angular radius is easy to produce.
(1) the cause of extrusion cracking of extrusion products.
extrusion wool temperature too high;
It's squeezing too fast;
The throttle valve is out of control;
The list of heating furnace fails;
... When the hole is extruded, the hole arrangement is too close to the center, so that the center metal supply is insufficient, so that the center and the side flow velocity are very different.
The design of the mold is not good;
‡ ingot homogenizing annealing is bad.
(2) elimination method of extruded product extrusion crack.
reduce extrusion temperature and extrusion speed;
To ensure the normal operation of the instrument and equipment;
The design of the mould design and elaboration, especially the transverse bridge, welding room and corner radius, should be reasonable. The edge radius of the extruded part is as large as possible;
... reduce Na content in high Mg alloys;
... The ingot is homogenized and improves the plasticity and uniformity.
3. Causes and elimination methods of shrinkage defects of extruded products?
The tail is the surface layer of the billet and the dirt attached to the extruded cylinder, or the lubricant, and the defects formed in the extrusion in the late extrusion. Metal discontinuous defects mostly ring or funnel-shaped. Because it is an internal defect, it can be found after corrosion. The shape of the extruded material is different and different, but most of them occur in the ring and the central part, and there is also the formation of tubular hollow holes. At the end of the extrusion, the center part of the billet gives priority to the surface layer of the billet. „
(1) the causes of the compression of the extrusion products.
scrap leave too short;
The end velocity is too fast or sudden;
The surface of the cast ingots is not clean, there is oil pollution, and there is no net segregation of the car.
The temperature of the extrusion cylinder is too high;
... The extrusion cylinder and the extrusion shaft are not correct;
The inner liner is not smooth or deformed in the extrusion cylinder, and the lining is not cleaned in time.
‡ dummy blocks size bad cooperation, gasket not cooling, surface with oil pollution or gasket anointed with oil.
(2) the elimination method of extruding products.
leave residual material according to the rules and cut the tail;
Keep the mould clean and clean;
To improve the surface quality of ingots;
The extrusion temperature and speed should be controlled reasonably, and the extrusion should be smooth.
... In addition to special cases, it is strictly prohibited to apply oil on the surface of the mold or mold.
The die gasket is cooled properly.
4. Causes and elimination methods for the defect of the extruded product?
Coarse grain ring: some aluminum alloy products from the low power inspection after quenching treatment, on the face grain sizes and grain surrounding the special thick, the defects of annular organization, the more close to the end of the greater depth of coarse grain ring.
(1) the causes of the extrusion of coarse crystal rings.
Uneven extrusion deformation, metal extrusion wall friction, deformation degree, grain serious breakage and heat treatment heating surface grain grew up and became thicker significantly;
The quenching temperature is too high or the heat preservation time is too long;
It is related to alloy composition and ingot.
(2) the elimination method of extruded product's coarse crystal ring.
extrusion cylinder wall smooth, form a complete set of aluminum, reduce the friction when extrusion;
The deformation is as uniform as possible (control temperature, speed, etc.);
Avoid quenching temperature too high;
() extruded by porous mold;
... Extrusion with anti-extrusion and hydrostatic extrusion;
The composition of alloy was adjusted to increase the recrystallization inhibition element.
‡ using high temperature extrusion;
ˆ some alloy homogenization processing, coarse grain ring shallow during extrusion.
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| ALUMINUM TEMPER DESIGNATIONS |
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Posted by: aluhm - 02-25-2018, 06:53 AM - Forum: Knowledge & Technique
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The temper designation follows the alloy code and is separated by a hyphen.
-F As Fabricated: Applies to products of rolling or forming where there is no special control over the thermal or work-hardening conditions. Since mechanical properties may vary widely, no limits have been assigned. This temper usually applies to sheet products which are at intermediate stages of production.
-H Strain-Hardened: Applies to wrought products which are strengthened by cold-rolling or cold-working.
-O Annealed: Applies to wrought products which have been heated above the recrystallization temperature to produce the lowest tensile strength condition of the alloy.
DESIGNATIONS OF THE –H STRAIN HARDENED TEMPERS
The First Digit
There are three different methods used to achieve the final temper of strain hardened material.
–H1 Strain Hardened Only: Applies to products which are strain hardened to obtain the desired strength level without any subsequent thermal treatment.
–H2 Strain Hardened And Partially Annealed: Applies to products that are strain hardened to a higher strength level than desired, followed by a partial anneal (or “back anneal”) which reduces the strength to the desired level.
–H3 Strain Hardened And Stabilized: This designation only applies to magnesium-containing alloys which gradually age- soften at room temperature after strain hardening. A low temperature anneal is applied which stabilizes the properties.
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| The Benefits of Aluminum |
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Posted by: aluhm - 02-25-2018, 06:52 AM - Forum: Knowledge & Technique
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- Aluminum is a light metal, about the third of the density of steel, copper, and brass.
- Aluminum has good corrosion resistance to common atmospheric and marine atmospheres. Its corrosion resistance and scratch resistance can be enhanced by anodizing.
- Aluminum has high reflectivity and can be used for decorative applications.
- Some aluminum alloys can match or even exceed the strength of common construction steel.
- Aluminum retains its toughness at very low temperatures, without becoming brittle like carbon steels.
- Aluminum is a good conductor of heat and electricity. When measured by equal cross-sectional area, electrical grade aluminum has conductivity which is approximately 62% of electrical grade annealed copper. However, when compared using equal weight, the conductivity of aluminum is 204% of copper.
- Aluminum is readily worked and formed using a wide variety of forming processes including deep- drawing and roll forming.
- Aluminum is non-toxic and is commonly used in contact with foodstuffs.
- Aluminum can be readily recycled.
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| Mechanical properties and common terminology of aluminum alloy |
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Posted by: haomeialu - 02-25-2018, 06:50 AM - Forum: Knowledge & Technique
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1, the intensity
Strength is the ability of metal materials to resist permanent deformation and fracture under external forces. It is commonly used in engineering to indicate that the strength of metal material has yield strength and tensile strength.
Yield strength is the limit of yield when metal materials yield, which is the stress of resistance to microplastic deformation.
The delta S = Fs/AO
Fs-- the maximum external force (N) when the sample yields the yield phenomenon
AO-- the original sectional area (mm2)
Delta S- yield strength (Mpa)
Tensile strength refers to the maximum stress the metal material can bear before pulling out.
FO-- the maximum external force before fracture (N)
AO-- the original sectional area (mm2)
Delta b- tensile strength (Mpa)
2. Elongation
The elongation ratio mainly measures the plastic properties of the material, i.e. the properties of permanent deformation without fracture.
The delta = (L - L0)/L0 * 100%
The delta - elongation
L0-- the original length of the sample.
L-- the length of the specimen after tensile fracture.
3, hardness
The ability of metal materials to resist the pressure of other harder objects is called hardness, or the resistance of the material to local plastic deformation. Therefore, hardness and strength have a certain relationship. According to the determination method of hardness, the most commonly used hardness values are  1) brinell hardness (code HB), (2) rockwell hardness (HRC); HRB), (3) vickers hardness (code HV), (4) weber hardness (code name HW). There is a certain conversion relationship between each hardness index, such as rockwell hardness HRC and brinell hardness HB: 1HRC is approximately 0.1hb.
4. Fatigue strength
Metal materials in the long-term repeated stress or under the action of alternating stress (stress generally are less than the yield limit of the delta S strength), the significant deformation occurs fracture phenomenon called fatigue or fatigue fracture.
5. Elastic modulus.
This is material on the elastic limit stress sigma and strain within the scope of the delta (corresponding to the stress deformation) ratio, expressed in E, unit of MPa (MPa) : E = sigma/delta tg = alpha type of alpha for tensile test curve o - E line and horizontal axis o - Angle x. Elastic modulus is the index that reflects the rigidity of metal materials (the ability to resist elastic deformation when metal materials are stressed is called rigidity).
6. Internal stress
The force on the sectional area of an object is called stress. Stress is called the working stress caused by external force, under the condition of without external force known as the internal stress of balances the object interior stress (such as stress, thermal stress, residual stress after the machining process of the... Etc.).
7. Stress annealing.
Stress annealing is also known as low temperature annealing (or high temperature tempering). This annealing is mainly used to eliminate residual stresses in castings, forgings, welding parts, hot rolled parts, cold drawing pieces and so on. If these stresses are not eliminated, the material will cause deformation or crack in the subsequent machining process after a certain period of time.
8. Solid solution heat treatment.
The alloy is heated to a high temperature single phase zone constant temperature, so that the excess phase is fully dissolved in the solid solution and then quickly cooled to obtain the heat treatment process of the supersaturated solid solution. Objective: to dissolve various phases in alloy, strengthen solid solution, improve toughness and corrosion resistance, stress and softening, so as to continue processing or forming.
9. Aging treatment
The metal workpiece after quenching should be kept at room temperature or high temperature to improve the metal heat treatment process. The aging treatment at room temperature is natural aging; The aging treatment at higher temperature is artificial aging. In mechanical production, the casting is usually placed at room temperature for a long time in order to stabilize the casting size. This measure is also known as aging. But this limitation does not belong to metal heat treatment process.
10. Conductivity and conductivity.
The resistance value of the unit cross-sectional area and the unit length metal conductor is called the volume resistivity (the resistivity), also known as the resistivity, denoted by the symbol P, and the unit is ohm. Mm 2/ m; The reciprocal of the volume resistivity is called the volume conductivity (the conductivity), also known as the conductivity factor, and the unit is msi /m (MS/m). The percentage of the conductivity of the sample and the ratio of a standard value is called the conductivity of the sample.
In 1913, the international annealing copper standard was determined: the use of the annealed copper wire with a density of 8.89 g/cm, with a length of 1 m, a weight of 1g and a resistance of 0.15328 ohm as the measurement standard. Under the temperature of 200 c, the resistance coefficient of the annealed copper wire is 0. 0172411 ohm. Was/m (or conductivity of 58.0 MS/m) determined to be 100% IACS (international standard annealed copper), the conductivity of the its him any material (% IACS) are available under the type of computing: conductivity (% IACS) = 0.017241 / P * 100% or conductivity (% IACS) = P / 58.0 * 100%.
11. SGS report
SGS is a third-party certification body, on the material chemical composition and mechanical properties for the third party inspection report, it can make management system certification, such as inspection, also can do product certification (can send CE, GS certificate), moreover is a chemical test. It usually takes 7 working days to do SGS chemical test.
Misunderstanding of SGS report:
A, "SGS report" is only test report, namely test report, not the ROHS certificate issued by SGS institution.
B. The "SGS report" is only responsible for the reliability of the data of the test items mentioned in the samples, but not in accordance with the ROHS directive.
C. The "SGS report" is permanent and valid for the data of the test items mentioned in the sample.
D, "SGS report" is not only "lead-free test".
E, "SGS" is the abbreviation of Societe Generale DE Surveillance S.A., which is translated as "general public license bank", and "SGS report" is not the only agency required to be tested by ROHS directive; There is also the report of ITS report, CQC report.
F and "SGS report" not only carry out the 6 items required by ROHS directive, but also carry out "environmental hazardous substances" detection, safety test and others listed in national regulations; SGS does not equal RoHS. The place to fill RoHS cannot be filled into SGS.
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| Defects in aluminum alloy material |
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Posted by: aluhm - 02-25-2018, 06:47 AM - Forum: Knowledge & Technique
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1 size error due to the unreasonable mold design or manufacturing error, improper extrusion technology and die and extrusion of the cylinder, lubrication, such as unreasonable bring various points in the metal flow velocity difference is too large, resulting in a deformation of the profile, internal stress due to the large QianDongLi or lead to large amount of stretch of the profile size deviation.
A circular section of a circular section, such as the transverse section of a bar or tube, of varying diameters in each azimuth.
The bending length is not straight in the direction of length or width, showing the degree of the curve.
4 pull mark straight hook shape, visible to the naked eye to the local or full-length distribution of aluminum.
The cracks are usually straight in line, sometimes in the Y shape, often in the same direction as the drawing direction, but there are other directions, and the general opening is acute.
The surface of the corrosion material is partially overlapped, and there are obvious folds.
In the section of the layered material, there is an obvious separation of the metal structure. In severe cases, there are two or three layers, with visible inclusions between the layers.
8 distribution of bubble surface without rules is round, big and small convex hull, its outer edge is smooth, mostly take, also some not pluck up and shine after pickling flat surface, the layered shear section
9. The point on the surface of the profile is either partial or continuous, with the appearance of different densities, with a trailing or very small tumor, and the sensation of sharp prickles. Severe hemp spots similar to orange peel, larger and deeper than hemp.
10 After anodizing of black spot profile, there are approximately circular black and gray spots, which are different in size.
11 An expression of loose material that is not dense. After the slice is eroded by acid, it is expanded into many caves, according to its distribution can be divided into general loose and center loose.
12 The distribution of chemical compositions and non-metallic inclusions in the materials is not uniform. It can be divided into dendritic segregation, box segregation, point segregation and reverse segregation according to its manifestation.
13 shrinkage cavity residual in the central part of the transverse acid test film, showing irregular cavity or crack. Foreign impurities often remain in holes or cracks.
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| Heat sensitivity considerations of aluminium |
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Posted by: aluhm - 02-25-2018, 06:39 AM - Forum: Knowledge & Technique
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Often, the metal's sensitivity to heat must also be considered. Even a relatively routine workshop procedure involving heating is complicated by the fact that aluminium, unlike steel, will melt without first glowing red. Forming operations where a blow torch is used can reverse or remove heat treating, therefore is not advised whatsoever. No visual signs reveal how the material is internally damaged. Much like welding heat treated, high strength link chain, all strength is now lost by heat of the torch. The chain is dangerous and must be discarded.
Aluminium is subject to internal stresses and strains. Sometimes years later, as is the tendency of improperly welded aluminium bicycle frames to gradually twist out of alignment from the stresses of the welding process. Thus, the aerospace industry avoids heat altogether by joining parts with rivets of like metal composition, other fasteners, or adhesives.
Stresses in overheated aluminium can be relieved by heat-treating the parts in an oven and gradually cooling it—in effect annealing the stresses. Yet these parts may still become distorted, so that heat-treating of welded bicycle frames, for instance, can result in a significant fraction becoming misaligned. If the misalignment is not too severe, the cooled parts may be bent into alignment. Of course, if the frame is properly designed for rigidity (see above), that bending will require enormous force.
Aluminium's intolerance to high temperatures has not precluded its use in rocketry; even for use in constructing combustion chambers where gases can reach 3500 K. The Agena upper stage engine used a regeneratively cooled aluminium design for some parts of the nozzle, including the thermally critical throat region; in fact the extremely high thermal conductivity of aluminium prevented the throat from reaching the melting point even under massive heat flux, resulting in a reliable, lightweight component.
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| Aluminium alloys versus types of steel |
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Posted by: aluhm - 02-25-2018, 06:36 AM - Forum: Knowledge & Technique
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Aluminium alloys typically have an elastic modulus of about 70 GPa, which is about one-third of the elastic modulus of most kinds of steel and steel alloys. Therefore, for a given load, a component or unit made of an aluminium alloy will experience a greater deformation in the elastic regime than a steel part of identical size and shape. Though there are aluminium alloys with somewhat-higher tensile strengths than the commonly used kinds of steel, simply replacing a steel part with an aluminium alloy might lead to problems.
With completely new metal products, the design choices are often governed by the choice of manufacturing technology. Extrusions are particularly important in this regard, owing to the ease with which aluminium alloys, particularly the Al–Mg–Si series, can be extruded to form complex profiles.
In general, stiffer and lighter designs can be achieved with Aluminium alloy than is feasible with steels. For instance, consider the bending of a thin-walled tube: the second moment of area is inversely related to the stress in the tube wall, i.e. stresses are lower for larger values. The second moment of area is proportional to the cube of the radius times the wall thickness, thus increasing the radius (and weight) by 26% will lead to a halving of the wall stress. For this reason, bicycle frames made of aluminium alloys make use of larger tube diameters than steel or titanium in order to yield the desired stiffness and strength. In automotive engineering, cars made of aluminium alloys employ space frames made of extruded profiles to ensure rigidity. This represents a radical change from the common approach for current steel car design, which depend on the body shells for stiffness, known as unibody design.
Aluminium alloys are widely used in automotive engines, particularly in cylinder blocks and crankcases due to the weight savings that are possible. Since aluminium alloys are susceptible to warping at elevated temperatures, the cooling system of such engines is critical. Manufacturing techniques and metallurgical advancements have also been instrumental for the successful application in automotive engines. In the 1960s, the aluminium cylinder heads of the Corvair earned a reputation for failure and stripping of threads, which is not seen in current aluminium cylinder heads.
An important structural limitation of aluminium alloys is their lower fatigue strength compared to steel. In controlled laboratory conditions, steels display a fatigue limit, which is the stress amplitude below which no failures occur – the metal does not continue to weaken with extended stress cycles. Aluminium alloys do not have this lower fatigue limit and will continue to weaken with continued stress cycles. Aluminium alloys are therefore sparsely used in parts that require high fatigue strength in the high cycle regime (more than 107 stress cycles).
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