Metal cold heading
Service:Metal cold heading,Metal impact heading
Short Description: Manufacture metal products with cold heading(or named impact heading) technology according to customer`s drawing or sample;
Material: Aluminium,Copper,Brass,Steel,Stainless Steel,etc;
Shape & Size: Customized according to drawing;
Place of Origin: China,Do Metal cold heading to World;
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|What can we do for you?–Metal cold heading|
|Benefits of Metal cold heading|
Most of machined parts could be re-designed and re-manufactured to be parts made by technology of cold heading,which help you to get significant cost savings.
- Improve production effience and reduced Production costs:Because of using high speed manufacturing process. The speed reaches range from 10 pieces per minute for low volume large press work to to 450 pieces per minute on the cold heading process.
- Save material cost: Compared to a traditional machining process, cold forming process can save up to 70%.
- Better control product tolerance: compared to more expensive machining processes,less tolerance can be achieved throughout the production process by coldforming
- Higher and better quality surface: compared to conventional machined surfaces ,cold forming process can get result . The cold forming process can eliminate the need for costly secondary operations, such as welding, machining, etc, with careful product and process design,
- Improved part performance and characteristics: due to the metal deformation resulting in improved grain structure, while work hardening can yield significantly improved product performance,cold forming process can improve metal part performance and its characteristics.
For many OEMs,cold heading represents clear opportunities for cost savings over traditional large component manufacturing methods.
Material and Process Cost Advantages:
See below charts to check how much you can save if made with cold heading technology:
The Result: Lower Costs of Product to the Customer
Better Quality and Consistency: cold heading is a purely mechanical process that forms metal into net or near net shapes, but unlike traditional alternatives, it is performed at room temperature without using additional heat, providing more precise tolerances and part to part consistency than any other method.
The products made with Cold Forging:
- Higher Strength: Cold forming work hardens the material raising its yield stress, making it significantly stronger than can be produced through other methods. With these higher strength properties, component design thickness can often be reduced offering further savings on weight, material and clearance.
- Higher yields for exceptional strength
- Most precise tolerances available
- Improved physical properties by refining grain structure
- Exceptional surface finish no scale
- Part-to-part uniformity/repeatability
- Better functional reliability
- Reduced/eliminated machining & waste
- May eliminate subsequent heat treating
Advantages of cold heading
|Speed||Depending upon the size and complexity of the part and the nature of the equipment of producing them, production rates of 4000 pieces per hour can be achieved.|
|Economy||When compared to casting and machining labor the metal savings alone justify the conversion to an impact extrusion.In some cases when the aluminum slug is sized accurately, little or no trimming or other secondary operations are required.|
|Strength||The impact process naturally work hardens non-heat treatable alloys, while the heat treatable alloys can be heat treated in normal fashion after processing.|
|Toughness||The impact extruding process produces parts that are dense and porous-free in structure. This condition cannot be obtained in a casting process or by machining of a bar material.|
|Versatility||After impacting, the product can be treated the same as any other piece of material. Secondary operations such as machining, grinding, welding, bending, plating or anodizing can be performed in the same way as any other piece manufactured by a more conventional process.|
|Consolidation||Impacts can directly replace machined components, or welded or riveted assemblies, in many designs. The process often reduces product costs for secondary machining operations and in many cases increases the strength of a product that was previously an assembly.|
|General Knowledge on “Metal Impact Extruding”|
What is Mtal Cold Heading Process?
Cold heading,also named impact heading,is volume specific and the process uses dies and punches to convert a specific “slug” or blank of a given volume into a finished intricately shaped part of the exact same volume.
Cold Heading process means to adopt quick automative “part formers” or “cold-headers” to cut off and push into or transform a metal wire or metal bar into a shaped die, then, in an outward direction,the protruding end is upset. Through the above process, the metal wire(bar) is shaped on the same axis and it always involves to change a diameter from the original wire size as an extrusion.It can do repetitive and tight tolerances by using a special tooling succession at a quick speed up to four hundred times every minute.It is a high efficient technology to manufacture metal fasteners,screws,nuts and custom various of metal parts and components according to your drawings or samples.
The secondary process after Metal cold heading:
Though metal parts coming from cold heading process are usually complete or near to be finished with very small minimal scrap, generating significant raw material savings compared to traditional screw machining process,it always still is used as the primary manufacturing process which produce as simple as a screw/nut blank. The part then always comes with secondary process including polishing,maching,etc to achieve more high precision part configuration with good tolerances grade.The best commen secondary process are:
- Heat Treatment. To achieve a desired result such as hardening or softening of a material. Heat Sometimes,heating and cooling are done for the specific purpose of altering properties intentionally, they often occur incidentally during forming.
- Polished.To polish the cold forming product,usually,they will be sprayed with mini stainless steel ball in a closed room,then all scraps,oils,burrs will be removed.
- machined or lathing.Machining process is usually to make screw thread or make a horizontal hole on the cold forming product.As cold forming process itself is diffcult to make thread or horizontal hole.
- Anodic oxidation or electroplating.After all processes are finished,some products are required to do electroplating.If the product is made from aluminium,it is always required to do anodic oxidation
Typical Design Considerations for Cold Heading Parts
The below designs are some typical metal part which are always to manufactured by the cold heading process :
- Metal Hexagonal Head
- Metal Round Head&Square Head
- Round Head with Slit
- Radial Slot & Recessed Drive
- Double Reverse Extrusion
- Diameter Reduction
- Cylindrical Extrusion
- Offset, Pierced and Embossed
- Multi-Diameter Extrusion
- Carriage Bolt
- Offset Head
Material for cold heading process
Usually,the following metal are always to do cold heading processs:
- Brass or Bronze
- All kinds of Aluminum
- Carbon Steels wire or bar
- Stainless steel
- Alloy Steel
- Nickle Alloys
With the development of computer and cold heading process machines, cold heading design capabilities will be more and more and “endless.”
Cold heading`s metallic materials requirements
1, the mechanical properties of metallic materials for cold heading request
According to metal cold heading process characteristics,here is the requirement on the mechanical properties of the steel:
1) Yield strength Re and deformation resistance should be as low as possible, it let the unit deformation force to be reduced accordingly, to extend the life of the die;
2) cold deformation performance of meterial should be good, that means the materials should have good plasticity performance, lower hardness, which can let product avoid cracking in a large degree of deformation . For example,when you are going to cold head high strength bolts ,you can use carbon steel which has higher carbon content, also can use low carbon steel, low alloy steel. If increase carbon content in the metal, it will increase the hardness, decrease plasticity performance, to let cold deformation performance reduce. But if you add a small amount of alloying elements (such as adding a small amount of boron 10B21,10B33 steel) in low carbon steel, the steel can significantly be improved the strength to meet the performance requirements of the product ,and without compromising its cold deformation properties;
3) It`s better to have the lower sensitivity of the work-hardening materials, so that it can avoid too large deformation force. The work hardening sensitivity of the available material can be reflected by the deformation resistance – strain curve slope. The larger the slope, the higher the hardening sensitivity. Such as stainless steel 0Cr18Ni9 (SUS304),it has the maximum slope of the curve. The hardening sensitivity of this material is more intense, as the deformation increases, the deformation resistance rise sharply.
The performance of the mechanical properties of steel not only t billets original Rm, Re, A, Z and hardness and other indicators, affected not only by the chemical composition of raw materials, macroscopic tissue microstructure, etc., but also by the material preparation process drawing various channels and also affect by heat treatment process between.
2,Requirements on chemical constituents.
⑴ carbon (C) is the most important element to effect carbon steel`s cold plastic deformation . The more carbon content, the higher the strength of steel,but the lower plasticity performance. Each carbon content increased by 0.1%, the yield strength Re improve 27.4MPa, tensile strength Rm increase (58.8-78.4MPa), while the lower elongation A 4.3% reduction of Z 7.3% lower. When the carbon content of steel <0.5%, manganese content of <1.2%, reduction of Z = 80%, the unit is cold deformation force P and the steel containing C, Mn approximate relationship between the amount as follows:
P = 1950C + 500Mn + 1860 (MPa) …………………… (1)
You can see, the carbon content of the steel for cold plastic deformation properties is significant. In the actual process,the metal cold heading extruding steel carbon content is greater than 0.25%, it is required to have the best annealing steel plastic tissue – a spherical pearlitic structure. For the degree of deformation of 65% -85% of the cold heading fasteners without intermediate heat treatment is performed three times upsetting deformation, the carbon content should not exceed 0.4%. When the carbon content exceeds 0.3% -0.5% in the carbon steel, it is necessary to increase the use of intermediate or adopt process of full annealing,or use warm heading.
⑵ The role of manganese (Mn) steel with iron smelting .
(Mn + FeO + MnO + Fe) mainly for steel deoxidation to join. Manganese in steel acts with iron sulfide (Mn + FeS + MnS + Fe), can reduce harmful sulfur to steel performance. The Manganese sulfide formed can improve the machinability of steel/metal. Manganese let steel strength increase, decrease plasticity,it is unfavorable for cold plastic deformation properties , but the impact of manganese on the deforming force is only about a quarter of carbon. Due to the special performance requirements of the finished product, allowing for the sulfur content of manganese five times. In addition to the special requirements of the finished product, but should not exceed 0.9%.
⑶ silicon (Si)
silicon is the deoxidizer`s residues in steel smelting . When the silicon content in steel increased by 0.1%, the increase 13.7mpa. Experience has shown that when the silicon content of more than 0.17%, and greater carbon content, has a great influence on the plasticity of lower steel. Appropriate increase in silicon content in the steel, mechanical properties of steel, especially advantageous elastic limit, can also enhance corrosion resistance of steel. But when silicon steel exceeds 0.15%, so that the formation of non-metallic inclusions sharp steel, high silicon steel annealing does not even soften dramatically reduced cold plastic deformation properties of steel. If silicon is present in the steel in the form of silicic acid, the dispersion of the fine particles in the steel will be too worn mold. Therefore, in addition to product performance requirements of high-strength, cold heading steel always try to reduce the content of silicon.
⑷ sulfur (S)
Sulfur are harmful impurities. The sulfur in steel causes cold heading separated from each other at the time caused the crack. The presence of sulfur has also prompted to produce hot brittle and rusted steel. Thus the sulfur content should be less than 0.06%. When heading high-strength fasteners, should be controlled within 0.04%. Since the compounds of sulfur, phosphorus and manganese can improve cutting performance, the sulfur content of cold heading steel nut can be raised to 0.08% -0.12%, to facilitate for tapping.
⑸ phosphorus (P)
Phosphorus to solution strengthening and work hardening is very good.Severe segregation in the steel, increasing cold brittleness and temper brittleness of steel,to let the steel erodible acid. phosphorus will worsen cold plastic deformation properties in the drawing manipulation wire breakage, cracking in cold heading workpiece manipulation. Phosphorus content of the steel should desirably be controlled 0.045% or less.
⑹The effect from other alloying elements chromium (Cr), molybdenum (Mo), nickel (Ni), vanadium (V), tungsten (W) and other alloying elements on the cold deformation properties of steel is lower than carbon. In general, increases in steel alloying elements, mechanical strength index steel hardenability increases, performance decreases cold deformation.
3, microstructure request
In order to better adapt to the cold steel forging process, for the distribution of steel structure and the size and form of non-metallic inclusions has certain requirements.
⑴ steel structure
In addition to the ferritic steels in vitro, as well as pearlite. The higher the carbon content, the more the number of pearlite. Soft ferrite matrix, in the soft matrix embedded with hard pearlite particles. Piles of pearlite distribution is disadvantageous for cold deformation, will be the formation of cracks. Organization of steel should be closely uniform, so. Cold heading steel use as uniformly distributed spherical grain structure.
⑵ grain size
Deformation of the metal is due to the deformation of crystal grains and grain itself slip occurs. Within a certain volume, the number of fine grains of metal grains more inevitable than coarse grains of metal, plastic deformation position when slip of the grain to the benefit is greater, distortion can be uniformly dispersed in each grain. Corresponding to the fine-grained metal deformation inhomogeneity and unevenness due to deformation caused by stress concentration are small, so the chance of cracking is also small, appear to increase the amount of plastic deformation can withstand before cracking, plastic is better reflects foreign . The smaller the grains, the grains produced by excitation of adjacent slip stress is smaller. For the deformation continues, the applied stress must be increased, reflecting a larger external deformation resistance. Therefore should not be used for cold heading steel too small grains. Grains too, will make the surface rough, resulting in significant scars and cracks. Coarse grained steel work hardening sensitivity than fine grain steels, and less plastic, cold deformation performance is poor. Cold heading steel grain size requirements for the 4-6 grade, grain size specification is as follows: the average grain diameter of about (0.02-0.06) mm; the number of grains per mm2 of about 250-2300 months; average grain an area of about (400-4000) μm2.
⑶ nonmetallic inclusions
Regardless of the method of smelting steel, there will always be more or less non-metallic inclusions. An oxide or sulfide inclusions, causes the crystal structure of the metal close intermittently. In the form of inclusions, the number and distribution of different properties of steel for cold deformation effects are different. Cold heading wire is a hot-rolled steel products for use after cold drawing, rolling and cold drawing process, these inclusions have been elongated along the direction of deformation. In general, fine, uniform distribution of inclusions little damage. Small and scattered sulfide inclusions can be better with the deformation direction deformation, thus representing a number of other inclusions smaller damage resulting deformation. Particularly harmful alumina inclusions. Alumina fine particles not only extremely hard, it will damage the mold; and hard to combine with the steel substrate, often tearing manipulation in severe cold deformation of the workpiece. Thick or thin and local concentration of inclusions, for cold heading steel properties influence.
4, the requirement of surface quality
Surface condition of the majority of ordinary hot-rolled steel is not good enough. Hot-rolled steel surface defects after cold drawing (if the compression ratio is too small) can not be eliminated, resulting in cold heading product surface defects and waste, will be unable to produce serious.
⑴ billet surface defects
Steel smelting, steel ingot leaving bubbles, shrinkage and other defects. After hot-rolled and cold drawn, the wire with a more serious penetrating longitudinal, upsetting significantly when exposed to the product surface. Defects folded ears, segregation, cracks and other raw materials in the rolling, cold heading will cause serious harm. Such as: bolts breakage, cracking nuts; workpiece while rubbing and thread, screw blanks crushed in half and so on. Improper handling of raw materials in pickling, the steel surface pitting, corrosion. If pitting, corrosion minor, after cold drawing, is elongated pits on the surface is basically not show signs of cold heading in Buzhi Yu therefore cracks. If the pits will form a serious gap; the gap is presented in more corners of the large deformation of the workpiece. Cracks and other surface defects deeper, cold deformation performance worse. Experiments show: Whether cold-drawn or cold heading, shape deformation degree for cracks little effect, but the impact is great crack depth. For larger deformation cold heading materials, critical depth of surface defects is 0.04-0.10mm, deeper defects must be avoided.
In the low-carbon steel is heated atmosphere will cause decarbonization. Although the quality of the products from the appearance of decarbonization not see anything, but any change in the carbon content of the surface have a significant effect on the mechanical properties of the workpiece. Especially on the carbon content of more than 0.30% of the steel, the surface of the workpiece decarbonization fatigue strength and wear resistance obviously harmful. Material in order to prevent decarburization annealing, the protective gas should be used.
Contrary to carburization and decarburization. High carbon steel in high temperature environments will produce carburizing. While the finished product is equivalent to the carburizing for hard shell is acceptable, sometimes need to adopt a method of producing the soft-core, but for the cold heading process is quite harmful. There carburizing steel surface layer as thin as eggshells hard. When the material restructuring or cold heading, the surface will produce cracks or peeling, reduce cold deformation properties of steel. Therefore, cold heading steel should completely avoid decarbonization and carburizing. Decarbonization and carburizing steel case can be microscope examination.
⑵ dimensional accuracy requirements
The dimensional accuracy of the wire for cold heading has a great influence on product quality and process. Cold heading wire and molds are usually processed separately specialization. If the wire diameter exceeds the maximum allowable value, when the upsetting piece of metal on the head too, will have adverse burrs or workpiece curving bar. Or because the wire diameter is larger than the diameter of the die hole leaving the die hard feed. And the stem portion of the workpiece to be brushed die hole, the hole in the mold to form a sharp metal tumors. If the wire diameter is less than the minimum allowable value, while not upsetting the metal mold cavity is completely filled, causing the workpiece edges unclear. So cold heading material to be sufficiently close to the true circle, uniform diameter. Cold heading wire diameter tolerance is generally 0.20-0.35mm, roundness tolerance of 1/2 of the diameter tolerance.
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