Forging

Forging is the non-cutting pressure forming of metals between two tools by changing cross section. Benefits are lower loss materials as opposed to machining and the targeted change in the fine structure, that is, the crystal structure. A disadvantage is the opposite cutting methods less accuracy.

The manual forging ( open die forging ) is one of the oldest crafts in human history. Here the blacksmith has the shape of his work piece on the anvil or today thanks to the air hammer work freely what empathy and above all experience presupposes. The blacksmith (also blacksmith ) works with forge hammer, anvil and coal or gas forge.

The industrial forging manufactures components for mechanical engineering and plant construction and the automotive, aerospace and shipbuilding. The industrial forging is an important industry in Germany. In 2006, the industrial production volume in Germany was 2.75 million tons, equivalent to at least 1.8 billion of formed parts. In 2008, the industrial production volume in Germany amounted to 3 million tonnes, representing 2 billion of formed parts.

• 4.1 Manually open die forging
• 4.2 Industrial Freiformschmieden
• 4.3 forging
• 4.4 Längschmieden
• 4.5 precision forging

History

Probably the metals gold, silver and copper were processed by human beings first. These three are found in nature pure ( metallic) ago - copper, however, rarely - and can be cold formed into sheets or tools in a cold state and thus be processed. So far the oldest finds of copper plates for jewelry date from the 8th millennium BC in Anatolia. The inhabitants of present-day Afghanistan should have been BC metals processed and finished by 6000. From about the same period are also the first evidence produced by smelting copper hatchets and chisels in today's Serbia ( Pločnik ) whose blades were cold forged and thus solidified superficially.

Also finds in Mesopotamia, Egypt and India ( Indus Valley Civilization ) have shown that there was probably already forged over 5,000 years ago in the hot state. In Central Europe the famous Nebra sky disk is about 4000 years ago, an important example of blacksmithing, had to have for their preparation has the former smithy oversized material experience.

The invention of the hardenable iron (steel) succeeded by historical scientific evidence for the first time around 1400 BC, the Hethitern.Bereits in the pre-Roman Iron Age found anvils made ​​of bronze or iron use. Because of their rare occurrence in an elegant shape and the elaborate production from alternative ores and the good properties compared to conventional materials, these and other metals had a high material and cultural value. They were much sought-after commodity, a cult object and status symbol.

With all the historical peoples forging has taken hold in Art and Culture:

• In mythology ( eg in the Greek myth of God " Hephaestus " and its helpers, the " cyclops " ( Cyclops ) or " Pythagoras in the forge ", in Roman mythology " Vulcanus ", in the Germanic " Wieland the blacksmith, " from the Hebrew Bible, the blacksmith" Tubal- Cain "or the wonder-Smith " Ilmarinen "in the Kalevala )
• In proverbs and sayings: ( " you have to strike while the iron while it " "is" hot ... " make plans " ... " drive someone to distraction " ... " two irons in the fire have " ... " everyone has his own fortune " )
• In the literature: (detailed in Karl Simrock Amelung song)
• In painting: ( Adolph Menzel The drop forge, Hans Leu the Elder Miracle of St. Eligius. )
• In music ( in Richard Wagner's Der Ring des Nibelungen )

Mircea Eliade studied in his work and alchemists forge the ideas and customs that were associated in ancient times with the mining industry, with the work of metallurgists and the forge.

As a global technology leader in the German forging and Massivumformer supply the key industry vehicle with around two thirds of the production and engineering with a further 20 percent. In addition, the aviation and space technology, the energy sector, medical technology and shipbuilding. In the area of ​​industrial forging about 250 mostly medium-sized companies employ over 31,000 employees in Germany. Industry turnover in 2006 was about 7.8 billion euros.

Forgeable materials

For forging are a few exceptions, all metals and metal alloys. From over 2500 types of steel, the variety can be selected for the most economical use. One speaks only from forging when the transformation above room temperature takes place, the workpiece is thus heated or the workpiece is significantly heated by the transformation.

Transformation

Molding is carried out at forging generally at higher temperatures than the temperature of use of the metal structure to change or at high pressure and at normal temperature. The processing temperature is either above the recrystallization temperature ( hot working ) or below the recrystallization temperature ( cold forming ).

On the process of forging includes the casting or rolling of the blank, the hardening and tempering and grinding. Compared to the casting of the material remains in the solid state and is using a hammer and anvil or with machines, such as air hammers and presses, edited.

Hot, warm, cold forming and thixoforging

Depending on the forming temperature differentiates:

• Hot forging forging of steel: Operating temperature is above the recrystallization temperature, 950-1250 ° C
• Large formability of the materials
• Low deformation forces
• No change in strength on the formed workpiece

• Warm forming for forging of steel: Working temperature for steel at 750-950 ° C
• No or low as oxidizing on the surface
• Less than forming forces during cold forming
• Closer tolerances than during hot forming
• Limited formability and greater forces required

• Cold forming ( cold forming is in the strict meaning no forging) steel: Working temperature is room temperature, self-heating up to 150 ° C by the forming energy
• Tight tolerances are within
• No scaling of the surface
• Increase the strength and decrease in elongation due to strain hardening

• Thixoforging: Working temperature is between solidus and liquidus temperature of the respective alloy steel, well above the hot forging temperature
• Formability similar to the casting
• Low deformation forces

In hot forging, the to be forged semifinished product is heated in a kiln to temperatures between 950 ° C and 1250 ° C and then forged by printing a hammer blow or the pressure between two die halves (also transformed ). In contrast to the coining of this entire material cross section is plasticized. At high forging temperatures steel is transferred in a different crystal structure and is softer. By forming the structure and the mechanical properties of the material change significantly.

For industrial processes the metals steel, iron, and their alloys are forged generally warm, with each metal requires a different deformation temperature. Brass, bronze, copper, precious metals and their alloys, however, are cold formed normally.

The method of forming by rolling originated from the forging. Seamless rolled rings are typical products of forging. The ring rolling allows seamless rings with square and rectangular cross sections as well as the inside and / or outside profiled rings. The largest diameter available in 2010 was 8.0 meters.

Shaping

Manually open die forging

Wrought use the forging especially in the restoration, in heritage conservation and in the creation of individual pieces such as canopies, grilles, gates, railings, fountains, etc., or even lights, wardrobes, candle holders.

The various techniques that will be used by the smith's forging on the anvil, forging process are the following:

• Add: welding
• Shrink

• Disconnect: Abschroten
• Cleave
• Punch holes

• Forming: sharpen
• Spread
• Settlement
• Compress
• Stretch
• Anti- clastic forging (especially for jewelry )
• Arbitrate
• Turn
• Twisting

• Other methods are: hustle and bustle
• Dengeln
• Fold

Both the blacksmith as the farrier heat their forgings in the forge. The workpiece absorbs heat, it says it has heat. Enough " heat " is not sufficient, it gets a " second heat".

While the coke-fueled fire is common in the UK, to use in Continental Europe almost exclusively by means of a special bituminous coal (called " fat nut" ) -fed coal fire and, more recently, gas-operated, occasionally filled with ceramic chips or volcanic fire. However, the occurrence of good blacksmith coal worldwide are exhausted or unprofitable for the usual large-scale industrial mining; the now mostly available coal has far too high a proportion of volatile components (up to about 30%).

Industrial Freiformschmieden

When forging is the forging between non- dimensionally bonded tools, saddles, formed by a press or a hammer ( air hammer ). In this case, the material can escape into the enclosed not by the tools areas.

Especially very large individual pieces are processed by industrial free-form forging; For example, crankshafts of marine diesel engines or generator rotor for turbo engines. Weights of up to 250 t are possible. Large forging manufacturer in Germany, for example, Buderus stainless steel, the forging Gröditz and Saarschmiede. The latter is Europe's largest forging.

The heating of large forgings done as well as the temperature-controlled cooling in fuel-heated chamber or bogie hearth furnaces.

For the movement of the workpiece are correspondingly large gripper, called forging manipulators.

Gesenkschmiede

Forging

The forging is different from the open-die forging is that the forging is almost completely enclosed by the closed mold, the die. The into the die introduced by mold makers negative mold determines the shape of the finished forging. By forging especially safety-related parts such as smaller crankshafts, connecting rods, gears, or tie rod ends, steering parts, transmission parts and wear parts are manufactured for construction machinery. The material obtained by forging a cheap grain. Thus, the crack sensitivity is decreased and component safety. The disadvantage of the die forging is that a minimum number of identical forgings to be produced, since the cost of a die is high. The manufacture of the dies by means of engraving or milling and / or sinker EDM for original forms in an oil bath.

The method of die forging process can be divided into the following five sections:

Typically a square or round steel is inductively heated or by means of gas-fired impact or rotary hearth furnace to the required molding temperature of 750 to 950 degrees Celsius at the warm and 950-1250 degrees C during hot forming in industrial forging.

If the forged component having a complex shape with very different mass distribution, it is preformed before the actual drop forging, ie it takes place a targeted mass distribution that already comes relatively close to the final forging. Thus, component failure can be due to locally high degrees of deformation or avoid high degrees of deformation in the first place. At the same time reducing costs through lower material consumption.

His final form receives the forging die forging in die consisting of two die halves. Under high pressure, a forging hammer or a forging press is here at forging temperature of approximately 1,200 degrees Celsius instead of the targeted mass distribution and final shaping.

A distinction is cold and Warmabgraten. The process Warmabgraten and punching the drop forging is directly downstream of the swaging. When trimming the ridge located outside of the part is removed. Case, the component is pressed by a punch by a cutting board. When punching the Innengrat ( slug ) is removed by means of a stamp. When Kaltabgraten is trimmed and punched after cooling of the workpiece in a process. This method is mainly used for very delicate forgings, such as cutlery.

(Heat treatment from the forging heat): Depending on how fast or slow done the cooling process ( in static ambient air, under a blower fan or in a liquid medium (water, oil, salt baths, aqueous polymer solution) ), or whether this in one or more increments takes place ( stepped cooling ), characterized the finished component, additional material properties may be added.

Längschmieden

By Längschmieden are manufactured with non-shape -dependent tools long workpieces with simple geometries (eg barrels ). In this method, it is an automated forging with particular accuracy of the workpieces. The forging is done in Längschmiedemaschinen in which perpendicular to the workpiece attached hammers work in pairs against each other. The feed and the appointment of hammers are programmatically it.

Precision forging

Will almost ready to install workpieces produced by forging, this is known as precision forging. It is irrelevant which forging process is used, only the achieved accuracy is defined as a forging process precision forging. They are normally here from a tolerance of up IT8 IT6 (better than / - 0.1 mm). Precision forging is used in industry in many cases. Above all parts in internal combustion engines (eg cams for " built " camshafts to control the valves ) and the drive train of motor vehicles - eg gear wheels - are produced in this way.

Forging Machines

A distinction is made between free-form, drop forging hammers and forging presses.

Hammers are suitable for large workpiece masses. Hammers are suitable depending on the design for the smallest to large forgings. The piece weights about 100 grams have up to 1,000 kilograms. In forging hammers occur large strain rates. The penetration depth of the deformation is limited because of the frictional losses in the workpiece. In forging presses the force is applied more slowly and so, the flow process to penetrate deeper into the material. This is particularly important for very large workpieces. The working capacity of drop forging is expressed in kJ and the work force in presses in kN.

The following are the types of forging machines:

• Work- bound Machines hammer for forging, for example, air hammer, hammer spring, hammer case
• Die forging
• Screw presses

• Crank presses
• Toggle Presses
• Eccentric
• Horizontal forging presses

• Hydraulic presses (slower strength building )