In today’s world, steel is an extremely desired material for many applications since it has the optimum strength and toughness. Therefore, structural works, transportation of various matters and several engineering applications use steel components. Besides that, a wide range of steel production facilities and vast raw materials make the usage of steel substantially cost-efficient. The ease of secondary production of steel also affects the customer demand because the manufacturing of steel from scrap materials decreases the number of expenses since the recycling process minimizes the requirement of raw materials and processes. Thus, the recycling or secondary metallurgy of steels enables a huge amount of steel production that reduces the cost of steel parts.
Steel fabrication
The fabrication process generally refers to a combination of various parts by using several steps. The newly fabricated products can be defined as value-added ones where combining of sub-products creates profit for the fabricator. Steel fabrication usually consists of definite steps such as cutting, bending, shaping, welding or assembling.
Cutting or burning of steels are made by very hard cutting tools or oxygen torches. The most common cutting method is the shearing where the raw material is cut by placing it on a die. The placed raw material is pressed by a cutter or punch which separates the raw material into the desired number of pieces. Therefore, the most common sheared steels are in sheet or plate shape. The shearing work generally covers the blanking and piercing processes. For cutting steel parts, band saws are also commonly utilized. A hardened abrasive band or disk turns against the raw material and sizes the steel material. Cutter torches are also used for cutting large cross-sectioned steels such as slabs. Torches effectively cut the slabs in a short time but the extreme temperatures may poses problems since cutting areas can also be defined as the heat-affected zones. The cooling style of the cut parts alters the microstructure of the steel that directly affects the mechanical properties of the steel. The cutter torches can also be computer-controlled (CNC type) for rapidly cutting numerous parts. These CNC torches generally use natural gas as the energy source but laser cutters and water-jets are also very useful for rapid works.
The bending of steels is done by press machines or hammering works. The desired angle of the steel can be achieved by manually forging the steel or using press brakes and tube benders. The stress during the bending of the steel is important because excessive forces during bending can cause deteriorations or the bent region may require further annealing processes.
The forming of the steel parts generally creates voluminous or bulky parts. During the forming processes, generally, removal of material can not be obtained since the forming procedure works with the existing mass of material. Hence, differently sized dies or punches can be used for forming processes. Deep drawing is a very common forming process where conical or cylindrical shapes can be fabricated.
The shaped steel components are finally assembled to yield the desired steel part. The assembling step is usually done by welding or soldering methods.
Shops for steel fabrication
The fabricated products can be several in numbers and it forces the facilities to specialize in the products. Therefore, the facilities which fabricate the special type or types of desired parts are called fabrication shops. Fabrication shops often focus on the technical drawings of the demanded products and fabricated the parts due to these drawings. The technical drawings must be coherent with the production capacity (the number of the machines or the size of the dies and punches) of the fabrication shops otherwise the sizes of the produced parts may be erroneous. Fabrication shops consist of several types of machines. During the fabrication, both machinery and labor works are utilized. The most important advantage of the fabrication shops is the ease of control by demander. Hence the fabrication shops perform many steps of the production in the same facility, the demander can easily control and change the fabrication of the desired parts.
Fig 1. Welding process during the fabrication of a pipe spool. Retrieved from: Smith, C. (2019).7 March 2020, https://www.engineeredmechanicalsystems.com/tag/budgeting/
Raw materials for steel fabrication
The manufacturing of steel parts involves many types of raw materials. A proper selection of the raw materials for specific purposes can be a matter of life and death because the raw materials strongly affect the strength, stiffness, and toughness of the fabricated part. Plate or sheet metals, castings, fittings, hardwares, expanded metals, and sectional metals are the most commonly used raw materials during fabrication processes.
Casting is extremely desired for the production of the complex geometries since the molten metal can be cooled and solidified in a desired-shaped sand mold. The molten metal is chosen specifically for different applications but the most common metals are the mild steels and stainless steels. Besides that, epoxy, clay concrete, and flux are used during the casting as the raw material.
Formed and or expanded sheets are also used in the fabrication processes as the raw materials. The sheet metal is expanded by stretching it with a rolling machine. The expanded sheet is very useful for the manufacturing of the furniture or doors. Furthermore, the sheet metal can be formed into a three-dimensional shape by using different forming methods.
The hardwares are the components that increase the strength of the produced part and make the fabrication easier. These hardwares consist of several fittings and functional parts such as; handles, laches, wires, and chains.
Fig 2. Stainless steel coils are used as raw materials for fabrication. Retrieved from Hot Rolled Steel Coil, Hot Rolled Stainless Steel Coils Exporters. (2020). 7 March 2020, http://www.aakashsteel.net/stainless-steel-coils.htm
Steel fabrication design and engineering
The design and understanding the design of the desired parts are the most crucial stages during the fabrication processes. A proper drawing of the desired part must be done by the demander. The technical drawing of the steel part must be comprehensible and the sizes of the steel part must be indicated. The fabrication steps must be designed properly. The engineering of the fabrication directly affects the quality of the final product as it performs the whole production from initial fabrication to finishing operations. The assembling methods must be chosen by taking into consideration the mechanical properties of the desired final part. The production parameters must be controlled before the fabrication and during the fabrication.
Common end products made by steel fabrication
The end products of steel fabrication are numerous because of the high demand for steel components. However, a highly desired end product group can be classified as; pipe spools, structural steels, pressure vessels, and metal machinery parts.
Pipe spools are the parts that are used for the integration of a whole piping system. Therefore, the spool components can be manufactured in several shapes and angles. Common piping systems consist of different tees, elbows, and flanges in addition to the main pipeline. These spooling parts are fabricated by welding and bending methods. The sizing of the spools is made by the cutter machines. The assembly of the components is done due to the application area of the piping system. The spools can vary by their specific mechanical properties. Hence, the type of flanges, tees or elbows is selected according to the operating conditions.
The fabrication of the structural steels is very similar to the fabrication of spools in principle. A complete technical drawing of the desired product is made by the demander or the vendor. After identification of the technical drawing, the sizing of the raw metal is initialized. In the sizing or cutting step, the raw steel is cut by shearing or sawing. Cutter machines can be laser cutters, water jets or band saws. During the cutting of the raw steel, drilling is also applied if necessary. The tube or straight parts can be shaped to the desired angles. These shaping operations are made by bending or hammering. Moreover, applications that require less force shaping can be done manually whereas for extreme force required applications bending machines are utilized. After shaping method, fabricated parts are assembled to ensure an integral part. Welding machines are used for a complete assembly of the fabricated parts. In addition to that, proper control of welding must be maintained by the controllers otherwise steel can fail from the welded zones. After control of the assembly, a final finishing operation is necessary to yield the desired shape of the steel. Here, machining operations are conducted by using mills and lathes.
The pressure vessels are fabricated according to ASME BPVC Standards Section 7. The fabrication process of the vessels involves similar steps with structural steels and pipe spools whereas the starting material is generally used as sheet steel. The sheet steel is cut into the desired sizes and machined. Furthermore, the welding method is applied to the sectioned parts. The weld beams are cooled and sandblasting is done if necessary. For corrosion protection, dyes are used for painting the surface.
Fig 3. Fabrication of a pressure vessel. Retrieved from: Hufford, T. (2020). Welding prep in pressure vessel fabrication. 8 March 2020, https://www.thefabricator.com/thefabricator/article/cuttingweldprep/welding-prep-in-pressure-vessel-fabrication
The machinery parts are used in several industries from agriculture to automotive. These parts are fabricated by the machining operations to succeed in the desired complex geometry of the components. CNC machining and drilling are commonly used for fabrication. Moreover, for applications that require enhanced surface hardness, different surface coating, and hardening methods are applied.
Steel fabrication methods:
There are numerous of applications used for fabrication processes. A steel sheet or slab is worked with different methods which are; cold working, machining operations, heat treatment, and coating.
Cold work generally refers to a strengthening mechanism for steels. During cold work, the number of dislocations increase and these dislocations lock each other. These locking mechanisms prevent the movement of the dislocations which means the steel is strengthened. Bending is a common example of cold work. Raw steel is bent by using bending machines and shaped into the desired form. During the bending process, steel is both plastically deformed and strengthened. Bending can be classified as section bending and plate bending. Section bending covers the shaping of the steel slabs or profiles in vertical rollers. The steel slab moves through the rollers and at each roll, the slab is bent step by step. The only difference between the section bending and the plate bending is the orientation of the rollers. In plate bending, the rollers are placed horizontally because of the shape of the raw material (steel sheet). Another common cold working method is squeezing. In the squeezing method, the raw steel is placed between a die and a punch. The die and the punch are in the desired shapes. Therefore, an external force is applied to the punch and the steel is pressed between the punch and the die. Finally, the steel is shaped by the die and the punch. Drawing is another method for cold working of the steels. In the drawing method, usually, tube steel is pulled from and orifice which makes the tube thinner. The cold drawing process is very desirable for applications that aim to fabricate thin steel wires.
Fig 4. A schematic of cold drawing. Retrieved from Corporation, O. (2020). The Cold Drawing Process for Steel Bars and Wire.8 March 2020, https://www.precisionkidd.com/technology.htm
The machining operations of the steels can be classified as turning, drilling and milling. In turning, the workpiece steel is placed o a rotating bar. Lathes are usually utilized for turning operations. The workpiece steel rotates while a cutter moves on the steel in different rotations. All movements, angles, and rotations of the cutter can be arranged by the computer numerical control (CNC). Different shapes of cutter tools can be used for different applications such as; roughing, finishing and facing. Another machining application is drilling. Drilling maintains a spherical hole in the steel body. Usually, a drill forced against a rotating steel body and creates a shelter in the body. The most important point of the drilling operations is the formation of excessive burrs and build-up edges. These excessive burrs and build-up edges may interrupt the shaping process. The last machining operation is the milling. Milling machines are consist of rotating ends with multiple points. These rotating ends perform material removal from the steel body.
Fig 5. A milling operation. Retrieved from: Machining Processes: Turning, Milling, and Drilling – Trimantec. (2020). 8 March 2020, https://trimantec.com/blogs/t/machining-processes-overview
One of the most important steps of the steel fabrication methods is the heat treatment of the steels. Heat treatment is applied for many purposes but the main purpose is the achievement of the optimum properties. Heat treatment covers the heating, soaking, and cooling of the steels. Heat treatment mechanisms create finer grains that ensure better mechanical properties. Moreover, during the cold work of the steels, the induced inner stresses increases. These inner stresses prevent the further shaping of the steel slabs or sheets. To reduce the inner stresses, annealing is done. During the annealing process, steel softens and shaping processes get easier. For several purposes and several types of steels, numerous heat treatment procedures can be performed.
Another fabrication method is welding. Welding is the most common method for joining steels. The metallurgy of the welding zones is extremely basic in principle. The microstructure of the filler metal is similar to cast one. The neighboring zones are called heat-affected zones (HAZ), and the microstructure of these zones is similar to heat-treated ones. Several energy sources can be employed for welding operations but the most popular ones are the gas flame, electric arc, and the laser sources.
Coating processes are very vital for steel treatment. Enhanced surface tribology can be achieved by surface coatings. Moreover, surface coatings develop the quality of the surface by removing the burrs or any extra material. Sandblasting, galvanizing and powder coating are the most common coating methods. Sandblasting ensures a smooth surface by removing the surface burrs. The removal of the extra material from the surface also enhances the fatigue and corrosion property of the steel material. A smooth surface is also compulsory for a good painting. In sandblasting, thin rigid particles are hit the surface and remove the unwanted particles. Galvanizing is the most common corrosion protection method where the steel surface is coated with a zinc layer. The thin zinc layer protects the steel from the corrosive environment. Final methods are the powder coating method where very fine powder particles are blown into to surface and cured. The powder coating method employs an electrostatic process where fine particles are attracted to the surface of the steel and cover the steel surface.
Steel fabrication standards and certifications: The steel fabrication process covers multiple steps and whole steps must be controlled due to proper standards. The fabrication process of structural steels is controlled by the AISC 207-16. The fabrication process of the piping spools is generally controlled by the ASME B31.3 standards. In addition to that, ASME BPVC Standards Section-7 is governed by the pressure vessel fabricators. For different machining operations such as; drilling, turning and milling, several standards exist and the operators must adjust the operations due to these standards.
Quality control and assurance of the fabrication
Quality control of the produced steel can be detrimental for the companies in the worst scenarios. Therefore, a decent quality control procedure is vital for fabrication shops. The control of the product is done by utilizing the proper standards for the product. The control can be either manual or machine-aided. The controller uses several techniques for different problems. For the detection of the leakages or corrosion pits, the non-destructive tests are very useful. The radiography, ultrasonic, magnetic and dye penetrant tests are the most common non-destructive testes. It is important that, before the initialization of each test, surface cleaning is extremely necessary. Welding fails can also be deleterious and proper examination of the welded beams are very crucial for the fabrication. The problems during the fabrication must be controlled by the experts and the precaution must be taken due to the standards.
High Quality Engineering & Procurement
YENA team would like to support your company by providing required machine parts with low cost and high quality according to your drawing and specifications.
We are capable to fabricate machinery parts both as carbon and stainless steel for ;
- Agricultural Industry
- Automotive Industry
- Food Industry
- Heavy Industry
YENA’s fabrication procedures are according to ISO 9000, ISO 14001, ISO 18001, EN 1090-1 and EN 3834 certifications.
For more information, check out https://yenaengineering.nl/metal-machinery-parts/
or feel free to contact us https://yenaengineering.nl/contact/
References
- All You Need to Know About the Structural Steel Fabrication Process. (2020). Retrieved 8 March 2020, from http://northern-weldarc.com/need-know-structural-steel-fabrication-process/
- What Are the Most Common Metal Fabrication Processes and What Are the Applications?. (2020). Retrieved 8 March 2020, from https://www.tuckey.com/blog/common-metal-fabrication-processes-applications/
- Difference Between Manufacturing & Fabrication | Alpha. (2020). Retrieved 8 March 2020, from https://www.alphamanufacturing.co.uk/blog/what-is-the-difference-between-manufacturing-and-fabrication
- Continelli, A. (2020). What is metal fabrication and where is the industry headed?. Retrieved 8 March 2020, from https://www.thefabricator.com/thefabricator/article/shopmanagement/what-is-metal-fabrication-and-where-is-the-industry-headed-
- Song, L., & AbouRizk, S. M. (2006). Virtual Shop Model for Experimental Planning of Steel Fabrication Projects. Journal of Computing in Civil Engineering, 20(5), 308–316. doi:10.1061/(asce)0887-3801(2006)20:5(308)
- Fabrication. (2020). Retrieved 8 March 2020, from https://www.steelconstruction.info/Fabrication
- (2020). Retrieved 8 March 2020, from https://www.teslacad.com.au/blog/complete-guide-of-structural-steel-fabrication-process/
- Davis. (2020). Pressure Vessel Fabrication: A Brief Overview | Blog – ALL-WELD Company Limited. Retrieved 8 March 2020, from http://www.allweld.ca/blog/pressure-vessel-fabrication-a-brief-overview/
- Machining Processes: Turning, Milling, and Drilling – Trimantec. (2020). Retrieved 8 March 2020, from https://trimantec.com/blogs/t/machining-processes-overview
