What is Steel Fabrication?
Steel Fabrication refers to making steel parts by performing various secondary metalworking operations, such as cutting, bending, and assembling. It also includes other steps of altering the metal, like heat treatment and finishing, which improves the steel’s overall properties.
This trade is one of the primary in almost every branch of industry, as steel materials are fundamental for construction, transportation, energy, mining, agriculture, and consumer goods manufacturing.
Steel fabrication is performed by master craftsmen trained in cutting, bending, and steel molding. These certified experts undergo extensive training and a thorough understanding of the attributes and characteristics of steel.
Primary vs. Secondary Metal Manufacturing Techniques
To better comprehend steel fabrication, it is important to understand the difference between primary and secondary metal manufacturing.
Primary manufacturing methods produce basic metal products, which are semi-finished, such as sheets, plates, bars, tubes, etc. These are produced from casting, forging, rolling, extrusion, wire drawing, and sintering.
All these processes transform raw metal ingots or billets into metal components which are to be used for other processes classified as secondary manufacturing. These operations are often conducted in steel mills and foundries.
Secondary manufacturing operations or fabrications is carried out by skilled steel fabricators whose job is to transform primary steel products into finished parts or structures.
At these stages, fabricators modify the provided semi-finished metals to fulfill specific customer needs, expectations, and specifications. Some of the custom fabricated steel items are storage tanks, automotive steel frames, steel trusses, and metal casings.
Depending on the type of fabrication needed and the customers’ specifications, fabrication is done at machine shops, ‘fab shops’, or even on-site.
Essential Raw Materials for Steel Fabrication
Steel is an alloy of iron and carbon, making it one of the most widely used metals due to its low cost and high availability.
Other metals like aluminum, copper, and nickel alloys are also used a lot in fabrication, but steel is still the most widely used. Although aluminum is more abundant, the fact that smelting iron requires less energy makes steel cheaper.
Unlike other alloys, one type of special steel is stainless steel which is similar in nature with steel in terms of uses and fabrication. Its polishing helps augment its corrosion resistance, offering a variety of options when it comes to stainless steel applications.
There are also different grades of stainless steels with each of them having their own pros and cons for respective uses.
The most popularly used steel grades are 300 and 400 series. Out of these 304 stands out as the most popular and durable grade.
With regards to high temperature exhaust applications, best suited stainless steel for such tasks would be grade 321 due to its alloy constituents of titanium that makes sure that tailing weld deterioration is done to the bare minimum.
Steel, being a metal alloy consisting of iron and carbon, is viewed as one of the metals that is most widely used due to its cost effectiveness and availability.
Despite the fact that other metals are most often used in fabrication like add copper, nickel, and aluminum, none come close to the popularity offered by steel.
Although aluminum is present in larger quantities, the process of iron smelting requires lower amounts of energy, helping lower the overall price of steel.
The rest of the industry that used composite metals for space exploration is recently shifting their focus towards stainless steel due to the lack of robust alternatives available.
Castings
These metal products are produced by melting and casting metal ingots. Castings are made to the shape of the final part, but the contours may have a slight oversize.
To add the part to the desired tolerances, additional operations such as machining, finishing, and heat treatment are performed.
Blooms
Blooms are semi-finished blocks of metal that have an approximately square cross-section equal to or exceeding 6 x 6 inches. They are made from the initial breakdown of metal ingots.
Slabs
Slabs are produced through rolling of the metal ingots in a steel plant. These slabs usually have rectangular cross-section and their thickness is 8 inches or above.
Billets
Billets are similar to blooms, having square cross-section of 2 x 2 inches to 5 x 5 inches. They are blooms with additional processing by rolling, forging, or extrusion.
Plates, Sheets, and Strips
These semi-finished products are produced by further rolling of blooms and slabs. Plates are more than a quarter inch thick; strips and sheets are thinner. Sheets are distinguished from strips by their width ratio to thickness, which is far larger.
Bars
These are robust and durable metal products with square, round, or rectangular cross-sections. The typical cross sections of bars range from 0.5 to 2 inches and are formed by rolling billets into smaller dimensions.
Rods
Rods are similar to bars, but have a smaller cross-section that typically ranges from 0.2 to 0.5 inches. More narrow rods are more flexible, allowing for easy bending. Rods are usually found in rolls or coils.
Beams, Channels, Angles, and Rails
Beams, channels, angles, and rails are all metal products formed from blooms, using a progressive rolling process to create them into more irregular cross sections. Grooved rolls with a gap between them create the required form as metal is drawn through the aperture.
Tubes and Pipes
Hollow metal products with square, rectangular, or round sections are referred to as tubes and pipes. Welded and seamless are the two standard classifications of tubes and pipes.
Welded tubes and pipes are formed by coiling plates or a slab of metal and electrically fusing the edges.
Other types of tubes and pipes include seamless, which are created by rolling around bar and piercing it with a cone-shaped rotator while shaping the tube at elevated temperatures near the metal’s transition temperature.
Wires
These metal products have a significant reduction in cross-section due to drawing. In this metalworking process, a metal rod is pulled through a die, forming wires. Drawing is classified as a cold working process because it is done at room temperature.
Preliminary Processes in Steel Fabrication
It is imperative to understand the steps preceding the actual steps in the fabrication processes. This involves developing a plan and a design for the final product. Adequate preparation of the workpiece is very critical in preventing errors as well as material wastage.
Design and Drafting
Design and drafting, the first phases in the fabrication process include:
- Obtaining the dimensions and physical characteristics of the final product.
- Estimating properties and attributes of design such as structural strength, deflection, surface hardness, and fatigue life.
- Determining the type and amount of raw material.
- Outline the work methods, operations, and precautionary measures necessary in producing the parts.
- Preparation of construction and assembly drawings.
Previously, design and drafting activities were carried out manually, which involved hand-drafting and computing engineering drawings. Nowadays, most of the design work is done using computer applications.
Design and Drafting programs, such as AutoCAD, SolidWorks, and Tekla Structures, employ sophisticated computation and modeling which facilitates advanced calculations alongside design work. There is less time spent on iterative design, and the entire process is made more efficient with the aid of technology.
Workpiece Preparation
As a rule, semi-finished metal products are supplied with the protective coating which must prevent corrosion. Even though this form of protection is not the most effective, some degree of rusting may still take place.
Additionally, dirt and dust may accumulate on the surface as a result of the handling, transfer, and storage processes. Coatings, scales, oils, old paint, rust, dirt, and any other contaminating substances that hinder fabrication processes, and compromise product quality need to be meticulously removed.
Some often employed techniques for workpiece preparation include pneumatic blasting, water jet cleaning, scraping, brushing, and mild pickling.
Marking
Marking refers to taking measurements as part of the preparation steps which are accompanied by marking the workpiece.
The processes of marking involves marking the edges, fold lines, and hole centers on the workpiece surfaces so that the marks can be visible during fabrication.
Marking is done using tools like metal scribers, pencils, chalks, dividers, and punches. Other than measuring instruments, accurate marking can also be done with rulers, center squares, and T-squares.
10 Steps Involved In The Typical Steel Fabrication Process
Steel Fabrication is a highly specialized procedure that requires tactful expertise. To ensure correct and efficient execution of the work, specific steps should be followed sequentially.
#1. Surface cleaning.
The first step that comes in the steel fabrication process is cleaning the surface of the workpiece, and it consists of picking up the mill scale and rust before fabrications. There are a number of ways that can perform the cleaning process.
The Surface cleaning is best done with hand tools such as wire brushes and emery paper. This will ensure the best removal of rust and roughening of the steel surface.
#2. Cutting and Machining.
We are progressing in the fabrication of steel. The subsequent stages after the cleaning of the steel surface are the cutting and machining of the steel.
Cutting encompasses operations such as sawing, shaped drilling, turning, grinding, and various others. Machining has three guiding principles: turning, drilling, and milling.
The processes included in ‘cutting and machining’ steel fabrication include the following:
- Shearing and cropping: In this stage, plate shears and hydraulic shears are applied. Steel sections are sawed into prescribed lengths and widths. Heavy plates are shaped and cut into sections of set lengths.
- Flame cutting or burning: This technique makes use of propane and oxygen, which are heated to cut steel using high-pressure flames. Flame cutting utilizes a jet of high-pressure oxygen released at 1500 degrees centigrade. Experts prefer this means of cutting for many reasons. One of the adds is that it does not need any power supply for cutting.
- Plasma Fusion Cutting: This technique utilizes an electric arc to heat gas and produce cutting energy which is applied by steel fabrication specialists. An Electric Arc is formed by an electrode of tungsten with the workpiece. Because of this, the technique is also referred to as Arc Plasma Cutting. Usually, a separate DC power supply is used as an Arc Source and is power hungry. The method gives better results for 150mm steel in thickness, but it is a time-consuming technique. The method is primarily used for welding of thin membranes such as architectural components and stainless steel.
- Cold Sawing Method: When all other steel cutting methods fail to yield results during the steel fabrication stage, the cold sawing method is the last resort. Its precision is robotically controlled to some extent.
#3. Punching and Drilling.
The subsequent step, which follows the cutting and machining procedures in steel fabrication, is punching and drilling. This stage requires the creation of holes in pieces of materials using large numerically controlled fabricators.
The fabricated holes are drilled according to the data entered into the machines. These drilled holes are essential in the bolts that will be placed in the flanges and rolled steel sections.
#4. Straightening, Bending, and Rolling.
The methods of steel transport, punching, and drilling often introduce steel that is rolled in a bend. This is why leveling or straightening in steel fabrication is done on sections, pipes, and other flat items after rolling.
Also, it has an aesthetic value when erecting certain structures such as tanks. The manipulation of shape is done predominantly for enhancement of beautification is:
- Roller Bending: This is a cold procedure. In this process, the steel member is passed through a series of rolls. The cross-section of the revolving rolls corresponds to the shape of the member. The curvature is achieved by repeatedly applying force across opposing sets of rolls by a roller.
#5. Fitting.
Fitting is the sequence done after the steps of straightening, bending, rolling, and steel fabrication. At this step, the parts are held in position and welded in place by the professional. It mostly involves tack welding to give support at proper angles. Experts can easily undo the joints if they are misaligned.
#6. Fastening.
Combining or putting together parts for the last assembly comes next as we approach the last steps in the Steel fabrication procedure. This step is known as fastening. The process of fastening is crucial since the entire structure’s strength relies on this.
Primarily, there are three distinct methods by which we can add joints to the parts of the structure.
- Bolting: Fasteners and bolts, such as nuts, form joints between structural elements and lock them together.
- Riveting: This technique employs permanent mechanical joiners, also called rivets, which aid in fastening structural components.
- Welding: Parts are secured together using heat and pressure, and the joined parts are transformed into a joint once they cool.
#7. Finishing or Surface cleaning.
After going through the entire steel fabrication procedure, the surface of the steel requires polishing. Surface cleaning is crucial because it improves the durability and aesthetic appeal of steel.
While carrying out the steel cutting, punching, straightening, joining, fastening, and others, oil and grease, along with welding marks, are accrued.
Finishing is when the professionals provide the completed structure with a final polish by eliminating any remaining oil and grease marks, along with welding marks.
This process is aimed at providing the structural steel with a smooth, clean surface and enhancing its aesthetic appeal. Grinding is the most popular method used in the latter step to get rid of dirt on the designed surface and refine the surface.
#8. Quality Control.
Quality control highlights the degree to which an organization’s clients’ needs and expectations are met, thus, it is vital in maintaining customer satisfaction.
It is one of the primary objectives to monitor if their needs are satisfied in the entire process of structural steel fabrication. For that reason, inspections are part of the set of policies called Quality control.
They include verification of the requirements and checking how each specification borders on the details provided by the clients.
The succeeding stage after compiling all of the provided documents is to issue a report of those inspections that were carried out for the specified invitation to tender.
#9. Surface Treatment.
Surface treatment is the last part of steel fabrication. During this step, a range of processes, including blasting, painting, and galvanizing, are used, which are believed to serve distinct purposes on the surface of the final product.
- Blasting and painting: After construction is completed, the rough surfaces are blasted to smoothen surface contours and remove any contaminats. The blasting step is followed by a two-layered painting process.
- Step 1 involves applying either Red oxide or Zinc oxide and forming a prime coat on the steel surface. This step is known as overcoating.
- Step 2 involves forming an outer layer of beauty and protection. This outer layer is made by applying oil, epoxy, or other types of paint.
- Galvanizing: In steel fabrication, the term Galvanizing or Galvanization refers to coating a zinc layer on the fabricated steel. This layer serves as protection against the oxidation of steel. The most common method is hot dip galvanizing. In this method, the structural steel is dipped into molten zinc, which forms the protective coat around the steel.
#10. Transportation.
Transportation serves as the 10th and last step after completing all the processes involved in the fabrication of structural steel. In total, Transportation has 3 sections.
- The first section is the Gathering stage, which contains the assembling of all the components of structural steel.
- The second section is the Bundled stage, which involves binding the components and properly covering them to minimize unintended accidents and damage.
- The last part includes the transferring of completed goods to the specified location. Transportation is done using a flatbed truck or any other vehicle that complies with the specifications of fabricated structural steel.
Steel vs. Metal Fabrication: Which is Better for Your Project?
When talking about steel, people often refer to it as “metal,” as many tend to generalize that plane of “steel is metal.”
Though some steel-like metals exist, each having a set of features, it is further distinct from other metals. While steel does have some metallic features, it does have some properties which other metals lack.
Metal and Steel Differences
A metal consists of a combination of various elements which can be found in the earth’s crust. Some metals include titanium, copper, and nickel. These metals which do not require any sort of mixture with elements to form an alloy are considered pure and are easily extracted from the earth.
However, steel is an alloy that consists of a blend of iron ore, which is a metal, and is naturally available on earth and is one of the most abundantly found metals in the earth’s crust.
Unlike naturally occurring metals, steel alloys have enhanced strength and resilience. Workable steel, unlike natural metals used for decorative and surgical implants due to their softness and malleability, is hard and demands extensive tooling and labor to shape.
The first step in steel production is extracting iron ore and purifying it by getting rid of the impurities such as sulfur, silica, and phosphorus. After the purification, carbon is added to the ore to further improve the durability, strength and machinability of the alloy.
Fabrication of Metals
Metal fabrication involves the forming and shaping of flat sheets of metal which are less than a quarter inch thick. This allows them to be pliably shaped and configured.
Much like in steel fabrication, the sheets undergo cutting, stamping, welding and folding to achieve the desired shape.
To improve strength and resilience of various metals, some processes like plating, expanding, wiring and the addition of different hardware, fittings, and castings can be conducted.
These methods are selected based on the design of the final product. For example, fabrication shops often begin with various types of metals and integrate all of them in one piece.
Metals, like steel, can be processed using the same methods, but they are more malleable and ductile. Unlike steel which requires drastic and violent procedures to shape metal, metals can be deformed using the same procedures but at a negligible degree of intensity.