Steel is a furnace-produced metal, an amalgam of iron and carbon. Production facilities use the intense heat of an open hearth furnace or graduate to the modern electric arc furnace to gift the metal with different characteristic, thus altering its density and ductility. The small percentage of carbon introduced into the furnace stage enables production engineers to manipulate these properties. Indeed, modern metallurgical science is taking steel production even further by introducing other exotic metals into this amalgamation process. Besides the production skill required to create a tough steel alloy, material selectors require knowledge on the SAE grading system. This engineering practice assigns a numerical code to each class of steel, thus identifying every member of the steel family, everything from stainless steel to the high-tensile alloys used in structural engineering projects.
Now that we’ve illustrated some of the issues involved in picking the right grade of steel, in selecting a member of the family that has the mechanical properties we need for the job at hand, there are other fabrication principles to consider. For example, one key characteristic of stainless steel is that it won’t tarnish, a property that’s handy to know if we’re fabricating contemporary cutlery or a set of steel tubes, but not necessarily a relevant feature for a structural job. A structural steel fits in with construction work. It is easy to weld and it will not become brittle. Imagine a welder kneeling down to weld a joint on a thick section of steel. The conductance properties of the metal will dissipate the heat too quickly and affect the weld quality. This phenomenon relates directly to the CEV (Carbon Equivalent Value) of the alloy. Complex equations are associated with CEV, but we can simplify the issue if we say the CEV of the steel should not exceed 0.45, a value that balances weldability against structural hardness.
The panels, supports, fasteners, and networks of beams used to construct a structure are all made from predefined components. There are sized panels to fasten and weld. These are fixed to standardized ‘i-beams,’ and rivets tie the majority of the parts together. A skilled fabricator uses the SAE value of the steel as a guide. The project manager incorporates common and uncommon welding practices into the work by knowing the carbon value of the steel or the presence of other exotic metals. This approach adds the aforementioned CEV rating to other documented specifications when evaluating what parts must be used as supplied and what parts will respond to onsite or factory bending techniques. As for those tough welding attributes, those are handled by TIG (Tungsten Inert Gas) and MIG (Metal Inert Gas) welding techniques, work practices that are used at the discretion of the construction company, though TIG work is more suited for thin-walled components.
If the engineer in charge is to complete the task with all due alacrity, he or she must know the type of steel that is to be worked upon. This knowledge will guide everything from the bending of the metal to how well it can be welded.