Characteristics of different types of steel, differences, and guidance on choosing the machining process

Steel is one of the most widely used materials in industry. From structural steelwork to automotive, from mechanics to foundry, through to the production of high-strength tools and components, its applications are virtually infinite.

However, simply speaking of “steel” is not enough.

In fact, there are numerous types of steel, characterized by different chemical compositions, mechanical properties, and behaviors during processing.

Distinguishing between various types of steel is important not only for choosing the most suitable material for a component but also for understanding how that component must be processed after casting or production—whether it involves cutting the casting gate, grinding, or robotic deburring.

In this article, we look at the main types of steel, their characteristics, and why the material must be considered right from the design stage of an automated finishing process.

What is steel?

Steel is a metal alloy consisting primarily of iron and carbon.

The amount of carbon and the potential presence of other alloying elements determine most of the material’s characteristics: hardness, mechanical strength, corrosion resistance, high-temperature behavior, machinability, and wear resistance.

For this very reason, there is no single “steel.” The composition of the alloy can be modified to obtain materials with very different characteristics intended for specific applications.

In general, we can distinguish several major families:

• carbon steels
• alloy steels
• tool steels
• stainless steels

Within these categories, there are numerous grades and classifications.

Carbon steel: characteristics and applications

Carbon steel consists primarily of iron and carbon and is one of the most common types. It is used in numerous industrial sectors: heavy industry, automotive, construction, structural steelwork, and mechanical component production. Carbon steel is the most common among the various existing types of steel: it is estimated that approximately 90% of total production belongs to this category.

One of the reasons for the widespread use of carbon steel is its relative ease of processing. However, as the carbon percentage increases, the mechanical characteristics of the material change:

• low-carbon steels, with carbon content below 0.3%
• medium-carbon steels, between 0.3% and 0.6%
• high-carbon steels, with carbon content exceeding 0.6%

For Trebi, this is an important detail. In the robotic deburring of mechanically processed carbon steel components, the variation in hardness is no small matter: it affects tool wear, processing speed, and, consequently, the cycle time that must be defined during the design phase of the robotic cell.

A small curiosity: did you know that there is a niche production of razor blades that use carbon steel instead of the other special steels typical of the sector? These blades do not resist moisture well but, according to experts, guarantee very smooth shaving experiences thanks to the particular mechanical properties of this specific type of steel.

Alloy steels: when composition changes performance

Alloy steels are produced by adding other chemical elements to iron and carbon—silicon, manganese, chromium, nickel, molybdenum, titanium, copper, vanadium—in quantities that modify the properties of the alloy, improving mechanical strength, hardness, wear resistance, corrosion resistance, or high-temperature resistance.

Alloy steels find application in the automotive and shipbuilding industries, machinery construction, piping, mechanical components, and systems subjected to high stress.

What does this mean at Trebi? What aspects should be kept in mind when designing robotic solutions to handle these types of steel? To answer this question, it is necessary to consider that high-strength alloy steels are the most complex materials to deburr when they come from mechanical processing. An alloy steel component should not be treated like carbon steel, because the stress on the tool and the vibrations it generates change. It is often necessary to choose abrasive tools and specific machines for these materials.

Another small curiosity: do you know why the world-famous Eiffel Tower was built of iron and not steel? At the time of construction, many types of steel were available and known, being very resistant and relatively light, but iron was preferred because it cost about 25% less. For the sake of completeness, we must remember that the tower was designed as a temporary architectural work, intended to last about 20 years before being dismantled. More info here.

Tool steels: hardness and wear resistance

Tool steels are types of steel designed for applications where high mechanical performance and, above all, wear resistance are required. Depending on the composition, they may contain vanadium, molybdenum, tungsten, cobalt, or chromium.

Applications include: hammers, chisels, blades, drill bits, molds, and tools for mechanical processing.

How do we at Trebi correctly manage these types of steel? High hardness is an advantage in the use of the component, but it becomes a critical variable in the grinding of these tools—think, for example, of a chisel, where the robot must grind the piece after forging to create the cutting profile. The choice of abrasive is decisive. A point often underestimated: to avoid ferrous contamination that can trigger surface corrosion, abrasives used on steel should never be shared with those used on aluminum or brass—a core principle we also apply in the design of multi-material robotic cells.

Stainless steel: corrosion resistance and surface finish

Stainless steels are among the most well-known and widely used materials. Their main characteristic is high corrosion resistance, achieved thanks to the presence of chromium in the alloy. They are used in the food industry, medical sector, furniture, construction, automotive, mechanics, and industrial components.

However, speaking generically of “stainless steel” is not enough: different families exist—austenitic, ferritic, martensitic—with very different mechanical behaviors.

The Trebi approach for managing various types of stainless steel.

Austenitic stainless steels (e.g., AISI 316L), the most common in the medical sector, tend to work-harden during abrasive processing: the surface hardens progressively under the action of the tool, compromising the abrasive’s performance if the process is not correctly calibrated. This is a particularly critical aspect in the grinding of orthopedic components—bone prostheses, screws, and fixation plates—where surface roughness and uniformity are not an aesthetic requirement but a requirement for biocompatibility and safety of the finished product.

How are the different types of steel classified?

The great variety of steels necessitates a precise classification. In Europe, codes and numbering defined by technical standards are used, including UNI EN 10027, which identifies a steel through an alphanumeric designation (describing its composition or use) or a material number.

For those designing a process, this classification is not a bureaucratic detail: from the code alone, it is often possible to immediately understand whether one is dealing with a non-alloy or alloy steel, and consequently adjust the choice of tools, parameters, and processing strategy—even before having the piece physically in hand.

From the type of steel to the production process

A steel component may require different operations depending on how it was produced:

• if it comes from casting (if you want details on the melting temperature of metals read this other article), the first operation is typically cutting the casting gate (or riser), followed by deburring and finishing of the attachment points;
• if it is a forged tool or component, it often requires precision grinding on edges, corners, or functional surfaces;
• if it is a medical or critical contact component, it requires fine and controlled grinding to ensure roughness and biocompatibility requirements;
• if it comes from mechanical processing (turning, milling), it typically requires deburring to eliminate burrs and residual edges from chip removal.

There is no single solution valid for all components. To correctly design the process, it is necessary to consider at least:

• the type of steel
• the geometry of the part
• the required operation (casting gate cutting, grinding, deburring…)
• the quantity and position of burrs or attachment points
• the amount of material to be removed
• the required surface result
• the production volume
• the required cycle time
• the necessary repeatability of the process

Why automate the finishing of different types of steel?

When production involves large quantities of identical or similar components, entrusting cutting, grinding, deburring or finishing exclusively to manual processing can create critical issues: the result depends on the operator, their experience, fatigue, and the ability to maintain constant speed, pressure, and trajectory. Cycle time can also vary from piece to piece.

Also because processing steel parts requires significant forces. The abrasives used need adequate pressure to “activate” and dress correctly: if the pressure is insufficient, the abrasive clogs quickly and loses effectiveness.

An industrial robot executes a programmed trajectory with defined and repeatable process parameters, applying the correct force at every point of the processing. On steel components, this always requires units equipped with force compensation, capable of maintaining constant pressure even as the part geometry varies.

Robotization becomes particularly interesting under certain conditions:

• Repetitive productions — Components processed hundreds or thousands of times benefit from a programmed and optimized process.
• Significant cycle times — When processing time significantly impacts the cost of the component, automating allows for better control of the time required for each piece.
• Need for constant quality — Reducing process variability becomes a competitive advantage when the customer requires a uniform result—decisive, for example, in the grinding of medical components.
• Heavy or repetitive processing — Casting gate cutting, grinding, and deburring can be physically demanding: automating reduces the operator’s exposure to the most strenuous activities.
• Difficulty in finding personnel — Automating also means transforming part of the process know-how into a repeatable and programmable system.

Trebi: from process to robotic solution

It is precisely on these issues that Trebi develops its solutions. For over forty years, we have been designing and building robotic systems for processing metal components, with applications including:

• casting gate cutting and deburring of foundry castings (aluminum, cast iron, steel)
• grinding of tools and forged components
• grinding for sectors with high quality requirements, such as orthopedic components
• deburring of mechanically processed components

The choice of robot, units, and machine is closely linked to the material to be processed and the process.

There are no standard solutions; there is a modularity of units and solutions that are combined to meet the specific needs of the customer.

Conclusion

There are many types of steel, and each presents specific characteristics. Carbon steel, alloy steels, tool steels, and stainless steels have very different properties, and these differences must be considered not only during the component design phase but also during processing.

Automating does not simply mean buying a robot: it means knowing the materials, processes, tools, and working parameters.

Do you have a steel component to process or finish and want to understand if it makes sense to automate the process? Contact us for a free technical analysis of your case: we always start from the process, not the robot.