Research project paves the way for lead-free machining of steel
Traditionally, manufacturers have used lead-alloyed steel to improve machinability. However, the toxicity of lead and its classification as carcinogenic by the EU has created an urgent need to find lead-free alternatives. This was the focus of the project Environmentally Friendly Steel, coordinated by DAMRC (Danish Advanced Manufacturing Research Center). Joakim Miinin, Area Sales Manager Nordic & Baltics at Ovako, and Ulrik Kirk Boesen, Product Specialist at Tibnor, present here the results supporting the feasibility of using lead-free steel alternatives.
Adding a small amount of lead to steel improves machinability by forming inclusions that deform with significantly less force than the surrounding material. This enables higher cutting speeds and thus reduces production costs. The challenge with lead, however, is that it is toxic to humans. To limit the consequences of lead toxicity, the EU has restricted its use by including it in the RoHS Directive (EU 2025).
Two of the most commonly used substitutes for lead to improve machinability are sulfur (S) and calcium (Ca). Both elements are considered to have a lubricating effect in the machining process. Calcium is added through treatment of the steel during deoxidation of the molten steel. This process transforms hard aluminum oxide (Al₂O₃) inclusions into softer calcium aluminates. These reduce tool wear by forming protective slag deposits on the tool during machining, thereby improving machinability. This forms the basis for Ovako’s M-Steel treatment, which can be applied to all steel grades and delivery conditions.
Project objective
The purpose of the DAMRC project was to evaluate and compare the machinability of five different steel compositions—specifically free-cutting lead-alloyed steel, lead-free structural steel, and lead-free steel modified with calcium and sulfur. The parameters were assessed through 3-axis milling operations with particular focus on drilling and tapping processes.
Evaluated steel grades
The steel types included in the test program were supplied by Tibnor and Ovako.
The selected grades were:
- 11SMnPb30
- 11SMn30
- S355J2
- 520M
- 550MW+
The chemical composition of the grades is shown in Table 1.
| Material | C% | Si% | Mn% | P% | S% | Cr% | Ni% | Mo% | Pb% | Cu% |
| 520M | 0,16 | 0,19 | 1,29 | 0,011 | 0,033 | 0,20 | 0,16 | 0,04 | 0,22 | |
| 11SMn | 0,12 | 0,11 | 1,22 | 0,025 | 0,286 | 0,12 | 0,10 | 0,02 | 0,17 | |
| 11SMnPb30 | 0,07 | 0,01 | 1,06 | 0,05 | 0,30 | 0,27 | 0,01 | |||
| S355J2 | 0,15 | 0,20 | 1,19 | 0,006 | 0,03 | 0,15 | 0,15 | 0,03 | 0,21 | |
| 550MW+ | 0,16 | 0,23 | 1,19 | 0,013 | 0,17 | 0,16 | 0,17 | 0,05 | 0,22 |
Table 1: Chemical composition of the steels used in the machining tests, in weight percent; the remainder is iron.
These alloys provided three different test variables in the project. The first and central variable was the presence of lead—with the lead-alloyed grade 11SMnPb30 and four lead-free grades. The main comparison between leaded and lead-free machinability was carried out between 11SMnPb30 and 11SMn, as these are identical in composition except for the lead content. The second and third variables were high sulfur content and calcium treatment, respectively. 520M has low sulfur content and is calcium-treated, S355J2 has low sulfur content without calcium treatment, 11SMn has high sulfur content without calcium treatment, and 550MW+ has high sulfur content and is calcium-treated.
From machinability to process stability
From Tibnor’s perspective—represented in the project by Product Specialist Ulrik Kirk Boesen—the work builds on many years of efforts to optimize machinability, traditionally via parameters such as sulfur content, while also taking the next step towards a broader focus on consistency and operational reliability in production.
The project demonstrates a shift toward evaluating how materials perform within an overall production context. This includes not only machining efficiency but also the ability to ensure stable and repeatable processes over time.
This development reflects the increasing demands of modern industry. It is no longer sufficient to focus solely on chip breaking or isolated machining performance. There is a growing need to ensure consistent and reproducible processes, where materials support stable production with minimal variation.
In practice, this means enabling a high level of operational reliability, where production can run continuously with great confidence—even in automated and unmanned processes. For Scandinavian industry, adapting to these new requirements is essential to remain competitive in a global market.
Test method
The test method consisted of gradually wearing down tools through successive machining operations, while the wear was monitored and documented. The process was repeated for each steel grade, using new tools each time.
Summary of results
The project has successfully evaluated the machinability of lead-free steel alternatives compared to traditional lead-alloyed steel using key performance indicators such as tool wear, chip formation, and hole diameter.
The results show that the tested lead-free steels have comparable or better machinability than the leaded 11SMnPb30. Overall, the findings support that lead-free alternatives are fully viable, provided that process parameters are carefully controlled.
