Cutting Processes for Thick Steel Plates

When fabricating heavy industrial components, cutting thick steel plates accurately is both a challenge and a necessity. Thicknesses above 50 mm demand robust processes that balance speed, edge quality, and heat control.
 
Oxy-Fuel Cutting remains the most widely used method for plates from 50 mm up to 300 mm. Operating at temperatures near 980°C, oxy-fuel uses a chemical reaction between pure oxygen and iron to cut. For a 100 mm carbon steel plate, typical cutting speeds range from 150 to 250 mm/min, with kerf widths of 3–6 mm. While tolerances are moderate (±1.5 mm), capital equipment costs are low, making it economical for very thick sections. However, oxy-fuel produces a significant heat-affected zone (HAZ) of 2–4 mm and requires post-cut cleaning.
 
Plasma Cutting, particularly high-definition plasma, is effective for plates up to 80 mm. At 50 mm thickness, cutting speeds reach 300–500 mm/min – approximately double that of oxy-fuel. Tolerance improves to ±0.8 mm with narrower kerf (1.5–2.5 mm). The HAZ is also shallower (0.8–1.5 mm). However, plasma equipment costs are higher, and consumable life shortens as thickness increases.
 
Laser Cutting is generally limited to plates under 40 mm due to power constraints. Above this threshold, cut quality degrades rapidly, and energy costs become prohibitive.
 
Waterjet Cutting offers zero HAZ and excellent edge quality on any thickness, but cutting a 75 mm plate is extremely slow (under 50 mm/min) and operating costs are high due to abrasive consumption.
 
Best Practice Recommendation: For carbon steel plates exceeding 75 mm, oxy-fuel provides the best cost-effectiveness. For thicknesses between 40 and 75 mm where tighter tolerances are required, high-definition plasma is the optimal choice. Waterjet should be reserved for heat-sensitive materials or applications requiring zero metallurgical alteration.