Materials & Cutting Methods for Crane Base

1. Main Materials of Crane Base (Classified by Lifting Capacity & Working Conditions)

Crane bases bear alternating loads, impact loads and ground extrusion forces, categorized into three types: general load-bearing structural steel, high-strength heavy-duty steel and wear-resistant lining plates. Below are domestic and equivalent European standard grades.

1.1 Small & Medium Overhead/Gantry/Truck Crane Base (≤50t, Conventional Indoor Service)

1.2 Heavy Crawler Cranes / Portal Harbour Cranes (50t–300t Heavy-Duty Base)

1.3 Wear-Resistant Lining Plates for Base Bottom

NM400, NM450, NM500 wear-resistant steel plates (GB/T24186), Brinell hardness 400–500HBW. Applied to anti-slip and anti-abrasion contact areas between base bottom and ground, only used for partial splicing instead of integral base load-bearing structures.

Key Material Selection Guidelines

1. Low-alloy high-strength structural steel is prioritized for integral bases for balanced strength, fatigue resistance and weldability.
2. Wear-resistant plates shall only serve as partial liners; full wear-resistant plates cannot be used for load-bearing bases due to insufficient toughness and risk of fracture.
3. Grades C/D/E with guaranteed impact toughness are mandatory for outdoor service below -20℃.

2. Four Main Cutting Processes for Crane Bases (Comparison & Applicable Conditions)

Base plate thickness ranges from 10mm to 120mm, mainly for blanking of oversized profiles, special-shaped clamping grooves, circular arcs and welding bevels. Comparison of four cutting processes is as follows:

2.1 CNC Flame Cutting (Oxy-Propane / Oxy-Acetylene Cutting, Preferred for Base Blanking)

Working Principle

Preheating by 3000℃ fuel gas, followed by high-pressure oxygen jet to oxidize and blow away molten slag. Only applicable to carbon steel and low-alloy high-strength steel (Q355/Q690 etc.); not suitable for wear-resistant steel or stainless steel.

Applicable Plate Thickness

10–300mm extra-thick base plates, oversized rectangular blanks, one-step forming of welding bevels.

Advantages

• Maximum cutting thickness limit, lowest material & operation cost, low equipment investment;
• V/X welding bevels can be cut simultaneously, eliminating secondary machining before base assembly welding;
• Compatible with 12m ultra-long base steel plates, mass blanking with multiple cutting torches synchronously.

Disadvantages

Wide heat-affected zone, slag adhesion on cutting edge and minor thermal deformation; moderate dimensional accuracy. Grinding and flaw detection are required for critical load-bearing components after cutting.

Typical Crane Base Applications

Blanking of thick plates for heavy-duty main bases, outrigger base slabs, box side panels and mass rough cutting.

2. CNC Plasma Cutting (Air Plasma / Fine Plasma)

Working Principle

Metal melting via 20,000℃ plasma arc, compatible with carbon steel and NM wear-resistant plates.

Applicable Plate Thickness

6–60mm medium & thin base plates, special-shaped wear-resistant lining plates NM400/NM500.

Advantages

Much faster cutting speed than flame cutting, less thermal deformation on thin plates; capable of cutting wear-resistant liners and stainless steel accessories.

Disadvantages

Sharp cost increase for plates thicker than 60mm, poor verticality of cutting face; nitrided hard layer forms on cutting edge. The hardened layer must be ground off for high-strength steel to avoid welding cold cracks.

Applicable Scenarios

Base wear-resistant liners, thin-plate bases for small cranes, special-shaped arc clamping groove parts.

2.3 Fiber Laser Cutting (High-Precision Small Base Components)

Applicable Plate Thickness

0.5–20mm thin plates, rarely used for thick main base structures.

Advantages

Ultra-high dimensional accuracy (±0.05mm), smooth slag-free cutting edges and minimal thermal deformation; one-step forming of complex round holes and irregular profiles.

Disadvantages

Extremely high cutting cost for plates over 20mm; incapable of machining extra-thick base slabs above 100mm.

Applicable Scenarios

Base connecting plates, lifting lugs for small cranes, precision positioning mounting plates.

2.4 Mechanical Shearing via Guillotine Shear

Only applicable to straight-line simple rectangular thin plates (≤12mm). Cannot cut circular arcs or welding bevels, almost unused for large crane base manufacturing.

3. Standard Cutting Process Flow for Crane Bases (Critical Specifications for High-Strength Steel)

3.1 Pre-Cutting Preparation

1. Plate flattening: Eliminate rolling deformation to prevent out-of-tolerance flatness of finished bases after cutting;
2. Rust & oxide scale removal on steel surface to avoid tempering and slag adhesion during cutting;
3. Carbon equivalent check for high-strength steel (Q690/S690). Stress relief treatment is mandatory if carbon equivalent exceeds 0.4%.

3.2 Standard CNC Flame Cutting Operation (Mainstream Process for Bases)

1. Nesting programming: Optimize material utilization via shared-edge cutting for large base components;
2. Preheating specification: Extend preheating duration for Q690 high-strength steel plates ≥50mm thick to prevent hardened layers on cutting edges;
3. Cutting nozzle selection: No.2 nozzle for 10–40mm plates, No.3 nozzle for 40–100mm plates, special heavy-duty cutting torches for plates over 100mm;
4. Integrated bevel cutting: One-step forming of V-type assembly welding bevels, surface roughness of bevels to meet welding requirements;
5. Post-cutting finishing: Remove bottom slag, grind off hardened layers on cutting edges (compulsory for all high-strength steel).

3.3 Critical Post-Cutting Procedures for High-Strength Steel (Prevent Base Cracking)

1. Large bases made of Q550/Q690/S690 high-strength steel: Low-temperature stress relief annealing (200–300℃ holding) to eliminate residual thermal cutting stress;
2. Repair welding and grinding are required for cutting surface grooves or notches deeper than 1mm; 100% visual flaw detection shall be implemented for load-bearing bases;
3. Grind off nitrided hardened layers on edges of plasma-cut wear-resistant plates to avoid cold welding cracks.

4. Cutting Process Selection Table for Crane Bases

5. Quality Acceptance Standards (Industry Specification T/CPARK 35—2023)

1. Cutting surfaces of critical load-bearing bases shall meet Class I cutting quality; verticality tolerance ≤3mm for 100mm thick plates;
2. Base flatness after cutting: ≤1mm per meter length;
3. No cracks, delamination or deep grooves permitted on cutting edges of high-strength steel;
4. Tolerance of bevel angle and width: ±1.5°, compatible with submerged arc welding / MAG welding processes.