I. Check the Material Report: Confirm the Basic Material Grade and Composition
The material type should be clearly marked as HT250 or HT300 gray cast iron (superior to Q345 steel), with a tensile strength >=300MPa;
Chemical composition analysis data (C, Si, Mn, P, S, etc.) should conform to GB/T 9439 standard;
Hardness value should be within the range of HB170-240, as excessively high or low values will affect stability.
The report should be issued by a third-party testing agency or stamped by the manufacturer's laboratory, and the information should be traceable;
The batch number should match the actual batch number, not a generic template.
If only "HT300" is verbally claimed without a report, or if the report is unclear or lacks a number, it is highly likely that inferior HT150-200 cast iron (dark gray surface, resembling a mixture of clay and iron slag) was used.
II. Verify Heat Treatment Records: Verify the Achievement of Internal Stress Relief
Clearly record the dual treatment process of "high-temperature aging + natural aging";
High-temperature aging temperature >=550℃, holding time >=24 hours;
Natural aging >=6 months, residual stress removal rate >=85%.
The treated platform shows no obvious deformation or cracking risk.
Platforms that have not undergone heat treatment may have acceptable accuracy in the short term, but are prone to deformation and breakage in the long term, and machining accuracy cannot be guaranteed.
III. On-site Inspection: Quickly identify authenticity through appearance and actual measurement
Qualified products: Surface is silver-gray or glossy black (nitrided), with no obvious pores, sand holes, or welding marks;
Inferior products: Surface is dark gray and rough, with casting defects or welding points of inconsistent color.
Use calipers to measure the spacing between adjacent holes to ensure it is 100±0.05mm.
The hole diameter should be φ28D7, with an error <=0.05mm. Inferior platforms often have misaligned hole spacing due to drilling jigs.
For the same specifications, a heavier weight indicates more material used. HT300 cast iron has a high density and is significantly heavier than inferior materials.
Request a comparison sample to determine if there is any "material skimping."
A qualified platform has densely packed cross-shaped stiffeners on the back, 12-15mm thick, and evenly distributed. Inferior products have fewer and thinner stiffeners, resulting in poor rigidity and easy deflection under load.
Apply a 250N load (approximately 25kg) to the center of the platform and measure the deflection using a dial indicator.
Acceptance standard: Deflection should not exceed 1μm; otherwise, it indicates insufficient stiffness, affecting welding accuracy.
