Polished Steel Strip (Migaki Rolled Strip)｜Mirror Finish and Micron-Level High Precision

Frequent Challenges in the Industry

In fields such as molds, machine parts, and electronic devices, the surface smoothness and thickness accuracy of steel sheets significantly impact the quality of the final product. However, in many manufacturing sites, problems such as surface irregularities, microscopic scratches, variations in sheet thickness, and even warping and distortion at the sheet edges still occur. These defects lead to a decrease in component assembly accuracy, and it is not uncommon for molds and products to fail inspection. As a result, the effort for polishing and re-processing increases, leading to a significant rise in production costs and lead times.

Root Cause of the Problem

General hot-rolled steel sheets have coarse crystal grains and an uneven surface. Therefore, they are unsuitable for molds and precision parts that require mirror finishes and micron-level dimensional accuracy. If steel sheets that have not undergone proper cold rolling and polishing processes (Cold Finishing / MIGAKI) are used, surface accuracy will be insufficient, necessitating repeated polishing steps. This is the main factor that generates waste of time and cost.

Solution: Yamaichi's Migaki Strip Steel

Yamaichi Special Steel (Thailand) offers Migaki strip steel manufactured based on Japanese quality standards. Through its unique precision rolling and mirror polishing processes, it achieves extremely high dimensional accuracy and a beautiful surface.

Main Grades and Characteristics of Migaki Strip Steel

1. SK85M – High Carbon Steel (for high hardness and mirror finish applications)

• Carbon content: 0.80-0.90%
• Basic hardness: HRB 95-105
• Mirror finish (Ra ≤ 0.5 µm)
• Suitable for quenching and tempering, exhibiting high wear resistance
• Excellent dimensional accuracy and machinability
• Applications: Punches, dies, blades, precision parts

2. S60CM – Medium Carbon Steel (balance of strength and toughness)

• Carbon content: 0.55-0.65%
• Hardness: HRB 85-95
• Smooth surface and sharp edges
• Good balance of strength and toughness, with minimal dimensional change after heat treatment
• Applications: Clamp plates, base plates, press die components

3. S45CM – Low Carbon Steel (machinability-focused type)

• Carbon content: 0.40-0.50%
• Hardness: HRB 75-85
• High toughness and easy to form
• Ensures dimensional accuracy while maintaining moderate hardness
• Applications: Spacers, support plates, general machine parts

Strengths of Yamaichi Migaki Strip Steel

• Compliant with Japanese quality standards
• ISO 9001:2015 certified
• Mirror finish of Ra ≤ 0.5 µm, thickness accuracy of ±0.03 mm
• Supports cut-to-size processing
• Integrated heat treatment and mirror polishing services within the same group
• Complete stock in Thailand – prompt shipment to the automotive, tool, and mold industries

※ For details, please download the PDF or feel free to contact us.

Glossary

• Migaki Rolled: Steel sheet that achieves both mirror finish and dimensional accuracy through high-precision polishing after cold rolling.
• Mirror Finish: A smooth surface finish with Ra ≤ 0.5 µm. Ideal for molds and precision parts.
• Cold Rolled Steel: Steel material with enhanced dimensional accuracy and surface smoothness achieved through low-temperature rolling.
• Residual Stress: Stress remaining internally due to uneven rolling or cooling. A cause of distortion.

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