1 Introduction
C45, H13, and P20 are essential steels accounting for over 70% of industrial manufacturing applications across structural components, hot work molds, and plastic molds. C45 (monthly searches: 14,800) leads in cost-performance for mechanical processing; H13 excels in die casting/forging due to high-temperature stability; P20 reduces mold processing cycles by 30% via pre-hardened properties. This article delivers actionable insights through a streamlined core table and key points, resolving material selection dilemmas and machining challenges with balanced technical rigor and practicality.
2 Core Properties Comparison Table
| Steel Grade | Core Positioning | Key Performances | Typical Applications |
| C45 Steel | Cost-effective structural steel | Tensile strength ≥ 600MPa, hardness 197-241HBW, easy to process | Shafts, gears, mold bases, high-strength bolts |
| H13 Steel | Special steel for high-temperature molds | Temperature resistance up to 650℃, hardness 42-48HRC, wear-resistant | Aluminum alloy die casting molds, hot extrusion molds, and forging molds |
| P20 Steel | Efficiency steel for plastic molds | Pre-hardened to 28-34HRC, excellent polishability, ±0.01mm accuracy | Home appliance casings, automotive interiors, high-precision injection molds |
3 Three-Step Quick Selection
- Check working temperature: For ≤ 300℃, choose C45 (e.g., ordinary transmission shafts, gear blanks) or P20 (e.g., mobile phone cases, home appliance casing injection molds); for ＞ 300℃, directly select H13 (e.g., engine block die casting molds, hot extrusion profile molds).
- Check production volume: For ≤ 10,000 pieces, choose C45 (low cost for small orders, reducing trial production risks); for ＞ 10,000 pieces, select P20/H13 (high stability reduces maintenance downtime and long-term costs).
- Check precision and scenario adaptability: Choose P20 for mirror polishing; C45 for simple structural components; H13 for high-temperature and high-precision working conditions; for international projects, interchangeable according to standards (C45 = AISI 1045, H13 = DIN 1.2344).
4 Quick Solutions to Machining Pain Points
- C45 Steel: Rough machining speed 800-1000rpm, feed rate 0.2-0.3mm/r; finish machining speed 1200-1500rpm, feed rate 0.1-0.15mm/r. Apply cutting fluid throughout to avoid surface hardening caused by high-speed cutting without cooling; preheat to 150-250℃ before welding to prevent cold cracks.
- H13 Steel: Use CBN or cemented carbide coated tools with extreme pressure cutting oil. Adopt stepwise heating for heat treatment (500℃ for 2h → 800℃ for 1h → 1030℃ quenching), oil cool to 200℃ then air cool, and naturally age for 24h after tempering to prevent deformation and cracking.
- P20 Steel: For tool sticking, reduce cutting speed to 80-100m/min and use TiAlN coated tools; for dimensional deviation, perform 24h aging treatment first and control finish milling allowance within 0.2mm; for polishing pitting, grind step by step with 400-mesh → 800-mesh → 1200-mesh sandpaper, combined with W3.5 diamond polishing paste.
5 Core FAQ (Supplemented with international standard questions)
1. Q: How to choose between C45 and P20 for simple molds?
A: Choose C45 for small batches (≤ 10,000 pieces) to save 30% procurement cost; choose P20 for large batches or when polishing is required (service life is 2-3 times that of C45).
2. Q: What is the core difference between H13 and P20?
A: H13 resists temperatures up to 650℃, suitable for high-temperature hot work molds; P20 is pre-hardened and focuses on efficient production of normal-temperature plastic molds.
3. Q: Should I use cutting fluid or cutting oil for P20 machining?
A: Use cutting fluid for rough machining (good cooling effect); use cutting oil before finish machining/polishing (reduces tool sticking and improves surface finish).
4. Q: Can C45 and H13 be directly replaced with international standard steels in international projects?
A: Interchangeable in basic scenarios (C45 = AISI 1045 = S45C, H13 = DIN 1.2344). For high-temperature and high-precision scenarios, it is recommended to conduct small-batch trial production first to confirm performance matching.