JIS SUP10 Spring Steel: Properties, Uses & Manufacturing Guide

If you work in Japanese automotive, industrial, or heavy machinery sectors—needing springs that handle high loads, frequent stress, and moderate heat—JIS SUP10 is a top-tier choice. This Japanese Industrial Standard (JIS) chromium-silicon alloy spring steel delivers exceptional elasticity, fatigue resistance, and strength, making it ideal for demanding applications where plain carbon steels fall short. This guide breaks down its key properties, real-world uses, manufacturing process, and how it compares to other materials, helping you solve tough spring challenges in Japanese and global markets.

1. Material Properties of JIS SUP10 Spring Steel

JIS SUP10’s unique blend of chromium (0.50–0.80%) and silicon (1.20–1.60%) sets it apart—it balances elasticity for spring recovery and strength for heavy loads. Let’s explore its properties in detail.

1.1 Chemical Composition

JIS SUP10 follows strict Japanese Industrial Standards (JIS G4801), ensuring consistency for high-stress spring applications. Below is its typical chemical makeup:

1.2 Physical Properties

These properties describe how JIS SUP10 behaves under physical conditions like temperature and magnetism:

• Density: 7.85 g/cm³ (consistent with most carbon-chromium-silicon steels)
• Melting Point: 1,410 – 1,450 °C (2,570 – 2,640 °F)
• Thermal Conductivity: 44.5 W/(m·K) at 20 °C (room temperature)—slightly lower than plain carbon steels but suitable for heat treatment
• Coefficient of Thermal Expansion: 11.6 × 10⁻⁶/°C (from 20 – 100 °C)—minimizes shape distortion during heating/cooling
• Magnetic Properties: Ferromagnetic (attracts magnets), useful for sorting, inspection, and manufacturing clamping.

1.3 Mechanical Properties

JIS SUP10’s mechanical performance excels after spring temper heat treatment. Below are typical values for annealed and spring-tempered conditions:

1.4 Other Properties

JIS SUP10’s key traits make it ideal for Japanese high-demand applications:

• Elastic Modulus: ~205 GPa—higher than plain carbon steels (e.g., JIS S65C), ensuring excellent spring recovery even after frequent heavy loads (e.g., truck suspensions).
• Spring Temper: Easy to achieve via tempering (350–450 °C)—balances hardness for strength and flexibility to avoid breaking.
• Hardenability: Excellent—chromium and silicon enable uniform hardening in sections up to 30 mm thick (perfect for large leaf springs or heavy-duty coil springs).
• Wear Resistance: Good—carbon-chromium carbides resist abrasion in dusty agricultural or industrial environments.
• Corrosion Resistance: Mild—better than plain carbon steels but needs coatings (like zinc plating) for wet/outdoor use.

2. Applications of JIS SUP10 Spring Steel

JIS SUP10’s high elasticity and strength make it a staple in Japanese heavy industries. Here are its top uses:

• Springs: Heavy-duty springs like coil springs (truck suspensions, industrial machinery), leaf springs (commercial vehicles, trailers), and torsion springs (heavy-duty door hinges).
• Automotive Suspension Components: Leaf springs and coil springs in Japanese trucks (e.g., Isuzu, Hino) and off-road vehicles—handling heavy weights and rough terrain.
• Valve Springs: Used in medium-to-large automotive engines (e.g., diesel truck engines) and industrial generators—reliable for moderate RPMs and frequent cycles.
• Industrial Machinery: Springs in press machines, conveyor systems, and heavy-duty valves—common in Japanese factories (e.g., Toyota Group suppliers) for high-load operations.
• Agricultural Machinery: Springs in tractor plows, rice harvester cutting heads, and manure spreaders—withstanding dirt, vibration, and heavy impacts on Japanese farms.
• Hand Tools: Heavy-duty tools like bolt cutters, industrial pliers, and jacks—needing strength to grip or cut tough materials.
• Gears: Small-to-medium gears in industrial gearboxes—JIS SUP10’s wear resistance handles repeated meshing contact.
• Railway Components: Springs in train bogies and brake systems—resisting vibration and heavy loads for Japanese rail networks (e.g., Shinkansen auxiliary parts).

3. Manufacturing Techniques for JIS SUP10

Producing JIS SUP10 aligns with Japanese manufacturing precision. Here’s the typical process:

1. Steelmaking:
   • JIS SUP10 is made using an Electric Arc Furnace (EAF) (common in Japan for scrap recycling, supporting sustainability goals) or Basic Oxygen Furnace (BOF). The process focuses on precise control of silicon (1.20–1.60%) and chromium to meet JIS G4801.
2. Rolling:
   • After steelmaking, the metal is Hot Rolled (1,100 – 1,200 °C) into bars, sheets, or coils—standard formats for Japanese spring manufacturers. For precision parts (e.g., valve springs), it’s Cold Rolled (room temperature) to improve surface finish and dimensional accuracy.
3. Precision Forming:
   • Springs are shaped using Japanese-standard techniques:
     • Spring Coiling: Wrapping cold-rolled wire around a mandrel to create coil springs (matching JIS dimensional specs).
     • Stamping: Pressing flat steel into flat springs (e.g., electrical switch contacts) using high-precision dies.
     • Bending/Forging: Heating and shaping steel into leaf springs or gear blanks—refining grain structure for strength.
4. Heat Treatment:
   • Critical for unlocking JIS SUP10’s spring performance:
     • Annealing: Heat to 800 – 850 °C, cool slowly to soften steel for forming.
     • Quenching: After forming, heat to 830 – 870 °C, rapid cool in oil to harden (chromium and silicon ensure uniform hardening).
     • Tempering: Reheat to 350 – 450 °C to achieve spring temper—reduces brittleness while retaining strength and elasticity.
5. Machining:
   • For complex parts (e.g., gears, custom springs), post-forming machining (Grinding, Milling) trims excess material and ensures tight tolerances (±0.01 mm for small springs).
6. Surface Treatment:
   • Optional steps for Japanese applications:
     • Plating: Zinc plating (per JIS H8610) for corrosion resistance—used for outdoor tools or automotive springs.
     • Coating: Powder coating (per JIS K5600) for aesthetics and extra rust protection—popular for visible components.
     • Blackening: Low-cost oxide layer (per JIS K5623) for indoor machinery springs.
7. Quality Control:
   • Rigorous testing ensures compliance with JIS standards:
     • Chemical analysis: Verify alloy content via spectrometry (JIS G1253).
     • Tensile testing: Check strength (JIS Z2241).
     • Spring load testing: Ensure shape retention after 100,000+ cycles (JIS B2704).
     • Dimensional inspection: Use CMMs to confirm JIS specs.

4. Case Studies: JIS SUP10 in Action

Real Japanese examples highlight JIS SUP10’s performance:

Case Study 1: Japanese Truck Leaf Spring Durability

A Tokyo-based truck manufacturer faced leaf spring failures (after 90,000 km) using JIS S65C. The springs cracked under the truck’s 25-ton load. Switching to JIS SUP10 leaf springs (tempered to 45 HRC and zinc-plated) extended life to 220,000 km. This reduced maintenance costs by 65% and improved fleet reliability for delivery companies.

Case Study 2: Agricultural Machinery Spring Performance

An Osaka-based tractor maker struggled with rice harvester spring failures (every 700 hours) using a low-silicon steel. The springs lost elasticity in muddy conditions. Replacing them with JIS SUP10 springs (tempered to 43 HRC) increased life to 2,100 hours. This cut farmer downtime by 66% and boosted tractor sales in Japan and Southeast Asia.

5. JIS SUP10 vs. Other Spring Materials

How does JIS SUP10 compare to other common spring steels (Japanese, European, and global)? The table below breaks it down:

Yigu Technology’s Perspective on JIS SUP10

At Yigu Technology, JIS SUP10 is our top choice for clients needing high-elasticity, heavy-duty springs in Japanese markets. Its high silicon content delivers superior spring recovery, outperforming JIS S65C or SUP9 in demanding apps like truck suspensions. We optimize heat treatment to 40–48 HRC and offer zinc plating per JIS H8610. For global clients, it’s a versatile alternative to AISI 6150 for non-extreme high-temp uses, ensuring consistency across Japan, North America, and Europe. It’s a reliable workhorse for heavy industries where elasticity and durability matter most.

FAQ About JIS SUP10 Spring Steel

1. What makes JIS SUP10 better than JIS SUP9?
   JIS SUP10 has high silicon (1.20–1.60%), which boosts elastic modulus—meaning it recovers shape better after heavy loads. JIS SUP9 lacks this high silicon, making it less ideal for springs needing frequent stress cycles (e.g., truck suspensions).
2. Can JIS SUP10 be used for valve springs in diesel truck engines?
   Yes—for medium-sized diesel truck engines (e.g., 5–8L) with moderate RPMs (up to 5,000 RPM). For large truck engines (10L+), use chromium-vanadium steels for extra heat resistance.
3. What surface treatment works best for JIS SUP10 in wet Japanese climates?
   Zinc plating (per JIS H8610) is ideal—it resists rust from rain and humidity. For extra protection in harsh environments (e.g., marine or agricultural use), add a clear powder coating over the zinc to prevent corrosion.