Automotive Valve Springs
Valve springs for
the engine’s valve train.
Compression springs that hold each valve against its seat and return it as the camshaft turns — wound to your drawing in Rayong, Thailand from 0.08 mm to 8.0 mm wire, with load and fatigue testing in-house.
Seat load, open load and a very long life
A valve spring does one job in the engine: keep the valve closed against its seat, let the camshaft open it, and bring it back without losing contact across the speed range the design is validated for.
Two numbers define the part. The load at installed height is the seat pressure; the load at full lift is the open pressure. Spring rate links them, and the wire, coil diameter, active coils and free length are what deliver both. Cycle life then decides the material grade and the stress the spring can carry.
The spring works hot, in oil, at millions of cycles. The drawing should state the installed height, both loads, the space available and the cycle target; we confirm the wire, the coil design and the heat treatment against those numbers.
- Wire diameters from 0.08 mm to 8.0 mm in current production
- Closed and ground ends, as defined on the drawing
- In-house stress relief and tempering
- Load checked at installed height and at full lift
- Prototype, pre-production and volume orders
Where a valve spring sits
A valve spring sits between the cylinder head and the retainer, around the valve stem. It is a high-cycle part: every revolution of the engine is a load cycle, so the design has to hold its load rather than simply survive one compression.
Valve spring specifications
Current production is shown below. Parameters outside it are reviewed at RFQ rather than assumed.
| Parameter | Capability |
|---|---|
| Wire diameter | 0.08–8.0 mm in current production. Planned expansion to 12.0 mm as new equipment is installed. |
| Materials | 65Mn, 72A, 82B and 60Si2Mn carbon spring steels; stainless steel 301, 302, 304 and 316. Other grades reviewed on request. |
| End form | Closed and ground ends, closed ends or open ends, as defined on the drawing. |
| Installed height and seat load | Measured at the installed height stated on the drawing; the load tolerance is agreed at RFQ. |
| Open height and load | Measured at full lift; the rate is confirmed from the two measured load points. |
| Heat treatment | In-house stress relief and tempering. |
| Surface finish | Anti-rust oil, electrophoresis (E-coat), zinc plating, nickel plating, spray coating. |
| Wire tolerance | JIS wire tolerance by grade (JIS G 3521, JIS G 3522 or JIS G 4309). ASTM wire specification and SMI commercial tolerances available for US programs. |
| Dimensional inspection | 2.5D vision measurement and dimensional checks against the drawing. |
| Fatigue testing | Cycle-life testing in-house, to the load range and cycle count agreed at RFQ. |
| Corrosion testing | Salt spray testing for plated and coated parts. |
| Quality system | ISO 9001:2015 and ISO 14001:2015. Automotive quality management certification in progress. |
| Samples | Prototype and pre-production samples against drawing. |
Please state installed height, seat load, open height, open load and the maximum outside diameter. Those five numbers decide the coil. Operating temperature and cycle life decide the material.
Materials and finishes
The wire grade follows the stress the spring carries, the temperature it works at and the corrosion protection the drawing calls for.
65Mn · 72A · 82B · 60Si2Mn
Selected for the strength and fatigue performance a high-cycle valve train needs, normally with a protective finish against the oil and moisture in the engine.
301 · 302 · 304 · 316
Used where the drawing calls for corrosion resistance without a coating, subject to the load and the operating temperature the application allows.
Oil · E-coat · zinc · nickel · spray
Anti-rust oil, electrophoresis, zinc plating, nickel plating and spray coating are available. The finish is chosen for the environment and the assembly process.
Load and life, measured before shipment
A valve spring that is right on the first part and wrong on the ten-thousandth is a warranty problem. Load, dimensions, material condition and cycle life are checked in-house.
- Raw material tensile strength and metallographic structure
- Load testing at installed height and full lift
- 2.5D vision measurement of coil geometry and end squareness
- Fatigue testing for cycle-life validation
- Salt spray testing for plated and coated parts
- Inspection records agreed at RFQ
What to send with your drawing
Valve spring quotes go wrong when the seat load is quoted without the installed height. Send both, and the rest follows.
- Wire diameter and material grade or specification
- Installed height and seat load
- Open height and open load, or the spring rate
- Maximum outside diameter and fitted length
- End form: closed and ground, closed or open
- Operating temperature and cycle-life target
- Surface finish and documentation requirements
- Annual quantity and delivery schedule
PDF, DXF, STEP or a clear photo
Email your drawing to info@aofengspringthailand.com. We confirm the wire, the coil design, the material and the test plan before quoting.
Valve spring questions
What is a valve spring?
A valve spring is a compression spring in an engine’s valve train. It holds the valve closed against its seat and returns it after the camshaft opens it. The part is defined by its seat load at installed height, its open load at full lift and the number of cycles it has to survive.
What do you need to quote a valve spring?
Installed height and seat load, open height and open load (or the spring rate), maximum outside diameter, wire diameter and material, end form, operating temperature, cycle-life target, finish and annual volume. With those we can confirm the coil design and the test plan.
Can you fatigue test valve springs?
Yes. Fatigue testing is carried out in-house to the load range and cycle count agreed at RFQ, and the load at installed height and full lift is measured on automatic spring testers.
Which materials do you use for valve springs?
65Mn, 72A, 82B and 60Si2Mn carbon spring steels, plus stainless steel 301, 302, 304 and 316. Other grades are reviewed against the drawing at RFQ.
Are you IATF 16949 certified?
Not yet. The Rayong plant is certified to ISO 9001:2015 and ISO 14001:2015, and certification of an automotive quality management system is in progress.
Send a drawing, get a quote
Tell us the installed height, the seat load and the cycle target. We will confirm the wire, the coil design and the test plan before quoting.
AOFENG SPRING (THAILAND) · Rayong, Thailand