Direct answer: How the housing is specified: pure iron, forming route, magnetic annealing and OD/ID control.

The housing carries the whole function

Carries the coil: the OD defines coil fit, external appearance and the assembly interface. Consistency here decides how cleanly the coil drops into production.
Guides the armature: the ID controls plunger guidance, internal clearance and the magnetic circuit. Repeatable ID geometry is what makes valve response predictable.
Seals and performs: sealing interfaces, roundness and concentricity determine leak-tight assembly. For proportional valves, magnetic performance decides force, response and repeatability.

A solenoid housing (also called a solenoid valve housing or a solenoid can) is not an ordinary metal shell. It carries the coil, guides the armature, seals the working fluid and completes the magnetic circuit.

Source: balford.net/applications/solenoid-valve-housing/.

Materials

Grade	What it is for	Notes
DT4 / DT4C pure iron	Magnetic circuits; the usual choice where magnetic performance is critical	Supplied annealed; formed and annealed again where performance demands it
DC04	Economical switching-valve housings	Deep drawing steel with excellent formability
SPHE	Drawn housings where strength and cost balance	Hot-rolled pickled steel

We work with magnetic steels and pure iron grades depending on the valve design and the magnetic requirement.

Coercivity is the number that decides the valve

For a magnetic solenoid housing, dimensional accuracy is only part of the story.

Cold rolling, cold extrusion and deep drawing introduce plastic deformation and residual stress. Residual stress raises coercivity (Hc) and reduces magnetic performance.

This matters most for proportional solenoid valves, where magnetic characteristics directly influence force, response and repeatability.

Lower coercivity means more stable force and more repeatable proportional-valve behaviour.

Practical consequence: the forming route is part of the magnetic specification, not only a cost decision.

A housing that measures perfectly can still behave wrongly if coercivity is not controlled.

Magnetic annealing after forming

Forming introduces residual stress.
Residual stress increases coercivity.
Magnetic annealing relieves internal stress and restores magnetic properties.
For proportional valves this is often what makes stable magnetic force and repeatable performance achievable.

Magnetic annealing process know-how (process windows, demagnetisation behaviour, and how magnetic properties change across materials and forming states) is in house.

Production heat treatment is performed by audited partner companies and is declared as such. Plating and passivation are partner operations for the same reason.

Ask two questions of any solenoid housing supplier: who anneals, and to what process window.

Two forming routes, chosen per part

	Cold extruded housing	Deep drawn housing
Best for	Demanding proportional valves	Efficient high-volume production
Dimensional consistency	High	Good, and repeatable with controlled tooling
Concentricity	Excellent	Controlled by tooling and ironing
Material utilisation	Lower	High
Typical cost profile	Higher unit cost, stronger structure	Competitive unit cost at volume
Magnetic annealing	Typically required for proportional valves	Typically applied for proportional valves; switching housings generally do not need it

Both routes are evaluated for every part against geometry, wall thickness, material, volume and the magnetic requirement, rather than chosen from a fixed template.

Switching valve vs proportional valve housing

Requirement	Switching solenoid valve	Proportional solenoid valve
Housing	Critical	Critical
Dimensional accuracy	High	Very high
Magnetic properties	Important	Extremely important
Forming stress	Needs control	Needs strict control
Magnetic annealing	Often not required	Typically required
Coercivity control	Important	Key parameter
CNC machining	Required	Required
Plating	Application dependent	Application dependent

The process is selected from the valve application, not from a fixed template.

A housing should look like a precision tube

The OD affects coil fit, external appearance, the assembly interface and dimensional consistency.
The ID affects armature and plunger guidance, internal clearance, the magnetic circuit, and sealing.

Deep drawing can leave visible circumferential rings on the outside diameter. For solenoid valve manufacturers that is not always acceptable.

The OD is controlled through tooling, material condition, forming parameters, machining and surface finishing together.

Target: smooth, bright, continuous, consistent. Not: heavy drawing rings, uneven surface, visible forming marks.

OD appearance and ID precision are engineered together, not traded against each other.

Capability envelope, and where we are honest

Presses 25-350 t, including transfer press; maximum deep draw diameter 250 mm; single-station, progressive die and transfer routes.
In-house tooling design and build. More than 4,000 single-operation draw dies built and kept since 2000 (predecessor business, Ruian Derlin Stampings Factory).
ISO 9001:2015 certified; process controls aligned with IATF 16949 requirements. Not certified to IATF 16949, and no ISO 14001.
Production heat treatment, plating, passivation, electropolishing, phosphating and powder coating are performed by audited partner companies and are declared as such. Slow-wire EDM is subcontracted.
Standard tolerance on deep drawn features about +/-0.05 to +/-0.25 mm; 0.001 mm only on selected critical machined features.
We do not run micro-stamping (blank under 3 mm), oversized stamping (blank over 600 mm or drawn height over 200 mm), high-speed stamping (maximum 120 SPM) or cosmetic-grade finishes.

Where a part sits outside that envelope we say which process it belongs to.

Printable version

This document is also available as a PDF: Solenoid Valve Housing Guide (PDF).

Solenoid Valve Housing Guide