1. What Is a Compressor Housing

The compressor housing (also called airend casing, compressor casing, or airend housing) is the pressure-containing body and precision mounting base of the compressor airend. It encloses the male and female rotors, bearings, mechanical seals, lubrication galleries, inlet/outlet ports, and mounting feet in a single rigid casting. The rotors mesh with minimal clearance inside a precision-bored "figure-eight" cavity, so the housing must simultaneously withstand internal discharge pressure, maintain tight geometric tolerances, and provide vibration damping.

2. Main Types

3. Standard Materials (Screw Airend)

4. Casting Process

1. Pattern: Wood or aluminum pattern, machined to include draft angle (1–2%), shrinkage allowance (1.0% for gray iron), and machining allowance (3–5 mm on faces, 5–8 mm on bores)
2. Core: The figure-eight rotor cavity and internal oil galleries require separate sand cores (shell cores or cold-box cores). The core must be precisely positioned with core prints to ensure bore alignment.
3. Core vents: Venting channels are critical — trapped gas during pouring causes blowholes.

1. Resin sand (furan resin + hardener) is mixed and blown/rammed around the pattern
2. Mold is cured at room temperature (24h) or oven-cured (200°C × 1h)
3. Mold parting surface is coated with refractory paint (zircon flour or graphite) to improve surface finish and prevent sand inclusion
4. Cores are placed in the mold and checked for centering

1. Furnace: Medium-frequency induction furnace (500 kg–5 t)
2. Charge: Foundry returns + pig iron + scrap steel + carburizer
3. Tapping temperature: 1420–1480°C for gray iron HT250
4. Inoculation: Ba-Si inoculant (0.3–0.5%) in the ladle to promote Type-A graphite and prevent chill
5. Pouring temperature: 1380–1420°C
6. Pouring system: Bottom gating with riser on top to feed the heavy sections (flanges, bearing bosses)

1. Housing cools in the mold for 4–8 hours (depending on size; 80–150 kg housing ≈ 6h)
2. Shakeout after casting temperature drops below 300°C
3. Core sand is removed by shakeout + pneumatic core gun

1. Gating/riser removal: Band saw or arc air gouging
2. grinding: Remove flash, fins, and runner residue with a grinding wheel
3. Shot blasting: Steel shot (S110/S170) to remove sand scale and surface oxide, clean the casting surface to Sa2.5
4. Visual inspection: Check for surface defects (sand holes, shrinkage, cracks, misrun)

1. Stress relief annealing: 550–600°C, hold 2–4 hours, furnace cool to 200°C before air cooling
2. Purpose: Eliminate casting residual stress to prevent machining distortion
3. For ductile iron QT450: normalize at 900°C + temper at 550°C to achieve required ferrite/pearlite structure and mechanical properties