Jaw Crusher swing Jaw Plates

Detailed Introduction to the Swing Jaw Plate of Jaw Crushers

I. Composition and Structure of the Swing Jaw Plate

1. Body: The main structure is a thick plate, typically made of high manganese steel (e.g., ZGMn13) (small-to-medium crushers may use high chromium cast iron). Thickness ranges from 50–300 mm depending on the crusher size, and length matches the swing jaw (usually 1–3 meters).
2. Toothed Working Surface: The material-contacting surface is machined with regularly arranged teeth (triangular or trapezoidal), with tooth height 8–20 mm and tooth pitch 20–50 mm. These teeth enhance material gripping and ensure uniform crushing. Most swing jaw plates are symmetrically designed, allowing reversal after one end wears to extend service life by over 50%.
3. Mounting Slots/Bolt Holes: The back surface features T-slots or countersunk bolt holes for connection to the swing jaw body, secured by wedge blocks or high-strength bolts to prevent loosening during operation (avoiding vibration-induced detachment).
4. Reinforcing Edges: Large swing jaw plates often have raised edges to enhance overall rigidity and prevent deformation from material impact.
5. Weight-Reduction Holes (Optional): Ultra-large swing jaw plates may include drilled holes on non-working surfaces to reduce weight without compromising strength.

II. Casting Process of the Swing Jaw Plate

1. Mold Preparation

• Sand casting (sodium silicate sand or resin sand) is used. Wooden or resin patterns are fabricated based on drawings (including teeth, bolt holes, etc.), with a 5–8 mm machining allowance (high manganese steel linear shrinkage rate ≈2%).

• The mold cavity surface must be smooth, with precise 成型 of toothed areas to avoid excessive post-casting deviations. A dedicated gating and riser system ensures full filling of complex structures like teeth.

2. Melting and Pouring

• High manganese steel melting: High-purity pig iron (P ≤0.07%, S ≤0.05%), low-carbon scrap steel, and ferromanganese (Mn ≥95%) are proportioned. Melting occurs in an electric arc furnace or medium-frequency furnace at 1500–1550°C, with chemical composition controlled (C: 1.0–1.4%, Mn: 11–14%, Si: 0.3–0.8%) to ensure a Mn/C ratio ≥10 (critical for austenitic structure).

• Deoxidation: Ferrosilicon and aluminum are added for final deoxidation, reducing oxygen content to ≤0.005% to prevent porosity.

• Pouring: A bottom-pouring system is used, with pouring temperature controlled at 1400–1450°C. Large swing jaw plates require segmented pouring (to avoid cold shuts), with duration 3–8 minutes depending on weight.

3. Shakeout and Cleaning

• The casting is shakeout after cooling to below 200°C. Risers are removed by flame cutting, and gate marks are ground flush with the body.

• Surface sand and flash are cleaned. Toothed areas are inspected for integrity, and bolt holes are checked for blockages.

4. Water Quenching Treatment (Critical Step)

• The casting is slowly heated to 1050–1100°C (heating rate ≤100°C/h to prevent cracking) and held for 2–4 hours (ensuring complete dissolution of carbides into austenite).

• Rapid water cooling (water temperature ≤30°C, cooling rate ≥50°C/s) inhibits carbide precipitation, forming a single austenitic structure (ensuring high toughness). Hardness after treatment is ≈200 HBW, with impact energy ≥180 J.

III. Manufacturing Process of the Swing Jaw Plate

1. Rough Machining

• Using the back surface as a reference, a gantry mill rough-mills the working surface, leaving a 2–3 mm finishing allowance to ensure flatness error ≤1 mm/m.

• Bolt holes are drilled with a radial drill, with diameter tolerance ±0.5 mm and depth 2–3 mm greater than bolt length.

2. Finishing

• Tooth machining: A dedicated forming milling cutter on a gantry mill machines the teeth, ensuring tooth height/pitch tolerance ±0.5 mm and surface roughness Ra ≤6.3 μm. Tooth symmetry error ≤0.3 mm (critical for reversal accuracy).

• Mounting surface machining: The back mounting surface and locating spigot are finish-milled to ensure ≥80% contact with the swing jaw body (gap ≤0.1 mm via feeler gauge) and flatness ≤0.5 mm/m.

• Stress relief: Post-machining low-temperature annealing (200–250°C, 1–2 hours) eliminates machining stress to prevent in-service deformation.

3. Surface Treatment

• Machining burrs are removed. Non-working surfaces are sandblasted (roughness Ra=25–50 μm) to enhance friction with the swing jaw body.

• Mounting hole interiors are tapped (if required) to 6H thread precision for secure bolt connection.

IV. Quality Control Process of the Swing Jaw Plate

1. Material Performance Control

• Chemical composition inspection: A spectrometer analyzes C, Mn, etc., ensuring compliance with ZGMn13 standards (Mn: 11–14%, C: 1.0–1.4%).

• Mechanical property testing: Samples undergo impact tests (-40°C low-temperature impact energy ≥120 J) and hardness measurements (≤230 HBW after water quenching). Metallographic inspection confirms no network carbides (which reduce toughness).

2. Casting Quality Control

• Visual defect inspection: 100% visual checks exclude cracks, shrinkage cavities, or misruns. Magnetic particle testing (MT) on toothed areas ensures no surface cracks.

• Internal quality inspection: Ultrasonic testing (UT) on large plates verifies no ≥φ3 mm pores or inclusions in critical areas (tooth roots, bolt holes).

3. Machining Accuracy Control

• Dimensional tolerance inspection: Calipers and tooth templates check tooth height/pitch. A coordinate measuring machine verifies mounting hole position tolerance (≤0.3 mm).

• Geometric tolerance inspection: A laser level checks working surface flatness (error ≤0.5 mm/m). A dial indicator verifies perpendicularity between mounting and working surfaces (≤0.1 mm/100 mm).

4. Assembly Verification

• Trial fitting: The swing jaw plate is mounted on the swing jaw body to check contact and tightness, with no loose noise when tapped manually.

• Wear simulation test: Sampled plates undergo bench testing (8 hours at rated load) to measure tooth wear (≤0.5 mm) and ensure no cracks or deformation.