Hot press cylinders are core components in industrial hot pressing equipment, responsible for providing stable pressure in high-temperature environments (usually 150–300°C) and ensuring precise control of workpiece forming. Their processing involves multiple sophisticated procedures, with strict requirements for material performance, dimensional accuracy, and high-temperature resistance. Each step from material selection to final testing directly affects the cylinder’s service life and operational safety.
The processing of hot press cylinders starts with material selection. Due to the need to withstand high pressure (often 25–50 MPa) and high temperatures, the cylinder barrel and piston rod must use high-strength alloy steels. The cylinder barrel is typically made of 42CrMo alloy structural steel, which has excellent tensile strength (≥1000 MPa) and impact toughness after heat treatment, ensuring it does not deform or crack under high pressure. The piston rod, as a moving part, requires better wear resistance and corrosion resistance, so 38CrMoAlA alloy steel is commonly used. This material forms a dense aluminum oxide film on the surface after nitriding treatment, with a hardness of up to HV900, effectively resisting wear caused by high-temperature friction. Forging is a key process to improve material density. The cylinder blank undergoes die forging at a high temperature of 1100–1200°C, which breaks the original casting structure of the steel, refines the grains, and eliminates internal defects such as pores and inclusions. For large hot press cylinders (with a diameter exceeding 500 mm), upsetting and stretching processes are repeated to ensure uniform material performance in all directions. After forging, the blank is subjected to normalizing treatment to reduce internal stress and prepare for subsequent machining.
Heat treatment is critical to ensuring the mechanical properties of hot press cylinders. The cylinder barrel undergoes quenching and tempering: first heated to 850–880°C for water cooling, then tempered at 550–600°C to obtain a tempered sorbite structure, which balances strength and toughness. The piston rod undergoes a specialized nitriding process: after precision machining, it is heated to 500–520°C in a nitrogen-rich atmosphere for 40–60 hours, allowing nitrogen atoms to diffuse into the surface layer to form a hard nitride layer (0.3–0.5 mm thick). This treatment not only improves wear resistance but also enhances the rod’s resistance to high-temperature oxidation.
Precision machining is essential to ensure dimensional accuracy and assembly performance. The inner hole of the cylinder barrel undergoes deep hole boring and honing. Deep hole boring uses a gun drill or BTA deep hole drilling system to ensure the straightness error of the inner hole is within 0.05 mm/m, while honing achieves a surface roughness of Ra 0.4–0.8 μm, reducing friction between the piston and the cylinder wall. The piston rod is processed using a high-precision cylindrical grinder, with the outer diameter tolerance controlled within IT7 (±0.015 mm) and the roundness error ≤0.005 mm, ensuring smooth movement and reliable sealing.
Surface treatment of hot press cylinders is tailored to high-temperature environments. The outer surface of the cylinder barrel is coated with high-temperature-resistant paint (能耐 300°C) to prevent oxidation and corrosion. The piston rod’s surface, after nitriding, is polished to a mirror finish and coated with a layer of molybdenum disulfide-based solid lubricant, which maintains lubrication performance at high temperatures and reduces seal wear. For cylinders used in corrosive environments (such as composite material hot presses), the surface is further treated with ceramic spraying (alumina or chromium oxide), with a coating thickness of 0.1–0.2 mm, achieving both high-temperature resistance and corrosion resistance.
Assembly of hot press cylinders emphasizes sealing performance and high-temperature stability. The sealing system uses high-temperature-resistant composite seals: the main seal is made of fluororubber (Viton), which can work stably at 200°C, and the auxiliary seal uses polytetrafluoroethylene (PTFE) with a stainless steel spring energizer to ensure tightness under pressure fluctuations. During assembly, a torque wrench is used to uniformly tighten the flange bolts to avoid uneven stress, and a pressure test is conducted after assembly—pressurizing to 1.5 times the rated pressure and holding for 30 minutes to check for leaks.
Finally, the finished hot press cylinder undergoes comprehensive performance testing. This includes a high-temperature pressure test (simulating the actual working temperature of 250°C, maintaining pressure for 2 hours), a stroke accuracy test (ensuring the piston rod’s movement error is within ±0.1 mm), and a fatigue test (performing 100,000 cycles of pressure loading and unloading to verify structural durability). Only cylinders that pass all tests are considered qualified, ensuring they can reliably operate in harsh hot pressing environments for long periods (typically 8,000–12,000 hours of service life).
Pусский
ไทย
Indonesia
Tiếng Việt
WhatsApp
Phone
Comment
（0）