Heat treatment process of seamless square and rectangular tubes

Seamless square tubes and rectangular tubes and fixtures should be cleaned of oil stains, residual salt, paint and other foreign matter before the heat treatment process; the tooling fixtures used for the first time in the vacuum heat treatment furnace should be cleaned in advance at no less than the requirements specified for the product workpiece. Degassing and purification treatment is performed in the vacuum value; the product workpiece is easily deformed during the heat treatment process and needs to be heated in a special fixture. Heating methods include: primary heating to 800°C, secondary heating to 500-550°C and 850°C. The rate at which the ambient temperature rises during primary heating should be controlled.

Workpieces that are messy in appearance or have significant changes in cross-section and large effective thickness should be heated; workpieces with concave grooves without buried holes, castings and weldments, as well as processed stainless steel workpieces, generally cannot Heating in a carburizing furnace; the heating of seamless square and rectangular tubes should have sufficient insulation and heat preservation time, and the standard thickness can be based on the effective thickness of the product workpiece (the specific thickness is multiplied by the shape coefficient of the product workpiece).

The use of heat treatment methods for seamless square tubes improves their quality and eliminates the environmental pollution caused by pickling and passivation. This type of furnace is suitable for quenching and tempering of large-scale models and large quantities of seamless square tubes. Seamless square and rectangular tubes play an important role in our country's economy.

For the rust removal level of seamless square and rectangular pipes, the construction technology of epoxy, vinyl, phenolic and other anti-corrosion coatings commonly used for seamless square and rectangular pipes generally requires that the surface of the alloy pipes reach a near white level, and spray removal The rust process can stably and reliably achieve near-white quality at a relatively low cost.

Heat treatment process of seamless square and rectangular tubes:

The heat treatment process of seamless square and rectangular tubes has the following three advantages:

(1) The specification reliability of high-precision seamless square and rectangular pipes requires that the precision of pipe fittings be maintained for a long time. Due to the low cooling speed, straightening in the air has a stable effect and increases the number of seamless square tubes remaining in the structure, which requires cooling.

(2) Due to the slenderness of seamless square and rectangular tubes, it is easy to deform due to reduced heat treatment deformation, and the deformation must be strictly controlled during the heat treatment process. The heat treatment process is a very important process. During the heat treatment and refrigeration process, the use of cold plastic deformation for direct calibration is an important factor to ensure that the compliance rate is improved. Therefore, heat treatment in a hot bath or in oil should be carried out. The substance is cooled for a certain period of time and thermal calibration is proposed. In addition, suspension heating should be carried out during the heating process to reduce heat treatment deformation. For high-precision slide rails, gas high-frequency quenching or low-temperature plasma high-frequency quenching should be carried out to reduce deformation.

(3) High toughness seamless square tubes are mainly affected by contact fatigue loads, so they must have high toughness. Therefore, heat treatment, induction hardening or chemical heat treatment process should be carried out, followed by low temperature quenching.