Drawn tube mould manufacturer Small make up to tell you heat treatment technology of the roll
Roll according to the working state can be divided into hot rolling and cold rolling, can be divided by the role of the work roll and intermediate roll and backup roll, according to the material can be divided into forging roll and casting roll (chilled cast iron). Normally roll service conditions are rigid, in the process of the work under high alternating stress, bending stress and contact stress, shear stress and friction. Prone to wear and spalling failure in the form. Different USES, different types of roll in their specific conditions, its general performance requirements are as follows: roll type, the main performance requirements, work roll hardness ℃ temperature.
Hot rolled
Hot rolled work roll thermal fatigue crack resistance, rough surface resistance performance of HB: room temperature 196 ~ 302 ~ 850, cold rolled work roll high hardness, wear resistance, fatigue spalling resistance HS: room temperature 90 ~ 105 ~ 90.
Does not allow for hot roll, roll surface, the surface crack defects cause stress concentration and accelerate the extension and disable roll. Thermal fatigue cracks are mainly caused by periodic alternating thermal stress, severe cases, the crack propagation may cause roller surface spalling, even roll breakage.
Main failure forms of cold roll including cut, glue roller and spalling, etc. Cold roll roll surface should be high and even hardness, their quality performance in the work layer of roll abrasion resistance, namely rough resistance.
Hot rolling work rolls are generally with heat treatment after forging and heat treatment of quenched and tempered.
(1) heat treatment after forging
The main purpose of heat treatment after forging is to eliminate stress after forging, refine grain and improve the cutting performance. Heat treatment after forging and diffusion hydrogen. Diffusion hydrogen time depending on the ingot hydrogen content, it is generally believed [H] 2 x 10-4% or less, can cancel the diffusion hydrogen processing.
(2) conditioning
Final heat treatment is the conditioning of hot rolling work rolls. The qualitative purpose is to guarantee the roll surface hardness and mechanical properties, and guarantee the core enough toughness.
Cold rolled
Cold rolled work roll time generally have heat treatment after forging, heat treatment and tempering and surface hardening.
(1) heat treatment after forging
Heat treatment after forging the purpose is to reduce the hardness, eliminate the residual stress, but also improve the organization, get fine pearlite, eliminate the carbide network. Heat treatment after forging and diffusion hydrogen. Diffusion hydrogen time depending on the ingot hydrogen content, it is generally believed [H] 2 x 10-4% or less, can cancel the diffusion hydrogen processing.
(2) conditioning
The quality objectives are to provide surface quenching organization, make the roll neck and roll heart get strong toughness with good spheroidal pearlite organization, good comprehensive mechanical properties, to withstand intense surface quenching.
(3) the surface hardening
The work roll surface quenching get high hardening layer. Surface hardening methods according to the heating method can be divided into the overall rapid quenching method and continuous induction heating quenching method, the latter is more widely used in the production practice.
In continuous induction heating quenching process approach double-frequency induction hardening has distinguishing feature very much, it USES the sensor matching of two different frequency induction heating, the roller surface temperature control and heating temperature distribution has obvious advantages. Typical double-frequency quenching equipment in large power frequency current penetration depth sensor as the main sensors, realize the deep heating, soaking after a period of time, and then use a medium frequency sensor to get deeper after isothermal austenitizing layer, to obtain the required after quenching hardening layer depth.
Scan two-dimensional code attention