METHOD OF ANNEALING OF PARTS FROM ALLOYED CAST IRON Russian patent published in 2015 - IPC C23C8/02 C23C8/24 C21D5/00 

FIELD: process engineering.

SUBSTANCE: invention relates to thermal processing of parts from alloyed cast iron with different graphite structure. This process comprises control over initial structure, thermal processing, nitride hardening and machining. Note here that the part initial structure content of graphite, cementite and ferrite is controlled. Thermal processing of parts from cast iron with structure including ball-shape graphite, that of other-than-ball-shape graphite in amount of 10% and ferrite in amount of up to 20% in executed by high tempering and aging while at the content of 10-80% of other-than-ball-shape graphite and 20-85% of ferrite austenitising is performed. Cooling is conducted at the rate of 5-15°C/s to temperature of upper beinite, isothermal tempering, high tempering and ageing. At content of 10-80% of other-than-ball-shape graphite and 20-85% of ferrite and up to 80% of cementite preliminary diffusion annealing, austenising and cooling at the rate of 5-15°C/s to temperature of upper beinite, isothermal tempering, high tempering and ageing are carried out. After thermal processing parts structure is controlled, part surface if machined with allowance for further machining to allow the removal of ε-phase ply after nitride hardening. Thereafter, parts sections with the least wall thickness are subjected to strain cold working. Now, the parts are phosphatised, subjected to low-temperature nitride hardening while part working surface is subjected to electrochemical etching, honing and phosphatising.

EFFECT: decreased deformation at nitride hardening.

7 cl, 1 ex