CN104611528A

CN104611528A - Heating method for refined 70# steel austenite grain

Info

Publication number: CN104611528A
Application number: CN201510061249.8A
Authority: CN
Inventors: 亓海全; 焦慧彬; 周伍
Original assignee: Guilin University of Technology
Current assignee: Guilin University of Technology
Priority date: 2015-02-06
Filing date: 2015-02-06
Publication date: 2015-05-13

Abstract

The invention discloses a heating method for a refined 70# steel austenite grain. The heating method comprises the steps of (1) rapidly heating 70# steel to 980-1000 DEG C at the speed of 5-1000 DEG C/s by using an electric contact heating, operating frequency induction heating or rapid electro-heating means, and preserving the heat for 1-5 seconds; (2) carrying out staged cooling and short-term heat preservation on the 70# steel obtained in the step (1), namely firstly, rapidly cooling to 950-980 DEG C and preserving the heat for 1-5 seconds, then, rapidly cooling to 900-950 DEG C and preserving the heat for 1-5 seconds, continuing to rapidly cool to 850-900 DEG C and preserving the heat for 1-5 seconds, and finally, rapidly cooling to 780-820 DEG C and preserving the heat for 5-20 seconds, wherein all the cooling speeds are larger than or equal to 10 DEG C/s; and (3) carrying out oil quenching on the 70# steel obtained in the step (2) or rapidly moving the 70# steel to a pit furnace or a bogie hearth furnace with the hearth temperature of 780-820 DEG C to preserve the heat for 5-60 minutes, and then, carrying out oil quenching to ensure that the austenite grain size can be up to 10-15 grades. The heating method is simple in process, free of additionally providing complex equipment, relatively low in cost and capable of generating few influences to production process flows.

Description

The heating means of a kind of refinement No. 70 steel austenite crystals

Technical field

The present invention relates to iron and steel technical field of heat treatment, particularly the heating means of a kind of refinement No. 70 steel austenite crystals.

Background technology

No. 70 steel are middle carbon carbon constructional quality steels, and usually use under modified or as-normalized condition, comprehensive mechanical property is good, are widely used in manufacturing the part such as spring, spring.When modified or normalizing treatment, in order to obtain the performance requriementss such as good toughness and hardness, people wish obtain tiny austenite grain size when heating.Affect austenite grain size because have heating cycle and original structure etc., therefore the prior heat treatment process of refinement No. 70 steel austenite grain sizes has rapid heating isothermal treatment for short time, reduces the means such as Heating temperature and circulating-heating quenching.But there is austenite not full and uniformization, the problem such as soaking time is long, grain refinement effect is limited in above-mentioned processing method.In view of this, the present invention proposes the heating process of a kind of refinement No. 70 steel austenite crystals.

Summary of the invention

The object of the invention is to overcome above-mentioned traditional technology Problems existing, to grow up theory based on austenite forming core, a kind of heating means of No. 70 steel austenite crystals are provided.

Concrete steps are:

(1) adopt the heating of Electricity Contact Heating, line-frequency induction or electroluminescent rapid heating means, rate of heating is 5 ~ 1000 DEG C/sec, and No. 70 steel are quickly heated up to 980 ~ 1000 DEG C, is incubated 1 ~ 5 second.

(2) step (1) gained No. 70 Steel Bar are carried out gradient cooling+isothermal treatment for short time, namely 950 ~ 980 DEG C are first quickly cooled to be incubated 1 ~ 5 second, 900 ~ 950 DEG C are quickly cooled to be incubated 1 ~ 5 second again, continue to be quickly cooled to 850 ~ 900 DEG C to be incubated 1 ~ 5 second, finally be quickly cooled to 780 ~ 820 DEG C to be incubated 5 ~ 20 seconds, speed of cooling is all more than or equal to 10 DEG C/sec.

(3) step (2) gained No. 70 steel being carried out oil quenching or is quickly moved to fire box temperature is insulation air cooling or oil quenching after 5 ~ 60 minutes in the pit furnace of 780 ~ 820 DEG C or desk stove, and autstenitic grain size can reach 10 ~ 15 grades.

The present invention has the following advantages compared with existing No. 70 steel heat treatment process:

(1) technique is simple, and without the need to increasing complex apparatus, cost is lower, little on technological process of production impact.

(2) autstenitic grain size after making prior heat treatment brings up to 10 ~ 15 grades by 8 ~ 10 grades.

Embodiment

embodiment 1:

(1) adopt Electricity Contact Heating, rate of heating is 100 DEG C/sec, will Φno. 70 steel pole materials of 10mm × 30mm quickly heat up to 1000 DEG C, are incubated 2 seconds.

(2) step (1) gained No. 70 steel pole materials are carried out gradient cooling+isothermal treatment for short time, namely 950 DEG C are first quickly cooled to be incubated 2 seconds, 900 DEG C are quickly cooled to be incubated 2 seconds again, continue to be quickly cooled to 850 DEG C to be incubated 4 seconds, finally be quickly cooled to 810 DEG C to be incubated 10 seconds, speed of cooling is 20 DEG C/sec.

(3) being carried out by step (2) gained No. 70 steel pole materials being quickly moved to fire box temperature is be incubated 10 minutes in the pit furnace of 800 DEG C, and then oil quenching, autstenitic grain size is 15 grades.

embodiment 2:

(1) adopt line-frequency induction heating, rate of heating is 100 DEG C/sec, will Φno. 70 steel pole materials of 10mm × 30mm quickly heat up to 1000 DEG C, are incubated 2 seconds.

(2) step (1) gained No. 70 steel pole materials are carried out gradient cooling+isothermal treatment for short time, namely 950 DEG C are first quickly cooled to be incubated 2 seconds, 900 DEG C are quickly cooled to be incubated 4 seconds again, continue to be quickly cooled to 850 DEG C to be incubated 4 seconds, finally be quickly cooled to 810 DEG C to be incubated 10 seconds, speed of cooling is 10 DEG C/sec.

(3) step (2) gained No. 70 steel pole materials are carried out oil quenching, autstenitic grain size is 14 grades.

embodiment 3:

(1) adopt electroluminescent rapid heating means, rate of heating is 100 DEG C/sec, will Φno. 70 steel pole materials of 10mm × 30mm quickly heat up to 1000 DEG C, are incubated 2 seconds.

Claims

1. heating means for refinement No. 70 steel austenite crystals, is characterized in that concrete steps are:

(1) adopt the heating or fast electroluminescent of Electricity Contact Heating, line-frequency induction, rate of heating is 5 ~ 1000 DEG C/sec, and No. 70 steel are quickly heated up to 980 ~ 1000 DEG C, is incubated 1 ~ 5 second;

(2) step (1) gained No. 70 Steel Bar are carried out gradient cooling+isothermal treatment for short time, namely 950 ~ 1000 DEG C are first quickly cooled to be incubated 1 ~ 5 second, 900 ~ 950 DEG C are quickly cooled to be incubated 1 ~ 5 second again, continue to be quickly cooled to 850 ~ 900 DEG C to be incubated 1 ~ 5 second, finally be quickly cooled to 780 ~ 820 DEG C to be incubated 5 ~ 20 seconds, speed of cooling is all more than or equal to 10 DEG C/sec;

(3) step (2) gained No. 70 steel being carried out oil quenching or is quickly moved to fire box temperature is insulation 5 ~ 60 minutes in the pit furnace of 800 DEG C or desk stove, and then oil quenching, autstenitic grain size can reach 10 ~ 15 grades.