CN102560244A

CN102560244A - Microalloying and heat treatment method for 20MnMo steel

Info

Publication number: CN102560244A
Application number: CN201110454851XA
Authority: CN
Inventors: 于慎君; 刘晓珂; 陶凯; 石如星; 代博杰; 李德福; 郎庆斌; 殷立涛; 张峰; 聂新林; 席志永; 陈艳芳; 李光; 林乙丑; 于文平
Original assignee: CITIC Heavy Industries Co Ltd
Current assignee: CITIC Heavy Industries Co Ltd
Priority date: 2011-12-30
Filing date: 2011-12-30
Publication date: 2012-07-11
Anticipated expiration: 2031-12-30
Also published as: CN102560244B

Abstract

The invention discloses a microalloying and heat treatment method for 20MnMo steel. In the 20MnMo steel microalloying method, a microalloy element Nb is added into the 20MnMo steel; and the Nb content is 0.03 to 0.06. In the 20MnMo steel heat treatment method, a workpiece is subjected to normalizing, quenching and tempering treatment; and proper process parameters are selected. According to the method, crystalline grains can be refined; the strength and the plastic toughness of the 20MnMo steel; and the material performance is further improved through precipitation enhancement and phase change enhancement.

Description

A kind of 20MnMo steel microalloying and heat treating method

Technical field

The invention belongs to the low-carbon alloy steel technical field, relate in particular to a kind of 20MnMo steel and heat treating method of Nb microalloying.

Background technology

Worldwide, have superior weldability can the low-carbon alloy steel consumption big and purposes is many.20MnMo belongs to pressurized vessel and use low-carbon alloy steel, and welding property is good, warm high pressure vessel in being widely used in, as high pressure heater tube sheet, import and export water pipe, end socket, bottom, cylindrical shell, etc. the core component in the boiler plant.Along with technical progress, the performance requriements of ferrous materials is improved constantly, under a lot of operating modes, not only require to have high intensity, good plasticity and toughness, also should have low ductile-brittle transition temperature and good processing characteristics.It is unstable and do not reach technical requirements usually to occur ballistic works such as 20MnMo tube sheet, module in the production, the situation that causes workpiece repeatedly to reprocess or scrap, and this is thick relevant with crystal grain according to one's analysis.

Summary of the invention

For addressing the above problem, the present invention provides a kind of 20MnMo steel microalloying and heat treating method, is applicable to the workpiece of free area 100 ~ 700mm.

For realizing the foregoing invention purpose, the present invention adopts following technical scheme:

A kind of 20MnMo steel microalloying, its chemical ingredients composition is counted with mass percent: C:0.17～0.23, Si:0.17～0.37, Mn:1.10～1.40, P :≤0.025, S :≤0.015, Ni :≤0.30, Cr :≤0.30, Cu :≤0.25, Mo:0.20～0.35; Also be added with microalloy element Nb, the content of Nb is 0.03～0.06.

The trace element niobium is widely used in the micro-alloyed steel, and the performance of steel is produced multiple influence.Mainly show two aspects: the one, in hot procedure, suppress austenitic deformation recrystallize and stop growing up of its crystal grain; The 2nd, can separate out carboritride through strain inducing, the precipitation strength effect of performance niobium.For the 20MnMo low-carbon low-alloy steel, the alloy element Nb that Xiang Gangzhong adds is very strong to the performance impact of steel.Minor N b just can play very large effect in steel, the Nb crystal grain thinning when improving intensity, improves the toughness of steel again.

A kind of microalloying 20MnMo steel heat treating method, its process step is:

(1) workpiece is put into heat treatment furnace, be warming up to 350 ± 10 ℃ of insulation 2 ~ 5h, and then be warming up to 600 ~ 700 ℃ of insulation 3 ~ 8h with the speed of 40 ~ 60 ℃/h with the speed of 40 ~ 60 ℃/h;

After (2) 600 ~ 700 ℃ of insulations, be warming up to 880 ~ 930 ℃ of insulations of quenching temperature, 3 ~ 20h with the speed of 50-80 ℃/h;

(3) workpiece being hung out from stove, put into quenching-in water 10 ~ 120min, from water, take out after surface temperature≤150 ℃, water temperature is controlled at≤and 20 ℃;

(4) cooling finishes back shove charge tempering in time, is warming up to 350 ~ 400 ℃, insulation 4 ~ 8h with the speed of 30-60 ℃/h;

After (5) 350 ~ 400 ℃ of insulations finish, be warming up to 580 ~ 650 ℃ of tempering temperatures, insulation 6 ~ 35h, the air cooling of coming out of the stove with the speed of 30 ~ 60 ℃/h.

Because adopt aforesaid technical scheme, the present invention has following meliority:

One, after property heat treatment, the 20MnMo steel mechanical property behind 20MnMo steel and the Nb microalloying is as shown in table 2.

The 20MnMo rigidity can contrast before and after table 2 added Nb

Performance	R _m / Mpa	R _eL / Mpa	A ₅ /%	Z/%	A _KV /J(0℃)
						Add Nb	745	570	25.5	71.0	121,108,115
Do not add Nb	590	470	24.5	70.0	150,40,87

Two, through in the 20MnMo steel, adding microalloy element Nb, both can suppress austenitic deformation recrystallize and stop growing up of its crystal grain; Can separate out carboritride through strain inducing again, the precipitation strength effect of performance niobium.Adding behind the micro-Nb element can crystal grain thinning, improves the intensity and the plasticity and toughness of 20MnMo steel simultaneously, and further improves material property through the mode of precipitation strength and phase transformation strengthening.

Embodiment

Below in conjunction with embodiment technical scheme of the present invention is elaborated.

With microalloying 20MnMo tube sheet is example, and the drawing of this tube sheet is of a size of Ф 3600 * 240mm, requires modifier treatment: R _EL>=370Mpa, R _m=530-700Mpa, A ₅>=18, Akv (0 ℃)>=60J.

This 20MnMo tube sheet chemical ingredients (mass percent) is: C:0.20, Si:0.21, Mn:1.25, P:0.0065, S:0.0047, Ni:0.25, Cr:0.21, Cu:0.004, Mo:0.31, Nb:0.034.

The heat treating method of this 20MnMo tube sheet, its process step is:

(1) workpiece is put into heat treatment furnace, be warming up to 350 ℃ with the speed of 40 ℃/h, insulation 3h, and then be warming up to 650 ℃, insulation 4h with the speed of 50 ℃/h;

After (2) 650 ℃ of insulations finish, be warming up to 910 ℃ of quenching temperatures, insulation 10h with the speed of 60 ℃/h;

(3) workpiece being hung out from stove, put into quenching-in water 90min, from water, take out after surface temperature≤150 ℃, water temperature is controlled at≤and 20 ℃;

(4) cooling finishes back shove charge in time, is warming up to 350 ℃, insulation 4h with the speed of 40 ℃/h;

After (5) 350 ℃ of insulations finish, be warming up to 650 ℃ of tempering temperatures, insulation 15h, the air cooling of coming out of the stove with the speed of 60 ℃/h.

After above process step thermal treatment, tube sheet each item index all meets the requirements, and is as shown in table 1.

Table 1 microalloying 20MnMo tube sheet heat treatment performance

Performance	R _m / Mpa	R _eL / Mpa	A ₅ /%	Z/%	A _KV /J(0℃)
						Technical requirements	530-700	370	18	?	60
Actual performance	615	485	27.5	72.5	120，127，130

Claims

1. 20MnMo steel microalloying, its chemical ingredients are formed and are counted with mass percent: C:0.17～0.23, Si:0.17～0.37, Mn:1.10～1.40, P :≤0.025, S :≤0.015, Ni :≤0.30, Cr :≤0.30, Cu :≤0.25, Mo:0.20～0.35; It is characterized in that: it also is added with microalloy element Nb, and the content of Nb is 0.03～0.06.

2. the described 20MnMo steel of claim 1 heat treating method, its process step is: