CN101381843B - 5Cr5MoWSiV cold roller heat treatment method - Google Patents

Abstract

The invention discloses a 5Cr5MoWSiV cold roll and a heat treatment method thereof. The invention is applicable to cold rolls with the hardness requirement of between 58 and 60 HRC and aims to have good accident resistance, fatigue resistance and wearing resistance as well as high hardness. The 5Cr5MoWSiV cold roll comprises the following compositions in percentage by weight: 0.5 to 0.55 percent of C, 0.8 to 1.2 percent of Si, 0.25 to 0.5 percent of Mn, 4.9 to 5.5 percent of Cr, 1.1 to 1.5 percent of Mo, 0.4 to 0.5 percent of V, 1.1 to 1.5 percent of W, and the balance being Fe. The heat treatment method of the 5Cr5MoWSiV cold roll is to adopt a high-temperature solid solution and high-temperature tempering process for pretreatment first, and then adopt a middle temperature quenching and high-temperature repeated tempering process for heat treatment.

Description

5Cr5MoWSiV cold roll heat treating method

Technical field

The present invention relates to a kind of 5Cr5MoWSiV material cold roll, and the metal heat treating methods of this cold roll.

Background technology

There are problems such as shallow, anti-accident of quench-hardened case and anti-fatigue performance difference in the general Cr2 section bar matter such as traditional 8Cr2MoV, 9Cr2Mo, Gr15 that adopt of the used forged steel roll of domestic cold-rolling mill, and work-ing life is lower.The sendzimir mill that Taiyuan Iron ﹠ Steel Corp introduces uses the 8Cr2MoV intermediate roll at first, because of material and thermal treatment process reason, fatigue resistance is relatively poor, in use often fall slag and roll surface bulk peeling phenomenon, and go up milling train steel rolling amount about 1000 tons at every turn, the roller consumption is the 0.37kg/t steel, has a strong impact on production efficiency, plate surface quality and the production cost of milling train.For addressing this problem, need carry out the thermal treatment process research of roll material design and roll.

Summary of the invention

The present invention seeks in order to overcome above-mentioned the deficiencies in the prior art, a kind of heat treating method that possesses the high 5Cr5MoWSiV cold roll of good anti-accident, fatigue resistance and wear resistance and hardness is provided.

The composition of 5Cr5MoWSiV cold roll of the present invention and weight percent thereof are: C 0.5-0.55%, Si 0.8-1.2%, Mn 0.25-0.5%, Cr 4.9-5.5%, Mo 1.1-1.5%, V 0.4-0.6%, W 1.1-1.5%, all the other compositions are Fe, and the weight percent sum of each composition is 100%.

Add 5%Cr and can make solid solution chromium increase when quenching, increase austenitic stability, thereby improve the hardening capacity of steel, increase the effective depth of hardening of roll.The steel that contains elements such as Cr, Mo, W, V is when the alloy degree increases to certain level and is furnished with suitable carbon content, after quenching in the drawing process, along with the rising of tempering temperature, because alloy carbide (Mo ₂C, W ₂C etc.) separate out transformation with residual austenite, the phenomenon that tempered-hardness raises is called secondary hardening.For making designed steel grade have secondary hardening phenomenon and high temper resistance, 1.1～1.5%Mo and W have been added in the steel respectively, V is the main dispersity vanadium carbide bigger, that hardness is higher (VC) that forms in steel, be the one of the chief elements that improves the steel wear resistance, therefore add 0.5% V at steel grade.

Relative proportioning between carbon and the carbide forming element is the key factor that influences the secondary hardening ability.According to Shi Diwen (G.Steven) balance carbon (Cp) calculating formula, can calculate required carbon content span of control: Cp=0.033W+0.063Mo+0.06Cr+0.2V=0.48～0.594%.Intensity and hardness after the thermal treatment of C content decision steel, but the C too high levels is unfavorable to toughness, therefore under the prerequisite that satisfies roll hardness and intensity, has reduced C content as far as possible, and obdurability is cooperated preferably, determines that C content is 0.50～0.55%.Si can improve the hardening capacity of steel, also can strengthen matrix, improves the temper resistance of steel, and Si content is controlled at 0.8～1.20%.

The heat treating method of 5Cr5MoWSiV cold roll of the present invention is:

(1) adopt high temperature solid solution to increase temperature tempering process and carry out pre-treatment: earlier with roll after 550 ℃ of air furnaces, 850 ℃ of two temperature section preheatings of salt stove, be heated to 1060～1140 ℃ with the salt stove, the insulation solid solution, roll is cooled to about 100 ℃ again in quenching oil, in air furnace, be heated to 720～780 ℃ then and carry out high tempering, stove is as cold as 500 ℃ after the tempering, and air cooling is to room temperature again.

Pretreated purpose is to eliminate ingot casting and caused inhomogeneity of structure when forging, and improves the form and the distribution characteristics thereof of carbide, carries out necessary original structure for final thermal treatment and prepares.Its principle is a solid solution carbide to greatest extent under the condition of high temperature, and the carbide particle dissolving is diminished, and small-particle all dissolves, the whole melt into fillets of all sharp wedge angles, and not molten carbide quantity tails off, and granularity reaches unanimity.Fast cold inhibition proeutectoid carbide is chain and separates out in crystal boundary; In the high tempering process, carbide is evenly separated out.

(2) adopt in temperature quench and increase temperature repeatedly tempering process and heat-treat: earlier with roll after 550 ℃ of air furnaces, 850 ℃ of two temperature section preheatings of salt stove, be heated to 1020～1080 ℃ of insulations with the salt stove, roll is cooled to about 100 ℃ then in quenching oil, change tempering in 530～580 ℃ of nitrate furnaces then over to, tempering 3-4 time, air cooling to 50 ℃ after each tempering changes next tempering; Adopt oil cooling after the last tempering.

Thermal treatment process can reach under the prerequisite of 58～60HRC at roll hardness, effectively eliminates the roll internal stress, and the Cr, the Mo that distribute of diffusion-precipitation, V carbide particle are to strengthen the wear resistance of roll.Structure stability height behind the high tempering, residual austenite content is controlled at below 3%, has avoided changing the roll cracking phenomena that causes because of residual austenite in the roll use.

The present invention is applicable to that it is cold roll manufacturing and the heat treating method thereof of 58～60HRC that hardness requires.Guaranteeing can at utmost to improve the roll structure stability under the prerequisite that roll hardness requires, eliminate structural stress, the thermal stresses of roll, make roll possess good anti-accident, fatigue resistance and wear resistance, thereby satisfy the service requirements of milling train.

5Cr5MoWSiV cold roll of the present invention all uses at 8 ZR22-52B types of the stainless cold rolling mill of Taiyuan Iron and Steel Co. milling train, intermediate roll roll breakage, cracking, surperficial bulk peeling phenomenon have in use been stopped fully, and roll is experiencing roll banding, broken belt, is taking out mishaies such as band, behind regrinding, still can continue normal use, shown good anti-accident, result of use reaches import roll level.The roller consumption is reduced to the 0.081Kg/ ton by original 0.37Kg/ ton steel, can save the roll procurement payment every year more than 1,000 ten thousand yuan.

Embodiment

By 90 on designed steel grade chemical ingredients production roll of the present invention, chemical ingredients and thermal treatment process see Table 1-3.

Table 1 roll chemical component table (%):

C	Si	Mn	Cr	Mo	V	W	S	P	Nb
										0.53	0.95	0.40	5.10	1.15	0.50	1.21	0.001	0.012	0.01

[0017]Table 2 roll pre-treatment information slip

Table 3 roll thermal treatment information slip

Table 4 roll quality and service condition table

Title	Hardness (HRC)	Uniformity of hardness (Hs)	Depth of hardening zone (mm)	Use roller consumption (kg/t steel)
					Standard-required	58～60	≤3	≥15	/
Actual effect	58～59.5	≤2.6	Through hardening	0.081

Roller consumption=roll consumption amount (kg)/steel rolling amount (t).

Claims (1)

1. the heat treating method of a 5Cr5MoWSiV cold roll is characterized in that:

(1) adopt high temperature solid solution to increase temperature tempering process and carry out pre-treatment: earlier with roll after 550 ℃ of air furnaces, 850 ℃ of two temperature section preheatings of salt stove, be heated to 1060～1140 ℃ with the salt stove, the insulation solid solution, again roll is cooled to 100 ℃ in quenching oil, in air furnace, be heated to 720～780 ℃ then and carry out high tempering, stove is as cold as 500 ℃ after the tempering, and air cooling is to room temperature again;

(2) adopt in temperature quench and increase temperature repeatedly tempering process and heat-treat: earlier with roll after 550 ℃ of air furnaces, 850 ℃ of two temperature section preheatings of salt stove, be heated to 1020～1080 ℃ of insulations with the salt stove, then roll is cooled to 100 ℃ in quenching oil, change tempering in 530～580 ℃ of nitrate furnaces then over to, tempering 3-4 time, air cooling to 50 ℃ after each tempering changes next tempering; Adopt oil cooling after the last tempering;

Above-mentioned roll is the 5Cr5MoWSiV cold roll, and roll component and weight percent thereof are:

C?0.5-0.55％，Si?0.8-1.2％，Mn?0.25-0.5％，Cr?4.9-5.5％，

Mo 1.1-1.5%, V 0.4-0.6%, W 1.1-1.5%, all the other compositions are Fe;

The weight percent sum of each composition is 100%.