CN102319734B

CN102319734B - Method for effectively controlling small pockmark defects on surface of medium plate

Info

Publication number: CN102319734B
Application number: CN 201110151898
Authority: CN
Inventors: 熊科; 郑翠军; 李秋; 尤利国; 沈开照; 李鑫磊; 余永光
Original assignee: Shougang Corp; Qinhuangdao Shouqin Metal Materials Co Ltd
Current assignee: Shougang Group Co Ltd
Priority date: 2011-06-08
Filing date: 2011-06-08
Publication date: 2013-08-14
Anticipated expiration: 2031-06-08
Also published as: CN102319734A

Abstract

The invention discloses a method for effectively controlling small pockmark defects on the surface of a medium plate, belonging to the technical field of steelmaking-steel rolling. The medium plate comprises the following components in percentage by weight: 0.14-0.17 percent of C, 0-0.30 percent of Si, 1.3-1.5 percent of Mn, 0-0.025 percent of P, 0-0.015 percent of S, 0.02-0.06 percent of Alt and 0-0.02 percent of Ti. The method comprises the following steps of: heating a continuously cast bloom to 1,180-1,240 DEG C, wherein the time inside furnace of a heating furnace is 200-300 minutes; discharging, and descaling with high-pressure water of which the pressure is 20MPa; feeding into a rolling machine for rolling; at a first rolling stage, rolling at the temperature of 1,150-1,000 DEG C with the maximum rolling torque of 3,200kNm, waiting after a thickness which is twice that of a finished product is achieved, and starting a second rolling stage after the temperature of a steel plate falls to a finish rolling starting temperature range; and at the second rolling stage, rolling at the temperature of 930-800 DEG C, making the steel plate quickly pass through a finish roller way and an ACC (Accelerated Cooling Control) roller way and enter a thermal straightening machine after rolling to a finished product thickness, and completing thermal straightening at the temperature of 740-760 DEG C. According to the method, the incidence rate of small pockmarks on the surface of the medium plate is controlled below 0.2 percent.

Description

The method of the little pockmark defective in a kind of effective control cut deal surface

Technical field

The invention belongs to steel-making-technical field of steel rolling, particularly the method for the little pockmark defective in a kind of effective control cut deal surface.

Background technology

It often is that a de-scaling is unclean that the cut deal iron scale is pressed into defective, perhaps the thicker secondary oxidation iron sheet of steel plate rolling process generation is pressed in the operation of rolling and causes, through improving the pressure of descaling system, increase the inferior mode in de-scaling road and improve means such as scale removal effect and control.Present the pitting shape but be pressed into for iron scale, the whole irregular distribution of plate face, and the bigger iron scale of distribution area is pressed into defective steel mill and is commonly called as to little pockmark defective, do not see any solution in other steel mills.Changing the steel rolling process parameter, all is favourable with the little pockmark incidence of control surface of steel plate for reduce cut deal band yield rate, reduce economic loss, the raising contract is cashed etc. in conjunction with the thermal straightening system of standard.Ji steel medium plate mill is the sub related measures such as operation of rolling surface of steel plate residual water, raising steel plate finishing temperature, raising roll dressing precision and increase cooling water filtration system of in time removing of reality employing also.The present invention is on existing theoretical direction basis, use the method for contrast statistical analysis, to rolling process might cause that operating process, equipment state and the technological parameter of the little pockmark defective of steel plate have carried out contrast experiment and analysis, summed up the method for the little pockmark defective in a kind of effective control control cut deal surface.

Summary of the invention

The object of the present invention is to provide the method for the little pockmark defective in thick surface in a kind of effective control, effectively reduce little pockmark incidence, improved the surface quality of steel plate greatly.

Technology point of the present invention is:

1, improves ship base Mn content.Steel-making Mn content internal control goal-setting is 1.35%, Mn content control range 1.3-1.5%

Utilize alloying element Mn to improve armor plate strength, replacing the method for utilizing water-cooling process to improve intensity.

The process for making route is: and desulfurizing iron skims → and converter smelting → LF gently handles → sheet billet continuous casting.

Composition internal control scope is as follows:

Element	C％	Si％	Mn％	P％	S％	Alt％	Ti％
								The internal control scope	0.14-0.17	0-0.30	1.3-1.5	0-0.025	0-0.015	0.02-0.06	0-0.02

Surplus is Fe, is percetage by weight

2, carry out controlled rolling technology.After improving steel billet Mn content, utilize water-cooled to improve the means cancellation of steel pole strength, directly adopt the controlled rolling process route, prevent that water-cooled from causing excessive phase transformation and thermal stress and causing the secondary oxidation iron sheet to rise cruelly surface of steel plate, improves plate surface quality.

The rolling mill practice route is: → de-scaling → roughing of steel billet heating → treat temperature → finish rolling → thermal straightening.It is as follows that each technological parameter arranges scope:

Time inside furnace	Tapping temperature	The finish rolling start rolling temperature	Temperature control thickness	Finishing temperature	Straightening temperature
						200～300min	1180～1240℃	910～930℃	〉=2 times of finished products are thick	800～840℃	740～760℃

Key technology scheme of the present invention is: continuous casting billet is heated to 1180～1240 ℃, heating furnace time inside furnace 200～300min, come out of the stove by the high-pressure water descaling of 20MPa, entering milling train is rolled, adopt two stage rolling, the phase I finishes between 1150～1000 ℃, and the maximum rolling force square is 3200kNm, roll behind 2 times of finished product thicknesses and wait for, the beginning second stage was rolling after steel billet temperature was reduced to finish rolling start rolling temperature scope.Second stage is finished between 930～800 ℃, be rolled down to finished product thickness after, steel plate enters thermal straightening machine after passing through finishing mill roller-way, ACC (acceleration cooling device) roller-way rapidly, finishes thermal straightening in 740～760 ℃ of scopes.In this straightening temperature scope, sudden and violent rising can not take place without the steel plate iron scale of water Quench in the surface, effectively prevented the generation of little pockmark.

According to above-mentioned technological process, the little pockmark of surface of steel plate substantially no longer takes place, and this invention can effectively be controlled the little pockmark incidence control in cut deal surface in the production process below 0.2%.

Description of drawings

Fig. 1 technology is carried out the surface of steel plate pattern that there is not little pockmark defective in deck of boat ball blast rear surface, back

The specific embodiment

32 grades of decks of boat producing with certain month in 2010 are example:

The process for making route is: and desulfurizing iron skims → and converter smelting → LF gently handles → sheet billet continuous casting.D32-1 steel billet actual constituent:

Element

C％

Si％

Mn％

P％

S％

Alt％

Its % of tools such as Fe

Content

0.15

0.23

1.35

0.02

0.008

0.O4

98.202

The rolling mill practice route is: → de-scaling → roughing of steel billet heating → treat temperature → finish rolling → thermal straightening.The rolling process actual process parameter:

Time inside furnace	Tapping temperature	The finish rolling start rolling temperature	Finishing temperature	Straightening temperature	The aligning passage
						267min	1221℃	923℃	817℃	753℃	1

Amount to 2823 of rolling 32 grades of motherboards, the motherboard that little pockmark defective takes place amounts to 5, and actual pockmark incidence is 0.18%.As seen, the little pockmark in cut deal surface has obtained good control.

Claims

1. effective method of the little pockmark defective in control cut deal surface, the process for making route is: and desulfurizing iron skims → and converter smelting → LF gently handles → sheet billet continuous casting; The rolling mill practice route is: → de-scaling → roughing of steel billet heating → treat temperature → finish rolling → thermal straightening; It is characterized in that the following technical parameter of control in technology:

The cut deal composition range is: C:0.14-0.17%, Si:0-0.30%, Mn:1.3-1.5%, P:0-0.025%, S:0-0.015%, Alt:0.02-0.06%, Ti; 0-0.02%, surplus is Fe, is percetage by weight;

Continuous casting billet is heated to 1180～1240 ℃, and heating furnace time inside furnace 200～300min comes out of the stove by the high-pressure water descaling of 20MPa, enters milling train and is rolled, and adopts two stage rolling;

Phase I finishes between 1150～1000 ℃, and the maximum rolling force square is 3200kNm, rolls behind 2 times of finished product thicknesses and waits for, the beginning second stage was rolling after steel billet temperature was reduced to finish rolling start rolling temperature scope;

Second stage is finished between 930～800 ℃, be rolled down to finished product thickness after, steel plate through entering thermal straightening machine behind finishing mill roller-way, the ACC roller-way, is finished thermal straightening rapidly in 740～760 ℃ of scopes.