CN103506382A - Production method for improving surface quality of thick-standard ship plate - Google Patents

Abstract

The invention discloses a production method for improving the surface quality of a thick-standard ship plate, and belongs to the technical field of structural steel for ships and ocean projects. The production method includes the technological processes of plate blank heating, coarse phosphorous removal, rolling through a 4300 rolling mill (finished phosphorous removal), ACC rapid cooling, sampling, detecting, storage and delivery. Proper technical parameters are controlled in the technology, the thickness standard is 18-50mm, and the production method is suitable for the ordinary-strength ship plate A/B/D, the high-strength ship plate A32/D32/E32 and the high-strength ship plate A36/D36/E36. The surface of the steel plate is black blue, a surface oxide scale is compact and firm, quality defects such as the coarse surface, the press-in oxide scale and pockmarks do not exist under irradiation of hard light, when mass production is carried out, the number of to-be-coped products and the number of products with the quality defects are greatly reduced compared with the number of to-be-coped products and the number of products with the quality defects of a conventional method, and the quality of steel plate entities obtains general consent of key users at home and abroad.

Description

A kind of production method of improving thick specification deck of boat surface quality

Technical field

The invention belongs to boats and ships and ocean engineering structural steel technical field, particularly a kind of production method of improving thick steel plates surface quality.

Background technology

Affected by global economic crisis; shipyard generally runs into shipowner and requires to defer delivery, find an excuse the variety of issues such as the abandoned ship; the various harshnesses that shipyard is reply shipowner require, deck of boat surface quality have been proposed to strict requirement; surface quality inspection becomes strong illumination inspection from visual inspection before; the quality objection that the surface quality band of each steel mill's deck of boat is produced significantly to be increased, cause thus thereupon also produces in batches; not only caused huge economic loss, and the product quality prestige of Gei Ge steel mill has been brought adverse effect.

Rough surface, iron scale are pressed in more the having of surface quality problems that shipyard proposes, pockmark etc., these defects visually observe less than, must be visible by strong illumination, surface of steel plate is roughness, can be more obvious after spraying paint.

The generation of above-mentioned defect, main relevant with iron scale: in heating process, the oxygen generation oxidation reaction in steel billet and heating furnace, the nascent iron scale of generation; In the operation of rolling, rolling temperature is higher, and billet surface continues to react and to produce secondary iron scale with airborne oxygen, and these iron sheets must be removed in time and remove thoroughly, otherwise will be pressed into surface of steel plate during rolling, produces above-mentioned defect.Reduce iron scale growing amount, strengthen the effect of dephosphorization, be to promote the key factor of rolling rear plate surface quality, method provided by the invention, effective head it off, product quality meets customer requirement.

Summary of the invention

The object of the present invention is to provide a kind of production method of improving thick specification deck of boat surface quality, thickness specification is 18-50mm, be applicable to common intensity deck of boat A/B/D, high strength steel plate for ship building A32/D32/E32, A36/D36/E36, reduced rough surface, iron scale and the blemish band product amount such as be pressed into, reduced the generation of quality objection, meet shipyard and shipowner's requirement, improved steel mill's prestige.

For defects such as reduction rough surface, iron scale are pressed into, the present invention be take existing ship slab as basis, take continuous casting billet as basis, by controlling furnace atmosphere, de-scaling pressure, rolling technological parameter and the relevant water-cooled systems such as the de-scaling mode of the adjustment operation of rolling, control temperature, finishing temperature, successfully solved the surface quality problems such as rough surface.

The present invention provides a kind of new milling method to the thick deck of boat without defects such as rough surface of 18-50mm, and the technological process of this method is: heating of plate blank → thick dephosphorization → 4300 mill millings (smart dephosphorization) → ACC cooling → sampling, check → warehouse-in, shipping fast.The concrete technical parameter of controlling is:

(1) continuous casting billet is sent into heating furnace, heating-up temperature is 1150～1220 ℃, heat time 150-360min, and residual Control for Oxygen Content is at 2-6 volume %;

(2) the steel billet laggard horizontal high voltage water dephosphorizing machine of coming out of the stove carries out thick dephosphorization, and dephosphorization pressure is controlled at 19-23MPa.

(3) after the thick dephosphorization of steel billet, enter 4300mm mill milling, adopt two stage rolling during rolling, doubly, rough rolling step and finish rolling stage parameter are as follows for the 2.0-2.5 that holding gauge is finished product thickness:

Rough rolling step: start rolling temperature: 1000-1150 ℃, mill speed: 1.0-3.0m/s, roll torque: 2000-3200kNm; When rolling the first passage and the 3rd passage, utilize the water under high pressure of milling train front and back to carry out smart dephosphorization;

Finish rolling stage: start rolling temperature: 820-860 ℃, finishing temperature: 750-800 ℃, mill speed: 2.0-5.0m/s; Must way during rolling odd-numbered pass utilize the water under high pressure before and after milling train to carry out smart dephosphorization, if the first passage is empty, cross open rolling again after machine, emptyly cross not dephosphorization of passage.

(4) rolling rear steel plate, to enter ACC laminar flow cooling, opens all side-blowns when cooling, begins to cool down temperature and be controlled at 740-770 ℃, and final cooling temperature is controlled at 560-680 ℃, and cooldown rate is controlled at 5-10 ℃/s.

(5) steel plate cooling after: 18-40mm steel plate air cooling; The slow cooling of 40-50mm steel plate stacking, heap cool time >=12 hour.

Production method provided by the invention, thickness specification is 18-50mm, be applicable to common intensity deck of boat A/B/D, high strength steel plate for ship building A32/D32/E32, A36/D36/E36, it is black-and-blue that surface of steel plate is, scale on surface densification is firm, under strong illumination, there is no the mass defects such as rough surface, iron scale are pressed into, pockmark, during batch production, reconditioning quality to be entered and band product amount significantly reduce compared with conventional method, and steel plate quality in kind has obtained emphasis user's the consistent approvals both at home and abroad such as Hyundai.

Accompanying drawing explanation

Fig. 1 is plate surface quality (macro surface).

Fig. 2 is plate surface quality (surface under strong illumination).

The specific embodiment

According to production method provided by the invention, take existing ship slab as basis, take continuous casting billet as basis, difference rolling 18-50mm steel plate on 4300mm wide and heavy plate mill, its chemical composition is in Table 1, and rolling parameter is in Table 2, performance situation is in Table 3, and surface quality is shown in Fig. 1, Fig. 2.

The chemical composition of table 1 trial-production steel plate (weight, %)

Heating, rolling and the water-cooling process parameter of table 2 trial-production steel plate

The mechanical property of table 3 trial-production steel plate

Claims (2)

1. improve a production method for thick steel plates surface quality, technological process is: heating of plate blank → thick dephosphorization → 4300 mill milling; → ACC is cooling → sampling, check → warehouse-in, shipping fast; It is characterized in that, the technical parameter of controlling in technique is:

(1) continuous casting billet is sent into heating furnace, heating-up temperature is 1150～1220 ℃, heat time 150-360min, and residual Control for Oxygen Content is at 2-6 volume %;

(2) the steel billet laggard horizontal high voltage water dephosphorizing machine of coming out of the stove carries out thick dephosphorization, and dephosphorization pressure is controlled at 19-23MPa;

(3) after the thick dephosphorization of steel billet, enter 4300mm mill milling, adopt two stage rolling during rolling, doubly, rough rolling step and finish rolling stage parameter are as follows for the 2.0-2.5 that holding gauge is finished product thickness:

Rough rolling step: start rolling temperature: 1000-1150 ℃, mill speed: 1.0-3.0m/s, roll torque: 2000-3200kNm; When rolling the first passage and the 3rd passage, utilize the water under high pressure of milling train front and back to carry out smart dephosphorization;

Finish rolling stage: start rolling temperature: 820-860 ℃, finishing temperature: 750-800 ℃, mill speed: 2.0-5.0m/s; Must way during rolling odd-numbered pass utilize the water under high pressure before and after milling train to carry out smart dephosphorization, if the first passage is empty, cross open rolling again after machine, emptyly cross not dephosphorization of passage;

(4) rolling rear steel plate, to enter ACC laminar flow cooling, opens all side-blowns when cooling, begins to cool down temperature and be controlled at 740-770 ℃, and final cooling temperature is controlled at 560-680 ℃, and cooldown rate is controlled at 5-10 ℃/s;

(5) steel plate cooling after: 18-40mm steel plate air cooling; The slow cooling of 40-50mm steel plate stacking, heap cool time >=12 hour.

2. method according to claim 1, is characterized in that, the thickness specification of described thick steel plates is 18-50mm.

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