The hot-rolled strip steel is one of the most vital steel varieties and is commonly utilized in numerous areas. With the increasingly severe steel market situation, market competitors are becoming a lot more and fiercer, and client need for items is additionally getting greater and greater. The usual issues of hot-rolled steel can be divided right into surface area flaws, structure characteristic issues, plate defects, geometric size problems, and volume look defects. This post research studies and sums up the common quality problems of hot-rolled steel strip items. Through the study of product flaws, systematic defect identification and cause analysis are performed, quality assurance is executed for equivalent flaws, and necessary preventive measures are developed.
1 Defect identification and cause analysis
Scratch
(1) Defect characteristics
The direct mechanical damage on the surface of the steel strip lower than the rolling surface is called scratch. Scratches at high temperature are frequently gray-black; scrapes at room temperature level are gray-white with metal appeal. Longitudinal direct issues along the rolling direction; with slim, clear, and regular boundaries; typically dispersed along the size instructions of the strip and the entire length instructions. Rolling mills manufacturer ensures quality rolling procedures to reduce such issues and boost the surface finish of steel strips.
(2) Causes and hazards
Cause:
There are sharp edges in the job roller table, side overview plate, guard plate and other tools in the steel rolling procedure or ending up process. The scrapes in the steel rolling process are mainly the scrapes of the F7 export guard plate flower stand of the completing rolling and the scrapes of the layer chilly roller table. The previous is frequently a continuous scratch; the latter is usually an intermittent scratch. Hazard: The iron oxide scale on the scratch is tough to remove by pickling; it may cause bending and splitting.
(3) Prevention and elimination methods
Inspect the job roller table, side overview plate, guard plate and various other equipment touching the strip steel to ensure that the surface is smooth and has no edges or edges.
(4) Inspection and judgment
Consult naked eyes;
Minor scratch problems are enabled, however their depth shall not surpass the range specified by the conventional [1]
2 Iron sheet
(1) Iron sheet (without descaling).
This problem covers a large location, the concentration of iron oxide fragments inside the flaw is not uniform, and the surface area around the issue is in good condition. As a result of the failure of the descaling water supply, high pressure water was not normally infused during the moving procedure to clean the surface area of the rolled piece, resulting in a huge surface area in the range of steel oxides being crushed in.
Reasons: Obstruction of the descaling tap brings about a decline in circulation rate; the angle variance of the descaling tap causes bad scouring impact in a specific area; the descaled water on the head is delayed due to the procedure.
(2) Iron sheet (little boat form).
This flaw is common on the edges, much less between, discontinuous, with a big facet ratio, and looks like a willow leaf. There are dense iron oxide fragments in the problem. The oxide prolongs parallel as the rolling instructions and has different sizes. The surface area around the defect is in good condition, and the circulation placement is irregular.
Based upon experience analysis, because of the huge facet proportion and presuming from the level of oxide fragment fragmentation, the problem took place in the front line; since the issue periphery is in good condition, the possibility of molting of the oxide movie on the surface of the roll is eliminated.
According to the results after pickling in the past, the locations with big oxidized particles and dark colors in the flaws are seriously compressed, and interest is required to be paid.
(3) Iron sheet (fine openings).
This issue is diffusely distributed and covers a huge area, which is a common oxide scale pore;
There are pinholes in the oxide film of the work roll of the finishing rolling F2-4 stand, the surface area of the steel plate is reasonably harsh, and there are a lot of little black spots. From the effect of pickling, individual spots will also have a certain deepness;
After rolling in the next process, the dense pores will certainly reveal small white bars after rolling, indicating that the defects are challenging to eliminate in the cool rolling procedure; the decision of defects needs to not only think about whether they can be cleaned by pickling, however also the degree of density
(4) Iron sheet (oxidized movie).
During the rolling process, the establishment and decomposition of the oxide movie are carried out at all times, so we want to develop a vibrant balance. Of course, this is also perfect.
For the oxide film, both are also thick and too slim is unfavorable. What we require is a fragile and steady framework.
(5) Iron sheet (sticky iron).
Glue iron issues generally show up at the head and tail parts of the strip. The defects are distributed randomly, with differing degrees of density, and might occur on the top and reduced surface areas;
The sticky iron is mainly the iron oxide particles or dust collected in the finishing rolling stand. Due to the poor impact of the completing rolling FS-7 dust elimination facility, it cannot be gotten rid of. It follows the surface area of the steel plate and is rolled into the surface area by the rollers. In severe cases, it can be seen ingrained shiny steel particles;
High-pressure water cleansing during shutdown is a reliable control procedure. This problem is easily confused with the typical oxide range issue in the cold rolling area.
(6) Iron sheet (point-like pressing against individuals).
The problems are meteor-shaped, with a size of about 30mm. They are randomly dispersed over the whole size of the top surface of the strip. The level of defects progressively intensifies from start to finish, and the occurrence regularity of silicon steel is reasonably high.
Considering that silicon steel rolling produces a lot of dirt after completing rolling, the dust removal system does unclean the dirt throughout the functioning process. Part of the dirt complies with the surface of the tools and blends with water vapour to fall on the surface area of the strip and is produced by the rolling of the rear rack.
(7) Iron sheet (red iron sheet).
Defect characteristics: as displayed in the number listed below, it is generally reddish-brown, dot-shaped, strip-shaped, or flake-shaped, dispersed on the entire steel strip, and may occur on the top and lower surface areas. It is common in unique steel grades.
Causes: high silicon material and high slab home heating temperature level.
Corrective procedures: maximize the quality design and lower the silicon material; manage the neutral or micro-oxidizing ambiance in the furnace; decrease the heating system temperature level throughout failing.
3 Edge cracks.
The source of the flaw is related to the finish rolling overview plate and the curling overview plate. There are three factors:
(1) The finishing rolling guide and guard system is in straight contact with the edge of the steel strip, the edge of the steel strip and the guide plate are violently scrubbed, and the edge is damaged;
( 2) In the later period of use of the coiling side overview, the side surface is massaged by the strip steel edge to develop a groove, and the strip steel side will certainly be caught on the side of the groove, thereby damaging;
(3) The side of some strips is not broken, however, not far from the side, there are pits. This flaw will likewise cause side tearing throughout chilly rolling; it is guessed that the root cause of this defect is the steel produced by the rubbing between the edge of the strip and the side overview plate. The fragments, not all diminishing, are squashed by the take-up pinch roller, causing the surface area layer to crack.
4 Alice.
Mechanism: There are physical damages on the surface of the slab, such as mechanical damages, piece fractures, etc. during the warm rolling process, it cannot be rolled and part of the metal is shown up; or the slab is brought on by slag addition.
Macroscopic characteristics: typically distributed in a solitary strip in the length instructions, with a fixed position in the width direction and a skin-like shape.
The occurrence of peeling: When the export descaling of rough rolling cannot be put into use, it can only be descaled by the populace (weird pass). Because of the existence of round splits and uneven extension at the tail of the strip, the peeling off will certainly take place.
Preventive measures: make complete use of red check and other devices to learn and control the influence of ring-shaped head and tail.
5 Waves (medium waves, reciprocal, independent waves).
(1) Defect characteristics.
The wave-shaped flexing phenomenon that turns up and down along the rolling instructions of the steel strip is called wave-shaped. According to different parts of the distribution, it is separated into center waves, rib waves, and side waves.
(2) Causes and hazards.
Reasons: unreasonable roll form, unequal roll wear; bad fit between roll shape and inbound plate form, too much rack reduction after ending up rolling; variance of the steel strip or improper roll gap adjustment; bad roll cooling down all.
(3) The temperature of the steel strip is uneven.
Hazard: Impact the look top quality of the steel plate, and the subsequent procedures cannot be refined and utilized in severe cases.
(4) Prevention and elimination methods.
Practical configuration of roll forms and practical substitute of rolls; reasonable arrangement of rolling strategies to ensure a reasonable change of different specifications of strip steel and a practical circulation of the decrease of each stand; strengthen the assessment of the wedge distinction of the roll gap, and keep the rolled items lined up during the rolling process. Moderately good; enhance roll cooling control; enhance slab heating and cooling control throughout rolling to guarantee consistent temperature level of the steel strip.
6 roll printing.
(1) Defect characteristics.
The convex and concave issues on the surface of the steel strip with periodic circulation and irregular appearance are called roll marks.
Causes and hazards.
(2) Cause.
The roller is cracked, part of the meat has gone down, or there is a contaminant externally. The part of the roller surface is concave or convex. During rolling or finishing, the surface of the journalism steel strip will certainly create convex and concave problems.
Hazard: Convex roll printing may cause folding problems in the succeeding rolling process; scooped roll printing might cause holes in the subsequent rolling procedure.
7 Prevention and elimination methods.
(1) Consistently examine the surface top quality of the roll, and deal with it in time when it is located that the roll has lost meat or contaminant.
(2) When there are uncommon problems such as steel jam, tail-flicking, and rolling throughout the moving procedure, examine the surface quality of the roll in time to stop damage to the roll surface area or attachment of contaminant.
(3) When the roll anilox is found in the assessment, instantly stop the maker to check the surface area high quality of the roll.
8 concluding remarks.
Hot-rolled strip steel items are an important part of the steel sector, used in a vast array of applications. As the steel market becomes a lot more competitive, customers are demanding better products. Usual flaws in hot-rolled steel strips include surface defects, part residential property issues, plate form irregularities, geometric dimension discrepancies, and general coil look imperfections.
Research studies show that over 70% of quality interest in hot-rolled steel coils come from surface area problems like peeling off, roll printing, pitting, and iron oxide. To take on these difficulties, section rolling mill Manufacturers are constantly boosting manufacturing methods to boost surface high quality and item efficiency. Furthermore, utilizing an automatic cooling bed in the rolling process makes certain also cooling, reduces interior stress and anxiety, and assists in accomplishing an extra refined final product. Inevitably, enhancing surface area high quality is key to remaining competitive in the ever-evolving steel market.
Know more about: Leading Rolling Mill Manufacturers in India for Superior Quality
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