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Hot roll steel has a oxidised mil scale on the surface of the steel as it forms in the upper heat ranges from mixing with oxygen at a steel mill. Upon slow cooling, scale oxides will form a scale mainly of a type of iron oxide(s) usually of 3 distinct layers. This mil scale has a ability to be somewhat porous and can retain some moisture and is more noble in galvanic charges and at some times will potentially cause the underlying steel to corrode. The scale is not uniform in nature and can be loose in some areas and tighter in other areas and can pose a problem for people that want to paint or coat over it. The scale should be removed prior to any painting or TIG welding. Scale can be removed with various acid pickling type applications, flame treating, and mechanical blast or abrasion methods and then the freshly exposed cleaned surface of the reactive steel surface should be then protected from forming a fast acting blush rust.
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What is process of making hot rolled structural steel?
Plate mill
What is ST 37 hot rolled or cold rolled steel?
(t)rolled
What is mill scale?
Mill scale is formed on the outer surfaces of plates, sheets or profiles when they are being produced by rolling red hot iron or steel billets in rolling or steel mills. Mill scale is composed of iron oxides mostly ferric and is bluish black in color. It is usually less than a millimetre thick and initially adheres to the steel surface and protects it from atmospheric corrosion provided no break occurs in this coating. Because it is electro-chemically cathodic to steel, any break in the mill scale coating will cause accelerated corrosion of steel exposed at the break. Mill scale is thus a boon for a while until its coating breaks due to handling of the steel product or due to any other mechanical cause. It is a nuisance when the steel is to be processed. Any paint applied over it is wasted since it will come off with the scale as moisture laden air get under it. Thus mill scale has to be removed from steel surfaces by flame heating, acid pickling or grit/sand blasting. All tedious operations wasteful of energy. This is why shipbuilders used to leave steel delivered freshly rolled from mills out in the open to allow it to 'weather' till most of the scale fell off due to atmospheric action. Now a days most steels mills can supply their produce with mill scale removed and steel coated with shop primers over which welding can be done safely.
Is hot-rolled steel magnetic?
Yes, hot-rolled steel is magnetic. A few types of steel have limited magnetic properties, but hot rolling is a process by which steel is prepared in a shape for marketing. The hot rolling does not affect the ability of the steel to be attracted to a magnet.
Is there a way to tell the difference between cold steel and hot rolled steel If so how can you tell?
Why does Hot Rolled Steel have a rough, blue-grey finish, while Cold Finished Steel has a smooth grey finish? Hot Rolled Steels are just that - They are heated up red-hot and pushed through rollers that squeeze the metal, literally squishing it into a particular profile, depending on the shape of the rollers. The process takes a long time, and because the steel is so hot for so long in the open air of the steel mill, the surface of the metal has has a long time to oxidize, producing a thick, tough oxide scale with the characteristic blue grey finish of the final product. Cold Finished Steels are just that - the final rolling is done when the steel is cold (room temperature), the whole operation bathed in oil, so the finished product is unoxidized, the grey of the actual steel, and as smooth as the rollers that do the processing. that was taken from metalrefrence.com
What color is mill scale after it is hot rolled?
http://site2.wikianswers.com/templates/images/saveBtn_enable.gif?v=48569 The color of mill scale after it is hot rolled is bluish black.
What is process of making hot rolled structural steel?
Plate mill
What must be done to hot-rolled steel in the mill before it can be cold finished?
Hot rolled steel must be descaled by pickling in acid with a lime water rinsebefore it can be cold finished
What is ST 37 hot rolled or cold rolled steel?
(t)rolled
Difference between Black mild steel and bright mild steel?
from what i can gather, which isn't alot:Cold Rolled Steel Strip is produced, as the term suggests by the further rolling of strip produced by the hot strip mills.Prior to cold rolling, the mill scale has to be removed, normally by the Pickling Process which uses mechanical manipulation (around small diameter rolls) and acid to dissolve the surface scale. The surface is then washed to remove the acid and a light oil added to prevent rusting.Mild steel sheet is manufactured generally in two grades, cold rolled and hot rolled.Hot rolled mild steel sheet is the initial product produced by the steel mill as a downstream process prior to further processing such as cold rolling.Hot rolled mild steel sheet has a mill scale which is usually black in colour. Hence the common name Black Mild Steel Sheet. Black mild steel sheet is commonly used in fabrication shops, it is more economical than cold rolled mild steel sheet.Black mild steel sheet will usually require more preparation work prior to any finishing system being applied.Cold rolling is done to:Reduce the thicknessImprove the surface finishImprove the thickness tolerancesTo offer a range of "tempers"As a preparation for surface coating
What causes mill scale?
Mill scale is a flaky surface that forms on hot-rolled steel and iron products during manufacturing. It results from the oxidation of iron at high temperatures, where the metal reacts with oxygen in the air, leading to the formation of iron oxides. The process is influenced by factors such as the temperature of the metal, the presence of moisture, and the duration of exposure to air. Mill scale can affect the surface quality and adhesion of coatings, making its removal important in subsequent processing.
What is mill scale?
Mill scale is formed on the outer surfaces of plates, sheets or profiles when they are being produced by rolling red hot iron or steel billets in rolling or steel mills. Mill scale is composed of iron oxides mostly ferric and is bluish black in color. It is usually less than a millimetre thick and initially adheres to the steel surface and protects it from atmospheric corrosion provided no break occurs in this coating. Because it is electro-chemically cathodic to steel, any break in the mill scale coating will cause accelerated corrosion of steel exposed at the break. Mill scale is thus a boon for a while until its coating breaks due to handling of the steel product or due to any other mechanical cause. It is a nuisance when the steel is to be processed. Any paint applied over it is wasted since it will come off with the scale as moisture laden air get under it. Thus mill scale has to be removed from steel surfaces by flame heating, acid pickling or grit/sand blasting. All tedious operations wasteful of energy. This is why shipbuilders used to leave steel delivered freshly rolled from mills out in the open to allow it to 'weather' till most of the scale fell off due to atmospheric action. Now a days most steels mills can supply their produce with mill scale removed and steel coated with shop primers over which welding can be done safely.
Is hot-rolled steel magnetic?
Yes, hot-rolled steel is magnetic. A few types of steel have limited magnetic properties, but hot rolling is a process by which steel is prepared in a shape for marketing. The hot rolling does not affect the ability of the steel to be attracted to a magnet.
Is there a way to tell the difference between cold steel and hot rolled steel If so how can you tell?
Why does Hot Rolled Steel have a rough, blue-grey finish, while Cold Finished Steel has a smooth grey finish? Hot Rolled Steels are just that - They are heated up red-hot and pushed through rollers that squeeze the metal, literally squishing it into a particular profile, depending on the shape of the rollers. The process takes a long time, and because the steel is so hot for so long in the open air of the steel mill, the surface of the metal has has a long time to oxidize, producing a thick, tough oxide scale with the characteristic blue grey finish of the final product. Cold Finished Steels are just that - the final rolling is done when the steel is cold (room temperature), the whole operation bathed in oil, so the finished product is unoxidized, the grey of the actual steel, and as smooth as the rollers that do the processing. that was taken from metalrefrence.com
Is cold rolled harder than hot rolled steel?
They are two different things. Zinc plated means it's coated in zinc. Cold rolled means it's "smashed" into shape without added heat. So you could have something that's cold rolled AND zinc plated!
What is the difference between Cold rolled steel and hot rolled steel?
Hot-rolled sheet has low hardness, easy processing, good ductility and cheaper price. Cold rolled sheet has high hardness, relatively difficult to process, but not easy to deformation, higher strength. If you want to buy cold-rolled steel, you can go to the official website of Changzheng, the price of Changzheng's steel is moderate, and it is the choice of the public. Buy cold-rolled steel plate recognized Changzeng.
What is the other name for ASTM-A36 Hot Rolled Steel?
cheap
