1045 C45 S45C 1.1191 CK45 Round Steel Bar
Medium carbon engineering bar in 0-500mm diameter hot rolled black or cold drawn bright
Specifications
Hot Rolled vs Cold Drawn Carbon Steel Round Bars
Hot rolled round bar is rolled above about 1000 degrees Celsius, carries mill scale and holds dimensional tolerances of roughly plus or minus 0.5mm to 1.5mm.
Hot rolled round bar is rolled above about 1000 degrees Celsius, carries mill scale and holds dimensional tolerances of roughly plus or minus 0.5mm to 1.5mm. Cold drawn round bar is pulled through precision dies at room temperature, comes out bright and scale free, holds plus or minus 0.1mm or even plus or minus 0.05mm and gains 20 to 50 percent in tensile strength and hardness from work hardening, at a price 10 to 30 percent above hot rolled. Choose hot rolled for large sizes, heavy welding and bending and a tight budget; choose cold drawn for small precision parts that go straight into an assembly.
Processing Route and Surface Condition
Hot rolled round steel is formed by rolling at high temperature, usually above 1000 degrees Celsius. Oxidation at that temperature leaves a rough dark surface covered with a layer of scale, which is why the trade calls it black steel. Surface finish is poor and the bar is normally machined, pickled or cleaned before any cosmetic use.
Cold drawn round steel starts as hot rolled bar and is pulled through precision dies at room temperature. The finished surface is smooth, clean and free of scale, which is why it is known as bright steel. The bar arrives with a neat appearance that does not need a separate cleaning operation.
- Hot rolled is rolled above about 1000 degrees Celsius and carries mill scale
- Cold drawn is drawn through dies at room temperature and is scale free
- Black steel and bright steel are the common shop names for the two conditions
- Cold drawn bar needs no descaling before assembly or plating
Dimensional Accuracy and Straightness
Hot rolled bar is affected by thermal expansion and contraction and by roll wear, so the diameter tolerance is wide, typically between plus or minus 0.5mm and plus or minus 1.5mm. Straightness is average, which makes the bar difficult to use directly in a precision assembly.
Cold drawn bar is forced to size through a die, so tolerance can be held within plus or minus 0.1mm and in tighter work within plus or minus 0.05mm. Roundness and straightness are both good, and the bar can be fitted straight into a mating part without a turning operation.
- Hot rolled tolerance typically plus or minus 0.5mm to plus or minus 1.5mm
- Cold drawn tolerance within plus or minus 0.1mm and as tight as plus or minus 0.05mm
- Cold drawn bar has better roundness and straightness for direct mating
- Hot rolled bar usually needs machining before it meets a precision fit
Mechanical Properties After Each Route
Hot rolling refines the internal grains and leaves a uniform structure. The result is good plasticity and toughness, so the bar takes impact loads well, but its strength and hardness are relatively low.
Cold drawing introduces work hardening. Tensile strength and hardness rise significantly, by 20 to 50 percent compared with hot rolled bar, and that gain is paid for with reduced plasticity and toughness. A part that has to absorb impact is usually better served by the hot rolled condition.
- Hot rolled bar has refined grains uniform structure good plasticity and toughness
- Hot rolled strength and hardness are relatively low
- Cold drawn tensile strength and hardness are 20 to 50 percent higher than hot rolled
- Cold drawing reduces plasticity and toughness
Machinability Welding and Cost
Hot rolled bar has good plasticity and low hardness, so it suits welding, cutting, bending and stamping. The production route is simple and the yield is high, which keeps the cost down and makes it the cost effective option for most structural work.
Cold drawn bar is harder and less plastic. It is prone to cracking if it is welded or bent directly and usually has to be annealed first to soften it. Pickling, cold drawing and the other added steps typically make it 10 to 30 percent more expensive than hot rolled round steel.
- Hot rolled bar welds cuts bends and stamps without pre treatment
- Cold drawn bar can crack during direct welding or bending
- Annealing is normally required before heavy forming of cold drawn bar
- Cold drawn bar costs 10 to 30 percent more than hot rolled round steel
- Hot rolled has a simpler process and a higher yield
Selection Rule of Thumb
Choose hot rolled round steel when the project involves large structural components, extensive welding or bending, low requirements for surface finish and dimensional accuracy, and a constrained budget. It is commonly used in building steel structures, machine bases and support frames.
Choose cold drawn round steel when the project involves small precision parts that are assembled directly, when surface finish matters and when higher strength is wanted. It is widely used in precision mechanical drive shafts, automotive chassis components, bolts and pins, and mold parts.
- Large size heavy welding budget limited choose hot rolled
- Small size high precision strength required choose cold drawn
- Hot rolled applications building steel structures mechanical bases support frames
- Cold drawn applications drive shafts chassis components bolts pins mold parts
- Bearings and shafts that go straight into an assembly favor cold drawn
Grades and Sizes Available From Stock
Tianyu Metal supplies 1045 C45 S45C 1.1191 CK45 round steel bar in diameters from 0 to 500mm and in 6m lengths or customized as required. It is a medium carbon general engineering structural steel with good machinability and high tensile properties, normally delivered at 18 to 25HRc, and it is available with a hot rolled black surface or a cold drawn bright surface.
For nitriding duty the same stock covers 41CrAlMo7 1.8509 round steel bar in diameters from 5mm to 500mm, hot rolled, used for gears, valve components and tools for hot forming.
- 1045 C45 S45C 1.1191 CK45 round bar diameter 0 to 500mm length 6m or customized
- Delivery hardness of 1045 C45 round bar 18 to 25HRc
- Hot rolled black surface or cold drawn bright surface on the same grade
- 41CrAlMo7 1.8509 round bar diameter 5mm to 500mm hot rolled
- Bar supplied with mill test certificate and processing by bending welding decoiling cutting and punching
What to Confirm Before You Order
The specification that matters is the pair of numbers that follow the grade: the diameter tolerance you can live with and the strength you need. Once those are fixed, the choice between the two conditions makes itself.
Where a part is welded at one end and machined at the other, it is often cheaper to buy hot rolled bar and machine the critical feature than to buy cold drawn bar and anneal it before welding.
- State the diameter tolerance you require not only the nominal diameter
- Say whether the bar will be welded or bent after delivery
- Say whether the surface will be visible plated or painted
- Ask for the mill test certificate with the order so the grade is documented
Referenced
Products In This Guide
41CrAlMo7 1.8509 Round Steel Bar
Nitrogen hardening chromium aluminium molybdenum bar from 5mm to 500mm diameter
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1045 C45 S45C 1.1191 CK45 Steel Plate
Medium carbon engineering plate that machines soft and hardens on the working face
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AISI 4130 4140 Steel Plate
Heat treatable chrome moly plate cut to blank size for stressed machined parts
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Questions On This Topic
What diameter tolerance can I expect on hot rolled round bar?
Typically between plus or minus 0.5mm and plus or minus 1.5mm, because thermal expansion and contraction and roll wear both affect the finished size. Straightness is average, so precision assemblies normally need a machining operation.
How much stronger is cold drawn round bar?
The drawing process work hardens the bar and raises tensile strength and hardness by 20 to 50 percent compared with hot rolled. Plasticity and toughness fall in the same step, so the gain is not free.
Can cold drawn round bar be welded directly?
It is prone to cracking during direct welding or bending because of its high hardness and low plasticity. Annealing to soften the bar first is the usual route. If the part is heavily welded, hot rolled bar is the simpler choice.
What is the price difference between the two?
Cold drawn round steel is typically 10 to 30 percent more expensive than hot rolled, because pickling, cold drawing and the other added operations sit on top of the hot rolling cost.
Which condition do you supply 1045 C45 round bar in?
Both. 1045 C45 S45C 1.1191 CK45 is normally provided with a hot rolled black surface or a cold drawn bright surface, in diameters from 0 to 500mm and 6m lengths or customized, at a delivery hardness of 18 to 25HRc.
Do you cut bar to length before shipment?
Yes. Processing covers bending, welding, decoiling, cutting and punching, so bar can be supplied cut to your list rather than in standard lengths. Send the cutting list when you Request A Quote.
Still Deciding After Reading This
If you are still asking "What diameter tolerance can I expect on hot rolled round bar?" send us the sizes and the duty and we will answer it against your actual order.