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Stainless Steel

Stainless Steel specifications held in the austenitic, martensitic and precipitation hardening varieties. Stocks are held in British Standard and International standards. Below is listed our most commonly supplied grades; please contact our sales office. Also stock is 301 stainless spring temper rolled strip.

Hi-Steel HSLA-80

Hi - Speed, high Speed Steel Tool Steel (made) : highly processed into the Tool Steel, carbon content high, while containing cr quantity is low (about 4%), reason burnish of Steel surface gloss darker, after heat can reach by HRc62 high hardness, resistance to rust performance not on a roll.

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Heat resistant steel. AS Orlov Izobret. Mashinostr. 3, 48-49, 7/2000. The purpose of this work was to increase plasticity of heat resistant steel after aging at the 500-1300 deg C temperature and to improve its operational reliability.

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Comprehensive stocks held of tool steel, including hot work, cold work and plastic mould tool steel specifications. Below we detail our most common grades. Other British Standard and international special steels and tool steels are also available, please contact our sales office.

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Carbon spring steel is held in a wide range of sizes. Detailed below are our most common specifications. Carbon steel strip and spring steel sheet is available most commonly in the hardened and tempered condition, though certain sizes are available in the annealed condition. Round and flat bar is stocked in the as rolled condition. Most spring steel specifications are held to British Standard steel specifications including BS1449 & BS970.

Alloy and Carbon Steel

Alloy steel is steel alloyed with a variety of elements in total amounts of between 1.0% and 50% by weight to improve its mechanical properties. Alloy steels are broken down into two groups: low alloy steels and high alloy steels. The difference between the two is somewhat arbitrary: Smith and Hashemi define the difference at 4.0%, while Degarmo, et al., define it at 8.0 %.[1][2] Most commonly, the phrase "alloy steel" refers to "low alloy" steels.

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Home » Stainless Steel-Maching

Upload time：2011.03.07 Sources:Special Steel - Supplies Special Steel, Supplies Tool Steel, Stainless steel, Steel Stockists Suppliers Special Steel Stockists Browse:

Stainless steel - Maching

FABRICATION - MACHINING

Austenitic Stainless steels are generally regarded as being difficult to machine, and this has led to the development of the free-machining Grade 303. There are also free-machining versions of the standard ferritic (Grade 430) and martensitic (Grade 410) grades - Grades 430F and 416 - these grades have improved machinability because of the inclusions of Manganese Sulphide (formed from the Sulphur added to the steel) which act as chip breakers.
The free-machining grades have significantly lower corrosion resistances than their non-free machining equivalents because of the presence of these non-metallic inclusions；these grades are particularly prone to pitting corrosion attack and must not be used in aggressive environments such as for marine exposure. The free-machining grades containing high sulphur levels also have reduced ductility, so cannot be bent around a tight radius nor cold forged. Because of the sulphur additions these grades are very difficult to weld, so again would not be chosen for welded fabrication.

Machinability is the term used to denote the machining performance of a material by a cutting tool. Due to their difference in properties when compared with carbon steels, slightly different techniques are required when machining stainless steels. The relative machinability of Columbus Stainless steels in the annealed condition compared with carbon steels (100) is: ferritic grades - 70 and austenitic grades - 50. This difference is due to Stainless steels being tough rather than hard with a tendency to seize and gall.

Columbus ferritic grades are usually supplied in the annealed condition and due to their toughness their machining characteristics are more similar to low alloy carbon steels rather than mild steels. Due to the difference in conductivity, care must be taken to ensure adequate removal heat from the workpiece and the tool. Overheating can result in blunting of the tool and localized burning of the workpiece surface.

Columbus austenitic grades are also normally supplied in the annealed condition and of more importance than their increased hardness over carbon steel, is the large difference between proof and tensile strengths. This increased ductility tends to produce stringy chips during machining and due to rapid work hardening can lead to problems. Heavier feeds and slower speeds are employed to reduce tool build up and minimise work hardening. Where possible it is recommended that cutting tools with chip breakers or curlers be used, especially for the high alloy grades such as types 309 and 310 where exceptionally tough and stringy chips are produced. As conductivity is even lower than for ferritic grades, heat removal is of greater importance.

When machining Stainless steels note must be taken of the following:

1. The machining equipment must be sturdy and rigid with up to 50% more power than equipment used for mild steels.

2. Machine tools and the workpiece must be firmly held to prevent vibration and chatter.

3. Cutting tools, either high speed steel or carbide must be kept sharp at all times, sharpening at regular intervals being preferable to sharpening when blunt.

4. Good lubricants should be used, especially for heavy cuts at relatively slow speeds. Thinning with paraffin is recommended for higher speed finishing cuts to keep the workpiece and tools as cool as possible.

5. The depth of cut must be such as to prevent the tool from riding in the workpiece. This is particularly important with austenitic grades to avoid work hardening and burnishing.

6. The largest possible tool must be used in order to dissipate heat.

7. Interrupted cutting must be avoided where possible as a greater degree of work hardening occurs as the tool enters the workpiece. The prime rule should be "get in and get out" with all tooling.

TOOL GEOMETRY

Tool geometries are similar for both austenitic and ferritic grades and the summarized below for HSS:

DRILLING:
Cutting edge angel ± 135, point angel ± 138, lip relief angle varies from 16°for 3mm diameter to 8° for 25mm diameter.

REAMING:
Rake angle 3°to 8°, margin width 0.125 to 0.35mm, relief angles primary 4d°to 6, secondary double primary chamfer angle 30°to 35°, chamfer relief angle 4° to 5°, helix angle ± 7°, lead angle ± 2.

TAPPING:
Straight fluted for > 12mm holes, spiral fluted for smaller holes hook/rake angle 15°to 20°, back relief angle 10°, chamfer angle/length plug taps 9° to 10°(3.5 to 4.5 threads) taper taps 4° to 5°, (8 to 10 threads).

DIE THREADING:
Rake angle 20°to 30°, throat angle 20°to 25°, face angle 1.5°.

SINGLE POINT TURNING:
Back rake angle ferritics 5°, austenitic 0°, side rake angle ferritics 8°, austenitics 10° to 15°, end relief, side relief and end cutting edge angles all 5°.

FORM TURNING:
Back rake angle 4° to 10°, end relief angles 7° to 10°, side relief and clearance angles 1° to 5°.

CUT OFF TOOLS:
Back rake angle 6° to 10°, end relief angle 7° to 10°, side relief angle 2° to 3°, end cutting edge angle 10° to 15° for small diameters and shallow cuts, decreasing to 5° for larger diameters.

CUTTING FLUIDS
Sulphurised, chlorinated or sulphur-chlorinated mineral oils and emulsifiable oils are used. In cases of high pressure the latter must contain sulphonated or chlorinated additions.

CLEANING
After machining it is essential to remove the cutting fluid and degrease the workpiece. This is usually done with conventional degreasing agents or solvents. In situations where the workpiece has been subjected to excessive heating or where maximum corrosion resistance is required, it may be necessary to passivate and/or pickle and passivate. If this is required refer to the section on post Fabrication Treatment.

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