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L6 STANDARD VALUES
C
Si
Mn
P
S
Cr
Mo
Ni
V
55NiCrMoV7
40 HRC - 54 HRC
max. 250HB
100MnCrW4
57-62 HRC
max. 229 HB
L6 PHYSICAL PROPERTIES
As an oil hardening chrome nickel tool steel, L6 is often used for applications needing a greater toughness. This steel grade has a better toughness due to the nickel content, at the same time retaining good hardness and wear resistance. With its lower carbon content, it has a slightly better shock resistance in comparison to higher alloyed steels and can be used if wear resistance is secondary to increased toughness.
L6 tool steel is not a corrosion resistant steel. In order to be corrosion resistant steel has to have a minimum chromium content of 10.5% to make it corrosion resistant like stainless steel.
Though the L6 has some corrosion resistance it will corrode when exposed to corrosive environments or moisture. To protect this steel grade, it can be coated or the surface may be additionally treated against corrosion.
L6 TECHNICAL PROPERTIES
The combination of high carbon, toughness, decent wear resistance and that the L6 is easy to sharpen and holds an edge reasonably well make this steel grade a steel that is suitable for knife making.
As L6 is not a stainless steel, knives should be maintained, kept dry and clean to prevent corrosion.
Hot working, hot rolling, forging and extrusion, unlike cold working, does not work harden the L6 tool steel. It can be formed extensively, can reduce porosity and can improve the overall structure.
Care, while hot working, needs to be taken to prevent scaling, potential distortion and excessive grain growth.
Cold working, cold drawing, rolling and cold forging, can induce work hardening, achieve tighter tolerances and a smooth surface finish without further machining.
The increased hardness might in turn aid cracking but can also lead to increased tool wear and any internal stresses introduced in this process might need to be followed up with a stress relieving treatment.
Typically the density of tool steel O1 is 0.282 lb/in3 (7.8g/cm3) at room temperature.
The heat conductivity for tool steel L6 is at 36.0 W/(m*K) (250 BTU/(h-ft*°F)) at room temperature.
| Value | By temperature |
|---|---|
| 236.0 | 68 °F |
| 38.0 | 662°F |
| 35.0 | 1292°F |
| 10-6m/(m • K) | At a temperature of |
|---|---|
| 12.2 | 68 - 212°F |
| 13.0 | 68 - 392°F |
| 13.3 | 68 - 572°F |
| 13.7 | 68 - 752°F |
| 14.2 | 68 - 932°F |
| 14.4 | 68 - 1112°F |
The specific heat capacity of the tool steel L6 at room temperature is 0.46 J/g-°C (0.109 BTU/lb-°F). This value shows how much heat is needed to heat 1lb of material by 1 Fahrenheit.
| Value | At a temperature of |
|---|---|
| 0.3 (Ohm*mm²)/m | 68 °F |
The stress and strain modulus or modulus of elasticity (Young’s modulus) for L6 tool steel is in the range of 27557 - 30457 KSI (190 - 210 GPa).
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L6 PROCEDURE
Heat the material slowly and uniformly to a temperature of 1202 - 1292°F (650 - 700°C) and hold at that temperature for 1 hour per inch (25.4 mm) of thickness, but a minimum of 2 hours. Cool slowly in the furnace by 50°F (10°C) per hour to 1000°F (538°C), then continue cooling in air.
For improved machinability, cool slowly in the furnace to a temperature of 1250°F (677°C) and hold at that temperature for 8 hours, then cool it to room temperature in air.
Preheat the parts uniformly to a temperature of 1250 - 1350°F (677 - 732°C), then continue to an austenitizing temperature of 1500 - 1550 (816 - 843°C) and hold for 10-30 minutes at this temperature.
To protect the material from excessive scale or decarburization either heat the parts in neutral salt, pack it in cast-iron chips or spend coke or heat in a protective atmosphere or vacuum furnace.
- Oil, warmed – parts should be cooled down to 120 - 150°F (49 - 66°C) or until it can be held by hand and then tempered immediately.
- Air – this method of quenching is done for tools with less than 1 inch (25.4 mm) sections. Air quenching is the safer option for intricate sections as air quenching compared to oil quenching will distort parts less.
To avoid cracking, temper L6 immediately after quenching. Hold at the chosen tempering temperature for 1 hour per inch (25.4 mm) of thickness, but for at least 4 hours and cool to room temperature. L6 can be tempered at a temperature range of 450 - 800°F (232 - 427°C) without getting brittle. To minimize internal stresses for parts with a greater cross section than 6 inches (152.4 mm) and/or to improve stability in tools being EDMed after the heat treatment, it is recommended to soak the material for 8 - 10 hours.
Sub-zero treatment can be done as an extension of a quench from the austenitizing treatment and before tempering.
Sub-zero treatment can improve the hardness of the L6, increase its wear resistance and stability, improve toughness, all of which are advantages that can give tools a longer service life. However duration of treatment and cooling rate have to be taken in consideration when deciding if sub-zero treatment is beneficial for this material grade.
To avoid cracking, temper L6 immediately after quenching. Hold at the chosen tempering temperature for 1 hour per inch (25.4 mm) of thickness, but for at least 4 hours and cool to room temperature. L6 can be tempered at a temperature range of 450 - 800°F (232 - 427°C) without getting brittle. To minimize internal stresses for parts with a greater cross section than 6 inches (152.4 mm) and/or to improve stability in tools being EDMed after the heat treatment, it is recommended to soak the material for 8 - 10 hours.
This diagram shows the micro changes at different temperatures which are important during heat treatment. They show the optimum condition for the hardening, annealing and normalizing process.
This diagram shows the structural changes at micro level over time at a constant temperature. It shows at what temperature and after what time different phases, e.g., perlite, martensite or bainite start to build.
L6 SURFACE TREATMENT
Shot peening is an impact treatment where multiple high velocity shots are blasted onto the material surface leaving small indentations which replace the tensile stress on the surface with a compressive layer. It solidifies the material and makes the surface more resistant which can prevent fatigue and can optimize the form and weight of the parts.
Note: Protective gear like goggles, masks, helmets, gloves and protective clothing should be worn and adequate ventilation or dust extraction should be provided.
Appropriate guards to prevent shot spillage should be in place, equipment regularly maintained and shot should be free from contaminants.
L6 PROCESSING
With good electrical conductivity and hardness the L6 can be EDMed, it is often used to achieve tight tolerances or cut intricate details out of hardened material.
L6 is generally weldable. Weld preparation, like a grease and dirt free surface and a rust and paint free surface, is important and the first step when welding. To avoid cracking, excessive hardening and loss of properties the material should be preheated slowly, fillers similar to the base material can be used and the weld process should be chosen in accordance with specific requirements of application needed.
Overheating can lead to grain growth which in turn can weaken the weld and can be avoided with the right combination of current, voltage and travel speed. To relieve stresses from welding a post weld temper can be beneficial.
L6 APPLICATION OPTIONS
L6 tool steel can withstand sudden stresses and impacts, has a good toughness and wear resistance as well as a reasonable hardness. These properties lend themselves to applications like knives and blades, cold work tools, bearings, bushings, woodwork tools, spindles, cams, and springs.
• Slides
• Punch heads
• Extruding stamps
• Press tools
• Hot shear knives
• Extrusion press tools
• Support tools
• Pressure plates
L6 CONCLUSION
L6 tool steel has a unique blend of properties, its high carbon content makes it a good choice for applications needing a high wear resistance. Its exceptional toughness gives the L6 a resistance to impacts and makes it less prone to chipping and breaking.
Possible corrosion should be managed and should be considered when choosing the L6 as well as the correct heat treatment needs to be chosen as many of the properties of the L6 may be affected when not heat treated correctly.
Practically, this means:
- High carbon content
- For applications that require high wear resistance
- Exceptional toughness makes it impact resistant
- Less susceptible to chipping and cracking
- High tempering resistance
- Good through hardenability
- Can be nitrided and eroded
- Working hardness is in the range of 40 - 54 HRC
- High compressive strength
- Water coolable
- High impact strength
L6 ALTERNATIVES
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L6 DATASHEET
Download the technical data sheet in PDF format here.
The data shown here has been compiled with the greatest diligence and is regularly updated with regard to the correctness and completeness of its content. The content is indicative only and should not be taken as a warranty of specific properties of the product described or a warranty of suitability for a particular purpose. All information presented is given in good faith and no liability will be accepted for actions taken by third parties in reliance on this information. ABRAMS Industries reserves the right to change or amend the information given here in full or parts without prior notice.