Elmax Stainless Steel | Uddeholm Elmax SuperClean

Elmax Stainless Steel | Uddeholm Elmax SuperClean is a high-quality stainless steel produced by the Uddeholm Group using powder metallurgy. It holds an edge well, is difficult to sharpen, and is quite strong. It is a very fine-grained steel, so it allows for very aggressive sharpening. It allows for hardening the material to 62 HRC while maintaining decent strength. Due to its high chromium content, it has high corrosion resistance.

ELMAX steel (stainless steel ELMAX) is a high-tech steel that is classified as a third-generation steel. It is one of the newest powder materials, and for quite a long time remains almost the optimal choice in terms of price / quality in the production of knives.

Elmax (Elmah steel) is stronger than S30V and has better edge holding than S35VN. It is produced using third generation stainless steel powder metallurgy. The grain size of the metal powder is very small.

Characteristics

Uddeholm Elmax SuperClean is a chromium-vanadium-molybdenum alloy steel with the following characteristics:

• High wear resistance
• High compressive strength
• Corrosion resistance
• Very good dimensional stability

High wear resistance is usually associated with low corrosion resistance and vice versa. However, Uddeholm Elmax SuperClean has achieved this unique combination of properties through powder metallurgy-based manufacturing. Uddeholm Elmax SuperClean offers the ability to produce durable, maintenance-free moulds for better overall moulding economy.

Chemical composition

Heat treatment

Soft annealing

Protect the steel and heat to 980 °C, holding time 2 hours. Then cool in the furnace at a rate of 20 °C/h to 850 °C. Holding time 10 hours. Slowly cool to 750 °C. Then freely in air.

Stress relieving

After rough machining, heat the workpiece to 650 °C, hold for 2 hours. Cool slowly to 500 °C, then freely in air.

Hardening

• Preheating temperature: 600 - 850 °C.
• Austenitization temperature: 1050 - 1100 °C, typically 1080 °C.

*Holding time = time at austenitizing temperature after the tool is fully heated through.

Protect the part against decarburization and oxidation during hardening.

Tempering

Choose the tempering temperature according to the hardness required by reference to the tempering graph. Temper twice with intermediate cooling to room temperature, the preferred tempering temperature is 250 °C or higher. In exceptional cases, a minimum tempering temperature of 180 °C can be used for small simple inserts and parts where toughness is of less importance. Holding time at tempering temperature minimum 2 hours.

Above tempering curves are obtained after heat treatment of samples with a size of 15x15x40 mm, cooling in forced air. Lower hardness can be expected after heat treatment of tools and dies due to factors like actual tool size and heat treatment parameters.

Phase diagram of continuous cooling ( CCT )

Austenitizing temperature 1050 °C (1920 °F). Holding time 30 minutes.

Quenching environment

• Forced air / gas.
• Fluidized bed or salt bath 200 - 550 °C (390 - 1020 °F), then cool in air

Note. Note: In order to obtain optimum properties, the cooling rate should be as fast as is concomitant with acceptable distortion. Temper immediately the tool reaches 50 - 70 °C (120 - 160 °F).

Changes in size during heat treatment

Illustration of the effect from austenitizing temperature and subzero cooling. The test has been performed on sample size: 40x40x40 mm (1,6x1,6x1,6 in.).

Processing at sub-zero temperatures

Sub-zero treatment falls into the broad categories of cold treatment and cryogenic treatment.

Parts requiring high dimensional stability should be sub-zero treated, otherwise volume changes may arise.

Uddeholm Elmax SuperClean is commonly sub-zero treated between -150 °C (-240 °F) and -196 °C (320 °F) (cryo treatment), although occasionally -40 °C (-40 °F) to -80 °C (-112 °F) (cold treatment) are used due to constraints of the sub-zero medium and equipment available.

The first sub-zero treatment should be carried out directly after hardening and before any tempering without delay. When maximum dimensional stability is required further sub-zero treatments may be necessary between the tempering operations. In this case it is important to always end with a tempering, as the last operation.

1 - 3 hours treatment results in an increased hardness of about 1 - 3 HRC.

Note. Avoid intricate shapes as there is a risk of cracking.

Mechanical processing: recommendations

The machining recommendations below are to be considered as guiding values which must be adapted to existing local conditions.

Turning

* Use a wear resistant Al₂O₃ coated carbide grade

Drilling

High speed ​​steel twist drills

* For coated HSS drills v_c = 18 - 20 m/min.

Carbide drills

• ¹⁾ Drill with replaceable or brazed carbide tip.
• ²⁾ Feed rate for drill diameter 20 - 40 mm.
• ³⁾ Feed rate for drill diameter 5 - 20 mm.
• ⁴⁾ Feed rate for drill diameter 10 - 20 mm.

Milling

Face and square shoulder milling

* Use a wear resistant Al₂O₃ coated carbide grade

End milling

• ¹⁾ For coated HSS end mill v_c = 14 - 16 m/min.
• ²⁾ Depending on radial depth of cut and cutter diameter.
• ³⁾ Use a wear resistant Al₂O₃ coated carbide grade.

Grinding

A general grinding wheel recommendation is given below.

* If possible, use CBN discs for this application.

Electrical discharge machining - EDM

If EDM’ing (“spark-erosion”) is performed in the hardened and tempered condition, the tool should then be given an additional temper at about 20 °C (50 °F) below the previous tem-pering temperature.

Application

New types of engineering plastics with a high filler content place higher demands on the tool material in terms of wear and corrosion resistance. Uddeholm Elmax SuperClean has been specially developed for high-tech programs. These include products in the electronics industry such as connectors, plugs, switches, resistors, integrated circuits, etc. Uddeholm Elmax SuperClean can also be used in the food industry, for the production of custom knives, where a combination of corrosion resistance and wear resistance is necessary.

Advantages and disadvantages of Elmax stainless steel as a knife steel

A good knife should not only please the eye. It should also have high performance properties and be easy to use. Let's consider how Elmax stainless steel has proven itself.

Advantages

• Possibility of polishing the surface to a mirror shine.
• High anti-corrosion properties.
• Plasticity.
• Ability to withstand lateral loads.
• Maintaining the sharpness of the edge for a long time.

Disadvantages

There are no obvious disadvantages to Elmax stainless steel, but it would be unfair not to point out a few downsides.

• The high price of knives is due to the high cost of this grade of steel.
• Not 100% corrosion resistance - with prolonged use in a humid environment (especially with salt content) and lack of proper care, pitting corrosion is possible.

Conclusions:

• Elmax steel knives are expensive, but this is compensated by their high technical characteristics.
• For steel with high strength - very good impact toughness.
• Requires only minimal maintenance.
• Holds sharpening for a long time and is easy to correct.

Welding recommendations

Uddeholm Elmax SuperClean is a high chromium-vanadium-molybdenum-alloyed steel with high wear resistance, high compressive strength, corrosion resistant and very good dimensional stability In Uddeholm Elmax SuperClean it has however been able to achieve this unique combination of properties by a powder-metallurgy-based production.

Welding of PM-steels is normally not recommended, due to the chance of failure, but good results when welding can be achieved if proper precautions are taken (joint preparation, choice of consumables and welding procedure). If the tool is to be polished, it is necessary to use a filler material that has the same chemical composition as the base material.

Dimensions of filler material

Recommended filling material

Parameters

*Note. In many cases, a high temperature tempering for 2 hours at ~750°C (1380°F) acts as a substitute for a full soft anneal when welding soft annealed material.

Procedures

• Clean weld area.
• Preheat material to 350°C ± 25°C / 660°F ± 50°F and maintain temperature during welding.
• Do not let the temperature in the vicinity of the weld (the HAZ) increase more than 150°C / 270°F above the preheating temperature. There is a risk of lowering (softening) the hardness of the base material or/and cracking in the HAZ. Use temple sticks or other temperature-measuring devices.
• For finishing layers use consumables which give suitable hardness.
• Wait a few minutes between each layer of strings, both for soft and hard filler, in order to let the layer equalize and minimize stresses, if possible use pre- heating furnace. Peen to minimize stresses.
• If possible, change welding direction 180° between each layer.
• Cool slowly after welding, 20 - 40°C/h, 35 - 70 °F/h for the first two hours and then freely in air < 70°C / 160°F.
• Temper 25°C / 50°F below previous tempering temperature for two hours.
• Tools welded in the annealed condition must undergo a full soft annealing immediately after welding. Allow tool to cool to room temperature before soft annealing. If a complete soft annealing cannot be done, a high temperature tempering at 750°C / 1380°F could be used. Be aware of that the working properties of the material will be somewhat reduced, if the high temperature tempering is used instead of the soft annealing.
• Shield Metal Arc Welding SMAW (MMA) and MIG Welding is not recommended.

Heat treatment guidelines

Heat treating stainless steel is the process of heating and cooling a metal to change its physical properties. There are several types of heat treating stainless steel, each with its own purpose.

Heat treatment of stainless steel can be used to achieve various goals, such as:

• Increased strength and hardness.
• Improved plasticity and toughness.
• Reduced internal stress.
• Improved machinability.
• Changed magnetic properties.

Characteristics

• High hardness PM stainless steel.
• Excellent polishability.
• Can be readily surface treated.
• Good corrosion resistance and very good abrasive wear resistance.

This information is based on the current state of knowledge and is intended to provide general notes on the products and their use. It should therefore not be construed as a guarantee of specific properties of the products described or a guarantee of fitness for a particular purpose. It is your responsibility to ensure that you have the latest version of the steel manufacturer's document and that you forward it to your heat treatment service provider. Failure to do so may result in deterioration of the material properties.

The choice of the type of heat treatment depends on both the grade of stainless steel and the desired properties of the metal that need to be obtained after such treatment.