Notation and characteristics of gas soft nitriding

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About gas soft nitriding

About JIS for gas soft nitriding

JIS: JIS B 6915

Characteristics of gas soft nitriding (bulleted)

Note the characteristics of gas soft nitrification below.

Feature Citation.

• Surface hardening treatment to obtain a "compound layer with high hardness and low coefficient of friction" on the surface
• Improves fatigue strength, corrosion resistance, and heat resistance
• Economical disposal method
• Milky white in color
• Distortion and dimensional changes are small (almost none) due to processing at relatively low temperatures
• Small or large parts, any shape
• Easily applicable to most steel materials
• Deep holes and slit shapes can be easily processed
• Clean finish with no adherence of impurities, oxide film, etc.
• Much shorter processing time than gas nitriding (2-5 hours heat retention)
• Easily applicable from small lot to mass production
• Surface hardness does not decrease at high temperatures.

Sources (in no particular order)

TOHKEN THERMOTEC Co.・asahi heat treatment industry co.・Parker S.N. Industries, Inc.・Shonan Nitriding Industry・

Supplement: Gas nitrocarburizing is also called SN treatment (ethnite treatment) and SN process.

Esnite treatment is a surface modification treatment in which iron sulfide and iron nitride are formed on the surface of steel materials by a gas process, also called sulfurizing-nitriding treatment.

How to describe and indicate gas soft nitrification

• Gas soft nitriding : HNC-G

Supplement: Reference (Notation of Other Processing)

• Nitrocarburizing (plasma nitrocarburizing: HNC-P , salt bath nitrocarburizing: HNC-S)
• Nitriding (gas nitriding: HNT-G , plasma nitriding: HNT-P)
• Oxynitridation (gas oxynitridation: HON-G, plasma oxynitridation: HON-P)

Characteristics of equipment for processing gas soft nitrification

Equipment for heating and nitrocarburizing processed materials in a "nitrocarburizing atmosphere

Supplement: Reference (What is equipment for processing gas nitriding?)

Equipment to heat and nitride processed materials in an atmosphere mainly composed of "ammonia gas".

What are the temperature variations in facilities that process gas soft nitrification?

Facilities for processing gas soft nitriding must be capable of maintaining temperature at ±10°C (Class 4) as specified in "JIS B 6901".

What is ammonia used in nitriding?

Ammonia used in gas nitriding and gas nitrocarburizing is an inorganic compound. It is a colorless gas at normal temperature and pressure, and has a peculiarly strong pungent odor, but is considered extremely important as the most "basic nitrogen source" in the chemical industry.

What happens when nitriding? Effects of Nitriding

Generally, from the topmost surface, the compound layer (white layer) - diffusion layer - material, forming the entire nitriding depth. This compound layer isImproves wear resistance, galling resistance, seizure resistance, reduction of coefficient of friction, and corrosion resistance.

Dimensional change of gas soft nitriding

Gas nitrocarburizing is a low-temperature (530-600°C) and short-time process, resulting in almost no dimensional change.

Variation in treated thickness of gas soft nitriding

The compound (nitride and carbide) layer formed by gas soft nitriding is 5μm to 20μm on the metal surface, with some variation depending on the furnace size. Generally, the layers are thinner on the door side of the furnace, but there may be more variation from lot to lot than there is variation within the furnace. (The variation in layers can be considered to be about 2.5 μm versus 10-15 μm for the compound layer.

Can the treatment thickness of gas soft nitriding be changed?

Possible. They may be available upon request.

How much hardness can be obtained by gas soft nitriding?

The following is a guideline. (It varies depending on the material, so it is necessary to check with the manufacturer who requested the treatment.

• SPCC, SS400, SUM series, S45C, etc:Hmv400 or higher
• SCM material, SNC, SMCM material, NAK, and prehardened steel:Hmv600 or higher
• SACM645, SKD-11, DC, die steel series, SKH series, HAP, high-speed steel:Hmv800 or higher
• SUS410, 420, 440:Hmv800 or higher

What if there is an area that you do not want nitrified

Prevention of partial nitriding by masking with chemicals, plating, etc. is possible by "indicating" areas where nitriding is not allowed on the drawing.

They say nitriding is weak under pressure, but why is it weak with high surface hardness?

Nitriding creates a compound layer on the surface to harden the material, but the material content is soft and vulnerable to deformation under pressure.

What if I want to know the degree of nitrification?

If you ask a nitriding manufacturer to measure the nitrided product, they will measure the nitrided product. Since the measurement requires looking at the cross section, the product to be requested for inspection is cut. The cut product is fixed by pressing a "copper plate or resin" against the nitrided surface, polished together with the material, and the depth of the compound layer and diffusion layer is measured in the image.

*The purpose of using copper sheet and resin is to make it easier to see. Resin is suitable for better adhesion.

That's it.