04-02-2016, 02:13 PM
Company Profile
Heat Treatment of Steel and Non-Ferrous Metals and Alloys including Carbo-Nitriding, Gaseous Nitro-Carburizing and Nitriding, and Vacuum Oil quench, Induction Hardening, Black Oxide Coating. Our laboratory has a complete complement of testing equipment that can be used to inspect and analyze the results of the various treatments performed in our plant.The Company is led by a senior Metallurgical Engineer with a Master's degree and over 30 years of expereince in an extensive range of heat treatment processes, he provides the necessary expertise for finding solutions to your heat treating problems. We take immense pride the best customer service in the industry including excellent delivery with top quality at a good price. Given our metallurgical background, we also offer valuable customer technical support and advice towards improving their products by changing material or through suggesting alternative heat-treatment processes.
Liquid Nitriding :-
Liquid nitriding or nitriding in a molten salt bath employs the same temperature range as gas nitriding, which is 510 to 580°C. The case hardening medium is a molten, nitrogen-bearing, fused-salt bath containing either cyanides or cyanates.
Unlike liquid carburizing and cyaniding, which employ baths of similar compositions, liquid nitriding is a sub-critical casehardening process; thus, processing of finished parts is possible because dimensional stability can be maintained. Also, liquid nitriding adds more nitrogen and less carbon to ferrous materials than that obtained through higher-temperature diffusion treatments.
The liquid nitriding process has several proprietary modifications and is applied to a wide variety of carbon, low-alloy steels, tool steels, stainless steels, and cast irons.
Liquid Nitriding Applications :-
Liquid nitriding processes are used primarily to improve wear resistance of surfaces and to increase the endurance limit in fatigue. For many steels, resistance to corrosion is improved. These processes are not suitable for many applications requiring deep cases and hardened cores, but they have successfully replaced other types of heat treatment on a performance or economic basis.
In general, the uses of liquid nitriding and gas nitriding are similar, and sometimes identical. Gas nitriding may be preferred in applications where heavier case depths and are required. Both processes, however, provide the same advantages: improved wear resistance and antigalling properties, increased fatigue resistance, and less distortion than other case-hardening processes employing through heating at higher temperatures.
The degree to which steel properties are affected by liquid nitriding may vary with the process used and the chemical control maintained.
Liquid Nitriding Systems :-
The term liquid nitriding has become a generic term for a number of different salt processes, all of which are performed at subcritical temperature. Operating at these temperatures, the treatments are based on chemical diffusion and influence metallurgical structures primarily through absorption and reaction of nitrogen rather than through the minor amount of carbon that is assimilated.
Although the different processes are represented by a number of commercial trade names, a typical commercial bath for liquid nitriding is composed of a mixture of sodium and potassium salts.
• The sodium salts, which comprise 60 to 70% (by weight) of the total mixture, consist of 96.5% NaCN, 2.5% Na2CO3, and 0.5% NaCNO.
• The potassium salts 30 to 40% of the mixture, consist of 96% KCN, 0.6% K2CO3, 0.75% KCNO, and 0.5% KCl. The operating temperature of this salt bath is 565°C. This bath is widely used for nitriding tool steels, including high-speed steels, and a variety of low-alloy steels, including the aluminum-containing nitriding steels.
• Another bath for nitriding tool steels has a composition as follows: 60 to 61% NaCN, 15.0 to 15.5% K2CO3, and 23 to 24% KCl.
Several special liquid nitriding processes employ proprietary additions, either gaseous or solid, that are intended to serve several purposes, such as accelerating the chemical activity of the bath, increasing the number of steels that can be processed, and improving the properties obtained as a result of nitriding.Cyanide-free liquid nitriding salt compositions have also been introduced. However, in the active bath, a small amount of cyanide, generally up to 5.0%, is produced as part of the reaction. This is a relatively low concentration, and these compositions have gainedwidespread acceptance within the heat-treating industry because they do contribute substantially to the alleviation of a potential source of pollution.
Three processes, liquid pressure nitriding, aerated bath nitriding, and aerated low-cyanide nitriding, are described in the sections that follow.
FURNACE SIZE :- 600 mm dia x 900 mm length, deep.
GAS NITRIDING :-
It is a case hardening process whereby nitrogen is introduced into the surface of a solid ferrous alloy by holding the metal at a suitable temperature in contact with a nitrogenous gas, usually ammonia. Quenching is not required for the production of a hard case. The nitriding temperature for all steels is between 925 and 1050 f.
Principal reasons for nitriding are :
1. To obtain high surface hardness.
2. To increase wear resistance & antigalling properties.
3. To improve fatigue life.
4. To improve corrosion resistance.
5. To obtain a surface that is resistant to the softening effect of heat at temperatures up to the nitriding temperatue.
Prior Heat Treatment :-
All hardenable steels must be hardened and tempered before being nitrided .The tempering temperature must be high enough to gurantee structural stability at nitriding temperature; the minimum tempering temperature is usually at least 50 F higher than the maximum temperature to be used in nitriding.
In certain alloys such as series 4100 and 4300 steels, hardness of the nitride case is modified appreciably by core hardness; that is a decrease in core hardness results in decrease in case hardness. Consequently, in order to obtain maximum case hardness, these steels are usually provided with maximum case hardness by being tempered at the minimum allowable tempering temperature.
Applications :-
Examples of gas nitriding applications are Hydraulic barrel, trigger of pneumatic hammer, tachometer shaft, helical timing gear, gear, generator shaft, oil pump gear etc..
Furnace Size :- 600 mm dia x 1900 mm length, deep.