RO132200A2

RO132200A2 - Nitrocarburizing process and plant

Info

Publication number: RO132200A2
Application number: ROA201600273A
Authority: RO
Inventors: Leontin Nicolae Druga; Cristian Badina; Gheorghe Toader
Original assignee: Uttis Industries S.R.L.
Priority date: 2016-04-18
Filing date: 2016-04-18
Publication date: 2017-10-30

Abstract

The invention relates to a process and a plant for nitrocarburizing large size pieces. According to the invention, the process comprises a series of stages: pre-oxidizing, nitrocarburizing and post-oxidizing, in an active atmosphere achieved in situ from mixtures of ammonia, methane and carbon dioxide, to obtain, after a time interval of 8 h, thicknesses of thermo-chemical diffusion layers with N, C, O of 0.15...0.20 mm. The plant, as claimed by the invention, comprises a horizontal enclosure (1.1) provided with a vacuuming system (1.4) for achieving a preliminary vacuum and a system (1.5) for forced cooling of nitrated pieces, in nitrogen.

Description

Invenția se refera la un procedeu pentru nitrocarburare in atmosfera gazoasa obtinuta in situ din amestecuri de amoniac, endogaz (metan) si dioxid de carbon, riguros prestabilite, măsurate si reglate prin intermediul a massflowcontrollere, senzori, automat programabil si software de proces.The invention relates to a process for nitrocarbonation in the gaseous atmosphere obtained in situ from mixtures of ammonia, endogas (methane) and carbon dioxide, rigorously predetermined, measured and regulated by means of massflow controllers, sensors, automatically programmable and process software.

Procedeul de nitrocarburare se realizează intr-o instalație de nitrocarburare prevăzută cu incinta orizontala pentru nitrocarburare, sistem de vidare care permite realizarea unui vid preliminar si sistem de răcire rapida după nitrocarburare a pieselor de dimensiuni mari, in atmosfera de azot, astfel incat se reduce semnificativ durata procesului de nitrurare.The nitrocarbon process is carried out in a nitrocarbon installation provided with the horizontal chamber for nitrocarbonization, a vacuum system that allows a preliminary vacuum and a rapid cooling system after the nitrocarbonization of large parts, in the nitrogen atmosphere, so that it is significantly reduced the duration of the nitriding process.

Este bine cunoscut faptul ca procedeul de nitrurare convenționala este un procedeu de tratament termochimic de durata mare, in funcție de natura încărcăturii, putând ajunge si la 30...40 ore. Prin realizarea procedeului si instalației de nitrurare accelerata conform invenției, se reduce cel puțin la jumătate durata procesului tehnologic.It is well known that the conventional nitriding process is a long-term thermochemical treatment process, depending on the nature of the load, and can reach 30 ... 40 hours. By carrying out the accelerated nitriding process and installation according to the invention, the duration of the technological process is reduced by at least half.

De asemenea, este bine cunoscut faptul ca stratul alb de compuși obtinut in suprafața pieselor metalice după aplicarea tratamentului termochimic de nitrurare convenționala consta din amestecuri Fe2-3N (faza ε) si Fe4N (faza γ'), strat care este dur si fragil, si care in timpul exploatării se poate exfolia si deteriora [1 ].It is also well known that the white layer of compounds obtained on the surface of the metal parts after the application of the conventional thermochemical treatment of conventional nitriding consists of mixtures Fe2-3N (phase ε) and Fe4N (phase γ '), a layer that is hard and fragile, and which during the operation can be exfoliated and damaged [1].

Procedeul de nitrocarburare conform invenției (combinație preoxidare- nitrocarburarepostoxidare) permite obținerea de configurații dedicate de strat nitrocarburat incat se asigure imbunatatirea rezistentei la uzura, oboseala si coroziune comparativ cu straturile nitrurate obținute prin nitrurare convenționala.The nitrocarbon process according to the invention (combination preoxidation - nitrocarburization and post-oxidation) allows to obtain dedicated configurations of the nitrocarbon layer that ensure the improvement of wear, fatigue and corrosion resistance compared to the nitrate layers obtained by conventional nitriding.

In acest sens, procedeul de nitrocarburare conform invenției asigura:In this sense, the nitrocarbon process according to the invention ensures:

- creșterea calitatii proceselor industriale de tratament termochimic;- increasing the quality of the industrial processes of thermochemical treatment;

- scurtarea duratei procesului tehnologic cu ~40 % fata de procedeul de nitrurare convenționala;- shortening the duration of the technological process by ~ 40% compared to the conventional nitriding process;

- reducerea consumurilor de fluide tehnologice cu ~ 30 %;- reducing the consumption of technological fluids by ~ 30%;

- realizarea unei game largi de tratamente de difuzie termochimica cu azot, carbon si oxigen;- carrying out a wide range of thermochemical diffusion treatments with nitrogen, carbon and oxygen;

- straturi de difuzie termochimica cu comportament superior la uzare si coroziune comparativ cu cel al straturilor obținute prin procedee de nitrurare convenționala.- thermochemical diffusion layers with superior wear and corrosion behavior compared to the layers obtained by conventional nitriding processes.

- imbunatatirea comportamentului in exploatare a pieselor de dimensiuni mari utilizate in industria eoliana, auto si navala;- improvement of the behavior in operation of large parts used in the wind, car and naval industry;

Instalația inovativa pentru aplicarea procedeului de nitrurare accelerata este formata, din următoarele subansamble principale (fig. 1): Cuptor de tratament termochimic propriu-zis (1) compus din: incinta orizontala (1.1), sistem încălzire electric cu rezistori metalici (1.2), sistem de alimentare cu gaze tehnologice (1.3), instalația de vidare a retortei (1.4), sistem de răcire rapida a încărcăturii) (1.5); rampa gaze tehnologice N2, NH3, CO2 ce include electroventile, robineti, massflowcontrollere (2); sistem de agitare atmosfera in incinta orizontala (3) compus din: agitator uniformitate temperatura (3.1), sistem de răcire agitator (3.2); sistem de control al temperaturii (4), compus din bucla de reglare cu termocuple (supratemperatura rezistori, temperatura incinta orizontala, temperatura piesa) si regulator de temperatura; senzori de măsurare, reglare si control a atmosferei din cuptor: sonda de oxigen si sonda de hidrogen (5); sistem de evacuare gazelor arse din retorta (6); instalație de automatizare cu automat programabil si software de proces (7).The innovative installation for applying the accelerated nitriding process consists of the following main subassemblies (fig. 1): Thermochemical treatment furnace itself (1) composed of: horizontal enclosure (1.1), electric heating system with metallic resistors (1.2), technological gas supply system (1.3), retort emptying system (1.4), rapid charge cooling system (1.5); N2, NH3, CO2 technology gas ramp including electric valves, valves, mass flow controllers (2); system of stirring the atmosphere in the horizontal enclosure (3) composed of: agitator uniformity temperature (3.1), cooling system agitator (3.2); temperature control system (4), composed of a control loop with thermocouples (over-temperature resistors, horizontal enclosure temperature, part temperature) and temperature regulator; sensors for measuring, regulating and controlling the atmosphere in the furnace: oxygen probe and hydrogen probe (5); flue gas exhaust system (6); automation system with programmable automatic and process software (7).

a 2016 00273to 2016 00273

18/04/201618/04/2016

Parametrii tehnologici principali asigurați de instalația de nitrocarburare sunt: temperaturi de lucru intre 450-650°C, masa șarjei maxim 1000 kg, presiunea de lucru 5 mbar, atmosfera in situ din amestecuri predeterminate de fluide tehnologice (azot, amoniac, dioxid de carbon, endogaz/metan).The main technological parameters provided by the nitrocarbon plant are: working temperatures between 450-650 ° C, mass of the maximum load 1000 kg, working pressure 5 mbar, in-situ atmosphere from predetermined mixtures of technological fluids (nitrogen, ammonia, carbon dioxide, endogaz / methane).

Elementele inovative aduse de instalația de nitrocarburare sunt prevederea incintei de lucru orizontale a cuptorului de difuzie termochimica cu C, N, O atat cu sistem de vidare cat si cu sistem de răcire rapida a pieselor si de asemenea soflware-ul de proces dedicat.The innovative elements brought by the nitrocarbon plant are the provision of the horizontal working chamber of the thermochemical diffusion furnace with C, N, O with both a vacuum system and a rapid cooling system of the parts and also the dedicated process soflware.

Sistemul de vidare al retortei instalației este constituit din pompe de vid de precizie si trasee tehnologice. Sistemul de răcire rapida asigura recircularea azotului de răcire prin intermediul unui schimbător de căldură apa-gaz si reintroducerea lui in procesul tehnologic.The vacuum system of the plant retort consists of precision vacuum pumps and technological routes. The rapid cooling system ensures the recirculation of the cooling nitrogen through a water-gas heat exchanger and reintroduces it into the technological process.

Software-ul dedicat de proces asigura achiziția următoarelor date: număr comanda,număr șarja,marca otel, compoziție chimica otel, diagrama de încălzire programata, diagrama de încălzire realizata, semnale senzori, monitorizare fluide tehnologice, funcționare încălzitori, setări si alarme, temperatura in cuptor.The dedicated process software ensures the acquisition of the following data: order number, batch number, steel mark, steel chemical composition, programmed heating diagram, realized heating diagram, sensor signals, technological fluid monitoring, operation of heaters, settings and alarms, temperature in oven.

Se prezintă in continuare un exemplu de realizare a procedeului de nitrocarburare accelerata in conformitate cu diagrama din figura 2, procedeu realizat in instalația de nitrocarburare prezentata in figura 1, care include următoarea secvența de operații: amplasare piese degresate pe dispozitiv de sarjare si introducere in retorta cuptor, vidare retorta, încălzire piese in azot, preoxidare in atmosfera obtinuta din azot si dioxid de carbon, admisie amoniac, saturare+ difuzie in amoniac+dioxid de carbon, subracire in amoniac, postoxidare in azot si dioxid de carbon, vidare si răcire accelerata in azot pana la 150°C, răcire in aer de la temperaturi mai mici de 150°C.The following is an example of an accelerated nitrocarbon process in accordance with the diagram in Figure 2, a process carried out in the nitrocarbon plant shown in Figure 1, which includes the following sequence of operations: placement of skimmed parts on the twisting device and insertion into the retort oven, retort emptying, heating parts in nitrogen, preoxidation in the atmosphere obtained from nitrogen and carbon dioxide, ammonia intake, saturation + diffusion in ammonia + carbon dioxide, sub-cooling in ammonia, postoxidation in nitrogen and carbon dioxide, vacuuming and accelerated cooling in nitrogen up to 150 ° C, cooling in air from temperatures below 150 ° C.

Claims

The nitrocarbon process according to the invention is characterized in that it ensures a certain succession of technological operations of pre-oxidation, nitrocarbonization, post-oxidation which lead to the shortening of the technological process duration in half compared to the conventional nitriding.

The process of nitrocarbonization in the active atmosphere obtained in situ from mixtures of ammonia, endogas (methane) and carbon dioxide, rigorously predetermined and regulated by means of sensors and process software.

Nitrocarbon plant, characterized by the fact that it consists of a horizontal enclosure with a vacuum system that allows a preliminary vacuum and controlled cooling system of the nitrated parts in nitrogen.