Abstract of thesis of master's degree work Konarevoi S.V.

master's degree of phisic-metallurgical faculty 

Leader - d.t.n., professor Gorbatenco V.P.


INFLUENCE OF DIFFERENT MODES OF HEAT TREATMENT ON STRUCTURE AND PROPERTIES OF THE TSEMENTOVANNOY STEEL 20Х


ENTRY

1 Metallurgical quality of staley, that are used for the presform pressing of heat-resistant wares

2 Influence of cementation and mode of heat treatment on the structure of property of steel 20Х

3 Influence of the initial state on the structure of steel 20Х after WHO

CONCLUSIONS

LIST OF REFERENCES

Entry

Presformi, which are intended for pressing of heat-resistant wares with shamotou, as of right it is possible to attribute to highly technological and naoucovomistcoi products. To decide Prihoditsya very intricate problems. Thus not only technological character, and often and it is enough contradictory.

         Demand on heat-resistant wares grows with development of industry. Necessities on presformi and, clearly, on steel for their production all time grows. The cheap and least metalomistca products of highly productive mass production are therefore needed. From other side, it is needed to provide reliability of work in the conditions of the protracted exploitation.

1. Metallurgical quality of staley, that are used for the presform pressing of heat-resistant wares

    In for some time past the Crasnogorivsciy factory of heat-resistant wares with shamotou uses the flags made from steel 20Х, which add to himico-termichescoy treatment – cementations in hard carbyorizatori with subsequent strengthening heat treatment. The temper mainly from the tsementatsiynogo heating with subsequent low vacation is such treatment. Flags from steel 20Х after such treatment use high-chromic permanent H12 in place of bolshcoshtovnoi.

         In a present tense a metallurgical combine is the suppliers of sheet of a different thickness from steel 20Х the “Azovstal and Alchevsciy metallurgical combine”. In this connection in work executed comparing analysis of indexes of quality of metal of leaves of these two producers with the use of the standards of metal, selected in the conditions of the Crasnogorivscogo factory of heat-resistant materials.

2. Influence of cementation and mode of heat treatment 

on the structure of property of steel 20Х 

         Research was executed in the direction of study  of influencing of temperature of pidstougouvannya after cementation at the temper from the tsementatsiynogo heating, and also influencing of double temper (first – from the tsementatsiynogo heating, second – from the separate heating). Thus cementation was executed  after the mode, that is used at the plant, without the substantial change to its pairs.

         In a pripoverhnevomou layer the structure  of martensitnogo type is formed, but through progartovouvanosti on martensit on the cut of standards did not get. Already in the distance 3.4 mm from the surface of sheet of production MC “Azovstal” the structure of mainly beynitnogo type was formed, and in a middle to the cut exposed the mixed structure of feritou and beynitou or even feritou, beynitou and perlitou.

         Implementation of temper from the separate heating, and also double temper results in the rise of hardness of superficial layer, growing of structure of sertsevini shallow .

The results of rengenostrouctournih researches allow to assume that by the principal reason of decline of hardness of steel hard-tempered from the tsementatsiynogo heating the amount of remaining aoustenitou can be promoted. So, as a result of computations, the amount of remaining aoustenitou in a pripoverhnevomou layer made 41%. Such amount of remaining aoustenitou is considered rather big for steel 20Х after cementation.

         It is known, that a considerable influence on the eventual structure of steel is had by the initial structure of aoustenitou, therefore in work the change of size of initial corn of aoustenitou is explored depending on the modes of himico-termichescoy treatment and thickness of sheet.        

3 Influence of the initial state on the structure of steel 20Х after WHO

      With the purpose of additional estimation of influencing of the initial state on the structure of steel 20Х after WHO executed two modes of previous heat treatment before cementation: previous annealing and previous temper.       Analysis of microstructure researches of svdchit about that without regard to enough long time self-controls during cementation, the initial structure of steel after previous heat treatment considerably affects eventual its structure.

So, in the cemented layer of standards, after the previous annealing the structure of croupnogolchastogo martensitou is formed. After the previous temper of martensit was more than shallow after the structure, that provided the receipt of more than high values of hardness (61 – 61 HRC in comparison with 59 – 60 after the previous annealing).

         Previous heat treatment was instrumental in the rise of progartovouvanosti steel in comparison with such after cementation from the initial garyachodeformovanogo state. Inwardly on the thickness of sheet the structure of beynitnogo type is formed with a two-bit structurally free feritou. It provides hardness of sertsevini at the level of 57 – 58 HRC after the previous temper.

         Conclusions

 Thus, the results of the executed researches testify to that the iihidniy state of metal, that is conditioned by the terms of his production that by previous heat treatment, largely affects a structure and properties of steel after himico-termichescoy treatment of wares. Such effect is observed without regard to that flags for presform for production of heat-resistant wares are added to the protracted self-control (10-12 hours at a temperature 930-950оС) during their cementation. Thus, previous preparation of structure  of steel can be an additional factor which affects ecstpouatatsiyni properties of presform. And this in the nvpryam influencing needs the detailed researches.

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