CN86100540A - The direct reaction preparation method of nitrogen group protecting atmosphere - Google Patents

Abstract

The invention relates to metal and alloy thermal treatment preparation method with nitrogen base protection heating atmosphere.

The present invention does not need accurate methyl alcohol adding set and low temperature pyrolyzer device, do not need complicated stage purification equipment, except original heat treatment heating furnace, only need in stove, to place the solid carbon material of certain altitude, can reach identical even better thermal effectiveness.

Description

The direct reaction preparation method of nitrogen group protecting atmosphere

The invention relates to the preparation method of the nitrogen group protecting atmosphere in metal and the alloy protecting atmosphere heat treatment technology.

For the used source of the gas of preparation nitrogen group protecting atmosphere has bottled general nitrogen, its purity is 99-99.8% at present; The purity of empty branch nitrogen is 99-99.5%; The purity of the nitrogen of 5A ° or coke molecular sieve preparation is 98-99.5%.They all can not be directly used in the protection heating.The purity of liquid nitrogen is higher, reaches 99.999%.Can be directly used in metal and heat treatment of alloy protection heating, but cost an arm and a leg.

Prior art, " metal heat treatmet " 1985 11 phases the 35th page of method that is proposed for example, the first nitrogen that elder generation makes with the coke molecular sieve, as unstripped gas, add methyl alcohol then, through low temperature pyrolyzer, generate carbon monoxide and hydrogen, mixed with unstripped gas, pass through the multiple tracks cleaning section again, enter working furnace then.The control techniques of addition requires very high.Addition very little, can not in and burner hearth in oxidizing atmosphere; Addition is too many, for different steel grades, then can cause carburetting or decarburization.Add and cracking all needs corresponding device thereof, and purification system to adopt activated alumina to plate the palladium deoxygenation heat exchange 5A ° of molecular sieve equipment such as dewater that dewaters.

The new preparation technology's method that the purpose of this invention is to provide the protection heating nitrogen-based atmosphere that a kind of thermal treatment uses.This technological process is simple, stable performance, except original heat treatment heating furnace, do not need to add any miscellaneous equipment, it can guarantee after the thermal treatment workpiece with through having additive and through having of handling of the nitrogen-based atmosphere that multiple tracks purifies same in addition the surperficial quality of better thermal treatment.Owing to saved the adding set that has accurate control and complicated treating plant, thereby made facility investment be lower than one of original percentage, the production cost of workpiece is original 1/2nd to 1/3rd, and easier operation and management.

The present invention realizes in the following way.The solid carbon material is placed in bottom or side at the thermal treatment working furnace, when temperature in the stove is between 500-1300 ℃, just nitrogen is by being placed in the stove and during the solid carbon material identical with temperature in the stove, just residual nitrogen and the solid carbon quality in the nitrogen plays oxidizing reaction, generate carbon monoxide, see reaction formula (1).Just the remaining oxygen in the nitrogen can change within the specific limits, and the reacted for a long time carbon monoxide of remaining oxygen is just many; The reacted after a little while carbon monoxide of remaining oxygen is just few, and promptly the solid carbon material spontaneously plays direct reaction with residual oxygen.Simultaneously, the trace water in the first nitrogen is also carrying out water-gas reaction with carbon material by reaction formula (2).Like this, residual oxygen in the first nitrogen and trace water all are eliminated and become and meet the nitrogen-based atmosphere of protecting heating condition.

The used solid carbon material of above-mentioned processing method it would be desirable graphite, also can be other harder carbon material of quality, as coke etc.The height of solid carbon material place mat in process furnace is generally at the 80-140 millimeter, and used first nitrogen can be other nitrogenous sources such as bottled general nitrogen or empty branch nitrogen, and the purity requirement of first nitrogen is more than 98%.

The nitrogen group protecting atmosphere that utilizes the direct reaction method to obtain has neutral character, promptly is in the not decarburization of high carbon steel workpiece in the same burner hearth, the not carburetting of soft steel workpiece.Fig. 1 has compared the stratographic analysis result of first nitrogen and the oven cavity atmosphere that utilizes the direct reaction method to make.Can find out significantly that the residual oxygen oxygen peak of the oven cavity atmosphere that the direct reaction method makes disappears.This atmosphere by analysis, dew point is below-40 ℃, carbon dioxide content is lower than 0.03%.The steel foil of high and low carbon steel placed utilize the atmosphere of the same burner hearth that the direct reaction method makes to handle, 840 ℃ of insulations 20-30 minute, measure the decarburization or the carburetting situation of high and low carbon steel steel foil with Weighing method after air cooling, it the results are shown in Table 1.

Table 1

To T10,45 ^#, 9C _iS _i, C _r12M _oV, 1C _r18N _i9T _i, W18C _r4V1, W6M _o5C _rThe sample of seven kinds of steel of 4V2 quenches with the atmosphere of present method preparation, extends to 1-2 hour heat-up time in order to examine the stability of atmosphere, will to quench.After sample quenches, carried out the metallurgical analysis and the micro-hardness testing of textura epidermoidea.The top layer metallographic structure analysis result of above-mentioned seven kinds of materials samples shows that the phenomenon of any decarburization (to high carbon steel or high-carbon alloy steel) or carburetting (to the low-carbon (LC) steel or stainless steel) does not appear in specimen surface, specimen surface light or bright and clean.Fig. 2 represents that the sample of above-mentioned steel grade quenches the back microhardness along with the curve that changes from the variation of surface distance, wherein, and 1-1C _r18N _i9T _i1100 ℃, be incubated 40 fens, water-cooled; 2-45 ^#, 860 ℃, be incubated 1 hour, oil cooling; 3-9C _rS _i, 870 ℃, be incubated 1 hour, oil cooling; 4-W18C _r4V1, is incubated 1 hour, oil cooling by 1270 ℃; 5-T10, is incubated 1 hour, water-cooled by 1200 ℃; 6-T10, is incubated 2 hours, water-cooled by 820 ℃; 7-C _r12M _oV, is incubated 1 hour, oil cooling by 1030 ℃; 8-W6M _o5C _r4V2, is incubated 1 hour, oil cooling by 1210 ℃.The nitrogen-based atmosphere that utilizes the method for direct reaction to make also can be used as the annealing of workpiece, the protection heating of high tempering.

Also to the low-carbon (LC) steel foil of 0.07%C, T10 high-carbon steel foil and 45 ^#Three kinds of grades of steel of steel; carried out with adding behind the methanol decomposition again that traditional nitrogen group protecting atmosphere through tight cleaning section quenches and quenching with the nitrogen-based atmosphere of present method preparation; with weighting method and metallographic method two class results after quenching are compared then, comparative result sees Table 1.

Inventive embodiment

Fig. 3 is W18C _rThe 4V milling cutter, 1280 ℃, oil quenching.

Fig. 4 is C _r12M _oV, the valve stamen (in), valve pocket (right side), 9C _r18 little axles (upper left) are all at 1030 ℃ of oil quenchings; 40C _r850 ℃ of oil quenchings of worm screw (lower-left).

Claims (4)

1, the preparation method of the nitrogen base protection heating atmosphere used of a kind of metal and alloy thermal treatment.Promptly spontaneously being formed to meet behind the heat treatment heating furnace between 500-1300 ℃ by temperature by first nitrogen does not have the neutral heating nitrogen-based atmosphere increase decarburization.It is characterized in that, place the solid carbon material in the bottom or the side of original heat treatment heating furnace.

2,, it is characterized in that described solid carbon material the best is graphite as claim 1 described method.

3,, it is characterized in that the height of described solid carbon material auxilliary pad in heat treatment heating furnace is the 80-140 millimeter as claim 1 described method.

4, as claim 1 described method, the purity requirement that it is characterized in that described nitrogen just is more than 98%.

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