US1373589A - Process of seasoning steel articles - Google Patents

Description

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-' citizen of the United States, residing at Hartford, in the county of Hartford and State of Connecticut, have invented certain new and useful Improvements in Processes of Seasoning Steel Articles, of which the following is a specification.

It is a recognized fact. that there is a marked tendency for small steel articles which have been hardened to vary in shape or size, either by'warping or distortion or by expansion or contraction. Such distortions or variations are ordinarily relatively small and they take place slowly, frequently gage blocks or other. articlesaftenhaving continuing over a period of months or even i of years. .F or certain classes of work these dlstortlons or varlatlons are so small as to be immaterial, but in work involving high precision the distortions or variations are large enough toseriously interfere with the accuracy required.

Distortions'or variations such as above referred to are particularly detrimental in the case of dimension gage blocks which are made with opposite parallel flat end faces at predetermined distances apart, the blocks being-furnished in sets with diflerentlengths so that by combining or selecting difierent blocks any desired dimension within the range of the set can be secured. It is now possible to make blocks of this class so that the maximum error in each block from the nominal size thereof is not more than five millionths of an inch and is he uently as low as one millionth of 'an inch. en ,accuracy of this order is attainable the matter of distortion or variation from the form and size of the block as originally made is of vital importance. It has been found that gage blocks that are initially accurate within the limits specified may after a period of some weeks or months have become so distorted or changed in shape or size as to have errors far in excess of the allowable maximum.

It is well known that these distortions or variations gradually diminish in extent, the steel slowly approachin a permanent condition, which condition however ma not be fully attained until after a period 0 months i or even of years following hardening. It

appears that a certain natural seasoning 0 eration takes place, probablyassisted by t e Specification of Letters Patent.

Application filed May 13, 1920. Serial No. 881,188.

PROCESS OF SEASONING STEEL ARTICLES.

weather conditions, and probably further as Patented Apr. 5, 1921.

sisted by the shocks and vibrations to which an article is subjected during use.

Ord 1nar1ly it is notpractical to rely upon this natural seasonin operation because of the longtime required and the objectof the present mvention is to provide a process of seasoning which is capable of securing the same or, substantially the same permanency that as secured by natural seasoning but which is capable of-being carried out in a relatively short period of time. In accordance with the invention the steel ordinarily from 300 to 450"F.. In any case it is preferably as high as can be used for the particular steel wlthout softening'it to an objectionable extent. The predetermined temperature having been reached the oil with the blocks therein is maintained at this temperature for a definite period, preferably about one to eight hours. For one grade of steel used for gage blocks it has been found that a temperature of 400 maintained for eight hours gives satisfacto results. At the end of the heating perio the oil bath with the blocks still therein is allowed to slowly return to normal temperature.- After the blocks are removed from the oil bath they are subjected to a large number of alternate dips in hot and cold' baths. The hot and cold baths have temperatures respectively somewhat above and below the normal temperature. Preferably. the hot bath is of oil, the temperature of which is maintained at about 250 to 285 F. Preferably the cold bath is of kerosene, the temperature of which is maintained at about 0 to -20 F. The. blocks are dipped alternately intothe hot oil and into the cold oil, being allowed to remain in each long enough to attain the temperature of the I themselves and thus relieve the stresses Set up by the hardening operation;

.The vibration may be effected 1n any de- 'sired way, as, for instance, by mounting the gages or other articles in a suitable frame and by subjecting the frame to the actlon of a pneumatic hammer.

As the result of the foregoing treatment the blocks or other articles have within a short time been causedto undergo those distortions or variations which would otherwise have been distributed over a period of months or years. Theblocks or other articles are in substantially permanent form and are ready to be subjected to final grinding or lapping operations whereby they are made accurate within the limits required.

What I claim is:

1; The herein described process of seasoning steel articles after hardening, which consists in placing the articles in a liquid bath,

slowly heating the bath with the articles to a relatively hih temperature, permitting the bathYwit the articles to slowly cool to normal temperature, and then alternately dipping the articles a large number of times in hot and cold baths at temperatures respectively above and below the normal. temperature.

2. The process as described in claim 1 in which the initial'bath is heated to a temperature as high as is possible without objectionably softening the steel.

3. The process a described in claim 1 in memes which the initial bath is heated to a temwhich the initial bath is maintained at its maximum temperature for a considerable period of time.

5. The process as described in claim 1 in which the initial bath is maintained at its maximum temperature for a period of from one to eight hours.

6. The process as described in claim 1 in which the temperatures of the hot and cold "baths are respectively from 250 to 285 F.

and from O to 20 F.

7. The process as described in claim 1 in which the articles are dipped approximately seventytime in each of the last said baths.

8? The herein described process of seasoning steel articles after hardening, which consists in placing the articles in a liquid bath, slowly heating the bath with the articles toa temperature from 300 to 450 F, maintaining the bath with the articles at the said temperature for a period of approximately from one to eight hours, permitting the bath with the articles to slowly cool to normal temperature, and then alternately dipping the articles approximately seventy times in hot and cold baths at temperatures respectively from 250 to 285? F. and from 0 to ,,--20"- F.

9. The process as described in claim 1 in which the articles are vibrated during at least a part of the process steps specified.

10. The process as described in claim 1 in which'the articles are vibrated while in the initial high. temperature bath.

11. The process as described in claim 1 in BRYANT H. BLOOD.