Patented Sept. 12, 1939 UNITED STATES METHOD OF INHIBITING THREAD SURFACE SEIZURE Charles E. S. Place, Detroit, Mich, assignor to Clare L. Brackett, Detroit, Mich.
Application January 21, 1937,
Serial No. 121,713
This invention relates to the procurement of thread surface seizure inhibition in screwthreaded connecting members.
When contacting threaded members such as 5 nuts, bolts, screws and the like are subjected to high temperatures in service, as in the case of the exhaust pipe or manifold assemblies of internal combustion engines, or in furnaces, boiler or superheater units, where temperatures range 10 from 600 F. to 1200 F., scale forms on the thread surfaces. This scale formation arises from various causes such as oxidization, fusing and brazing. As a result the contacting thread surfaces become firmly bound together, making their 15 disengagement a matter of great difiiculty. Thisbinding is termed thread surface seizure and often occurs to such an extent that it is impossible to disconnect the members without fracture or distortion. Frequently the use of a chisel or hack- 2 saw must be resorted to.
An object of this invention is to provide a method of inhibiting thread surface seizure in screw-threaded connecting members by processing the same in a manner to render their thread surfaces impervious to the destructive effects of high temperatures.
Another object is to provide a method of processing screw-threaded elements to render their thread surfaces resistant to scale formation, oxi- 30 dization, fusing or brazing under service conditions' of high temperatures.
A further object is to provide a method of coating the thread surfaces of screw-threaded elements with a stable heat resistant material, the
5 condition of which will remain unaltered under high temperatures.
Still another object is to provide screwthreaded elements having thread surfaces inherently incapable of scaling, oxidizing, fusing or 40 brazing under high temperatures encountered in service.
Attempts have been made to overcome thread surface seizure by lubricating the threads with grease, oil and other mobile materials, but owing 5 to the fact that under high temperatures such materials volatilize, evaporate, carbonize and otherwise alter their character their efficiency for the purpose is destroyed.
I have found that graphite or other equivalent 50 metallic carbon provides a seizure inhibiting material that is stable, heat resistant and non-oxidizing. Its condition will not alter under high temperatures. The present invention contemplates the application of this material to thread 55 surfaces so that it coats or otherwise forms thereon a protective skin the character of which remains unchanged under high temperatures, thus obviating the occurrence of thread surface seizure.
The processing of screw-threaded elements in accordance with this invention may be carried out in various ways. Where such elements are screwthreaded by a rolling operation, powdered graphite or equivalent metallic carbon suspended in water solution may be introduced to the rolling dies while they are originally acting upon the blank, and the graphite or equivalent metallic carbon rolled in and caused to penetrate or become impregnated in the thread surface by the rolling die pressure, or graphite or equivalent metallic carbon may be rolled onto the thread surface after the original rolling by second pass or a finishing pass through rolling dies, or by other suitable means.
Where the thread is formed by cutting, graphite or equivalent metallic carbon may be applied to the blank as the cutis made, or it may be applied by rolling it on after the thread is cut. In some cases the thread may be cut a little less than gauge size and then rolled to finish size and the graphite or equivalent metallic carbon applied as the final roll is made.
Alternatively, screw-threaded elements to be treated may be submerged in a solution containing powdered graphite or equivalent metallic carbon in suspension, and the solution be brought to a temperature close to the boiling point and agitated, as by injected steam, for a suitable length of time. The submerged elements will absorb sulficient heat so that when they are removed from the solution the adhering liquid will be evaporated, leaving a deposited hard film of the graphite or other material fully covering the thread surfaces, the innumerable surface irregularities acting as retainer crevices or pockets for the deposited material. If desired, the solu- ,tion may be mechanically applied in a cold state to the threads and the elements subsequently heated to evaporate the solution and deposit the carbon film.
The graphite, or equivalent metallic carbon, whether rolled into or evaporated onto the surface of the threads, will not deteriorate under high temperatures and serves to protect the threads against the initial formation of scale or oxidization and will thus prevent seizing, fusing or brazing of the contacting thread surfaces so that nuts, cap screws or other threaded members may be readily released from their cooperating parts without difliculty and without destroying, de-
forming, mutilating or otherwise injuring the same.
Having thus described the invention, what is claimed is:
1. The method of inhibiting screw-threaded members against thread surface seizure, which comprises submerging such members in a solution containing powdered graphite in suspension, heating the solution, causing the submerged members to absorb heat from the solution, and then removing the members whereby the absorbed heat evaporates the adhering solution to deposit a film of graphite.
2. The method of inhibiting screw-threaded members against thread surface seizure, which comprises applying powdered graphite to the thread surfaces as a coating, and mechanically forcing the graphite thereinto.
3. The method of inhibiting screw-threaded members against thread surface seizure, which comprises rolling into the thread surfaces a covering coating of graphite.
4. A process for treating threaded members which comprises applying a heat resistant material suspended in a solution to the threads of said members while applying pressure to the material and threads.
5. A process for treating threaded members which comprises applying graphite suspended in a solution to the threads of said members while applying pressure to the graphite and the threads.
6. A process for treating threaded members which comprises introducing a heat resistant material suspended in a solution to the threads of said members when said threads are being formed by rolling.
7. A process for producing protected threaded members which comprises forming threads on a connecting member and rolling under pressure a heat resistant and protective material into the threads during the formation of the threads.
8. A process for producing protected threaded members which comprises forming threads on a connecting member and rolling graphite under pressure into the threads during the formation of said threads.
9. A process for producing protected threaded members which comprises forming threads on a connecting member and while rolling the threads applying a heat resistant and protective material thereto.
10. A process for impregnating the threads of connecting members with a heat resistant and protective material which comprises introducing graphite suspended in a solution to the threads during the rolling operation for the formation and completion of the threads while maintaining the graphite under pressure to cause said graphite to impregnate said threads.
CHARLES E. S. PLACE.