US2406539A - Manufacture of hollow staybolts - Google Patents

Description

Patented Aug. 27, 1946 MANUFACTURE OF HOLLOW STAYBOLTS Grover R. Greenslade, Scott Township, Allegheny County, and Frederick K. Landgraf, Grafton,

assignors" to Flannery Bolt Company,

Bridgeville, Pa., a. corporation of Delaware No Drawing. Application January 30, 1941, Serial No. 376,600

1 This invention pertains to the manufacture of hollow staybolts and is for a method for the manufacture of staybolts of the type having a longitudinally extending telltale hole therein. This application is a continuation-in-part of our co-pending application Serial No. 322,950, filed March 8, 1940, now Patent No. 2,332,569 issued October 26, 1943, entitled Hollow staybolts.

Staybolts for use in boilers, particularly locomotive boilers, are commonly provided with a longitudinally extending bore which is open at one end and which is closed at the other end of the bolt but which extends throughout the greater portion of the length of the'bolt. This hole,

which is known in the art as a telltale hole, is for the purpose of indicating a fracture in the.

bolt as is well understood by those skilled in the art. The bolts are formed of a ferrous metal, wrought iron usually being used. Under the conditions of operation corrosion and oxidation take place in the hole, tending to close the hole and defeat its purpose. For the purpose of retarding the oxidation of the metal copperplating of the interior of the hole is commonly practiced. Due to the fact that these bolts are quite long in proportion to the diameter of the hole, the length of the bolts often exceeding 30 inches, the limitations of space make the electroplating of the interior of the hole with copper a difiicult operation and there is no adequate Way for inspecting the bolt after it has been plated to determine if the film of copper is continuous. Moreover, due to the presence of slag in the metal in the surface of the wall forming the hole the electrodeposition of the film may not be continuous as the copper is deposited only on metal surfaces.

In our above-identified co-pendin application we have disclosed a staybolt having an applied coating" of a non-ferrous metal on the interior walls of the hole which coating is applied to the interior of the hole in a molten state. An alloy predominantly of lead, such as terne metal,

is preferably employed. This coating forms a continuous oxidation-resistant film over the interior of the hole notwithstanding the possible presence of slag in the metal. If desired the coating thus formed may be covered in turn by an electrolytically deposited film of copper. The film of copper will be continuously deposited under the underlying coating of non-ferrous metal. If for mechanical reasons the copperplating should not be continuous there is the added protection provided by the heat-applied metal coat- 2 Claims. (Cl. 14819) staybolts, particularly the so-called flexible staybolts, have a case-hardened head. In the case of a flexible staybolt, the head is of a spherical form for cooperation with a spherically curved seat on the boiler plate and the case hardening of the head of the bolt reduces wear between the contacting surfaces. If the low melting point metal with which the interior of the telltale hole is coated is applied before the carburizing or case-hardening process, the subsequent heating of the bolt to case-harden the head will melt the film and destroy it. On the other hand, if the head of the bolt is first carburlzed and then the hot coating is applied, the

subsequent heating of the bolt for the hot coating process is detrimental to the case-hardening. The present invention provides a method by means of which the coating of the telltale hole may be accomplished along with the case-hardening so that Withthe completion of one operation the other is also completed. Moreover, the invention provides a method wherein the steps of carburizing and coatingthe interior of the telltale hole of the bolt may be practiced economically and rapidly. Our invention may be fully understood by reference to the accompanying drawings, in which Figure 1 is a'vertical section through a staybolt with a charge of coating metal therein and with a weighted rod on the charge for spreading the coating metal when the same melts and;

' tom of the hole.

Figure 2 is a view similar to Figure 1 showing a. modified arrangement in which a rod of coating metal longer than the bolt is initially inserted in the bolt.

In practicing the invention the staybolts, one of which is shown in detail in Figure 1 and which is designated A, is supported in an upright position with the head of the bolt down and With the open end of the bolt up. The bolt is filled with a liquid fluxing agent, such as a solution of zinc chloride. According to one preferred method of practicing the invention, a cylindrical slug of coating metal designated B in Figure 1 is dropped into the hole in the bolt, the slug of coating metal being of a diameter less than the diameter of the hole so that it will fall freely to the botweight 36 at its upper end is then placed in the hole so as to rest on the top of its slug B. When the bolt is heated up the slug of coating metal B liquifies and the weighted rod 35 sinks down through the molten metal displacing the molten metal and forcing it upwardly around the tube to the top of the hole. The slug B is preferably A wire or rod 35 having a 3 large enough so that there will be a light excess of molten metal running out of the top of the bolt. The rod is thereafter retained in the bolt until the process has been completed.

After the bolts have been filled with flux and after the slugs have been placed in them and. the weighted rods 35 have been put in place, the bolts are transferred to a basket in which they remain during the heat treating process. a

The bolts after being prepared in the manne described for treatment are loaded into one of the baskets or carriers and transported toa staftionary preheating furnace.

furnace for the necessary length of time.

After the bolts have been carburized and are moved to an unloading station the head or ithe bolt should be quenched but the body of the bold should be cooled gradually.

The operator transfers the bolts one at a time from the basket at the unloading stat-ion to a basket at a quenching station. "ln' so doing he "removes the weighted rods 35- 36 from the bolt; inverts the bolt and taps it against a solid surface; causing excess coating metal to be ex- ,jpelled from the hole in the bolt. He then turns ing operation and just before the quenching of the bolts the holes Within the bolts shall be kept run of boating metal and "this coating metal of io'ourse remains in a molten condition until the excess'lis expelled. One method of accomplish- .ing' this .is that previously described and illustrated'in Figure 1. Another way of filling the holes 'in the bolts and maintaining an adequate supply of meta1 therein is illustrated 'in'Figure 2.

.- ;In-this lfi ure the bolt, also designated A, has a .rod or coating .rnetal designatedB inserted therein.- smaller than the diameter of the hole and in Fi ure:2 the .rodo'fcoating metal ismade longer than the .bolt. inorderthat the excess length-of coat-- ing metal projecting beyond the end of the bolt cannot melt down and flow away the arrangement shown in Figure 2 contemplates the use of a removable-extension '91 having a flange 9.2 which embraces the upper end of. the bolt A and which i has a hole therethrough that registers with the hole in the bolt. This extension 9! supports the projecting upper end of the rod of coatingmaterial so that when the rod of coating material melts all of the coating material will flow into the hole in the bolt. Because of the smaller diameter of the coating rod with relation to the diameter of the hole in the bolt it is necessary that the rod of coating material initially be madelonger inorder to assure of the bolt being filled.

The method shown in Figure 1 in which the weighted rods are used is more economical in that less extruded metal is required than the method The heads of the bolts are then immersed in the cyanide bath in a The rod of coating metal has a diameter shown in Figure 2 but expenses are involved in the provision and maintenance of the weighted rods 3,6. Ihe' method shown in Figure 32 elimihates the weighted rods but requires a greater length of extruded metal. The excess metal is not lost as it is recovered when the bolt is tapped to expel excess metal just before quenching, th accumulated excess metal being subsequently remelted. Either method is satisfactory for the purpose of accomplishing the invention. After the bolt has been terne-plated the removable extension 91 may be readily removed and placed on another bolt for .re-use.

After the bolts have been terne-plated or coated with alow melting point metal they may be electroplated onthe interior thereof in the usual way.

In some cases it may be desirable to reverse the.

process and "electroplate the interior of the bolt and then apply the terne coating, and my invenltion contemplates such reversal of the process.

The metal referred to as terne coating metal is an alloy of lead and tin in which the lead very greatly predominates. In lieu of terne coating metal other soft or low point melting metals may be used, as, for example, lead or tin or zinc or various mixtures thereof. Under any circumstances the metal or alloy used for coating the interior of the bolt should "be one which is not melted at the temperature reached inside the boiler. Usually ametal or alloy of the class comprising lead, tin and Zinc, "or mixtures thereof, would be employed.

According to our method as herein described the spreading of the metal over the interior of the hole to form a coating is accomplished with the same heating-up process that "is required for cyanidin'g or case-hardening the headofthe bolt. Excessive heatinglip of the bolt is thereby avoided. Moreover, since the hole in the bolt is "full of metal during the process either by using the weighted rod as shown in Figure 1 or by using the extension "9! as shown in'Figure 2, the coating on the interior of the hole is not oxidized or .injtlrec'l. The heads 'o'fthe bolts must remain in the cyanide bath a'pr'ede'terminedperiod of time and 'theib'olts should'be heated to a proper temperature before they are carburized. A hoist which may be intermittently operated in conjunction with the several stations provided for the heating up of the bolts and the keeping of the bolts 'hot until the excess coating metal has been ejected therefrom and the bolt is ready .to be quenched provides a convenient arrangement for the practicing-of the process. The capacity of the hoist and of the preheating furnaces is increased by the provision of auxiliary preheating stations. The provision of means for quenching the heads of the bolts and permitting the bolts to cool immediately adjacent the loading and unloading station enables the bolts to be-quicklymovedfrom the carrier and the excess coating material expelled therefrom before it has a chance .to cool, and enables the bolt to .be'quenched beforeit has had an Opportunity to-cool. The separate washing operation is performed without .removing the bolts which have been quenched from'the carrier in which they areplaced for quenching. flihis arrangement enables .the apparatus to be used :to its fullest capacity.

While we have illustrated and :describedcertain specific apparatus for practicing :the method, :it

will be understood that various modifications and changes may be made .in the apparatus within the contemplation of our invention and under the scope of the following claims. We claim: 7

staybolt, and thereafter removing the rod and i any excess coating metal which may be present in the bolt and rapidly cooling the bolt at a rate suflicient to harden the head and freeze the coating metal before the coating metal sloughs off,

the coating metal being a solid at normal room temperature and being molten at the temperature of carburization, the bolts being maintained in an upright position throughout the heating and carburizing to prevent the coating metal from flowing .1

out of the interiors of the bolts.

2. The method of processing ferrous staybolts which have one end closed and which have a telltale hole therein opening through the other'end of the bolt which comprises setting the bolts upright with, the closed end down and supplying a charge of coating metal and flux to the interior of the bolt, thereafter placing a rod in the open end of the bolt and supporting it on the charge, heating the bolt while maintaining it in an upright position whereupon when said coating metal is melted the said rod sinks through the molten metal and forces it upwardly along the interior of the bolt, thereafter removing the rod and cooling the bolt, the coating metal being a metal of the group consisting of lead, zinc, and tin and their mixtures.

GROVER R. GREENSLADE. FREDERICK K. LANDGRAF.