CN103196755A

CN103196755A - Method for measuring combination strength of investment casting shells

Info

Publication number: CN103196755A
Application number: CN2013101053020A
Authority: CN
Inventors: 郭馨; 吕志刚
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2013-03-28
Filing date: 2013-03-28
Publication date: 2013-07-10
Anticipated expiration: 2033-03-28
Also published as: CN103196755B

Abstract

The invention discloses a method for measuring combination strength of investment casting shells. The method comprises the following steps of: (1) gradually preparing a multi-layer shell I in a wax mould recess, and grinding the part not being filled by the shells I on the upper part of the recess to make the depth of the recess be equal to the average thickness of the shells; (2) splicing wax moulds to form a wax mould III provided with a recess and utilizing the shells I and a wax plate as bottom surface, and gradually preparing a multi-layer shell II in the recess; (3) clamping a step-shaped shell obtained by dewaxing or roasting in a mould of a universal tester, locating the shell by the cooperation of fillers, baffles and upper and lower moulds with the universal tester, and measuring the combination strength of the layers; and (4) calculating shear strength T through critical load F and shearing area A, T is equal to F/A. The method for measuring combination strength of investment casting shells disclosed by the invention can be used for accurately locating the combination surface of the layers of the shell to directly measure the combination strength of the layers, the preparation of the shell is in accordance with the actual condition, the reliability is strong, the operation is simple, and the problem that the combination force of the investment casting shells is difficult to evaluate is solved.

Description

A kind of method of measuring bond strength between investment casting shell

Technical field

The present invention relates to the investment casting shell technical field, be specifically related to a kind of method of measuring bond strength between investment casting shell.

Background technology

In the investment cast, shell is the die cavity of metal liquid moulding, and its quality will produce material impact to foundry goods.Because shell is layering preparation, two interlayers in conjunction with situation audient multifactor impact, the shakiness of any technological process is established a capital and may be caused two-layer separation and fragmentation to be peeled off, and causes one of major defect of investment-casting---be mingled with.Especially, the different layers of shell generally is that interlayer is very complicated in conjunction with situation by the different slurry viscosities of different materials or same material, stucco size composition.

The relevant report that does not also have at present investment casting shell interlayer adhesion to measure, adhesion detection means commonly used is not suitable for the mensuration of shell interfacial bonding strength.The interlayer adhesion of shell is very big, surpass general adhesive strength, and the intensity of shell own, especially normal temperature strength is not high, can't bear the local acting force that clamps, so it can't make the method that sticks with glue or be installed and break.Shell prepares at wax-pattern, and hanging and stucco process have certain randomness, and sample thickness there are differences, and the interlayer faying face is the uneven surface that is a mass of the stucco particle, makes the location of shell interlayer faying face very difficult.Shell interfacial bonding strength and preparation process are closely related, only the shell of under the actual process condition, preparing could characterize shell interlayer in conjunction with situation, for the mensuration of bond strength has increased difficulty.

Summary of the invention

In order to solve the problem that above-mentioned prior art exists, the object of the present invention is to provide a kind of method of measuring bond strength between investment casting shell, have the high and characteristics simple to operate of measurement result reliability.

For reaching above purpose, the present invention adopts following technical scheme:

A kind of method of measuring bond strength between investment casting shell is estimated the shell interlayer in conjunction with situation by the shear resistance between the shell faying face, comprises the steps:

Step 1: the preparation of shell specifically comprises the steps:

1): in the groove I2 of the wax-pattern I1 that has groove 2, successively prepare shell I3, the preparation multilayer makes the gross thickness of shell I3 greater than 2mm, polish off the part that groove top is not filled by shell I3 then, form the wax-pattern I4 after the polishing, make the depth of groove of the wax-pattern I4 after the polishing identical with shell I3 average thickness;

2): width is identical with wax-pattern I4 after the polishing, have a wax-pattern I4 splicing after groove II6, bottom one side do not have wax-pattern and do not have the area at wax-pattern place the wax-pattern II5 identical with the top surface area of the wax-pattern I4 after the polishing and polishing, wax-pattern I4 after the polishing is placed no wax-pattern place, wax-pattern II5 bottom, form new groove wax-pattern III7, successively prepare shell II8 then in the groove II6 of groove wax-pattern III7, the preparation multilayer makes its thickness greater than 4mm;

3): the above-mentioned wax-pattern for preparing shell I3 and shell II8 is dewaxed, obtain the stepped shell 9 that shell I3 links to each other with shell II8, be used for the mensuration of normal temperature bond strength; Or continue stepped shell 9 is carried out roasting and is cooled to room temperature, be used for the mensuration of residual bond strength;

Step 2: measure and calculate the shear resistance between shell, specifically comprise the steps:

1): the length of measurement shell I3 and shell II8 surface of contact and wide, and the calculating surface of contact is the shear zone area A;

2): be the lower platform 11 that universal testing machine is fixed in the bottom of the counterdie 10 of U-lag with top, then stepped shell 9 is placed counterdie 10 tops, the surface of contact of shell I3 and shell II8 and the center of counterdie 10U shape groove are leveled up and down, shell I3 places the bottom, in shell II8 counterdie 10U shape groove on one side, fill full filling material 12, in the groove of counterdie 10, insert baffle plate 13, the patrix 14 that will the have cutting head then universal testing machine of packing into moves in the draw-in groove 15, make the cutting head blade parallel with shell and place between the surface of contact of shell I3 and shell II8, open universal testing machine, make the cutting head blade cut shell I3 and shell II8, read critical load F by dynamometer simultaneously;

3): usefulness critical load F and shear zone area A are calculated shear resistance τ: τ=F/A, measure a plurality of test pieces, remove the bigger data of deviation, the shell I(3 that on average obtains) and shell II(8) normal temperature bond strength or residual bond strength.

The cutting head thickness of knife edge of described patrix 14 is 1mm, and the translational speed of cutting head is 0.5～5mm/min.

Advantage of the present invention is as follows:

1) adopt the present invention can directly record the interfacial bonding strength of investment casting shell.To the accurate location of faying face, the stencil plate of splicing can be fitted shell and cutting head fully during stepped sample had guaranteed to test, and guaranteed that pressure vertically acts on faying face;

2) technological process of the preparation of investment shell sample and actual shell comprises the infiltration conditionally complete unanimity of interlayer, can finish in factory, laboratory etc., actual response the interlayer of investment casting shell in conjunction with situation;

3) the present invention utilizes the location of realizing shell that cooperates of filling material, baffle plate and upper and lower mould and universal testing machine, has reduced the requirement to investment shell intensity;

4) mould of the present invention can be loaded into universal testing machine, test method is simple, be applicable to the shell of different materials, different-thickness, the various stucco granularities of moltening mold castings are all had good pardon (the shell roughness of stucco coarse size is big), can realize the interfacial bonding strength evaluation of various shells.

Description of drawings

Fig. 1 is the preparation flow synoptic diagram of shell of the present invention.

Fig. 2 measures the assembling synoptic diagram of the interlaminar shear strength of investment casting shell for the present invention utilizes universal testing machine.

Fig. 3 is the patrix structural representation.

Fig. 4 is the counterdie structural representation.

Embodiment

Below in conjunction with drawings and the specific embodiments, the present invention is described in further detail.

Interfacial bonding strength with mensuration titanium alloy investment cast shell yttria surface layer commonly used and bauxite transition bed is example.

As shown in Figure 1, successively prepare yttria surface shell I3 in the groove I2 of the wax-pattern I1 that has 20mm*10mm groove 2, the viscosity of slurry, stucco granularity are consistent with practical condition, 20 ℃ of baking temperatures, drying time 24h.After preparing three layers, the gross thickness of shell I3 is about 2.5mm, polish off the part that groove top is not filled by shell I3, form the wax-pattern I4 that has the yttria shell after the polishing, make the depth of groove of the wax-pattern I4 that has the yttria shell after the polishing identical with shell I3 average thickness.To note avoiding wax material to sneak into the yttria shell in the time of polishing.

Then with have after width and the polishing wax-pattern I4 of yttria shell identical, have 20mm*40mm groove II6, bottom one side do not have wax-pattern and do not have the area at wax-pattern place and polishing after have the wax-pattern I4 splicing that has the yttria shell after the identical wax-pattern II5 of the top surface area of wax-pattern I4 of yttria shell and the polishing, the wax-pattern I4 that has the yttria shell after the polishing is placed no wax-pattern place, wax-pattern II5 bottom, form new groove wax-pattern III7, note avoiding wax material to infiltrate the yttria shell during splicing.Then among the groove II6s of groove wax-pattern III7 successively prepare bauxite shell II8 when reaching 24h the drying time for the treatment of the 3rd layer of yttria shell.The viscosity of slurry, stucco granularity are consistent with practical condition, 20 ℃ of baking temperatures, drying time 24h.After preparing four layers, its thickness is about 4mm, for increasing the flatness of shell, is convenient to be installed, and has done the envelope slurry at last and has handled.

The wax-pattern that will prepare yttria surface shell I3 and bauxite shell II8 at last dewaxes, and obtains the stepped shell 9 that shell I3 links to each other with shell II8, is used for the mensuration of normal temperature bond strength; Or continue stepped shell 9 is carried out roasting and is cooled to room temperature, being used for the mensuration of residual bond strength, the preparation of shell is finished like this.

Utilize the length of vernier caliper measurement shell I3 and shell II8 surface of contact and wide, and to calculate surface of contact be the shear zone area A.

As shown in Figure 2, be the lower platform 11 that universal testing machine is fixed in the bottom of the counterdie 10 of U-lag with top, then stepped shell 9 is placed counterdie 10 tops, the surface of contact of shell I3 and shell II8 and the center of counterdie 10U shape groove are leveled up and down, shell I3 places the bottom, in shell II8 counterdie 10U shape groove on one side, fill full filling material 12, the filling material of present embodiment is wax disk(-sc) and wax bar, in the groove of counterdie 10, insert baffle plate 13, the patrix 14 that will the have cutting head then universal testing machine of packing into moves in the draw-in groove 15, make the cutting head blade parallel with shell and place between the surface of contact of shell I3 and shell II8, open universal testing machine, make the cutting head blade cut shell I3 and shell II8, it is 2mm/min that present embodiment is set the cutting head translational speed, reads critical load F by dynamometer simultaneously;

Utilize τ=F/A to calculate the interlaminar shear strength of shell.Measure a plurality of test pieces, remove the bigger data of deviation, on average obtain normal temperature bond strength or the residual bond strength of this investment shell sample yttrium oxide layer and bauxite layer.

As shown in Figure 3, be patrix structural representation of the present invention, the lower end of patrix 14 has cutting head, and the thickness of preferred cutting head is 1mm.

As shown in Figure 4, be counterdie structural representation of the present invention, the top of counterdie 10 is U-lag, the bottom for ease of with the fixing boss of the lower platform of universal testing machine, the U-lag outside is provided with is convenient to the groove that baffle plate inserts.

Claims

1. a method of measuring bond strength between investment casting shell is characterized in that: estimate the shell interlayer in conjunction with situation by the shear resistance between the shell faying face, comprise the steps:

Step 1: the preparation of shell specifically comprises the steps:

1) successively prepares shell I(3 groove I(2: at the wax-pattern I(1 that has groove (2)))), the preparation multilayer make shell I(3) gross thickness greater than 2mm, polish off groove top then not by shell I(3) part of filling, form the wax-pattern I(4 after the polishing), make the wax-pattern I(4 after the polishing) depth of groove and shell I(3) average thickness is identical;

2): with the wax-pattern I(4 after width and the polishing) identical, have a groove II(6), bottom one side do not have wax-pattern and do not have the area at wax-pattern place and the wax-pattern I(4 after the polishing) the identical wax-pattern II(5 of top surface area) with polishing after wax-pattern I(4) splicing, with the wax-pattern I(4 after the polishing) place wax-pattern II(5) no wax-pattern place, bottom, form new groove wax-pattern III(7), then at groove wax-pattern III(7) groove II(6) in successively prepare shell II(8), the preparation multilayer make its thickness greater than 4mm;

3): with the above-mentioned shell I(3 for preparing) and shell II(8) wax-pattern dewax, obtain shell I(3) with shell II(8) the stepped shell (9) that links to each other, be used for the mensuration of normal temperature bond strength; Or continue stepped shell (9) is carried out roasting, be used for the mensuration of residual bond strength;

1): measure shell I(3) and shell II(8) length of surface of contact and wide, and the calculating surface of contact is the shear zone area A;

2): be the lower platform (11) that universal testing machine is fixed in the bottom of the counterdie (10) of U-lag with top, then stepped shell (9) is placed counterdie (10) top, make shell I(3) and shell II(8) surface of contact and the center of counterdie (10) U-lag be leveled up and down, shell I(3) places the bottom, at shell II(8) fill completely filling material (12) on one side counterdie (10) U-lag, in the groove of counterdie (10), insert baffle plate (13), the patrix (14) that will the have cutting head then universal testing machine of packing into moves in the draw-in groove (15), make the cutting head blade parallel with shell and place shell I(3) and shell II(8) surface of contact between, open universal testing machine, make the cutting head blade cut shell I(3) and shell II(8), read critical load F by dynamometer simultaneously;

2. a kind of method of measuring bond strength between investment casting shell according to claim 1, it is characterized in that: the cutting head thickness of knife edge of described patrix (14) is 1mm, the translational speed of cutting head is 0.5～5mm/min.