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GB/T 14235 comprises the following parts under the general title Low temperature pattern wax materials for investment casting:
—— Part 1: Testing methods for physical properties;
—— Part 2: Testing methods for usability properties.
This is part 1 of GB/T 14235.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
This part replaces GB/T 14235.1-1993 Testing method for melting point of pattern materials for investment casting, GB/T 14235.3-1993 Testing method for ash content of pattern materials in investment casting, GB/T 14235.4-1993 Testing method for linear contraction of pattern materials in investment casting, GB/T 14235.6-1993 Testing method for acid number of pattern materials in investment casting, GB/T 14235.7-1993 Testing method for fluidity of pattern materials in investment casting, and GB/T 14235.8-1993 Testing method for viscosity of pattern materials in investment casting.
This part is an integrated revision of six standards, including GB/T 14235.1-1993, GB/T 14235.3-1993, GB/T 14235.4-1993, GB/T 14235.6-1993, GB/T 14235.7-1993, and GB/T 14235.8-1993. The following main technical changes have been made with respect to the previous standards:
—— GB/T 14235.1-1993 is replaced with testing method for softening point;
—— GB/T 14235.4-1993 is replaced with testing method for linear shrinkage;
—— the solvent used in the acid value testing is modified and the amount of solvent added in the blank test is specified (see 5.4.4 of this standard, and 5.1 of GB/T 14235.6-1993);
—— the testing method for fluidity in GB/T 14235.7-1993 is deleted;
—— the format of test report is modified (see clause 8 of this standard);
—— Annex A gives a comparison of the differences between this part and the previous standards.
This part was proposed by and is under the jurisdiction of SAC/TC 54 the National Technical Committee on Foundry of Standardization Administration of China.
The previous editions replaced by this part are as follows:
——GB/T 14235.1-1993;
——GB/T 14235.3-1993;
——GB/T 14235.4-1993;
——GB/T 14235.6-1993;
——GB/T 14235.7-1993;
——GB/T 14235.8-1993.
Low temperature pattern wax material for investment casting - Part 1: Testing methods for physical properties
1 Scope
This part of GB/T 14235 specifies the testing methods for softening point, rotational viscosity, acid number, linear shrinkage and ash content of low temperature pattern wax materials for investment casting and the basic requirements for test reports.
This part is applicable to testing physical properties of low temperature pattern wax materials for investment casting.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 514-2005 Specification for liquid-in-glass thermometers for testing of petroleum products
GB/T 601 Chemical reagent - Preparations of reference titration solutions
GB/T 602 Chemical reagent - Preparations of standard solutions for impurity
GB/T 603 Chemical reagent - Preparations of reagent solutions for use in test methods
GB/T 1800.1-2009 Geometrical product specifications (GPS) - Limits and fits - Part 1: bases of tolerances, deviations and fits
GB/T 6682-2008 Water for analytical laboratory use - Specification and test methods
3 Testing method for softening point
3.1 Overview of testing method for softening point of low temperature pattern wax materials
Place two horizontal specimen discs in a shoulder or conical brass ring, which is heated in distilled water at a certain speed. On each specimen disc there is a steel ball. The softening point shall be the average value of the temperatures measured when the specimens are softened to make the two steel balls on them sink by 25 mm.
3.2 Instruments and apparatus
3.2.1 Rings: two brass shoulder rings or conical rings, with dimensions and specifications shown in Figures 1a) and 1b).
3.2.2 Support plate: flat and smooth brass plate, with a dimension of about 50 mm×75 mm.
3.2.3 Steel balls: two steel balls in a diameter of 9.5 mm, each weighing (3.50±0.05) g.
3.2.4 Steel ball fixtures: two steel ball fixtures which are used to fix the steel column in the center of the specimen; see Figure 1c) for the general shape and dimension.
3.2.5 Bath: A heatable glass container with an inner diameter of not less than 85 mm and a depth of not less than 120 mm from the bottom to be heated.
3.2.6 Ring bracing frame and bracket: a copper bracing frame which is used to support the two rings at horizontal position; see Figure 1d) for its shape and dimension, and Figure 1e) for its installation drawing. The bottom of the shoulder ring on the bracing frame shall be 25 mm from the upper surface of the lower support plate, and the lower surface of the lower support plate shall be (16±3) mm from the bottom of the bath.
3.2.7 Thermometers: they shall conform to the technical requirements for GB-42 thermometer as specified in GB/T 514-2005, namely total immersion thermometers capable of measuring temperatures ranging from 30 ℃ to 180 ℃, with a minimum dividing value of 0.5 ℃.
Suspend an appropriate thermometer on the bracket as shown in Figure 1e) so that the bottom of the mercury bulb is parallel to the bottom of the ring, with a spacing of less than 13 mm, but it shall not contact the ring or the bracing frame. Such a thermometer shall not be replaced with other ones.
3.2.8 Knife: to cut the pattern wax materials.
3.2.9 Electric furnace: to heat the pattern wax materials.
In: mm
a) Shoulder ring
b) Conical ring
Note: This diameter is about 0.05 mm greater than that of the steel ball (9.5 mm), so that it can fix the steel ball in the center exactly.
c) Steel ball fixture
In: mm
Note: With a diameter of 19.0mm, it can be precisely fit into the shoulder ring.
d) Bracket
e) Aggregate unit
Figure 1 Rings, steel ball fixtures, bracket, and aggregate unit
3.3 Reagents and materials
Heating medium: distilled water.
3.4 Preparation of specimen
3.4.1 Heat the specimens of pattern wax material with electric furnace. After the pattern wax material is completely melted, increase the temperature by 20 ℃ and keep stirring the pattern wax material to make it mix evenly. After the bubbles contained escape, pour a slightly excessive amount of specimen into each ring and cool the specimens at room temperature for at least 30 min. The preparation and testing of all specimens of the pattern wax material shall be completed within 6 h.
3.4.2 If the test is repeated, the samples shall not be reheated, and specimens shall be prepared again with fresh samples in a clean container.
3.4.3 After the specimens are cooled, scrape off the residual specimen with a knife or scraper so that each disc is full and flush with the top of the ring.
3.5 Test procedure
3.5.1 Fill distilled water into the bath and place the bath in cooling water so that the initial temperature of distilled water reaches (5±1) ℃.
3.5.2 Place the instruments in the fume hood and configure two sample rings and steel ball fixtures, insert the thermometers into appropriate positions, fill the bath with distilled water, and situate the instrument at appropriate positions. Place the steel balls at the bottom of the bath with tweezers to so that they have the same initial temperature as other parts of the bracket. Finally, insert the thermometers into appropriate positions. Clamp the steel balls at the bottom of the bath again with tweezers and place them into the fixture.
3.5.3 Heat the bottom of the bath so that the temperature rises at a constant rate of 5 ℃/min. During the test, the average heating rate shall not be taken, but after 3 min, the heating rate shall reach (5±0.5) ℃/min. If the temperature rise rate exceeds this limit, the test will fail.
3.5.4 When the balls on the two test rings just come into contact with the lower support plate, record the temperatures displayed on the thermometers respectively, and take the average as the softening point of the pattern wax material. If the difference between the two temperatures exceeds 1 ℃, repeat the test.
3.6 Measurement accuracy and error
3.6.1 Repeatability
The difference between the results of two repeated testing shall not exceed 1.0 ℃.
3.6.2 Reproducibility
The difference between the test results provided by two laboratories for the same specimen shall not exceed 1.5 ℃.
4 Testing method for rotational viscosity
4.1 Overview of testing method for rotational viscosity of low temperature pattern wax materials
The change of viscosity of the liquid pattern wax material at the specified temperature is measured by changing the shearing rate of the rotor on the rotational viscometer.
4.2 Instruments and apparatus
Instruments for rotational viscosity testing:
—— Rotational viscometer: with a measurement range of 0.01 Pa s ~ 10 Pa s, and a measurement error of 5%.
—— Precision Mercury-in-glass thermometer: with a temperature range of 50 ℃ ~ 100 ℃, and a minimum scale division of 0.1 ℃.
—— Thermostatic bath: with a temperature control precision of ±1 ℃.
—— Mercury-in-glass thermometer: partial immersion type; with a temperature measuring range of 0 ℃ to 200 ℃, and a minimum scale division of 1 ℃.
—— Barrel-shaped specimen container: with a diameter not less than 35 mm, depth not less than 165 mm; suitable for single-rotor viscometer.
Foreword i
1 Scope
2 Normative references
3 Testing method for softening point
4 Testing method for rotational viscosity
5 Testing method for acid number
6 Testing method for linear shrinkage
7 Testing method for ash content
8 Test report
Annex A (Informative) Comparison of the structure difference between the new and previous standards
Annex B (Informative) Specimen for linear shrinkage testing
