Method of debinding for injection molded objects

Abstract: A debinding method for use in a process for producing a sintered object, by effecting a debinding pre-treatment by heating the injection-molded object in an atmosphere of reduced pressure at a temperature at which the vapor pressure of the component of the organic binder having the highest vapor pressure does not exceed the pressure of the atmosphere, thereby removing the organic binder in the amount of at least about 18 wt%; and effecting a further debinding heat treatment in which the injection-molded object is heated to and maintained at a temperature higher than the temperature in the debinding pre-treatment.

Description: The present invention relates to a method of producing a debound object, for subsequent sintering, by removing binder from shaped objects formed by injection molding a binder and a powder of, for example, metal, ceramic or cermet. Injection molding is a well-known technique suitable for use in the production of sintered objects having complicated configurations from powders such as metal powders, ceramics and cermets. Since organic binders are needed in the procedure, objects that are injection molded from such binder-containing powder require debinding, i.e., removal of the binder components. Various debinding methods have been proposed for this purpose. For instance, Japanese Patent Publication No. 61-48563 discloses a debinding method in which an injection-molded object containing binder components is placed on a binder absorbing body and is then heated so that the binder components elute in the liquid phase in the order of their melting points, i.e. such that the binder component having the lowest melting point is extracted first. An inert gas is supplied to the injection-molded object and to the binder absorbing body so as to promote evaporation of the extracted liquified binder components. This method basically relies upon elution of the binder components in the liquid phase, so that the resulting debound object inevitably has defects in the surface which was in contact with the binder absorption material. When the rate of elution of the binder component is small, the strength of the injection-molded object is reduced since molten binder component remains in the injection-molded object; this often results in defects such as droop. United States Patent No. 4,404,166 discloses a debinding method in which an unsaturated, chemically inert atmosphere is blown over the injection-molded object to cause the atmosphere proximate to the surface of the object to be turbulent and unsaturated, thereby removing a predetermined amount of binder components. Unfortunately, however, this method also fails to provide a solution to the problem of defect generation. Defect generation is also encountered with other known techniques. The present invention aims to provide a debinding method appropriate for injection-molded objects which is capable of effecting debinding without reducing the dimensional precision of the debound object and while eliminating defect generation, thereby overcoming the problems of the prior art. Another aim of the invention is to provide a method for making injection-molded objects from a mixture containing a binder and removing all or part of the binder after molding without significantly distorting the shape of the object. According to the present invention there is provided a method of producing a debound object by injection molding a mixture of a powder and an organic binder, wherein the organic binder includes one or more thermoplastic resins and one or more plasticiser components, to form a shaped object and subjecting the shaped object to a debinding heat treatment to remove binder characterised in that the debinding heat treatment includes: a) subjecting the shaped object to a debinding pre-treatment step in which the shaped object is heated, under a pressure which is less than atmospheric pressure, to a first temperature of not more than 300°C and which is less than the temperature at which the vapour pressure of a most volatile component of the organic binder is equal to said pressure, in order to remove at least 18% by weight of the total amount of organic binder, and b) thereafter subjecting the shaped object to further heat treatment at a second temperature which is greater than the first temperature, in order to complete debinding. The present invention is based upon a detailed study conducted by the present inventors on the mechanism of defect generation during the production of sintered objects from fine powders by injection molding. The invention provides a debinding method for use in a process for producing sintered objects. The sintered object is prepared by admixing the powder and the organic binder (generally comprising plasticizer components and binder components); subjecting the resulting admixture to injection molding to form an injection-molded object; removing part or all of the organic binder from the injection-molded object to obtain a debound object; and sintering the debound object in a heated atmosphere to form a sintered object. The debinding method of the present invention includes the steps of (a) effecting a debinding pretreatment step by heating the injection-molded object in a reduced pressure atmosphere to a temperature at which the vapour pressure of the most volatile component of the organic binder does not exceed the pressure of the surrounding atmosphere at the pressure of the surrounding atmosphere, and (b) effecting a subsequent debinding heat treatment step in which the injection-molded object is heated to and maintained at a temperature higher than the temperature used in the debinding pre-treatment step (a), thereby removing sufficient organic binder without significantly distorting the shape of the object. The deformation, in particular the droop, of the injection-molded object during debinding is dependant on the viscosity of the material of the inject-molded object. More specifically, less deformation occurs when the viscosity of the material is increased. However, the viscosity of the material of the injection-molded object varies with the temperature and the extent of binder removal. A higher viscosity results when the temperature is lowered and the extent of binder removal is increased. Thus, both a reduction in the viscosity (due to a temperature increase) and an increase in the viscosity (due to binder removal) take place simultaneously as the injection-molded object is heated. In order to prevent deformation, and in particularly droop during debinding, it is necessary to remove sufficient binder while the temperature of the injection-molded object is still relatively low, and whilst the viscosity of the material is still high enough, so that the object will have a high enough viscosity to resist deforming on heating to a higher temperature. The present invention effectively achieves this goal by exploiting the phenomenon that the evaporation temperature of the plasticiser component (which may be a wax and a plasticizer) of the binder is lowered when the pressure of the surrounding atmosphere is lowered. The debinding method used in the present invention is characterised by the combination of a debinding pre-treatment and a subsequent debinding heat treatment. It will be appreciated that the organic binder used in the practice of this invention may comprise one or more binder components and one or more plasticizer components, and that when more than one binder component is used the different binder components may have different vapour pressure-temperature relationships. The debinding pretreatment according to this invention involves heating the injection molded object to a temperature at which the vapour pressure of the most volatile binder component is less than the pressure of the surrounding atmosphere. If this condition is not met the binder tends to evaporate in the injection molded object, thereby causing unwelcome expansion or inflation of the object. The pre-debound object obtained by the debinding pre-treatment in accordance with the present invention is resistant to deformation during the subsequent debinding heat-treatment. There is no practical limitation on the pressure of the atmosphere in which the debinding pre-treatment is conducted, provided that a sufficiently large reduction in the evaporation temperature of the plasticizer component of the binder is obtained as a result of a reduction in the applied pressure. However, in general the pre-treatment atmospheric pressure is preferably not higher than 1.33 x 10³Pa (10 Torr), more preferably not higher than 1.33 x 10²Pa (1 Torr). Typical examples of plasticizer components of the binder include phthalate esters and paraffin waxes; these generally exhibit boiling temperatures ranging between about 250 and 350°C and between about 350 and 450°C, respectively. The temperatures at which these plasticizer components exhibit a vapour pressure of 1.33 x 10³Pa (10 Torr) are between 130 and 180°C and between 180 and 250°C, respectively. When the temperatures of these plasticizer components are reduced to below about 130°C and below about 180°C, respectively, the vapour pressure is reduced to 1.33 x 10²Pa (1 Torr). Removal of the plasticizer component of the binder at a low temperature cannot be effected satisfactorily without a reduction in the evaporation temperature, and thus a reduction in the pressure of the pre-treating atmosphere. Preferably, the debinding pre-treatment is conducted at a temperature which is 10°C or more lower than the temperature at which the vapour pressure of the most volatile binder component equals the pressure of the pre-treatment atmosphere. The debinding pre-treatment is performed effectively when the pre-treatment temperature is not greater than about 300°C. Pre-treatment at temperatures above about 300°C tends to cause decomposition of the thermoplastic resin which is the major binder component. Monomer components produced as a result of the decomposition of the resin are vapourised immediately since the boiling temperatures of the monomers are lower than the temperature at which the decomposition reaction occurs. Thus, the gas pressure is influenced by the speed or rate of the decomposition reaction. The speed or rate of the decomposition reaction is in turn influenced by factors such as the temperature or the number of remaining bonds in a partially decomposed resin. It is therefore difficult to maintain the gas pressure below the pressure of the surrounding atmosphere at temperatures above about 300°C. Consequently, the risk of debinding defects occurring increases if the pressure of the atmosphere is reduced at temperatures exceeding 300°C. For this reason, the effective upper limit of the debinding pre-treatment temperature is preferably about 300°C. More specifically, the maximum debinding pre-treatment temperature is preferably selected within the range of from about 100 to 200°C, while the debinding pre-treatment time is not more than about 10 hours. Even when the organic binder contains two or more plasticizer components adequate pre-treatment temperatures can be easily determined, based on the nature of the components. It is necessary that about 18 wt% or more of the total amount of binder is removed by the novel debinding pre-treatment of this invention. When the amount of the binder removed by the pre-treatment is below about 18 wt%, it is virtually impossible to obtain an appreciable rise in the viscosity which is caused by mutual contact of powder particles in the injection molded object. In addition, the viscosity is undesirably lowered when the temperature is raised, with consequent deformation of the injection molded object. In practice it is therefore necessary to remove about 18 wt% or more of the total amount of the binder in the novel debinding pre-treatment. It is thus possible to obtain a pre-debound object which, when subjected to subsequent debinding heat treatment, does not exhibit any significant deformation, since the debinding pre-treatment was conducted under the conditions described above. The subsequent debinding heat treatment is conducted, so that the debound object is obtained with a high dimensional precision, i.e, without any significant deformation. The maximum debinding heat treating temperature in this step preferably ranges from about 450 to 650°C, and the holding time for heat treatment is preferably not more than about 6 hours. Too rapid a temperature rise of the pre-debound object may cause difficulties such as cracking or inflation; the rate of temperature rise, therefore, is preferably selected to be in the range between 5°C/h and 300°C/h. The debinding heat treatment is preferably conducted in a non-oxidizing atmosphere, more preferably in a nitrogen atmosphere, an argon atmosphere or a mixture of nitrogen and argon. The debinding method of the present invention is used in the production of sintered objects. Thus, the steps executed before and after the debinding may be those which are ordinarily employed in the production of sintered objects. The powder used in the method of the present invention may be metal, ceramic or cermet powder. The powder may be particles of an alloy or a metal obtained through a suitable procedure such as atomizing, reduction, a carbonyl process, pulverising and so forth, or ceramic or cermet particles. The powder is prepared by classifying and/or blending desired powders. The use of the atomizing method is preferred because other methods such as the reduction method, the carbonyl process and pulverising restrict the kinds of powder compositions that can be used. The powder conveniently used in the present invention has a mean particle size of about 20µm or smaller. In order to obtain a sintered object with superior properties, it is preferable that the powder has a mean particle size of about 7 to 14µm. The powder can be chosen from a wide selection of materials, for example stainless steel, pure iron, an Fe-Ni alloy, an Fe-Si alloy, an Fe-Co alloy and so forth, or a ceramic material such as SiC, Si₃N₄, SiO₂, TiC and so forth, or magnetic materials or cermets. Production of an injection-molded object is accomplished as follows: the powder material, which may be one of the above-mentioned materials, preferably having a mean particle size not greater than about 20 µm, is mixed and kneaded together with the organic binder as a molding aid, to prepare an injection molding mixture. Any known organic binders, which are mainly composed of a thermoplastic resin, a wax, a plasticizer or a mixture thereof may be used. A lubricant, a debinding promoter and/or another additive or additives may be included as required in the binder. Suitable thermoplastic resins include acrylic resins, polyethylene resins, polypropylene resins and polystyrene resins. Any of these resins may be used singly, or in combination as a resin mixture, when formulating the binder. The plasticizer may be selected as appropriate to the composition of the main component of the binder. Examples of suitable plasticizers are di-2-ethylhexyl phthalate (DOP), diethyl phthalate (DEP) and di-n-butyl phthalate (DBP). A wax also can serve as a plasticizer. Suitable waxes include natural waxes, for example beeswax, Japan wax or montan wax, and synthetic waxes, for example low-molecular weight polyethylene, microcrystalline wax and paraffin wax. These waxes may be used singly or in combination as a wax mixture. Examples of suitable lubricants include higher fatty acids, fatty acid amides and fatty acid esters. When a wax is used, the wax can serve also as a lubricant. The debinding promoter may be a substance capable of sublimation such as camphor, for example. In connection with the above, it is desirable that the organic binder is mainly composed of a thermoplastic resin, a wax, and a plasticizer or a plasticizer mixture, wherein the total amount of wax and plasticizer is not less than about 18 wt% of the total amount of the organic binder. The mix ratio of the binder to the material powder generally ranges between about 50:50 and 40:60 parts by volume. The powder and the binder may be mixed in any suitable manner and apparatus such as a pressurizing kneader, a Banbury mixer or a twin extruder may be used for mixing the powder and the binder. The injection molding mixture thus prepared may be pelletized by means of a pelletizer or a pulverizer. The injection molding mixture is then injection molded to form the shaped object. The injection molding step can be effected using an ordinary injection molding machine suitable for plastics, or an injection molding machine for ceramics and metal powders. The injection molding step is preferably conducted at an injection pressure of from about 3.92 x 10⁷ to 2.45 x 10⁸Pa (400 to 2500 kgf/cm²) and at a temperature of from about 10 to 180°C. The resulting injection-molded object is then subjected to debinding heat treatment in accordance with the present invention. The debinding is conducted by the debinding pre-treatment combined with the subsequent debinding heat treatment described previously. In the present invention, pressure control of the atmosphere in the pre-debinding process can be achieved by using a heating furnace provided with a gas inlet port for introducing a small amount of gas, as well as a gas discharging system for evacuating the furnace. The debound object is sintered following the debinding heat treatment to produce a metallic or ceramic sintered object. When the powder is a stainless steel, sintering may be achieved by maintaining the debound object in a reduced pressure atmosphere of about 1.33 to 1.33 x 10⁻² Pa (10⁻² to 10⁻⁴ Torr) at 1050 to 1300°C for about 0.5 to 4 hours, introducing an inert gas such as argon or nitrogen, and holding the object from about 0.5 to 2 hours at an elevated temperature of about 1200 to 1370°C. When the powder contains metal having a limited tendency toward oxidation, such as Fe, Fe-Ni or an Fe-Co alloy, sintering may be effected by maintaining the object at a temperature of about 800 to 1300°C in a reducing gas atmosphere such as hydrogen gas for 0.5 to 4 hours. In the case where metal having a strong tendency toward oxidation is used, such as Fe-Si, sintering is conducted in the same manner as that described for stainless steel. Using the series of steps described in this invention enables metallic or ceramic sintered objects having superior properties to be obtained. The steps comprising the debinding pre-treatment, the subsequent debinding heat treatment and the sintering may be conducted in independent furnaces or in a common furnace or oven. These steps may be executed according to any of the following methods: (1) a method in which each of these steps is carried out in a single furnace or oven, (2) a method in which any two successive steps are carried out in a single furnace or oven while the other step is carried in a different furnace or oven, or (3) all the three steps are executed in a single common furnace or oven. When two consecutive steps are executed in a single furnace or oven it is not necessary to cool the object between the steps unless the properties of the object need to be checked after completion of the earlier step. It will be appreciated that the omission of any cooling of the object in such an intermediate period contributes to an energy saving. The invention is further described with reference to the following examples of the invention which are illustrative of the invention. EXAMPLE 1 Power was prepared from stainless steel SUS 316 L in which the mean particle diameter was 10 µm. A binder was prepared which contained 22 wt% of phthalate ester, 18 wt% of paraffin wax and 60 wt% of methacrylate ester-vinyl acetate copolymer. The binder was mixed with the powder, in an amount of 9.8 wt% of binder to the powder, using a pressurizing kneader. The mixture was then pulverized to provide a mixture suitable for injection molding. Test pieces were fabricated from this mixture in rectangular parallelepiped form, 20 mm long, 5 mm wide and 5 mm high. The test pieces were placed in a stainless steel sheet in an oven such that one of the longer surfaces of each test piece contacted the stainless steel sheet. Steps (a) and (b) were then performed in accordance with the present invention. Alternatively, steps (c) and (d) were then performed for comparative purposes. (a) The test piece was heated to 70°C at a rate of 150°C/h and at a pressure of 133Pa (1 Torr), and was held at this temperature for 8 hours to conduct a debinding pre-treatment. The extent of the removal of the binder resulting from this pre-treatment was 22.0 wt% based upon the total weight of the test piece. (b) The test piece was heated to 70°C at a rate of 150°C/h and at a pressure of 133Pa (1 Torr), and was held at this temperature for 8 hours. The test piece was further heated to 150°C at a rate of 150°C/h and held for 1 hour at that temperature, thereby concluding the debinding pre-treatment. The extent of the removal of the binder resulting from this pre-treatment was 32.4 wt% based upon the total weight of the test piece. Subsequently, debinding heat-treatment was performed by heating the test piece to 650°C at a rate of 5°C/h in a nitrogen gas atmosphere at 1.01 x 10⁵Pa (1 atmosphere) pressure and holding it at this temperature for 30 minutes. (c) Debinding heat treatment was performed by heating the test piece to 650°C at a rate of 5°C/h in a nitrogen gas atmosphere at 1.01 x 10⁵Pa (1 atmosphere) pressure and holding it as this temperature for 30 minutes. (d) Debinding heat treatment was performed by heating the test piece to 650°C at a rate of 20°C/h in a nitrogen gas atmosphere at 1.01 x 10⁵Pa (1 atmosphere) pressure and holding it as this temperature for 30 minutes. Each test piece was then subjected to a sintering process in which the test piece was held for 90 minutes at a pressure of 0.133Pa (0.001 Torr) and a temperature of 1150°C, and, after introducing argon gas at 1.01 x 10⁵Pa (1 atmosphere) pressure, each test piece was heated to and maintained at 1350°C for 2 hours. The sintered test pieces were visually checked and changes of dimension and sintering properties were measured; the results of these measurements are shown in Table 1. In this Example, phthalic acid ester and paraffin wax were used as the plasticizer components. The phthalic acid ester and paraffin wax exhibited boiling points of about 115°C and 165°C at a total pressure of 133Pa (1 Torr). Thus, the vapour pressure of these plasticizers did not exceed 133Pa (1 Torr) under the conditions of the debinding pre-treatment step (a) mentioned above. It will be seen that the debinding pre-treatment step (a) enabled the phthalic acid ester to be removed completely, because the amount removed by this treatment equalled the amount initially added. Therefore, subsequent heating to 150°C did not result in the vapour pressures of the binder components exceeding the pressure of the treating atmosphere. In Table 1, a change in dimensions exceeding -0.3% suggests that droop had taken place due to flow of the binder resin. The heightwise contraction of the sintered products obtained according to this Example of the invention was 16.5% which means that the height should be reduced to 4.175 mm on sintering. Taking into account a tolerance of ± 0.3%, samples having heights ranging between 4.162 mm and 4.188 mm were and are regarded as having good or acceptable dimensional precision. EXAMPLE 2 Debinding pre-treatment was executed on the same test pieces as Example 1, under the treating conditions shown in Table 2. Then, debinding heat-treatment was conducted under the same conditions as step (a) in Example 1, followed by sintering. The results of visual appearance checks of the pre-debounded test pieces and of the debound test pieces, as well as the results of measurements of heightwise dimensions of the test pieces after debinding and after sintering, are also shown in Table 2. From the test results shown in Tables 1 and 2, it can be seen that the debinding method of the present invention enabled sintered objects to be produced with a high dimensional precision which could not be attained by conventional methods. EXAMPLE 3 Test pieces corresponding to run Nos. 1-1 to 1-3 in Table 2, obtained through debinding pre-treatments according to the present invention and having different rates of binder removal, were subjected to debinding heat-treatments by heating these test pieces from room temperature to 270°C at a rate of 100°C/h in a nitrogen gas atmosphere at a pressure of 1.01 x 10⁵Pa (1 atmosphere), holding the test pieces under these conditions for 30 minutes, heating the test pieces to 650°C at a rate of 300°C/h and maintaining the test pieces at this temperature and pressure for 30 minutes. The test pieces were cooled after the debinding pre-treatment. For the purpose of comparison, pre-debound test pieces were directly subjected to the debinding heat treatment without cooling, by introducing nitrogen gas at 1.01 x 10⁵Pa (1 atmosphere) pressure, heating the test pieces to 270°C at a rate of 100°C/h, maintaining the test pieces under these conditions for 30 minutes, heating the test pieces to 650°C at a rate of 300°C/h and holding the test pieces at this temperature for 30 minutes. These test pieces were then subjected to sintering in the same manner as those in Example 1. The results of visual appearance checks of the test pieces after debinding, and of heightwise dimension measurements after debinding and after sintering are shown in Table 3. In the method of the present invention, the binder is removed in an amount of at least about 18 wt% by the debinding pre-treatment. It will be appreciated that sound debound objects can be obtained irrespective of any intermediate cooling after the debinding pre-treatment and regardless of whether the heating is executed at a high rate of 100 to 300°C/h (see samples Nos. 4-1, 4-2, 5-1 and 5-2 in Table 3) or at a relatively low rate of 5°C/h (see samples Nos. 1-1 and 1-2 in Table 2). It will also be seen that, if the extent of binder removal is below 18 wt% after the debinding pre-treatment, the quality of the debound object is reduced due to inflation which occurs when the debinding heat treatment is conducted at a high rate of temperature increase (as in the cases of samples Nos.4-3 and 5-3 in Table 3). If the extent of binder removal is below about 18 wt% defects such as droop also occur; this appears as a large negative dimensional change when the debinding heat treatment is performed at a low rate of temperature rise (as in the case of sample No. 1-3 in Table 2). It can therefore be seen that the debinding pre-treatment executed in accordance with the present invention provides the additional advantage that debinding heat treatment at elevated temperatures, can be accomplished in a shorter time because heating can be performed more rapidly, regardless of whether or not cooling is performed after the debinding pre-treatment. Debinding process Appearance Dimensional Change (%) Height change (mm) Density ratio (%) C content (%) O content (%) Remarks (a) Good -0.165 4.167 96.4 0.03 0.15 Sample according to invention (b) Good -0.173 4.163 96.2 0.02 0.12 Sample according to invention (c) Defect in bottom surface -5.23 3.971 96.4 0.02 0.10 Comparison sample (d) Inflation Not measurable Comparison sample

Claims: A method of producing a debound object by injection molding a mixture of a powder and an organic binder, wherein the organic binder includes one or more thermoplastic resins and one or more plasticiser components, to form a shaped object and subjecting the shaped object to a debinding heat treatment to remove binder characterised in that the debinding heat treatment includes: a) subjecting the shaped object to a debinding pre-treatment step in which the shaped object is heated, under a pressure which is less than atmospheric pressure, to a first temperature of not more than 300°C and which is less than the temperature at which the vapour pressure of a most volatile component of the organic binder is equal to said pressure, in order to remove at least 18% by weight of the total amount of organic binder, and b) thereafter subjecting the shaped object to further heat treatment at a second temperature which is greater than the first temperature, in order to complete debinding. A method as claimed in claim 1 wherein the organic binder includes at least 18% by weight of the plasticiser component. A method as claimed in claim 1 or 2 wherein the organic binder further includes a lubricant and/or a debinding promoter. A method as claimed in claim 1, 2 or 3 wherein the first temperature is from not less than 100°C to not more than 200°C. A method as claimed in claim 1, 2, 3 or 4 wherein the first temperature is at least 10°C lower than the temperature at which the vapour pressure of the most volatile component equals said reduced pressure. A method as claimed in any one of claims 1 to 5 wherein the second temperature is from not less than 450°C to not greater than 650°C. A method as claimed in any preceding claim wherein the reduced pressure is not more than 1.33 x 10³Pa (10 Torr). A method as claimed in any preceding claim wherein the holding time of the debinding pre-treatment step is not more than 10 hours. A method as claimed in any preceding claim wherein the rate of further heating is from not less than 5° C/h to not more than 300° C/h. A method as claimed in any preceding claim wherein the debinding heat treatment is performed in a non-oxidising or an inert gas atmosphere. A method as claimed in any preceding claim wherein the powder has a mean particle size of not more than 20 µm. A method as claimed in any preceding claim wherein the mean particle size is from not less than 7 µm to not greater than 14 µm. A method as claimed in any preceding claim wherein the powder is selected from: stainless steel, iron, iron-nickel alloy, iron-silicon alloy, iron-cobalt alloy, SiC, Si₃N₄, SiO₂ and TiC. A method as claimed in any preceding claim wherein the binder comprises from not less than 40 to not more than 50 % by volume of the shaped mixture. A method of producing a sintered object comprising producing a debound object by the method claimed in any preceding claim and sintering the debound object.

Inventors: KIYOTA YOSHISATO TECHNICAL RES, MATSUSHITA MASAKAZU TECHNICAL, OHTA JUNICHI TOKYO HEAD OFFICE, OHTSUBO HIROSHI TECHNICAL RESE, KIYOTA, YOSHISATO TECHNICAL RESEARCH DIVISION, MATSUSHITA, MASAKAZU TECHNICAL RESEARCH DIVISION, OHTA, JUNICHI TOKYO HEAD OFFICE KAWASAKI ST. CORP., OHTSUBO, HIROSHI TECHNICAL RESEARCH DIVISION
Applicants: KAWASAKI STEEL CO, KAWASAKI STEEL CORPORATION
Application year: 1989
Main classification: B22F3
IPC codes: B22F3, C04B35