Binding agent and feedstock preparation and removal methods for powder injection formingTechnical field
The invention belongs to powder metallurgical technology, be specifically related to a kind of powder injection forming binding agent, and relate to feedstock preparation and the removal methods of this powder injection forming binding agent.
Background technology
Powder injection forming (english abbreviation is that the English full name of PIM < is: Powder Injection Molding >) technology have workpiece, the workpiece size precision of the complicated shape that once can be shaped high, without machining and be easy to realize the strong points such as high-efficiency automatic production, thereby the extremely favor of industry.It is plastic shaping and the powder sintered forming technique combining, and evenly mixes with metal (pottery) powder by organic binder bond, is shaped and is obtained injection molded blank by mold injects, and injection molded blank, through degreasing, sintering, obtains near-net-shape workpiece.Aforesaid organic binder bond plays the effect for metal dust (metallurgical powder) mobility, and organic binder bond is broadly divided into following a few class: the one, and water-soluble binder; The 2nd, paraffinic base binding agent; The 3rd, mould based binder.Water-soluble binder is generally used for being difficult for the metallurgical powder that reacts with water, and its removal methods is injection moulding workpiece is soaked in water and to use and remove water-soluble constituent element; Paraffinic base binding agent adopts paraffin and high poly-composition, conventionally first removes the paraffin in injection member by organic solvent, then removes high polymer constituent element by the method for thermal decomposition.Although it is comparatively extensive that paraffinic base binding agent is applied in power injection molding, exist organic solvent to have the thickness of injury, injection moulding workpiece to be restricted to human body, because thickness is thicker, the time that removes is longer and production efficiency is restricted; Mould based binder taking polyformaldehyde as major components, taking polyethylene or polypropylene as skeleton constituent element, injection member first removes polyformaldehyde by red fuming nitric acid (RFNA), and skeleton constituent element removes in follow-up heating process.Mould based binder and water-soluble binder and paraffinic base binder phase comparatively speaking, there is the workpiece that removal efficiency is high and applicable forming thickness is larger.But it is large to mould based binder equipment investment, and pyrolysis product is poisonous, especially because China lacks desirable independent intellectual property right to moulding based binder, thereby can only be at high price to buying the feeding preparing abroad.
In disclosed Chinese patent literature, can be seen in the technical information about powder injection forming binding agent and feeding and removal methods, " preparation method of catalysis degreasing type adhesive for powder injection moulding and feeding thereof " who typically recommends as invention patent mandate notification number CN101353561B.The degreasing type adhesive of mentioning due to this patent belongs to aforementioned and moulds based binder category, thereby has aforesaid corresponding shortcoming." powder injection forming and micro-powder injection molding adhesive special and preparation method thereof " that and for example application for a patent for invention publication No. CN102719080A provides, the binding agent of mentioning due to this patent application scheme is aforesaid water-soluble binder, thereby there is aforesaid deficiency, and dusty material is had to fastidious property, water for example can not use for iron powder or iron alloy powder, because can cause iron powder and ferroalloy powder to get rusty.
For above-mentioned prior art situation, the applicant has done positive and useful exploration, and has formed technical scheme described below.
Summary of the invention
Top priority of the present invention is to provide a kind of powder injection forming binding agent, and that this binding agent has is easy to prepare, the strong adaptability to dusty material, raw material are cheap and easy to get and environmental protection and be easy to remove.
Another task of the present invention is to provide feedstock preparation and the removal methods of a kind of powder injection forming binding agent, the method processing step is terse, to thickness of workpiece without fastidious, removal effect good and not harsh to equipment requirement.
For having embodied top priority of the present invention, technical scheme provided by the invention is; A kind of powder injection forming binding agent, it is by forming by the raw material of mass percent proportioning below: Brazil wax 20-49%, naphthalene 50-70% and stearic acid 1-10%.
In a specific embodiment of the present invention, described Brazil wax is 49%, and naphthalene is 50%, and stearic acid is 1%.
In another specific embodiment of the present invention, described Brazil wax is 20%, and naphthalene is 70%, and stearic acid is 10%.
In another specific embodiment of the present invention, described Brazil wax is 35%, and naphthalene is 60%, and stearic acid is 5%.
For having embodied another task of the present invention, technical scheme provided by the invention is: feedstock preparation and the removal methods of binding agent for a kind of powder injection forming, comprise the following steps:
A) batch mixing, the metal dust that is 87-92% with binding agent and mass percent by the powder injection forming that is 8-13% by mass percent or ceramic powders drop in batch mixer and stir under heated condition, control heating-up temperature, control mixing speed and control mixing time, go out cooling after batch mixer and pulverize, transferring to screw extruder extrudes, obtain the feeding that injection moulding is used, wherein: described powder injection forming with binding agent by forming by the raw material of mass percent proportioning below: Brazil wax 20-49%, naphthalene 50-70% and stearic acid 1-10%;
B) injection moulding, will be by steps A) the injection moulding feeding obtaining introduces the hopper of injection machine, by injection machine injection moulding, obtains injection molded blank;
C) remove, will be by step B) injection molded blank that obtains introduces de-naphthalene in baking oven, and control oven temperature and control the de-naphthalene time, obtain metal works injection moulding and de-naphthalene or ceramic workpiece, remaining binding agent is removed by follow-up hot degreasing.
In another specific embodiment of the present invention, steps A) described in control heating-up temperature be to be 90-100 DEG C by heating and temperature control; Described control mixing speed is to be 500-700rpm by mixing speed control, and described control mixing time is to be 30-60min by mixing time control.
Also have in a specific embodiment steps A of the present invention) described in screw extruder extrude number of times for once or twice.
More of the present invention and in a specific embodiment, steps A) in before metal dust is dropped into batch mixer, first metal dust is carried out to anti-oxidation processing; Described anti-oxidation processing is that metal dust is introduced in the container that fills acetone and soaked, and the time of immersion is 3-5min.
In of the present invention and then a specific embodiment, step B) described in the temperature of injection moulding be 100-120 DEG C.
Of the present invention again more and in a specific embodiment, step C) described in to control oven temperature be to be 45-60 DEG C by oven temperature control, the de-naphthalene time of described control is that the de-naphthalene time is controlled is 150-330min.
Technical scheme provided by the invention is owing to having adopted Brazil wax, naphthalene and stearic acid to form powder injection forming binding agent, thereby the raw materials used kind of filling a prescription is few and simple, all can be suitable for metal and ceramic powders, and raw material is cheap and easy to get, and be easy to remove and have the good feature of environmental protection; The feedstock preparation providing and removal methods have processing step brief, require without harshness to thickness of workpiece strong adaptability, to equipment and removal effect good, can meet industrial amplification production requirement.
Detailed description of the invention
Embodiment 1:
A) batch mixing, be to heat while stirring in Stainless steel 316 L powder input batch mixer the powder injection forming that is 8% by mass percent with the trade mark that binding agent and mass percent are 92%, heating-up temperature is 100 DEG C, the mixing speed of batch mixer is 600rpm, mixing time is 30min, go out cooling after batch mixer and pulverize, transferring to screw extruder extrudes, extruding number of times is twice, after extruding for the first time, repeat again to extrude once, make feeding further even, obtain the feeding that injection moulding is used, in the present embodiment, aforesaid powder injection forming with binding agent by forming by the raw material of mass percent proportioning below: Brazil wax 49%, naphthalene 50% and stearic acid 1%, because the present embodiment is Stainless steel 316 L powder, therefore soak 3min dropping in the container that first its input is filled to acetone before batch mixer, make Stainless steel 316 L powder fully wetting, to embody the anti-oxidation processing to Stainless steel 316 L powder, because acetone can volatilize totally in follow-up batch mixing process, thereby exert an influence can to feeding ratio, in addition, as preferred scheme, also Brazil wax and stearic acid can be melted in advance and drop in batch mixer again,
B) injection moulding, by by steps A) feeding used of the injection moulding that obtains introduces the hopper of injection machine, by injection machine injection moulding, the temperature control of injection moulding is 110 DEG C, obtain injection molded blank, obtain powder of stainless steel injection molded blank, and the weight of record single injection molded blank now (extract one or several and weigh record), for example weight is m1;
C) remove, will be by step B) injection molded blank that obtains introduces de-naphthalene in baking oven, oven temperature control is 50 DEG C, the de-naphthalene time is controlled as 180min, goes out baking oven, obtains metal works injection moulding and de-naphthalene, and record the single-piece weight of metal works, for example weight is m2, determines the removal efficiency of naphthalene according to the difference of m2 and m1, and the constituent element of remaining binding agent is if Brazil wax, stearic acid are by follow-up hot degreasing removal.
Embodiment 2:
A) batch mixing, the zirconia ceramics powder that is 87% with binding agent and mass percent by the powder injection forming that is 13% by mass percent drops in batch mixer and heats while stirring, heating-up temperature is 90 DEG C, the mixing speed of batch mixer is 500rpm, mixing time is 60min, go out cooling after batch mixer and pulverize, transferring to screw extruder extrudes, extruding number of times is twice, after extruding for the first time, repeat again to extrude once, make feeding further even, obtain the feeding that injection moulding is used, in the present embodiment, aforesaid powder injection forming with binding agent by forming by the raw material of mass percent proportioning below: Brazil wax 20%, naphthalene 70% and stearic acid 10%, in addition, Brazil wax and stearic acid can be melted in advance, drop into again in batch mixer,
B) injection moulding, by by steps A) feeding used of the injection moulding that obtains introduces the hopper of injection machine, by injection machine injection moulding, the temperature control of injection moulding is 120 DEG C, obtain injection molded blank, obtain zirconia ceramics powder injection molded blank, and the weight of record single injection molded blank now (extract one or several and weigh record), for example weight is m1;
C) remove, will be by step B) injection molded blank that obtains introduces de-naphthalene in baking oven, oven temperature control is 55 DEG C, the de-naphthalene time is controlled as 300min, goes out baking oven, obtains ceramic workpiece injection moulding and de-naphthalene, and record the single-piece weight of ceramic workpiece, for example weight is m2, determines the removal efficiency of naphthalene according to the difference of m2 and m1, and the constituent element of remaining binding agent is removed by follow-up hot degreasing as Brazil wax and stearic acid.
Embodiment 3:
Only by steps A) in the mass percent of the binding agent used of powder injection forming change 11% into, using Stainless steel 316 L powder instead mass percent is 89% iron powder or ferroalloy powder, the heating-up temperature of batch mixer changes 95 DEG C into, mixing speed changes 600rpm into, mixing time is 45min, change the mass percent of Brazil wax into 35%, change the mass percent of naphthalene into 60%, change stearic mass percent into 5%, the number of times of extruding of screw extruder is changed into 1 time, change the soak time in acetone into 5min; By step B) in the temperature of injection moulding change 100 DEG C into; By step C) in oven temperature change 45 DEG C into, the de-naphthalene time changes 240min into.All the other are all with the description to embodiment 1.