CN113084718B - Forming and sintering process of metal bond diamond grinding head - Google Patents
Forming and sintering process of metal bond diamond grinding head Download PDFInfo
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- CN113084718B CN113084718B CN202110391722.4A CN202110391722A CN113084718B CN 113084718 B CN113084718 B CN 113084718B CN 202110391722 A CN202110391722 A CN 202110391722A CN 113084718 B CN113084718 B CN 113084718B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
- B24D18/00—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for
- B24D18/0009—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for using moulds or presses
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
- B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
- B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
- B24D3/04—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially inorganic
- B24D3/06—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially inorganic metallic or mixture of metals with ceramic materials, e.g. hard metals, "cermets", cements
- B24D3/10—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially inorganic metallic or mixture of metals with ceramic materials, e.g. hard metals, "cermets", cements for porous or cellular structure, e.g. for use with diamonds as abrasives
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Abstract
The invention provides a forming and sintering process of a metal bond diamond grinding head, belonging to the technical field of powder metallurgy, and the process comprises the following steps: cold press molding the diamond grinding head powder, and then baking to obtain a plurality of split blanks; embedding and assembling a plurality of the split blanks to obtain a diamond grinding head blank; sintering the diamond grinding head blank in vacuum to obtain a metal bond diamond grinding head; and in the diamond grinding head blanks, the radial contact surfaces between two adjacent split blanks are coated with a mixing agent, and the mixing agent comprises a metal bonding agent and a binding agent. The process adopts a sectional molding-embedding sintering mode, solves the problems of cracking and holes after the metal bond diamond grinding head with large length-diameter ratio is sintered, improves the yield and reduces the cost.
Description
Technical Field
The invention belongs to the technical field of powder metallurgy, and particularly relates to a forming and sintering process of a metal bond diamond grinding head.
Background
Sapphire, optical glass, crystalline silicon, alumina, zirconia ceramic and other materials belong to hard and brittle materials. Due to its excellent optical, mechanical and dielectric properties, it is widely used in many fields including photovoltaic power generation, semiconductors, consumer electronics, etc. The hard and brittle material is processed mainly through the links of blank material selection, directional cutting, rough grinding, precise grinding, polishing, ultra-precise polishing, detection, application and the like, and with the continuous improvement of the technical level, the high hard and brittle material can be processed through the links of cutting, grinding, polishing, drilling and the like by a machine tool, and finally, the processing requirement is met. Because hard and brittle materials are difficult to process, diamond grinding heads are generally adopted in the industry for drilling, milling, punching and edge sweeping. The diamond is the substance with highest hardness in nature, and is fixed on the substrate in an electroplating or bonding manner by a bonding agent, so that various diamond grinding heads can be formed. The electroplating grinding head is characterized by better shape retention, low cost and defects of too short service life and larger pollution in the production process. The metal bond sintering grinding head can realize multilayer self sharpening, has long service life, does not cause environmental pollution in the production process, gradually improves the performance in recent years, has gradually competitive cost performance, and has the tendency of replacing the backward electroplating grinding head.
In some hard and brittle material processing with special requirements, such as optical glass chamfering, in order to improve efficiency, a plurality of pieces of optical glass are often stacked, and then a diamond grinding head is used for processing the edge of the optical glass by using the side edge part of the diamond grinding head. The efficiency of the processing mode is greatly improved, and the chamfering processing of dozens of pieces of optical glass can be finished by one-time circular processing of the diamond grinding head. Or, the processing side usually designs and arranges a plurality of edge-shaped areas with different shape requirements on the grinding head along the axial direction for the cost of the grinding head, so that the grinding head can be processed in different sizes, and the grinding head can complete the work of a plurality of grinding heads only by setting different cutting depths.
The application scenes of the two grinding heads are widely applied in the industry, and at present, a large number of grinding heads are electroplated with diamond, but a few sintered grinding heads are applied. The grinding head has the advantages that the axial size of the grinding head is long, the length-diameter ratio is large, the manufacturing process of the electroplating grinding head is naturally free of any problem, but if the metal binding agent sintering grinding head is used, the pressure forming-high-temperature sintering process is inevitably involved, the pressure is difficult to conduct smoothly in metallurgical powder in the pressure forming process due to the large length-diameter ratio, the pressure intensity in each part of the pressed blank is different, cracking, hole breaking and other phenomena can occur during high-temperature sintering, the yield is greatly reduced, and the cost is increased. Alternatively, the grinding head can be manufactured by hot pressing/hot isostatic pressing, but the equipment cost is huge and the process is also very complicated. Therefore, the application of the metal bond diamond sintering grinding head in the processing scenes is greatly limited by the cost problem, and the huge technical advantages of the original sintering grinding head to the electroplating grinding head are difficult to exert in the field.
Disclosure of Invention
In order to solve the technical problem that the existing forming and sintering process is difficult to manufacture the diamond grinding head with large length-diameter ratio, the invention provides the forming and sintering process of the metal bond diamond grinding head.
The invention is realized by the following technical scheme:
the application provides a shaping sintering process of metal bond diamond bistrique, technology includes:
cold press molding the diamond grinding head powder, and then baking to obtain a plurality of split blanks;
embedding and assembling a plurality of the split blanks to obtain a diamond grinding head blank;
sintering the diamond grinding head blank in vacuum to obtain a metal bond diamond grinding head;
and in the diamond grinding head blank, the radial contact surface between two adjacent split blanks is coated with a mixing agent, and the mixing agent comprises a metal bonding agent and a bonding agent.
Optionally, in the diamond bistrique material base, adjacent two through connector and spread groove gomphosis each other between the components of a whole that can function independently material base, the connector with the spread groove sets up adjacent two respectively on the terminal surface of components of a whole that can function independently material base, the connector with the radial contact surface coating of spread groove has the mixing agent.
Optionally, a gap is formed between the outer wall of the connector and the inner wall of the connecting groove, and the following relationship exists between the size of the gap and the diameter of the split blank:
the diameter of the split blank is 6-12 mm, and the size of the gap is 0.1-0.2 mm;
the diameter of the split blank is 12-18 mm, and the size of the gap is 0.2-0.3 mm;
the diameter of the split blank is more than or equal to 18mm, and the size of the gap is 0.3-0.4 mm.
Optionally, the split blank is cylindrical, the length-diameter ratio of the split blank is less than or equal to 2, and the length of the split blank is 15-50% of that of the diamond grinding head blank.
Optionally, before the plurality of split blanks are subjected to tabling assembly, coating and drying of the mixture are completed;
in the mixture, the mass ratio of the metal bonding agent to the binder is 8-15: 1;
the mass of the mixing agent coated on the radial contact surface between two adjacent split blanks is 0.5-1 g.
Optionally, the diamond grinding head powder is subjected to cold press molding and then baked to obtain a plurality of split blanks, and the method specifically comprises the following steps:
cold pressing the diamond grinding head powder for molding, maintaining the pressure for 3-5 min after point pressing for 10-15 times under the pressure of 30-50 Mpa, wherein the pressure in the mold is 150-200 Mpa in the pressure maintaining process, and then baking for 6-8 h under the temperature of 80-120 ℃ to obtain a plurality of split blanks.
Optionally, the axial length of the diamond grinding head blank is 110-130% of the axial length of the metal bond diamond grinding head, and the diameter of the diamond grinding head blank is 110-125% of the diameter of the metal bond diamond grinding head.
Optionally, the vacuum sintering specifically includes:
a first temperature rise stage: raising the temperature to 200 ℃ at room temperature, wherein the required time is 15-20 min, and keeping the temperature for 10-15 min;
a second temperature rise stage: heating to 600 ℃, keeping the temperature for 25-35 min, and keeping the temperature for 10-15 min;
a third temperature rise stage: heating to 850-900 deg.c for 20-25 min and maintaining for 10-15 min;
a first cooling stage: cooling to 600 ℃, wherein the required time is 30-40 mm;
and a second cooling stage: naturally cooling to room temperature at 600 ℃;
in the vacuum sintering, the air pressure is controlled to be less than or equal to 1 x 10 -3 pa。
Optionally, the preparation method of the diamond grinding head powder comprises the following steps:
mixing a metal binder, diamond powder and an additive according to the mass ratio of 1: 0.05-0.15: 0.025-0.05 to obtain a mixture:
mixing the mixture with a binder to obtain the diamond grinding head powder;
wherein the mass of the binder is 5-10% of the mass of the mixture;
the additive comprises at least one of graphite, silicon carbide, ceramic microspheres and tungsten powder.
Optionally, the chemical composition of the metal bond comprises, in mass fraction:
tin: 30% -50%, copper: 40-60%, titanium: 2-15 percent of the total weight of the components, and the proportion of other components is less than or equal to 10 percent;
the components of the binder comprise at least one of cellulose, water, ethanol and isopropanol in mass fraction.
One or more technical schemes in the invention at least have the following technical effects or advantages:
1. the invention relates to a molding and sintering process of a metal bond diamond grinding head, which is characterized in that cold press molding is carried out on diamond grinding head powder to obtain a plurality of split blanks, the split blanks are embedded and assembled into a complete diamond grinding head blank, and then vacuum sintering is carried out.
2. The invention relates to a forming and sintering process of a metal binder diamond grinding head, wherein a mixing agent is coated on the radial contact surface between two adjacent split blanks, the mixing agent comprises a metal binder and a binder, the purpose of coating the mixing agent is to utilize the lower liquid phase point of a pure metal binder to melt, wet and strengthen the welding effect on the assembly surfaces of the two adjacent split blanks, in the vacuum sintering process, the split blanks are firstly changed into a solid-liquid mixed phase from a loose powder solid phase, and then are gradually cooled and changed into a compact solid phase from the solid-liquid mixed phase, in the process, the binder in an assembly gap is firstly liquefied and flows, the assembly gap between the radial contact surfaces is filled, the split blanks on the two sides are wetted, and when the split blanks start to generate solid-liquid phase conversion along with the increase of the temperature, the split blanks can be fused with the binder into a whole, so as to realize the fusion of the radial contact surfaces of the two adjacent split blanks.
The above description is only an overview of the present invention,
in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the content of the specification, and in order to make the above and other objects, features and advantages of the present invention more comprehensible, specific embodiments thereof are described below.
Drawings
In order to more clearly illustrate the technical solutions in the present application, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a flow chart of a forming and sintering process of a metal bond diamond grinding head according to the present invention;
FIG. 2 is a schematic view of the cold press molding of split preforms according to example 1 of the present invention;
FIG. 3 is a schematic view of cold press molding of a split preform II according to example 1 of the present invention;
FIG. 4 is a schematic view showing the fitting of the split preforms in example 1 of the present invention;
FIG. 5 is a schematic view of a dispensing position according to the present invention;
fig. 6 is a schematic view of a metal bond diamond grinding head made in example 1 of the present invention.
In the figure: 1-upper pressing ring, 2-lower pressing plate, 3-split material blank I, 4-split material blank II, 5-mould, 6-connecting groove, 7-connecting head, 8-gap, 9-dispensing position, 10-metal bond diamond grinding head and 11-steel substrate.
Detailed Description
The present invention will be specifically explained below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly presented thereby. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
It should be further noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
It is noted that, in this document, relational terms such as "first" and "second," and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.
In order to solve the technical problems, the general idea is as follows:
the existing common pressure forming-sintering process can be divided into cold pressing and hot pressing, wherein the cold pressing comprises common cold pressing and cold isostatic pressing, and the hot pressing comprises common hot pressing and hot isostatic pressing. The most common, and also the least costly, cold-pressed sintering method is a low-cost process for obtaining high-density powder metallurgical components, and process research has focused on producing powder metallurgical components with the highest possible density. In order to reduce the friction between the die wall and the powder during the pressing process and improve the density and uniformity of the unsintered part, a lubricant is added during the mixing of the element powder in the conventional powder pressing and sintering processes, but the large amount of residual lubricant limits the densification of the pressed part and reduces the wet strength. Therefore, the residual lubricant is removed at the initial stage of sintering, and the lubricant is melted at 150 ℃ and starts to decompose at about 600 ℃. Decomposition of the lubricant reduces the sintered density and, on the other hand, the gas in the pores of the compact also reduces the density of the part. For the conditions of high requirement on the pressed compact, large volume of the pressed compact and complex shape, an isostatic pressing technology can be adopted, rubber or plastic is usually used as a sheathing die material, and liquid is used as a pressure medium to provide uniform pressure forming pressed compact. The pressure is generally 100 to 630MPa. As a molding process, compared with the conventional cold press molding technology, the density of the isostatic pressing molded product is high, and is generally 5-15% higher than that of one-way and two-way compression molding.
The disadvantages of the above technique are: cold press forming usually adopts the mould to come the integrated molding, and is comparatively good to less blank, but to in above-mentioned processing scene, the major diameter of work portion is bigger bistrique, and the pressed compact that needs the shaping also has its special shape, and cold press forming's pressure conduction is always an old and difficult problem. The pressure distribution in the pressed blank can be improved by designing a mold core, and the self friction of powder can also be improved by adding a lubricant, but the improvement has considerable limitations. If the pressure inside the pressed compact is unevenly distributed, the phenomena of cracking, holes and the like are easy to occur in the sintering process, and the product is scrapped.
The characteristics of hot-pressing sintering: because the hot-pressing sintering is carried out simultaneously by heating and pressurizing, the powder is in a thermoplastic state, which is beneficial to the contact diffusion of particles and the process of flow mass transfer, and the forming pressure is only 1/10 of that of cold pressing; but also can reduce the sintering temperature and shorten the sintering time, thereby resisting the growth of crystal grains and obtaining products with fine crystal grains, high density and good mechanical and electrical properties. The powder metallurgy product with ultrahigh purity can be produced without adding sintering aids or molding aids.
The hot isostatic pressing process is to place the product inside a sealed container and apply the same pressure and high temperature to the product to sinter and densify the product. Hot isostatic pressing is an indispensable means for high performance material production and new material development; hot isostatic pressing can be performed by direct powder molding, the powder is filled in a sheath (similar to the action of a mold), the sheath can be made of metal or ceramics (low-carbon steel, ni, mo, glass and the like), and then nitrogen and argon are used as pressurizing media to directly heat, pressurize and sinter the powder.
The disadvantages of the above technique are: the hot pressing/hot isostatic pressing mode has high requirement on equipment, and one piece of equipment is more than millions of yuan, so that the hot pressing/hot isostatic pressing mode is mostly applied to the industries with higher added values, such as aerospace, military industry, high-precision processing and the like, and is difficult to widely popularize in the common civil market.
Based on the above, the invention develops a sectional embedded type molding and sintering process for a metal bond diamond grinding head, which utilizes the densification and shrinkage phenomena generated during solid-liquid phase transition in the sintering process of metal bond powder and adopts a sectional molding-embedded sintering process, thereby solving the problems of sintering cracking and holes caused by uneven pressure conduction and inconsistent density of single large pressed compact, improving the yield, reducing the cost and being suitable for manufacturing the metal bond diamond sintering grinding head with large length-diameter ratio (the ratio of axial length to radial diameter).
According to an exemplary embodiment of the present invention, there is provided a shape sintering process of a metal bond diamond grinding head, as shown in fig. 1, the process including:
s1, carrying out cold press molding on diamond grinding head powder, and then baking to obtain a plurality of split blanks;
s2, embedding and assembling the split blanks to obtain diamond grinding head blanks;
s3, carrying out vacuum sintering on the diamond grinding head blank to obtain a metal bond diamond grinding head;
and in the diamond grinding head blank, the radial contact surface between two adjacent split blanks is coated with a mixing agent, and the mixing agent comprises a metal bonding agent and a bonding agent.
The invention adopts the modes of sectional molding and embedding assembly sintering, for the diamond grinding head with large length-diameter ratio, the length-diameter ratio of a single split blank is smaller, the problems that the pressure is difficult to be smoothly conducted in metallurgical powder in the pressure molding process caused by large length-diameter ratio, so that the pressure intensity in each part inside the pressed blank is different, cracking, hole breaking and the like can occur during high-temperature sintering are solved, the yield of the diamond grinding head with large length-diameter ratio is improved, the cold press molding and vacuum sintering processes are adopted, the requirement on equipment is low, and the production cost of the diamond grinding head with large length-diameter ratio is further reduced.
In the invention, the radial contact surface between two adjacent split blanks is coated with a mixing agent, the mixing agent comprises a metal binder and a binder, the purpose of coating the mixing agent is to utilize the lower liquidus point of a pure metal binder to play roles of melting, wetting and reinforcing welding on the assembly surfaces of the two adjacent split blanks, in the vacuum sintering process, the split blanks are firstly changed from a loose powder solid phase into a solid-liquid mixed phase, and then are gradually cooled from the solid-liquid mixed phase into a compact solid phase, in the process, the binder in an assembly gap is liquefied and flows in advance, the assembly gap between the radial contact surfaces is filled, simultaneously the split blanks on two sides are wetted, and along with the increase of the temperature, when the split blanks start to generate solid-liquid phase conversion, the split blanks and the binding agent are fused into a whole, so that the fusion of the radial contact surfaces of the two adjacent split blanks is realized.
As an optional implementation mode, in the diamond grinding head material base, adjacent two through connector and spread groove gomphosis each other between the components of a whole that can function independently material base, the connector with the spread groove sets up adjacent two respectively on the terminal surface of components of a whole that can function independently material base, the connector with the radial contact surface coating of spread groove has the admixture.
In this application, adjacent two through connector and spread groove gomphosis each other between the components of a whole that can function independently material base, aim at makes adjacent two cooperate closely between the components of a whole that can function independently material base, avoid the interval too big to lead to being difficult to the sintering to become a whole.
As an alternative embodiment, a gap is formed between the outer wall of the connecting head and the inner wall of the connecting groove, and the size of the gap and the diameter of the split blank have the following relationship:
the diameter of the split blank is 6-12 mm, and the size of the gap is 0.1-0.2 mm;
the diameter of the split blank is 12-18 mm, and the size of the gap is 0.2-0.3 mm;
the diameter of the split blank is more than or equal to 18mm, and the size of the gap is 0.3-0.4 mm.
In the application, the gap is different according to the diameter of the blank, and because the split blank can generate radial contraction in the sintering process, the gap can be gradually reduced and attached along with the solid-liquid phase transition of the blank, and the blank are integrated in a high-temperature heat preservation section, and the whole assembly body forms a compact whole after being cooled.
In this application, the components of a whole that can function independently blank after the stoving is cracked easily, the assembly of being not convenient for, design clearance between the outer wall of connector and the inner wall of spread groove, can avoid at assembly gomphosis in-process, connector outer wall and spread groove inner wall produce along axial friction, lead to the powder on inner wall and the outer wall to drop, the clearance size increases along with the increase of components of a whole that can function independently blank diameter to be favorable to going on smoothly of assembly gomphosis process.
On the other hand, the reason for designing the clearance is that: during sintering of the diamond grinding head blank, when solid-liquid phase is converted, large volume shrinkage can be generated, the shrinkage direction is radial or axial, the gap is designed for radial shrinkage, and the radial shrinkage is more severe when the diameter of the blank is larger. For the connector part, as the steel substrate penetrates through the inner core of the blank in the sintering process, the radial shrinkage space of the connector is limited, and more axial shrinkage can be generated; the blank part outside the connecting groove is sleeved on the periphery of the connector, the local diameter of the blank on the periphery is larger, so that severe shrinkage can be caused, the radial shrinkage amount of the blank is different from that of the embedded connector, if a gap is not designed, a free shrinkage space is provided for the blank on the outside, the connector can be extruded in the shrinkage process of solid-liquid phase transformation, and the phenomena of bulging, deformation and even holes can be caused after sintering, and after the reserved gap is filled by the blank shrinkage effect, a plurality of split blanks also form a complete compact body.
As an optional embodiment, the split blank is cylindrical, the length-diameter ratio of the split blank is less than or equal to 2, and the length of the split blank is 15-50% of that of the diamond grinding head blank.
In this application, the draw ratio of components of a whole that can function independently blank is less than or equal to 2, can effectively avoid because of great draw ratio for among the pressure forming process, pressure is difficult to smoothly conduct in the metallurgical powder, makes the inside pressure of pressed compact everywhere differ, can appear the fracture when high-temperature sintering, phenomenons such as broken hole, and the length of components of a whole that can function independently blank is 15 ~ 50% of diamond bistrique blank length, can divide it into 2 ~ 5 sections components of a whole that can function independently blank shaping resintering according to actual diamond bistrique draw ratio, through reducing single components of a whole that can function independently blank draw ratio, improves sintering bistrique yield.
As an alternative embodiment, the coating and drying of the mixture is done before the fitting of several of the separate blanks;
in the mixture, the mass ratio of the metal bonding agent to the binder is 8-15: 1;
the mass of the mixing agent coated on the radial contact surface between two adjacent split blanks is 0.5-1 g.
In this application, the metal bond with the mass ratio of binder is 8 ~ 15:1, the benefit is the bonding agent powder and the binder mixing, the viscosity and the mobility of mucus are good, be fit for the mixer and stir, still can dry into moderate dry powder granule of size after stirring, the dry powder granule is good at the cold pressing technology fluidity, be convenient for shaping, the mixing dose of the radial contact surface coating between two adjacent components of a whole that can function independently blanks is 0.5 ~ 1g, can play the effect of effective welding components of a whole that can function independently blank after melting, the quantity is low excessively, then can not effectively weld, the too high component that can influence diamond bistrique blank splice constitutes, thereby influence the mechanical properties and the durability of diamond bistrique.
As an optional embodiment, the diamond grinding head powder is subjected to cold press molding and then is baked to obtain a plurality of split blanks, and the method specifically comprises the following steps:
cold press molding the diamond grinding head powder, performing 30-50 Mpa point pressing for 10-15 times, then maintaining the pressure for 3-5 min, wherein the pressure in the die is 150-200 Mpa in the pressure maintaining process, and then baking for 6-8 h at 80-120 ℃ to obtain a plurality of split blanks.
In this application, cold press forming adopts above-mentioned technological parameter, can effectively realize the shaping of components of a whole that can function independently blank, and the guarantee pressure smoothly conducts in metallurgical powder, makes the inside pressure of pressed compact everywhere balanced, avoids appearing phenomenons such as fracture, broken hole when high temperature sintering, and the purpose of toasting is to increase components of a whole that can function independently blank intensity to do benefit to the gomphosis assembly.
As an alternative embodiment, the axial length of the diamond grinding head blank is 110 to 130% of the axial length of the metal bond diamond grinding head, and the diameter is 110 to 125% of the diameter of the metal bond diamond grinding head.
In the application, the size of the split blank is designed by considering the clearance and sintering shrinkage: the total axial length of the assembled diamond grinding head blank is 110-130% of the finished product length, and the total radial diameter is 110-125% of the finished product diameter.
As an optional embodiment, the vacuum sintering specifically includes:
a first temperature rise stage: raising the temperature to 200 ℃ at room temperature, carrying out heat preservation for 10-15 min after the required time is 15-20 min;
a second temperature rise stage: heating to 600 ℃, keeping the temperature for 25-35 min, and keeping the temperature for 10-15 min;
a third temperature rise stage: heating to 850-900 deg.c for 20-25 min and maintaining for 10-15 min;
a first cooling stage: cooling to 600 ℃, wherein the required time is 30-40 mm;
and a second cooling stage: naturally cooling to room temperature at 600 ℃;
the vacuum firingIn the structure, the air pressure is controlled to be less than or equal to 1 x 10 -3 Pa。
In the present application, a conventional sintering process may be adopted in the vacuum sintering process, and the above process may also be referred to.
As an alternative embodiment, the preparation method of the diamond grinding head powder comprises the following steps:
mixing a metal binder, diamond powder and an additive according to the mass ratio of 1: 0.05-0.15: 0.025-0.05 to obtain a mixture:
mixing the mixture with a binder to obtain the diamond grinding head powder;
wherein the mass of the binder is 5-10% of the mass of the mixture;
the additive comprises at least one of graphite, silicon carbide, ceramic microspheres and tungsten powder.
In the application, the diamond grinding head powder is conventional powder, and the diamond grinding head powder with the components can also be adopted, in the sintering process, the blank is changed from a solid phase to a solid-liquid mixed phase and then changed into the solid phase, the structure of the blank is also changed from a loose structure to a compact structure, the volume of the blank shrinks towards the center, the diamond grinding head powder adopts the components and the proportion, and the radial shrinkage can be controlled to be 10-15% in the sintering process.
In the present application, the following relationship is satisfied between the dosage ratio and the particle size of diamond powder:
the mass ratio of the diamond powder of 200 meshes to the metal binding agent is 1: 8-10;
the mass ratio of the 300-mesh diamond powder to the metal bond is 1: 10-12;
the mass ratio of the 400-mesh diamond powder to the metal bonding agent is 1: 12-15;
the mass ratio of the 600-mesh diamond powder to the metal bonding agent is 1: 15-20.
As an alternative embodiment, the chemical composition of the metal bond includes, in mass fraction:
tin: 30% -50%, copper: 40% -60%, titanium: 2-15 percent of the total weight of the components, and the proportion of other components is less than or equal to 10 percent;
the granularity of the metal bonding agent is less than or equal to 200 meshes;
the components of the binder comprise at least one of cellulose, water, ethanol and isopropanol in mass fraction.
In the application, the metal bonding agent adopts a conventional bonding agent of a metal bonding agent diamond grinding head, and the metal bonding agent has the function of forming a solid phase structure after sintering, so that the requirement of the overall dimension of a processing condition is met; in addition, a mechanical embedding and wrapping structure is formed on the diamond, and the diamond is held; finally, materials such as Cu, sn and Ti in the bonding agent can form chemical covalent bonds with diamond, the holding force on diamond abrasive particles is further enhanced, the bonding agent is conventionally used for the metal bonding agent diamond grinding head, and the function of the bonding agent is to enable the diamond grinding head powder or the mixture to have certain viscosity, so that the forming is facilitated.
In the application, the other components in the metal binder are trace components such as iron, cobalt, nickel and the like which are conventionally existing in the existing metal binder.
The forming and sintering process of a metal bond diamond grinding head according to the present application will be described in detail with reference to examples, comparative examples, and experimental data.
Example 1
The forming and sintering process for the metal bond diamond grinding head comprises the following steps of preparing the metal bond diamond grinding head (the length-diameter ratio is 7) with the blade part having the axial length of 50mm and the diameter of 7mm, wherein the process comprises the following steps:
(1) Preparing materials:
preparing diamond grinding head powder:
mixing a metal binding agent, diamond powder and an additive according to the mass ratio of 1: 0.1: 0.03, wherein the type of the diamond powder is MBD10-300 meshes, and obtaining a mixture: mixing the mixture with a binder to obtain the diamond grinding head powder; the mass of the binder is 7.5% of that of the mixture;
the additives include graphite and silicon carbide.
The chemical composition of the metal binding agent comprises the following components in percentage by mass:
tin: 37%, copper: 52%, titanium: 2% of iron, 2% of cobalt and 2% of nickel;
the components of the binder comprise, by mass fraction: 1 part of methyl cellulose, 50 parts of water and 10 parts of ethylene glycol.
Preparing a mixture: mixing the metal bonding agent and the binder according to the mass ratio of 10: 1.
(2) The method comprises the steps of preparing 6 split blanks with the length of 10mm and the diameter of 8mm by using a bidirectional cold press molding process for diamond grinding head powder, driving a lower pressing plate 2 and an upper pressing ring 1 by using a pneumatic press, carrying out spot pressing at 50MPa for 10 times, then carrying out pressure maintaining for 3min, and baking at 120 ℃ for 6 hours under the pressure of 150-200MPa in a mold 5 during pressure maintaining to obtain the split blanks.
As shown in fig. 2-4, in fig. 2, diamond grinding head powder is filled into a die 5, a lower pressing plate 2 and an upper pressing ring 1 are driven by a pneumatic press to press a first split blank 3, one end of the first split blank 3 is provided with a connecting groove 6, in fig. 3, the lower pressing plate 2 and the upper pressing ring 1 are driven by the pneumatic press to press a second split blank 4, one end of the second split blank 4 is provided with a connecting head 7, as shown in fig. 4, the first split blank 3 and the second split blank 4 are embedded with the connecting head 7 through the connecting groove 6 to be assembled into a whole, and a gap 8 is formed between the outer wall of the connecting head 7 and the inner wall of the connecting groove 6.
(3) And (3) embedding assembly: and (3) embedding the split blanks prepared in the step (2) in pairs through the structures of the connecting heads 7 and the connecting grooves 6 at the end parts of the split blanks to assemble a diamond grinding head blank with the length of 55mm and the diameter of 8mm, wherein the gap 8 between the outer wall of the connecting head 7 and the inner wall of the connecting groove 6 is 0.2mm.
Before the embedding, the mixing agent is coated on the radial contact surface between two adjacent split blanks in a dispensing manner, as shown in fig. 5, the number of dispensing positions 9 is 4-5 points, and the total dispensing amount between two adjacent split blanks is 0.5g.
(4) And (3) vacuum sintering: a steel substrate 11 penetrates through a diamond grinding head blank and is sent into a hearth for sintering, and the temperature curve of the vacuum sintering in the embodiment is as follows:
a first temperature rise stage: heating to 200 deg.C at room temperature for 15min, and keeping the temperature for 10min;
a second temperature rise stage: heating to 600 deg.C for 25min, and keeping the temperature for 10min;
a third temperature rise stage: heating to 850 deg.C, holding for 20min, and keeping the temperature for 10min;
a first cooling stage: cooling to 600 ℃, wherein the required time is 30mim;
and a second cooling stage: naturally cooling to room temperature at 600 ℃;
in vacuum sintering, the air pressure is controlled to be less than or equal to 1 × 10 -3 Pa。
(5) After sintering, the metal bond diamond grinding head 10 shown in fig. 6 is obtained, and grinding modification or electric spark modification is performed on the surface of the metal bond diamond grinding head 10 according to a design drawing, so that a target shape is obtained.
Example 2
The difference between the embodiment and the embodiment 1 is as follows, and the rest processes are the same:
the axial length of the finished product of the metal bond diamond grinding head is 31mm, and the diameter of the finished product of the metal bond diamond grinding head is 10mm;
the axial length of the total 2 split blanks is 17mm, and the diameter of the split blanks is 11.5mm;
the axial length of the diamond grinding head blank is 33mm, and the gap between the outer wall of the connector and the inner wall of the connecting groove is 0.2mm;
the total amount of glue dispensed between two adjacent split blanks is 1g.
Comparative example 1
This comparative example is a molding sintering process of a metal bond diamond grinding head, prepares the metal bond diamond grinding head (length-diameter ratio is 7) that axial length is 50mm, diameter 7mm, the technology includes:
(1) Adopting the same diamond grinding head powder as the diamond grinding head powder in the embodiment 1, molding by a two-way cold press molding process, and baking for 5 hours at 120 ℃ to prepare a diamond grinding head blank with the length of 55mm and the diameter of 8 mm;
the specific parameters of the bidirectional cold press molding process are as follows: and keeping the pressure for 5min after point pressing for 10 times at the pressure of 45MPa, wherein the pressure in the die is 200MPa during pressure keeping.
(2) And (3) sintering the diamond grinding head blank in vacuum, wherein the sintering temperature curve and the gas pressure are the same as those in the example 1, and finally shaping.
Related experiments:
30 sintered samples were prepared according to the processes of examples 1 and 2 and comparative example 1, and the metal bond diamond grinding head samples prepared in examples 1 and 2 and comparative example 1 were subjected to structural and mechanical property tests, the test results being shown in table 1.
The related test method comprises the following steps:
the test method of the sintering structure of the metal bond diamond grinding head comprises the following steps: after sintering is completed, the grinding head is cut into half parts along the axial direction by using a linear cutting machine, then the half parts are further cut into 6 equal parts along the radial direction, and the appearance of an abrasive grain layer on the cut surface is observed to see whether internal holes and cracks exist.
The method for testing the processing performance of the metal bond diamond grinding head comprises the following steps: and (3) sharpening the grinding wheel, and clamping the grinding wheel on a ceramic engraving and milling machine to process the zirconia ceramic plate. The processing mode is side edge Z-shaped feed, the processing mode is F1500, the rotating speed is 24000rpm, the cutting depth is 1mm, and the thickness of the Z-axis lower cutter is covered on the ceramic plate. The volume of the ceramic plate was cumulatively processed to 100000mm3. And after finishing the machining test, measuring the radial abrasion of the machined surface of the grinding wheel.
Table 1 metal bond diamond grinding head for structure and mechanical properties
| Surface cracks/stripes | Internal cracks/bars | Surface hole/hole | Inner cavity/an | MachiningPerformance/wear | |
| Example 1 | 1 | 0 | 0 | 0 | 0.37mm |
| Example 2 | 0 | 0 | 0 | 0 | 0.06mm |
| Comparative example 1 | 4 | 12 | 9 | 17 | 0.39mm |
In table 1, the processability is the measured average of the total number of occurrences recorded for each set of samples for cracks and holes.
As can be seen from table 1, in examples 1 and 2, the metal bond diamond grinding head manufactured by using the forming and sintering process of the metal bond diamond grinding head of the present invention has no cracks or holes on the surface or inside, the processing performance is excellent, and the wear values of example 1 are substantially the same as those of comparative example 1 having similar dimensions. The yield is high.
Comparative example 1 the conventional integral sintering process was used, and the obtained metal bond diamond grinding head had many cracks or holes on the surface and inside, and had a low yield, and the processability was substantially the same as that of example 1 having similar dimensions.
One or more technical solutions in the present application at least have the following technical effects or advantages:
(1) The invention relates to a forming and sintering process of a metal bond diamond grinding head, which comprises the steps of carrying out cold press forming on diamond grinding head powder to obtain a plurality of split blanks, embedding and assembling the split blanks into a complete diamond grinding head blank, and then carrying out vacuum sintering.
(2) The forming and sintering process of the metal bond diamond grinding head is characterized in that a mixing agent is coated on the radial contact surface between two adjacent split blanks, the mixing agent comprises a metal bond and a binder, the purpose of coating the mixing agent is to utilize the lower liquid phase point of a pure metal bond to melt, wet and strengthen the welding effect on the assembly surfaces of the two adjacent split blanks, in the vacuum sintering process, the split blanks are firstly changed into a solid-liquid mixed phase from a loose powder solid phase, and then are gradually cooled and changed into a compact solid phase from the solid-liquid mixed phase, in the process, the binder in an assembly gap is liquefied and flows, when the assembly gap between the radial contact surfaces is filled, the split blanks on two sides are wetted, and when the split blanks start to generate solid-liquid phase conversion along with the increase of temperature, the split blanks and the binder are fused into a whole, so that the radial contact surfaces of the two adjacent split blanks are fused.
(3) The forming and sintering process of the metal bond diamond grinding head adopts the sectional forming process, avoids integral forming, has simple sectional forming technical means, simple mold design and high forming yield, is difficult to generate cracks and holes because the split blanks are smaller and have uniform internal density distribution, needs isostatic pressing equipment when facing special shapes, has high equipment cost, complex process and low yield,
finally, it should be further noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (4)
1. A molding sintering process of a metal bond diamond grinding head is characterized by comprising the following steps:
cold press molding is carried out on the diamond grinding head powder, pressure maintaining is carried out for 3-5 min after point pressing for 10-15 times under the pressure of 30-50 Mpa, the pressure in a mold is 150-200 Mpa in the pressure maintaining process, then baking is carried out for 6-8 h under the temperature of 80-120 ℃, a plurality of split blanks are obtained, the split blanks are cylindrical, the length-diameter ratio of the split blanks is less than or equal to 2, and the length of the split blanks is 15-50% of that of the diamond grinding head blank;
embedding and assembling the split blanks to obtain diamond grinding head blanks, wherein in the diamond grinding head blanks, every two adjacent split blanks are embedded into each other through a connector and a connecting groove, a gap is reserved between the outer wall of the connector and the inner wall of the connecting groove, the connector and the connecting groove are respectively arranged on the end surfaces of every two adjacent split blanks, and the radial contact surfaces of the connector and the connecting groove are coated with a mixing agent;
sintering the diamond grinding head blank in vacuum to obtain a metal bond diamond grinding head;
the mixed agent comprises a metal bonding agent and a binder, wherein the mass ratio of the metal bonding agent to the binder in the mixed agent is (8-15): 1; the chemical components of the metal bonding agent comprise: tin: 30% -50%, copper: 40-60%, titanium: 2-15 percent of the total weight of the components, and the proportion of other components is less than or equal to 10 percent; the components of the binder comprise at least one of cellulose, water, ethanol and isopropanol by mass fraction, the mass of the mixture coated on the radial contact surface between two adjacent split blanks is 0.5-1 g, the axial length of the diamond grinding head blank is 110-130% of the axial length of the metal bond diamond grinding head, the diameter of the diamond grinding head blank is 110-125% of the diameter of the metal bond diamond grinding head, and the size of the gap and the diameter of the split blanks have the following relationship:
the diameter of the split blank is 6-12 mm, and the size of the gap is 0.1-0.2 mm;
the diameter of the split blank is 12-18 mm, and the size of the gap is 0.2-0.3 mm;
the diameter of the split blank is more than or equal to 18mm, and the size of the gap is 0.3-0.4 mm.
2. The forming and sintering process of a metal bond diamond grinding head according to claim 1,
and finishing the coating and drying of the mixture before the embedding and assembling of the plurality of split blanks.
3. The forming and sintering process of the metal bond diamond grinding head according to claim 1, wherein the vacuum sintering specifically comprises:
a first temperature rise stage: raising the temperature to 200 ℃ at room temperature, wherein the required time is 15-20 min, and keeping the temperature for 10-15 min;
a second temperature rise stage: heating to 600 ℃, keeping the temperature for 25-35 min, and keeping the temperature for 10-15 min;
a third temperature rise stage: heating to 850-900 deg.c for 20-25 min and maintaining for 10-15 min;
a first cooling stage: cooling to 600 ℃, wherein the required time is 30-40 mm;
and a second cooling stage: naturally cooling to room temperature at 600 ℃;
in the vacuum sintering, the air pressure is controlled to be less than or equal to 1 x 10 -3 Pa。
4. The forming and sintering process of the metal bond diamond grinding head according to claim 1, wherein the preparation method of the diamond grinding head powder comprises the following steps:
the preparation method comprises the following steps of (1) mixing a metal binder, diamond powder and an additive in a mass ratio of 1: (0.05-0.15): (0.025-0.05) mixing to obtain a mixture:
mixing the mixture with a binder to obtain the diamond grinding head powder;
wherein the mass of the binder is 5-10% of the mass of the mixture;
the additive comprises at least one of graphite, silicon carbide, ceramic microspheres and tungsten powder.
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