Boriding method for metal workpiece hole and metal workpiece

Abstract

The present invention belongs to the field of chemical heat treatment, and specifically relates to a boronizing method for metal workpiece holes and a metal workpiece. The boronizing method comprises: spraying and granulating a solid boronizing agent and a molten salt boronizing agent respectively to obtain solid boronizing agent particles and molten salt boronizing agent particles, uniformly mixing the solid boronizing agent particles and the molten salt boronizing agent particles to obtain a mixed boronizing agent, wherein the ratio of the D50 of the solid boronizing agent particles to the D50 of the molten salt boronizing agent particles is 1 to 5, and in the mixed boronizing agent, the volume proportion of the solid boronizing agent particles is 30 vol% to 60 vol%, and the volume proportion of the molten salt boronizing agent particles is 40 vol% to 70 vol%, and after the holes are filled with the mixed boronizing agent, the boronizing treatment is carried out in three stages, wherein the first stage removes the binder from the mixed boronizing agent, the second stage melts the molten salt boronizing agent particles in the mixed boronizing agent, and the third stage simultaneously boronizes the holes with the solid boronizing agent and the molten salt boronizing agent; a continuous, uniform and thick boronizing layer with an easy-to-clean surface can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical heat treatment, and in particular, relates to a boronizing method for holes in a metal workpiece and the metal workpiece. Background Art

[0002] Boriding the surface of a metal workpiece to form a boriding layer is used to improve the surface hardness, wear resistance, heat resistance, corrosion resistance, etc. of the metal workpiece. The existing boriding methods mainly include gas phase boriding, molten salt boriding and solid phase boriding. Gas phase boriding refers to boriding with gases such as B2H4 and H2. Solid phase boriding refers to burying the workpiece in boron-containing boriding agent particles or powder, and performing heat treatment to form a boride layer. During the heat treatment, the boriding agent remains in a solid state. Molten salt boriding refers to heat treating the workpiece in a salt bath to form a boride layer. Since gases such as B2H4 are highly toxic, the commonly used boriding methods are molten salt boriding and solid phase boriding.

[0003] It is inevitable that the surface of metal workpieces has a porous structure. However, for holes with a diameter of millimeter level, when molten salt boronizing is used, the residual salt after boronizing is not easy to clean. When solid phase boronizing is used, the continuity and uniformity of the boronized layer are poor because the penetrant cannot continuously contact the hole surface. At present, it is impossible to obtain a continuous, uniformly thick and easily cleaned boronized layer in millimeter-level holes.

[0004] It should be noted that this part of the present invention only provides background technology related to the present invention and does not necessarily constitute prior art or known technology. Summary of the invention

[0005] The purpose of the present invention is to overcome the defect that the existing boronizing method cannot obtain a continuous, uniformly thick, and easily cleaned boronized layer in millimeter-level holes, and to provide a boronizing method for metal workpiece holes and a metal workpiece, wherein the boronized layer is continuous and uniform and the surface is easy to clean.

[0006] In order to achieve the above object, in a first aspect, the present invention provides a boronizing method for holes in a metal workpiece, comprising:

[0007] After uniformly mixing a solid boriding agent, a solvent and a binder, spray granulation is performed to obtain solid boriding agent particles; after uniformly mixing a molten salt boriding agent, a solvent and a binder, spray granulation is performed to obtain molten salt boriding agent particles; after uniformly mixing the solid boriding agent particles and the molten salt boriding agent particles, a mixed boriding agent is obtained, wherein the ratio of D50 of the solid boriding agent particles to D50 of the molten salt boriding agent particles is 1-5, and in the mixed boriding agent, the volume proportion of the solid boriding agent particles is 30 vol%-60 vol%, and the volume proportion of the molten salt boriding agent particles is 40 vol%-70 vol%;

[0008] After the holes of the metal workpiece are filled with the mixed boronizing agent, a boronizing treatment is performed, and the boronizing treatment includes: heating to a first preset temperature and then performing a first heat preservation to remove the binder from the mixed boronizing agent, continuing to heat to a second preset temperature and then performing a second heat preservation to melt the molten salt boronizing agent particles in the mixed boronizing agent, and continuing to heat to a third preset temperature and then performing a third heat preservation to allow the solid boronizing agent and the molten salt boronizing agent to perform boronizing treatment on the holes at the same time.

[0009] In some preferred embodiments, the ratio of D50 of the solid boriding agent particles to D50 of the molten salt boriding agent particles is 2~4, and in the mixed boriding agent, the volume proportion of the solid boriding agent particles is 30vol%~40vol%, and the volume proportion of the molten salt boriding agent particles is 60vol%~70vol%.

[0010] Preferably, the D50 of the solid boronizing agent particles is 200 μm to 800 μm, and the D50 of the molten salt boronizing agent particles is 100 μm to 200 μm.

[0011] In some preferred embodiments, the solid boronizing agent includes a first component, a second component and a third component, the first component includes at least one of boron carbide and ferroboron, the second component includes at least one of silicon carbide and aluminum oxide, and the third component includes at least one of sodium fluorosilicate, sodium fluoroaluminate and potassium fluoroborate; and / or, the molten salt boronizing agent includes a fourth component and a fifth component, the fourth component includes borax, and the fifth component includes at least one of silicon carbide and aluminum.

[0012] Preferably, the second preset temperature is 750°C to 850°C, and the third preset temperature is 800°C to 1000°C.

[0013] Preferably, the second insulation time is 1h~3h, and the third insulation time is 2h~8h.

[0014] In some preferred embodiments, the binder includes at least one of gelatin, silica gel, polyvinyl alcohol, and polyethylene glycol; the first preset temperature is 500° C. to 700° C., and the first insulation time is 2 h to 8 h.

[0015] In some preferred embodiments, the process further includes: after the boronizing treatment, quenching the metal workpiece in 5wt%~15wt% brine, washing the metal workpiece with 90℃~100℃ brine, and tempering the metal workpiece at 150℃~200℃ for 5h~24h.

[0016] In some preferred embodiments, the method further comprises: before the boronizing treatment, laying the mixed boronizing agent on the surface around the hole of the metal workpiece.

[0017] In a second aspect, the present invention provides a metal workpiece having a boronized layer in a hole, wherein the boronized layer is obtained by boronizing using the boronizing method described in the first aspect.

[0018] The boronizing method of the present invention adopts a mixed boronizing agent including solid boronizing agent particles and molten salt boronizing agent particles, the ratio of D50 of the solid boronizing agent particles to D50 of the molten salt boronizing agent particles is 1-5, the volume proportion of the solid boronizing agent particles is 30vol%-60vol%, and the volume proportion of the molten salt boronizing agent particles is 40vol%-70vol%. After heating to a first preset temperature, a first heat preservation is performed, and a binder in the solid boronizing agent particles and the molten salt boronizing agent particles is removed. After heating to a second preset temperature, a second heat preservation is performed, and the molten salt boronizing agent particles in the mixed boronizing agent are melted, and the molten salt boronizing agent in a molten state fills the pores between the solid boronizing agent particles. After heating to a third preset temperature, a third heat preservation is performed, and the molten salt boronizing agent and the solid boronizing agent jointly perform boronizing treatment on the surface of the hole. In the boronizing process of the present invention, the solid boronizing agent generates a gaseous The active boron atoms of the present invention are partly directly borided by gaseous boron atoms, and partly gaseous boron atoms are absorbed in the surrounding molten salt boriding agent in the molten state. The molten salt boriding agent in the molten state itself has boron atoms in the molten state. This part of active boron atoms produced by the solid boriding agent and the active boron atoms produced by the molten salt boriding agent are both borided in the molten state, wherein the direct boriding of gaseous boron atoms mainly occurs at the point contact position between the solid boriding agent particles and the workpiece surface, and the periphery of the point contact position is mainly borided by the boron atoms produced by the solid boriding agent and the boron atoms produced by the molten salt boriding agent in the molten state. The concentration of active boron atoms in the molten salt is high. After the boron atoms penetrate into the workpiece surface, they will diffuse to the surrounding area due to the concentration gradient. The boriding layer of the present invention is continuous, uniform in thickness and relatively thick, and can give full play to the role of the boriding layer in improving the surface hardness, wear resistance, heat resistance and corrosion resistance of the metal workpiece. The solid boronizing agent particles of the present invention form a solid honeycomb skeleton in the molten salt, the workpiece surface is in point contact with the solid boronizing agent particles, the adhesion between the molten salt and the workpiece surface is reduced, and during the residual salt cleaning process, the residual salt in the millimeter-level holes can be cleaned away, thereby improving the surface state of the holes.

[0019] In the boronizing method of the present invention, a part of the gaseous active boron atoms generated by the solid boronizing agent are directly boronized, and a part of them are absorbed into the molten salt and are boronized together with the active boron atoms generated by the molten salt boronizing agent in a molten state. The solid boronizing agent particles form a honeycomb skeleton in the molten salt. Compared with only molten salt boronizing, the residual salt is easy to clean, and compared with only solid boronizing, a continuous and uniformly thick boronized layer can be obtained. If the present invention adopts other forms of skeletons, since the skeleton does not serve to provide the boronizing agent, in order to achieve the same boronizing effect (same thickness, etc.), more stringent boronizing conditions are required, the boronizing temperature needs to be higher, the boronizing time needs to be longer, and it is easy to cause the problem that the thickness of the boronized layer at the point contact between the skeleton and the workpiece surface is greatly different from the thickness of the boronized layer at other parts.

[0020] When the ratio of D50 of the solid boriding agent particles of the present invention to D50 of the molten salt boriding agent particles is not 1-5, and the volume proportion of the solid boriding agent particles is not 30 vol%-60 vol%, and the volume proportion of the molten salt boriding agent particles is not 40 vol%-70 vol%, the molten salt boriding agent cannot completely fill the pores between the solid boriding agent particles, affecting the continuous uniformity of the boriding layer, and the solid honeycomb skeleton formed by the solid boriding agent cannot play a sufficient supporting role, affecting the cleaning of residual salt.

[0021] If the present invention is not kept warm at the first preset temperature and the process of removing the binder is not carried out separately, on the one hand, the problem of incomplete binder removal is likely to occur, affecting the performance of the boriding layer. On the other hand, the problem of binder being doped in the boriding agent and inability to be uniformly borided is likely to occur, affecting the continuity and uniformity of the boriding layer. If the second preset temperature is not kept warm and the process of melting the molten salt boriding agent particles is not carried out separately, the problem of boriding chemical reaction starting before the molten salt boriding agent fills the pores between the solid boriding agent particles is likely to occur, affecting the continuity and uniformity of the boriding layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 This is a scanning electron microscope photograph of the boronized layer in the pores of Example 1 of the present invention.

[0024] Figure 2 This is the XRD phase structure detection diagram of the boronized layer in the pores of Example 1 of the present invention.

[0025] Figure 3This is a microscopic photograph of the hole surface after residual salt cleaning in Example 1 of the present invention.

[0026] Figure 4 This is a microscopic photograph of the hole surface after residual salt cleaning in comparative example 2 of the present invention. DETAILED DESCRIPTION

[0027] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0028] The inventors of the present invention have found that the existing boronizing method cannot obtain a continuous boronizing layer with uniform thickness and easy surface cleaning in millimeter-level holes.

[0029] In this first aspect, the present invention provides a method for boronizing a hole in a metal workpiece, comprising:

[0030] After uniformly mixing a solid boriding agent, a solvent and a binder, spray granulation is performed to obtain solid boriding agent particles; after uniformly mixing a molten salt boriding agent, a solvent and a binder, spray granulation is performed to obtain molten salt boriding agent particles; after uniformly mixing the solid boriding agent particles and the molten salt boriding agent particles, a mixed boriding agent is obtained, wherein the ratio of D50 of the solid boriding agent particles to D50 of the molten salt boriding agent particles is 1-5, and in the mixed boriding agent, the volume proportion of the solid boriding agent particles is 30 vol%-60 vol%, and the volume proportion of the molten salt boriding agent particles is 40 vol%-70 vol%;

[0031] After the holes of the metal workpiece are filled with the mixed boronizing agent, a boronizing treatment is performed, and the boronizing treatment includes: heating to a first preset temperature and then performing a first heat preservation to remove the binder from the mixed boronizing agent, continuing to heat to a second preset temperature and then performing a second heat preservation to melt the molten salt boronizing agent particles in the mixed boronizing agent, and continuing to heat to a third preset temperature and then performing a third heat preservation to allow the solid boronizing agent and the molten salt boronizing agent to perform boronizing treatment on the holes at the same time.

[0032] The boronizing method of the present invention adopts a mixed boronizing agent including solid boronizing agent particles and molten salt boronizing agent particles, the ratio of D50 of the solid boronizing agent particles to D50 of the molten salt boronizing agent particles is 1-5, the volume proportion of the solid boronizing agent particles is 30vol%-60vol%, and the volume proportion of the molten salt boronizing agent particles is 40vol%-70vol%. After heating to a first preset temperature, a first heat preservation is performed, and a binder in the solid boronizing agent particles and the molten salt boronizing agent particles is removed. After heating to a second preset temperature, a second heat preservation is performed, and the molten salt boronizing agent particles in the mixed boronizing agent are melted, and the molten salt boronizing agent in a molten state fills the pores between the solid boronizing agent particles. After heating to a third preset temperature, a third heat preservation is performed, and the molten salt boronizing agent and the solid boronizing agent jointly perform boronizing treatment on the surface of the hole. In the boronizing process of the present invention, the solid boronizing agent generates a gaseous The active boron atoms of the present invention are partly directly borided by gaseous boron atoms, and partly gaseous boron atoms are absorbed in the surrounding molten salt boriding agent in the molten state. The molten salt boriding agent in the molten state itself has boron atoms in the molten state. This part of active boron atoms produced by the solid boriding agent and the active boron atoms produced by the molten salt boriding agent are both borided in the molten state, wherein the direct boriding of gaseous boron atoms mainly occurs at the point contact position between the solid boriding agent particles and the workpiece surface, and the periphery of the point contact position is mainly borided by the boron atoms produced by the solid boriding agent and the boron atoms produced by the molten salt boriding agent in the molten state. The concentration of active boron atoms in the molten salt is high. After the boron atoms penetrate into the workpiece surface, they will diffuse to the surrounding area due to the concentration gradient. The boriding layer of the present invention is continuous, uniform in thickness and relatively thick, and can give full play to the role of the boriding layer in improving the surface hardness, wear resistance, heat resistance and corrosion resistance of the metal workpiece. The solid boronizing agent particles of the present invention form a solid honeycomb skeleton in the molten salt, and the surface of the workpiece is in point contact with the solid boronizing agent particles. The adhesion between the molten salt and the surface of the workpiece is reduced. In the residual salt cleaning process, the residual salt in the millimeter-level holes can be cleaned off, thereby improving the surface state of the holes. If the present invention is not kept warm at the first preset temperature and the process of removing the binder is not performed separately, on the first hand, it is easy to cause the problem of incomplete removal of the binder, affecting the performance of the boronizing layer. On the second hand, it is easy to cause the problem that the boronizing agent is doped with a binder and cannot be uniformly boronized, affecting the continuity and uniformity of the boronizing layer. If the second preset temperature is not kept warm and the melting process of the molten salt boronizing agent particles is not performed separately, it is easy to cause the problem that the molten salt boronizing agent has not yet filled the pores between the solid boronizing agent particles, and the boronizing chemical reaction begins, affecting the continuity and uniformity of the boronizing layer.

[0033] If the present invention adopts other forms of skeletons, since the skeleton cannot provide the function of the boronizing agent, in order to achieve the same boronizing effect (same thickness, etc.), more stringent boronizing conditions are required, the boronizing temperature needs to be higher, and the boronizing time needs to be longer.

[0034] The ratio of D50 of the solid boriding agent particles of the present invention to D50 of the molten salt boriding agent particles is, for example, 1, 2, 3, 4 and 5, and the volume proportion of the solid boriding agent particles is, for example, 30 vol%, 35 vol%, 40 vol%, 45 vol%, 50 vol%, 55 vol% and 60 vol%.

[0035] In some preferred embodiments, the ratio of D50 of the solid boriding agent particles to D50 of the molten salt boriding agent particles is 2-4, and in the mixed boriding agent, the volume proportion of the solid boriding agent particles is 30vol%-40vol%, and the volume proportion of the molten salt boriding agent particles is 60vol%-70vol%. Under this preferred scheme, it is more conducive to the residual salt cleaning process, the residual salt is fully cleaned, and after heating to the second preset temperature for the second insulation, the molten salt boriding agent fills the pores between the solid boriding agent particles, and after heating to the third preset temperature for the third insulation, a continuous and uniform boriding layer is obtained on the surface of the hole.

[0036] Preferably, the D50 of the solid boronizing agent particles is 200μm~800μm, and the D50 of the molten salt boronizing agent particles is 100μm~200μm. Under this preferred embodiment, while being more conducive to the sufficient cleaning of residual salt, the molten salt boronizing agent in the molten state fills the pores between the solid boronizing agent particles, and a continuous and uniform boronizing layer is obtained on the surface of the holes. The D50 of the solid boronizing agent particles is, for example, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm and 800μm, and the D50 of the molten salt boronizing agent particles is, for example, 100μm, 120μm, 140μm, 160μm, 180μm and 200μm.

[0037] In some preferred embodiments, the solid boriding agent includes a first component, a second component and a third component, wherein the first component includes at least one of boron carbide and ferroboron, the second component includes at least one of silicon carbide and aluminum trioxide, and the third component includes at least one of sodium fluorosilicate, sodium fluoroaluminate and potassium fluoroborate; and / or, the molten salt boriding agent includes a fourth component and a fifth component, wherein the fourth component includes borax, and the fifth component includes at least one of silicon carbide and aluminum. Based on the molten state of the molten salt boriding agent filling the pores between the solid boriding agent particles, part of the gaseous active boron atoms generated by the solid boriding agent are directly borided, and part of them are absorbed into the molten salt and are borided together with the active boron atoms generated by the molten salt boriding agent in a molten state. Under this preferred scheme, it is more conducive to obtaining a continuous, dense, uniformly thick and thick boriding layer on the surface of the millimeter-level holes, thereby improving the wear resistance of the boriding layer. Preferably, the mass proportion of the first component in the solid boriding agent is 5wt%~15wt%, the mass proportion of the second component is 70wt%~90wt%, the mass proportion of the third component is 5wt%~15%, the mass proportion of the fourth component in the molten salt boriding agent is 60wt%~90wt%, and the mass proportion of the fifth component is 10wt%~40wt%.

[0038] Preferably, the second preset temperature is 750°C to 850°C, and the third preset temperature is 800°C to 1000°C. Under this preferred solution, the second preset temperature is 750°C to 850°C, which is more conducive to the full melting of the molten salt boronizing agent particles, and a continuous and uniform boronizing layer is obtained on the surface of the hole. The third preset temperature is 800°C to 1000°C, which is more conducive to the solid boronizing agent to produce gaseous active boron atoms, and the gaseous active boron atoms are boronized in gaseous form. The gaseous active boron atoms are absorbed into the molten salt and are boronized together with the active boron atoms generated by the molten salt boronizing agent in a molten state, and a continuous, dense, uniform and thick boronizing layer is obtained on the surface of the hole. The second preset temperature is, for example, 750°C, 770°C, 790°C, 810°C, 830°C and 850°C, and the third preset temperature is, for example, 800°C, 850°C, 900°C, 950°C and 1000°C.

[0039] Preferably, the second insulation time is 1h~3h, and the third insulation time is 2h~8h. Under this preferred embodiment, the second insulation time is 1h~3h, which is more conducive to the full melting of the molten salt boronizing agent particles and obtaining a continuous and uniform boronizing layer on the hole surface. The third insulation time is 2h~8h, which is more conducive to obtaining a continuous, dense, uniform and thick boronizing layer on the hole surface. The second insulation time is, for example, 1h, 1.5h, 2h, 2.5h and 3h, and the third insulation time is, for example, 2h, 3h, 4h, 5h, 6h, 7h and 8h.

[0040] In some preferred embodiments, the binder includes at least one of gelatin, silica gel, polyvinyl alcohol, and polyethylene glycol; the first preset temperature is 500°C to 700°C, and the first insulation time is 2h to 8h. The first preset temperature is, for example, 500°C, 550°C, 600°C, 650°C, and 700°C, and the first insulation time is, for example, 2h, 3h, 4h, 5h, 6h, 7h, and 8h.

[0041] The present invention does not limit the type of solvent, such as ethanol, acetone, etc.

[0042] In some preferred embodiments, the boronizing treatment is performed in sequence, the metal workpiece is quenched in 5wt%~15wt% brine, the metal workpiece is washed with 90℃~100℃ brine, and the metal workpiece is tempered at 150℃~200℃ for 5h~24h. Under this preferred scheme, the metal workpiece is quenched in 5wt%~15wt% brine, and the metal workpiece is washed with 90℃~100℃ brine, which is more conducive to sufficient cleaning of residual salt, and the metal workpiece is tempered at 150℃~200℃ for 5h~24h, which is more conducive to sufficient diffusion of the boronizing layer and improves the uniformity of the boronizing layer. The tempering temperature is, for example, 150℃, 160℃, 170℃, 180℃, 190℃ and 200℃, and the tempering time is, for example, 5h, 10h, 15h, 20h and 24h.

[0043] In some preferred embodiments, before the boronizing treatment, the mixed boronizing agent is laid on the surface around the hole of the metal workpiece. Under this preferred scheme, on the one hand, the hole and the surface outside the hole of the metal workpiece can be boronized at the same time, and on the other hand, it is more conducive to reducing the oxygen around the sample, preventing too much oxygen from entering the hole, inhibiting the reaction between the hole and oxygen, and obtaining a continuous, dense, uniform and thick boronized layer on the surface of the hole. Preferably, a mixed boronizing agent layer with a thickness of more than 3 cm is laid on the surface around the hole of the metal workpiece.

[0044] In a second aspect, the present invention provides a metal workpiece having a boronized layer in a hole, wherein the boronized layer is obtained by boronizing using the boronizing method described in the first aspect. The boronized layer on the surface of the hole is continuous, dense, uniform and thick, and can improve the surface hardness, wear resistance, heat resistance and corrosion resistance of the metal workpiece.

[0045] The present invention is further described in detail below with reference to specific embodiments.

[0046] Example 1

[0047] A method for boronizing holes in a metal workpiece, the material of the metal workpiece is 316L, and the steps are as follows:

[0048] Step 1: boron carbide, ferroboron, aluminum oxide, sodium fluorosilicate, gelatin and ethanol are mixed by roller ball milling to obtain a solid boronizing agent slurry, and solid boronizing agent particles are obtained by spray granulation. The D50 of the solid boronizing agent particles is 450 μm. Borax, silicon carbide, gelatin and ethanol are mixed by roller ball milling to obtain a molten salt boronizing agent slurry, and molten salt boronizing agent particles are obtained by spray granulation. The D50 of the molten salt boronizing agent particles is 160 μm. The ratio of the D50 of the solid boronizing agent particles to the D50 of the molten salt boronizing agent particles is 2.81. According to the mixed boronizing agent, the volume proportion of the solid boronizing agent particles is 35 vol%, and the volume proportion of the molten salt boronizing agent particles is 65 vol%. The solid boronizing agent particles and the molten salt boronizing agent particles are evenly mixed to obtain a mixed boronizing agent;

[0049] Step 2: pour the mixed boronizing agent of step 1 into a hole with a diameter of 5 mm in the metal workpiece, put the metal workpiece filled with the mixed boronizing agent in the hole into a stainless steel crucible, lay the mixed boronizing agent around the workpiece, the thickness of the mixed boronizing agent layer around the workpiece is more than 3 cm, fill the crucible with the mixed boronizing agent, and put the crucible into a high-temperature furnace for boronizing treatment, specifically, heating to 600°C and keeping warm for 3 hours to remove the glue of the solid boronizing agent particles and the molten salt boronizing agent particles, and then continue to heat to 800°C and keep warm for 2 hours to melt the molten salt boronizing agent particles, and then continue to heat to 900°C and keep warm for 5 hours, so that the solid boronizing agent and the molten salt boronizing agent simultaneously perform boronizing treatment on the holes;

[0050] Step 3: Quench the boronized metal workpiece in 10wt% brine, clean the surface of the quenched metal workpiece including the holes with 100°C brine, and temper the cleaned metal workpiece at 150°C for 15h.

[0051] The morphology of the boronized layer in the pores of this embodiment is shown in Figure 1 The boronized layer is continuous, uniform and dense. The XRD phase structure of the boronized layer is tested. The results are shown in Figure 2 The boronized layer is a Fe2B single-phase layer. See the microscopic photograph of the hole surface after residual salt cleaning. Figure 3 , basically no residual salt remains.

[0052] Example 2

[0053] Referring to the boriding method of Example 1, the difference is that in step one, the D50 of the solid boriding agent particles is 850 μm, the D50 of the molten salt boriding agent particles is 300 μm, and the ratio of the D50 of the solid boriding agent particles to the D50 of the molten salt boriding agent particles is 2.83.

[0054] Example 3

[0055] Referring to the boronizing method of Example 1, the difference is that in step one, the D50 of the solid boronizing agent particles is 200 μm, the D50 of the molten salt boronizing agent particles is 160 μm, and the ratio of the D50 of the solid boronizing agent particles to the D50 of the molten salt boronizing agent particles is 1.25.

[0056] Example 4

[0057] Refer to the boronizing method of Example 1, except that the aluminum oxide component is not added in step one.

[0058] Comparative Example 1

[0059] Referring to the boronizing method of Example 1, the difference is that in step 1, the volume proportion of the solid boronizing agent particles is 70 vol%, and the volume proportion of the molten salt boronizing agent particles is 30 vol%.

[0060] Comparative Example 2

[0061] Refer to the boronizing method of Example 1, except that in step 1, the volume proportion of solid boronizing agent particles is 10 vol%, and the volume proportion of molten salt boronizing agent particles is 90 vol%. There is a lot of residual salt after cleaning. The microscopic photo of the hole surface after cleaning the residual salt is shown in Figure 4 .

[0062] Comparative Example 3

[0063] Referring to the boronizing method of Example 1, the difference is that in step 2, during the boronizing treatment, the temperature is not raised to 600° C. and then kept warm for 3 hours, but directly raised to 800° C. and then kept warm for 2.5 hours.

[0064] Comparative Example 4

[0065] Referring to the boronizing method of Example 1, the difference is that in step 2, during the boronizing treatment, the temperature is not raised to 800°C and then kept warm for 2 hours. Instead, the temperature is raised to 600°C and kept warm for 3 hours, and then directly raised to 900°C and kept warm for 5 hours.

[0066] Comparative Example 5

[0067] Referring to the boronizing method of Example 1, the difference is that only molten salt boronizing agent particles are used. A large amount of residual salt remains after cleaning.

[0068] Comparative Example 6

[0069] Refer to the boriding method of Example 1, except that only solid boriding agent particles are used.

[0070] The thickness uniformity and thickness characterization of the borided layer in the pores obtained in the embodiment and the comparative example are performed. The thickness uniformity is calculated as follows: under a 500x SEM field of view, the thickness of the borided layer is randomly measured at 10 locations, and the standard deviation of the thickness results of the borided layer at 10 locations is calculated. The standard deviation value is used to characterize the thickness uniformity. The smaller the standard deviation, the better the thickness uniformity. Conversely, the thickness uniformity is poor. The results are shown in Table 1. The wear resistance of the borided layer of the embodiment and the comparative example is characterized. The friction and wear experimental conditions are as follows: the grinding pair is a φ3GCr15 ball, the load is 10N, the stroke is 2mm, the frequency is 5Hz, and the friction time is 30min. The results are shown in Table 1.

[0071] Table 1

[0072]

[0073] Comparing the embodiment and comparative examples 1~2, the volume proportion of solid boronizing agent particles is 30vol%~60vol%, and the volume proportion of molten salt boronizing agent particles is 40vol%~70vol%, which can improve the thickness and thickness uniformity of the boronizing layer, improve the wear resistance of the boronizing layer, and promote the cleaning of residual salt. Compared with the embodiment and comparative example 3, compared with not keeping warm at the first preset temperature and not performing the process of removing the binder separately, the first heat preservation is performed after heating to the first preset temperature, so that the mixed boronizing agent removes the binder, which can improve the thickness and thickness uniformity of the boronizing layer, and improve the wear resistance of the boronizing layer. Damage performance, comparing the embodiment and comparative example 4, compared with not keeping warm at the second preset temperature, not separately carrying out the molten salt boronizing agent particle melting process, heating to the second preset temperature and then carrying out the second keeping warm, it is more conducive to improving the thickness and thickness uniformity of the boronizing layer, and improving the wear resistance of the boronizing layer. For the embodiments and comparative examples 5~6, molten salt boronizing agent particles and solid boronizing agent particles are used for mixed boronizing. Compared with boronizing with only molten salt boronizing agent particles, it can greatly promote the cleaning of residual salt. Compared with boronizing with only solid boronizing agent particles, it can improve the thickness and thickness uniformity of the boronizing layer, and improve the wear resistance of the boronizing layer.

[0074] Comparing Example 1 and Example 2, the D50 of the solid boriding agent particles is 200μm~800μm, and the D50 of the molten salt boriding agent particles is 100μm~200μm, which is more conducive to improving the thickness and thickness uniformity of the boriding layer, and improving the wear resistance of the boriding layer. Comparing Example 1 and Example 3, the ratio of D50 of the solid boriding agent particles to D50 of the molten salt boriding agent particles is 2~4, which is more conducive to improving the thickness and thickness uniformity of the boriding layer, and improving the wear resistance of the boriding layer. Comparing Example 1 and Example 4, the solid boriding agent includes a second component, and the second component includes at least one of silicon carbide and aluminum oxide, which is more conducive to increasing the thickness of the boriding layer and improving the wear resistance of the boriding layer.

[0075] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for boronizing holes in a metal workpiece, characterized in that: include: After uniformly mixing a solid boriding agent, a solvent and a binder, spray granulation is performed to obtain solid boriding agent particles; after uniformly mixing a molten salt boriding agent, a solvent and a binder, spray granulation is performed to obtain molten salt boriding agent particles; after uniformly mixing the solid boriding agent particles and the molten salt boriding agent particles, a mixed boriding agent is obtained, wherein the ratio of D50 of the solid boriding agent particles to D50 of the molten salt boriding agent particles is 1-5, and in the mixed boriding agent, the volume proportion of the solid boriding agent particles is 30 vol%-60 vol%, and the volume proportion of the molten salt boriding agent particles is 40 vol%-70 vol%; After the holes of the metal workpiece are filled with the mixed boronizing agent, a boronizing treatment is performed, and the boronizing treatment includes: heating to a first preset temperature and then performing a first heat preservation to remove the binder from the mixed boronizing agent, continuing to heat to a second preset temperature and then performing a second heat preservation to melt the molten salt boronizing agent particles in the mixed boronizing agent, and continuing to heat to a third preset temperature and then performing a third heat preservation to allow the solid boronizing agent and the molten salt boronizing agent to perform boronizing treatment on the holes at the same time.

2. The boronizing method according to claim 1, characterized in that: The ratio of D50 of the solid boriding agent particles to D50 of the molten salt boriding agent particles is 2-4. In the mixed boriding agent, the volume proportion of the solid boriding agent particles is 30 vol%-40 vol%, and the volume proportion of the molten salt boriding agent particles is 60 vol%-70 vol%.

3. The boronizing method according to claim 2, characterized in that: The D50 of the solid boronizing agent particles is 200 μm to 800 μm, and the D50 of the molten salt boronizing agent particles is 100 μm to 200 μm.

4. The boronizing method according to claim 1, characterized in that: The solid boronizing agent includes a first component, a second component and a third component, wherein the first component includes at least one of boron carbide and ferroboron, the second component includes at least one of silicon carbide and aluminum oxide, and the third component includes at least one of sodium fluorosilicate, sodium fluoroaluminate and potassium fluoroborate; and / or, the molten salt boronizing agent includes a fourth component and a fifth component, wherein the fourth component includes borax, and the fifth component includes at least one of silicon carbide and aluminum.

5. The boronizing method according to claim 4, characterized in that: The second preset temperature is 750°C to 850°C, and the third preset temperature is 800°C to 1000°C.

6. The boronizing method according to claim 5, characterized in that: The second insulation time is 1h~3h, and the third insulation time is 2h~8h.

7. The boronizing method according to claim 1, characterized in that: The adhesive includes at least one of gelatin, silica gel, polyvinyl alcohol, and polyethylene glycol; the first preset temperature is 500° C. to 700° C., and the first insulation time is 2 h to 8 h.

8. The boronizing method according to claim 1, characterized in that: Also includes: After the boronizing treatment, the metal workpiece is sequentially quenched in 5wt%~15wt% brine, the metal workpiece is cleaned with 90℃~100℃ brine, and the metal workpiece is tempered at 150℃~200℃ for 5h~24h.

9. The boronizing method according to claim 1, characterized in that: Also includes: Before the boronizing treatment, the mixed boronizing agent is spread on the surface around the hole of the metal workpiece.

10. A metal workpiece having a boronized layer in a hole, characterized in that: The borided layer is obtained by boriding using the boriding method according to any one of claims 1 to 9.

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