阅读说明：本技术 一种粉末渗锌工艺 (Powder zinc impregnation process ) 是由 陈志根 陈志财 沈斌男 于 2020-12-10 设计创作，主要内容包括：本申请涉及金属加工领域,具体公开一种粉末渗锌工艺,包括以下工艺步骤：S1：对工件进行前处理,除去工件表面杂质；S2：装炉：将前处理后的工件送入转动炉中,并同时添加锌粉、石英砂和氯化铵并混合均匀；S3：密封转动炉并使转动炉转动,在转动过程中对转动炉进行加热,使转动炉内部升温至190-195℃,然后保温15-20min；S4：继续对转动炉进行加热,使转动炉内部升温至250-255℃,再保温25-30min；S5：继续对转动炉进行加热,使转动炉内部升温至380-450℃,保温150-180min；S6：完成第三次加热和保温过程后,使转动炉自然冷却至70-80℃,对内容物进行趁热筛分,得渗锌后的工件；S7：将渗锌后的工件进行水洗、钝化、清洗和烘干,得成品工件。本申请的工艺加工得到的渗锌层具有更好的均匀性。(The application relates to the field of metal processing, and particularly discloses a powder zinc impregnation process, which comprises the following process steps: s1: pre-treating the workpiece, and removing impurities on the surface of the workpiece; s2: charging: feeding the pretreated workpiece into a rotary furnace, and adding zinc powder, quartz sand and ammonium chloride at the same time and uniformly mixing; s3: sealing the rotary furnace and rotating the rotary furnace, heating the rotary furnace in the rotating process to raise the temperature inside the rotary furnace to 190-; s4: continuously heating the rotary furnace to raise the temperature inside the rotary furnace to 250-; s5: continuously heating the rotary furnace to raise the temperature inside the rotary furnace to 450 ℃ for 150 min; s6: after the third heating and heat preservation process is finished, naturally cooling the rotary furnace to 70-80 ℃, and screening the contents while the contents are hot to obtain a workpiece after zinc impregnation; s7: and (5) washing, passivating, cleaning and drying the workpiece subjected to zinc impregnation to obtain a finished workpiece. The zincizing layer processed by the process has better uniformity.)

1. The powder zinc impregnation process is characterized by comprising the following steps: the method comprises the following process steps:

s1: pre-treating the workpiece, and removing impurities on the surface of the workpiece;

s2: charging: sending the pretreated workpiece into a rotating furnace, adding zinc powder, quartz sand and ammonium chloride at the same time, and uniformly mixing, wherein 75-85 parts of zinc powder, 190-200 parts of quartz sand and 1.5-2 parts of ammonium chloride are required to be added for every 1000 parts of workpiece by mass; the total volume of the workpiece and each component after charging accounts for 80-85% of the volume of the rotary furnace;

s3: heating for the first time: sealing the rotary furnace and rotating the rotary furnace, heating the rotary furnace in the rotating process to raise the temperature inside the rotary furnace to 190-;

s4: and (3) heating for the second time: the rotary furnace keeps rotating, the rotary furnace is continuously heated, the temperature in the rotary furnace is raised to 250-255 ℃, and then the temperature is kept for 25-30 min;

s5: heating for the third time: the rotating furnace keeps rotating, the rotating furnace is continuously heated, the temperature in the rotating furnace is raised to 380-;

s6: after the third heating and heat preservation process is finished, naturally cooling the rotary furnace to 70-80 ℃, opening the rotary furnace and screening the contents while the contents are hot to obtain a workpiece subjected to zinc impregnation;

s7: and (5) sequentially washing, passivating, cleaning and drying the workpiece subjected to zinc impregnation to obtain a finished workpiece.

2. The powder zincating process according to claim 1, wherein: and S2, in the charging process, adding lanthanum sulfate into the rotary furnace, wherein the addition amount of the lanthanum sulfate is 0.5-1 part per 1000 parts by mass of the workpiece.

3. The powder zincating process according to claim 1, wherein: in step S2, the mesh number of the zinc powder is 350-400, and the particle size of the quartz sand is 2-3 mm.

4. The powder zincating process according to claim 1, wherein: the specific process of the pretreatment in the step S1 is as follows: soaking the workpiece in a sodium hydroxide solution with the concentration of 50-55% and the temperature of 40-60 ℃ for 4-6min, then soaking the workpiece in a normal-temperature hydrochloric acid solution with the concentration of 30-35% for 8-10min, finally soaking the workpiece in a sodium hydroxide solution with the concentration of 4-6% and the temperature of 80-85 ℃ for 3-5S, and finally centrifugally drying.

5. The powder zincating process according to claim 1, wherein: the specific process of passivation in step S7 is: soaking the washed workpiece in a normal-temperature chromium trichloride solution with the concentration of 15% -20% for 5-8min, taking out the workpiece, washing the workpiece with water for the second time, and soaking the workpiece in silica sol with the concentration of 8% -10% for 1-3 min.

6. The powder zincating process according to claim 5, wherein: the silica sol has inner colloidal particle diameter of 10-20nm and viscosity of 5 × 10 at 20 deg.C^-3-6×10^-3Pa •S。

7. The powder zincating process according to claim 1, wherein: the rotating speed of the rotating furnace in the steps S3 and S4 is 15-18r/min, and the rotating speed of the rotating furnace in the step S5 is 23-25 r/min.

8. The powder zincating process according to claim 1, wherein: in step S6, the rotary furnace is kept rotating continuously in the cooling process, and the rotating speed of the rotary furnace is 10-12 r/min.

Technical Field

The application relates to the technical field of metal processing, in particular to a powder zinc impregnation process.

Background

At present, in the metal processing process, the surface of a finished metal workpiece is often required to be plated for preventing the metal workpiece from being corroded by various kinds, and the service life of the metal workpiece is prolonged. Powder zincing is a metal surface coating treatment process, a zinc-iron alloy layer is obtained on the surface of steel by a thermal diffusion method, and the powder zincing has the advantages of high hardness, raw material saving, simple operation, no hydrogen embrittlement and the like.

The powder zincizing comprises an embedding method and a mechanical energy assisted zincizing method, wherein the embedding method is to directly embed a workpiece in a zincizing agent and heat the zincizing agent to ensure that zinc atoms in the zincizing agent permeate to the surface of metal to form a zinc protective film; on the basis of an embedding method, the mechanical energy assisted zincification method is characterized in that a workpiece and a zincification agent are placed in a rotating container together, the container is rotated in the heating process, the zincification agent continuously impacts the surface of the heated workpiece under the action of mechanical energy, the efficiency of zincification is improved by means of the mechanical energy after impact, the formation of a zinc layer can be accelerated, and the method is a mainstream powder zincification process at present.

However, the mechanical energy assisted infiltration method is not stable enough in the technical process, and the condition that the surface of a workpiece is not uniformly impacted by the zincizing agent is easy to occur in the rotating and heating process, so that the zincizing layer is easily uneven.

Disclosure of Invention

In order to improve the flatness of a zincizing layer of a workpiece prepared by a mechanical energy permeation-assisted method, the application provides a powder zincizing process.

The application provides a powder zincizing technology, which adopts the following technical scheme:

s1: pre-treating the workpiece, and removing impurities on the surface of the workpiece;

s2: charging: sending the pretreated workpiece into a rotating furnace, adding zinc powder, quartz sand and ammonium chloride at the same time, and uniformly mixing, wherein 75-85 parts of zinc powder, 190-200 parts of quartz sand and 1.5-2 parts of ammonium chloride are required to be added for every 1000 parts of workpiece by mass; the total volume of the workpiece and each component after charging accounts for 80-85% of the volume of the rotary furnace;

s3: heating for the first time: sealing the rotary furnace and rotating the rotary furnace, heating the rotary furnace in the rotating process to raise the temperature inside the rotary furnace to 190-;

s4: and (3) heating for the second time: the rotary furnace keeps rotating, the rotary furnace is continuously heated, the temperature in the rotary furnace is raised to 250-255 ℃, and then the temperature is kept for 25-30 min;

s5: heating for the third time: the rotating furnace keeps rotating, the rotating furnace is continuously heated, the temperature in the rotating furnace is raised to 380-;

s6: after the third heating and heat preservation process is finished, naturally cooling the rotary furnace to 70-80 ℃, opening the rotary furnace and screening the contents while the contents are hot to obtain a workpiece subjected to zinc impregnation;

s7: and (5) sequentially washing, passivating, cleaning and drying the workpiece subjected to zinc impregnation to obtain a finished workpiece.

By adopting the technical scheme, the workpiece is pretreated by S1, impurities and oxide films on the surface of the metal workpiece are removed, so that the surface of the workpiece is smoother, and the workpiece can be better subjected to zinc impregnation; in the step S2, zinc powder, quartz sand and ammonium chloride are selected as a zincizing agent, compared with mixed metal powder, pure zinc powder is selected, the uniformity of a coating in the zincizing process can be greatly improved, the heat infiltration instability caused by coatings with various components is prevented, and the quartz sand does not participate in reaction, so that the mechanical energy of the zinc powder impacting a workpiece is improved due to zincizing, the zincizing efficiency is improved, and the specific dosage ratio among the workpiece, the zinc powder and the quartz sand is given, and a zincizing layer can have better uniformity under the dosage ratio; and the ammonium chloride is used as a permeation aid, ammonia gas and hydrogen chloride are released in the heating process, the hydrogen chloride reacts with the zinc powder to generate zinc chloride, and the zinc chloride is further heated to form single [ Zn ] atoms, so that the atom migration energy required in the zinc impregnation process is reduced, and the zinc impregnation layer is more uniform. 15% -20% of the volume is reserved in the rotary furnace after charging, so that the zinc powder and the workpiece can be provided with a movement space, and the zinc powder and the workpiece can have enough impulse in collision.

In the process of zincizing, heating is divided into three steps of S3, S4 and S5, ammonium chloride is fully heated and decomposed under the condition of 190-195 ℃ during the first heating, the ammonium chloride is fully decomposed to generate enough hydrogen chloride before the zinc powder reaches the zincizing temperature, and the hydrogen chloride is fully contacted with the zinc powder in the heat preservation process; in the second heating process, the temperature is kept at the temperature of 250-255 ℃, and at the temperature, the hydrogen chloride can fully react with the zinc powder to generate zinc chloride without thermal decomposition of the generated zinc chloride, so that the zinc chloride content in the system is continuously improved; in the third heating process, the generated zinc chloride can be decomposed at the temperature of 380-450 ℃, and because enough zinc chloride is fully formed in the second heating and heat preservation process, high-density Zn atoms can effectively collide with a workpiece from the early stage in the zinc impregnation process, the condition that the zinc impregnation layer is uneven due to uneven distribution of the Zn atoms in the environment in the early stage of reaction is reduced, and the zinc impregnation efficiency can be improved. In the heat preservation process of 150-180min, chlorine generated by the decomposition of zinc chloride and zinc powder continuously generate new zinc chloride, so that a higher zinc chloride content is continuously kept in the system and a dynamic balance is kept, and the workpiece can be effectively impacted by the Zn atom in the whole process.

And after the zincification is finished, cooling the rotary furnace to 70-80 ℃, screening while the rotary furnace is hot so as to prevent the zinc powder from being bonded with the surface of the workpiece after being completely cooled, and improving the corrosion resistance of a zincification layer through the cleaning and passivating treatment of the step S7 to obtain the finished zincification workpiece.

Preferably, in the charging process of the step S2, lanthanum sulfate is added into the rotary furnace, and the addition amount of the lanthanum sulfate is 0.5-1 part per 1000 parts by mass of the workpiece.

By adopting the technical scheme, a small amount of lanthanum sulfate is added in the zincizing process, so that the corrosion resistance and stability of the zincizing layer can be improved.

Preferably, in step S2, the mesh number of the zinc powder used is 350-400, and the particle size of the quartz sand used is 2-3 mm.

By adopting the technical scheme, the grain sizes of the used zinc powder and quartz sand are limited, and the zinc powder and the quartz sand with the grain sizes can better impact a workpiece when being subjected to zinc impregnation, so that the zinc impregnation efficiency and the zinc impregnation layer smoothness are improved.

Preferably, the specific process of the pretreatment in step S1 is: soaking the workpiece in a sodium hydroxide solution with the concentration of 50-55% and the temperature of 40-60 ℃ for 4-6min, then soaking the workpiece in a normal-temperature hydrochloric acid solution with the concentration of 30-35% for 8-10min, finally soaking the workpiece in a sodium hydroxide solution with the concentration of 4-6% and the temperature of 80-85 ℃ for 3-5S, and finally centrifugally drying.

By adopting the technical scheme, the specific process of pretreatment is published and explained, a workpiece is soaked in a sodium hydroxide solution with the concentration of 50-55% and the temperature of 40-60 ℃ for 4-6min, alkali washing is carried out, oil stains on the surface of the metal can be better removed, then acid washing is carried out, an oxide film on the surface of the workpiece is removed, and the corrosion of the metal can be reduced as much as possible while the oxide film is fully reacted by controlling the concentration, the temperature and the acid washing time of a hydrogen chloride solution; and finally, secondary alkali washing is carried out, the workpiece after acid washing is soaked in low-concentration sodium hydroxide for a short time, residual hydrogen chloride on the surface of the workpiece can be removed, and the low-concentration sodium hydroxide does not influence the workpiece, so that the workpiece does not need to be washed by clear water after secondary alkali washing, the process steps are simplified, and the production efficiency is improved. And finally, the workpiece can be dehydrated more quickly to meet the drying requirement of the subsequent process by centrifugal drying, the production efficiency is improved, and the influence of the high temperature of the traditional drying process on the workpiece can be reduced.

Preferably, the specific process of passivation in step S7 is as follows: soaking the washed workpiece in a normal-temperature chromium trichloride solution with the concentration of 15% -20% for 5-8min, taking out the workpiece, washing the workpiece with water for the second time, and soaking the workpiece in silica sol with the concentration of 8% -10% for 1-3 min.

By adopting the technical scheme, the workpiece is passivated in the trivalent chromium solution to generate a chromium passivation film, and then the workpiece is soaked in the silica sol to form a layer of sealing film on the surface of the passivation film, so that the corrosion resistance of the passivation film is greatly improved. And also provides more optimal concentrations of chromium trichloride and silica sol, and a more uniform and stable passivation film and sealing film can be obtained under the concentrations.

Preferably, the silica sol used has a colloidal particle size of 10-20nm and a viscosity of 5X 10 at 20 deg.C^-3-6×10^-3Pa·S。

By adopting the technical scheme, the grain diameter and the viscosity of colloidal particles of the silica sol are limited, and the prepared sealing film has better uniformity and corrosion resistance under the parameter.

Preferably, the rotating speed of the rotating furnace in steps S3 and S4 is 15-18r/min, and the rotating speed of the rotating furnace in step S5 is 23-25 r/min.

By adopting the technical scheme, when the first heating and the second heating are carried out, the lower rotating speed is adopted firstly, in the processes of decomposing ammonium chloride and generating zinc chloride, the mechanical energy of the impact of zinc powder and a workpiece is reduced, part of zinc powder is prevented from directly reacting with the workpiece to destroy the flatness of a subsequent zinc impregnation layer, and when the third heating is carried out, the higher rotating speed is adopted, the zinc impregnation efficiency of [ Zn ] atoms can be improved, and the zinc impregnation layer is more uniform.

Preferably, in step S6, the rotary furnace is kept rotating continuously during the cooling process, and the rotating speed of the rotary furnace is 10-12 r/min.

By adopting the technical scheme, the zinc powder continuously rotates at low speed in the cooling process, so that the zinc powder is prevented from being solidified on the surface of a workpiece in the cooling process, and a zincizing layer of the workpiece is kept flat.

In summary, the present application includes at least one of the following beneficial technical effects:

1. pure zinc powder is used for zinc impregnation, so that the uniformity of a zinc impregnation layer structure can be improved, and the impact mechanical energy during zinc impregnation can be improved by adding quartz sand, so that the zinc impregnation efficiency is improved; ammonium chloride is added in the zincizing process, and the zincizing process is more uniform through a three-stage step heating process, so that the flatness of the zincizing layer and the zincizing efficiency are further improved. In addition, parameters of each process step are also given, and the zincizing layer can be more flat under the process parameters.

2. Lanthanum sulfate is added in the zincizing process, so that the corrosion resistance of the zincizing layer can be improved.

3. The application also provides the optimized particle sizes of the zinc powder and the quartz sand, and the smoothness and the zinc impregnation efficiency of a zinc impregnation layer can be improved.

4. The application also preferably provides a specific process for pretreatment and passivation, and the specific process can improve the production efficiency and enable the zincized layer to have better corrosion resistance.

5. The application provides the preferred rotational speed of cubic heating and rotation furnace among the cooling process, has improved the zinc impregnation effect, has further improved the planarization on zinc impregnation layer.

Detailed Description

Examples

Example 1: a powder zinc impregnation process, which relates to a zinc impregnation process,

the method comprises the following specific steps:

s1: pretreatment: soaking a workpiece in a sodium hydroxide solution with the concentration of 50% and the temperature of 40 ℃ for 5min, then soaking the workpiece in a normal-temperature hydrochloric acid solution with the concentration of 30% for 10min, finally soaking the workpiece in a sodium hydroxide solution with the concentration of 5% and the temperature of 80 ℃ for 5S, and finally centrifugally spin-drying;

s2: charging: feeding 1000kg of the pretreated workpiece into a rotary furnace, simultaneously adding 75kg of zinc powder, 190kg of quartz sand and 1.5kg of ammonium chloride, and uniformly mixing, wherein the mesh number of the used zinc powder is 300 meshes, and the particle size of the quartz sand is 1 mm; and selecting a rotary furnace with a proper size, so that the total volume of the workpiece and the components after charging accounts for 80% of the volume of the rotary furnace.

S3: heating for the first time: sealing the rotary furnace and rotating the rotary furnace at the rotating speed of 20r/min, heating the rotary furnace in the rotating process to raise the temperature inside the rotary furnace to 190 ℃, and then preserving the heat for 15 min;

s4: and (3) heating for the second time: the rotary furnace keeps rotating at the rotating speed of 20r/min, the rotary furnace is continuously heated, the temperature in the rotary furnace is raised to 250 ℃, and then the temperature is kept for 25 min;

s5: heating for the third time: the rotary furnace keeps rotating at the rotating speed of 20r/min, and is continuously heated, so that the temperature inside the rotary furnace is raised to 380 ℃, and the temperature is kept for 150 min;

s6: after the third heating and heat preservation process is finished, naturally cooling the rotary furnace to 70 ℃, opening the rotary furnace and screening the contents while the contents are hot to obtain a workpiece subjected to zinc impregnation;

s7: washing the workpiece after zincification in clear water to remove residual zinc powder on the surface and reduce the temperature of the workpiece to normal temperature, soaking the workpiece in a normal-temperature chromium trichloride solution with the concentration of 15% for 5min, taking out the workpiece, washing the workpiece for the second time to remove residual chromium ions on the surface, soaking the workpiece in silica sol with the concentration of 8% for 2min for surface sealing, and sealing the surface of the workpiece with siliconThe average colloidal particle diameter of the sol is 7nm, and the viscosity of the silica sol is 4 x 10^-3Pa.S, finally washing with water for the third time, and drying to obtain the finished product workpiece.

Example 2: a powder zinc impregnation process, which relates to a zinc impregnation process,

the difference from the example 1 is that the amount of zinc powder, quartz sand and ammonium chloride is different, and the technological parameters are different. The amounts of the components and the process parameters are shown in table 1 below.

Examples 3 to 4: a powder zinc impregnation process, which relates to a zinc impregnation process,

the difference from the example 1 is that lanthanum sulfate is also added into the rotary furnace during charging in step S2, and the usage of lanthanum sulfate and various process parameters are shown in table 1 below.

Examples 5 to 6: a powder zinc impregnation process, which relates to a zinc impregnation process,

the difference from example 1 is that the number of zinc powders used and the particle size of the quartz sand used are different, and the specific parameters are shown in table 1 below.

Examples 7 to 8: a powder zinc impregnation process, which relates to a zinc impregnation process,

the difference from the example 1 is that the rotation speed of the rotary furnace in the steps S3, S4 and S5 is different, and the specific parameters are as shown in the following table 1.

Examples 9 to 10: a powder zinc impregnation process, which relates to a zinc impregnation process,

the difference from example 1 is that the silica sol particle size and the silica sol viscosity in step S7 are different, and the specific parameters are shown in table 1 below.

Example 11: a powder zinc impregnation process, which relates to a zinc impregnation process,

the difference from embodiment 1 is that step S6 is: and after the third heating and heat preservation process is finished, naturally cooling the rotary furnace, keeping the rotary furnace rotating at the rotating speed of 10r/min in the cooling process until the rotary furnace is cooled to 70 ℃, opening the rotary furnace, and screening the contents while the contents are hot to obtain the zinc-infiltrated workpiece.

The rest of the process steps and parameters were the same as in example 1.

Table 1: EXAMPLES 1-10 raw material usage and various process parameter tables

Comparative example

Comparative example 1: a powder zincing process is different from the process of example 1 in that ammonium chloride is not added during charging in step S2, and only a single heating and holding is performed during zincing.

The method comprises the following specific steps:

s1: pretreatment: soaking a workpiece in a sodium hydroxide solution with the concentration of 50% and the temperature of 40 ℃ for 5min, then soaking the workpiece in a normal-temperature hydrochloric acid solution with the concentration of 30% for 10min, finally soaking the workpiece in a sodium hydroxide solution with the concentration of 5% and the temperature of 80 ℃ for 5S, and finally centrifugally spin-drying;

s2: charging: feeding 1000kg of the pretreated workpiece into a rotary furnace, and simultaneously adding 75kg of zinc powder and 190kg of quartz sand, uniformly mixing, wherein the mesh number of the used zinc powder is 300 meshes, and the particle size of the quartz sand is 1 mm; selecting a rotary furnace with a proper size, so that the total volume of the workpiece and each component after charging accounts for 80% of the volume of the rotary furnace;

s3: heating and zinc impregnation: sealing the rotary furnace and rotating the rotary furnace at the rotating speed of 20r/min, heating the rotary furnace in the rotating process to raise the temperature inside the rotary furnace to 380 ℃, and then preserving the heat for 190 min;

s4: after the heating and heat preservation processes are finished, naturally cooling the rotary furnace to 70 ℃, opening the rotary furnace and screening the contents while the contents are hot to obtain a workpiece subjected to zinc impregnation;

s5: washing the workpiece after zinc impregnation in clear water to remove residual zinc powder on the surface and cooling the workpiece to normal temperature, then soaking the workpiece in a normal-temperature chromium trichloride solution with the concentration of 15% for 5min, taking out the workpiece, washing the workpiece with water for the second time to remove residual chromium ions on the surface, soaking the workpiece in silica sol with the concentration of 8% for 2min for surface sealing, wherein the average colloidal particle size of the silica sol is 7nm, and the viscosity of the silica sol is 4 x 10 < -3 > Pa.S, finally washing with water for the third time, and drying to obtain the finished workpiece.

Comparative example 2: a powder zinc impregnation process, which relates to a zinc impregnation process,

the difference from example 1 is that only a single heating and incubation is performed during zincing.

The method comprises the following specific steps:

s1: pretreatment: soaking a workpiece in a sodium hydroxide solution with the concentration of 50% and the temperature of 40 ℃ for 5min, then soaking the workpiece in a normal-temperature hydrochloric acid solution with the concentration of 30% for 10min, finally soaking the workpiece in a sodium hydroxide solution with the concentration of 5% and the temperature of 80 ℃ for 5S, and finally centrifugally spin-drying;

s2: charging: feeding 1000kg of the pretreated workpiece into a rotary furnace, simultaneously adding 75kg of zinc powder, 190kg of quartz sand and 1.5kg of ammonium chloride, and uniformly mixing, wherein the mesh number of the used zinc powder is 300 meshes, and the particle size of the quartz sand is 1 mm; selecting a rotary furnace with a proper size, so that the total volume of the workpiece and each component after charging accounts for 80% of the volume of the rotary furnace;

s3: heating and zinc impregnation: sealing the rotary furnace and rotating the rotary furnace at the rotating speed of 20r/min, heating the rotary furnace in the rotating process to raise the temperature inside the rotary furnace to 380 ℃, and then preserving the heat for 190 min;

s4: after the heating and heat preservation processes are finished, naturally cooling the rotary furnace to 70 ℃, opening the rotary furnace and screening the contents while the contents are hot to obtain a workpiece subjected to zinc impregnation;

s5: washing the workpiece after zinc impregnation in clear water to remove residual zinc powder on the surface and cooling the workpiece to normal temperature, then soaking the workpiece in a normal-temperature chromium trichloride solution with the concentration of 15% for 5min, taking out the workpiece, washing the workpiece with water for the second time to remove residual chromium ions on the surface, soaking the workpiece in silica sol with the concentration of 8% for 2min for surface sealing, wherein the average colloidal particle size of the silica sol is 7nm, and the viscosity of the silica sol is 4 x 10 < -3 > Pa.S, finally washing with water for the third time, and drying to obtain the finished workpiece.

Comparative examples 3 to 4: a powder zinc impregnation process, which relates to a zinc impregnation process,

the difference from example 1 is that the zinc powder, quartz sand and ammonium chloride are used in different amounts in step S2, and the specific amounts are shown in table 3 below.

Comparative examples 5 to 6: a powder zinc impregnation process, which relates to a zinc impregnation process,

the difference from example 1 is that the heating temperature and the holding time in steps S3, S4 and S5 are different, and the specific parameters are shown in Table 2 below.

Comparative example 7: a powder zinc impregnation process, which relates to a zinc impregnation process,

the difference from embodiment 1 is that step S6 is: and after the third heating and heat preservation process is finished, cooling the rotary furnace to the room temperature of 25 ℃, opening the rotary furnace and screening the contents to obtain the workpiece subjected to zinc impregnation. Specific parameters are shown in table 2 below.

Table 2: comparative examples 3-7 raw material usage and various process parameter record table

Performance test

According to the method, the uniformity and the corrosion resistance of the zincizing layer on the surface of the workpiece after zincizing are improved mainly through a process, so that detection tests are mainly carried out around the two aspects.

Test one: the principle of the zincizing layer uniformity detection test is as follows: the thickness of the zincification layer at different positions of the same workpiece is detected by a thickness gauge, and the uniformity of the zincification layer is judged by comparing the thickness of the zincification layer at different positions on the workpiece.

Test subjects: examples 1-2, 5-8, comparative examples 1-7.

Test equipment: CT300 coating thickness gauge.

The test steps are as follows: using a flat workpiece with a cross section of 3cm × 3cm and a thickness of 0.5cm as a processing object, randomly extracting 5 workpiece samples from the workpieces processed in examples 1-2, 5-8 and comparative examples 1-7 respectively, dividing the workpiece samples into different test groups, randomly extracting 3 measurement points from each workpiece sample, detecting the coating thickness of 15 measurement points in each test group by using a CT300 coating thickness gauge, and calculating a sample standard deviation S of the thickness, wherein the calculation formula is as follows:

in the formula d_iIs the thickness of each measurement point.

The test results are shown in table 3 below:

table 3: standard deviation S (. mu.m) of samples of examples 1-2, examples 5-8 and comparative examples 1-7

Comparing the data of examples 1-2 and comparative examples 1-2 in Table 3, it can be seen that the S values of examples 1-2 are significantly less than those of comparative examples 1-2, and that the S value of comparative example 2 is also less than that of comparative example 1, which indicates that the workpieces processed by examples 1-2 have better uniformity of zincated layer. Therefore, the uniformity of the zincizing layer can be obviously improved by adding ammonium chloride in the zincizing process and adopting a multi-step heating and heat preservation process at a specific temperature, and the effect is not obvious if only the ammonium chloride is simply added and a process which is not heated is not adopted.

Comparing the data of examples 1-2 and comparative examples 3-4 in Table 3, it can be seen that the S value of examples 1-2 is significantly less than that of comparative examples 3-4, indicating that the zincated layer uniformity of the workpiece processed by examples 1-2 is better. This is because the amounts of zinc powder, quartz sand and ammonium chloride used in examples 1-2 and comparative examples 3-4 were different, thus illustrating that the amounts of zinc powder, quartz sand and ammonium chloride used in examples 1-2 were in a more preferable range.

Comparing the data of examples 1-2 and comparative examples 5-6 in Table 3, it can be seen that the S value of examples 1-2 is smaller than that of comparative examples 5-6, indicating that the zincating layer of the workpiece processed by examples 1-2 has better uniformity. This is because the heating temperatures and holding times for the first, second and third times in examples 1-2 and comparative examples 5-6 are different, and thus it can be illustrated that the heating temperatures and holding times for the first, second and third times in examples 1-2 are more preferable process parameter ranges.

Table 3 comparing the data of examples 1-2 and comparative example 7, it can be seen that the S value of examples 1-2 is smaller than that of comparative example 7, indicating that the workpieces processed by examples 1-2 have better uniformity of zincated layer. This is because comparative example 7 lowered the temperature of the work piece to too low before the screening, the work piece could not be screened while it was hot, and part of the zinc powder adhered to the surface of the work piece to affect the uniformity of the zincified layer.

Comparing the data in Table 3 for examples 1-2 and examples 5-6, it can be seen that the S values for examples 5-6 are less than those for examples 1-2, thus illustrating the better uniformity of the zincated layer on the workpiece processed in examples 5-6. This is because the zinc powders of different mesh numbers and the silica sands of different particle sizes were used in examples 5 to 6, thereby illustrating that the mesh numbers of the zinc powders and the particle sizes of the silica sands in examples 5 to 6 are in more preferable ranges.

Comparing the data of examples 1-2 and examples 7-8 in Table 3, it can be seen that the S values of examples 7-8 are less than those of examples 1-2, thus demonstrating that the zinciferous layers of the workpieces processed by examples 7-8 are more uniform. This is because the rotating furnace in the third heating and heat-insulating process in examples 7 to 8 uses different rotation speeds, and the lower rotation speed is used first for the first heating and the second heating, and the mechanical energy of the impact between the zinc powder and the workpiece is reduced in the processes of decomposition of ammonium chloride and generation of zinc chloride, thereby preventing part of the zinc powder from directly reacting with the workpiece and damaging the flatness of the subsequent zincized layer, and the higher rotation speed is used for the third heating, thereby improving the zincizing efficiency of the [ Zn ] atom.

And (2) test II: corrosion resistance test principle: the corrosion resistance of the workpiece after zinc impregnation can be compared by placing the workpiece in a corrosive environment and comparing the time when the workpiece starts to corrode.

Test subjects: examples 1 to 10, comparative examples 1 to 7.

The test steps are as follows: taking a flat workpiece with the cross section of 3cm multiplied by 3cm and the thickness of 0.5cm as a processing object, randomly extracting 3 workpiece samples from the workpieces processed in the examples 1-10 and the comparative examples 1-7 respectively, dividing the workpiece samples into different test groups, and carrying out ' accelerated test of cyclic exposure under salt fog, dry and wet conditions ' on the workpiece samples of each test group according to the national standard GB/T20854-2007 of the people's republic of China, wherein each test parameter is as follows:

1. test equipment: the volume of the exposure box adopted in the standard appendix A is 0.8m³The pressure of the compressed air of the spraying device is 80 kPa;

2. test parameters are as follows: the temperature under the condition of salt fog is 30 ℃, and the concentration of the salt solution is 50 g/L; the temperature under "dry" conditions was 60 ℃ and the relative humidity was 20% RH; the temperature under "wet" conditions was 50 ℃ and the relative humidity was 98% RH; the time required for the transition between the salt spray, "dry" and "wet" conditions was 10 min; the collection rate of the salt spray solution in the test preparation stage is 1.4ml/h, the concentration of the collected sodium chloride solution is 50.6g/L, and the pH value is 6.8;

the end of the test was taken as the corrosion of all the workpieces, during which the salt spray, "dry" and "wet" conditions were cycled continuously. The time at which corrosion began to occur was recorded for each set of workpieces, and the average time t at which corrosion began to occur for each test set was calculated, and the results of the experiment are shown in table 4 below.

Table 4: average time t (h) to onset of corrosion for examples 1-10 and comparative examples 1-7

Comparing the data of examples 1-2 and examples 3-4 in Table 4, it can be seen that the t values of examples 3-4 are significantly higher than those of examples 1-2, which indicates that the zincated layers of examples 3-4 have better corrosion resistance. This is because the lanthanum sulfate is added in the zincating process in examples 3 to 4, which can effectively improve the corrosion resistance of the zincating layer.

Comparing the data in Table 4 for examples 1-2 and examples 9-10, it can be seen that the t values for examples 9-10 are significantly higher than for examples 1-2, which illustrates the better corrosion resistance of the zincated layers of examples 9-10, since examples 9-10 use silica sols of different colloidal particle sizes and viscosities during passivation. Thus, the ranges of the parameters in examples 9 to 10 in which the particle diameter and viscosity of the silica sol were more preferable were shown.

Comparing the data of examples 1-2, examples 5-8 and comparative examples 1-7 in table 4, and analyzing the test results and conclusions of test one, it can be seen that the corrosion resistance of the zincated layer is related to the uniformity of the zincated layer, and the more uniform the zincated layer is, the higher the corrosion resistance is under the influence of the process steps and parameters, thus illustrating the effect of the various processes and parameters of the present application on the corrosion resistance of the zincated layer.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.