Direct current electric field enhanced powder chromizing method for inner surface of tubular part, and apparatus thereof

A technology of DC electric field and inner surface, applied in the field of chemical heat treatment on the surface of metal parts, can solve the problems of high price, high cost, long processing time, etc., to improve the performance and life, increase the concentration and activity, and shorten the holding time. Effect

Inactive Publication Date: 2012-04-25
CHANGZHOU UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The concentration of active chromium atoms increases with the increase of chromizing temperature, but chromizing at high temperature for a long time not only consumes high energy, but also coarsens the structure of the matrix material of the part and reduces the mechanical properties of the matrix material of the part. When the subsequent heat treatment is used to adjust the matrix In a certain range, increasing the content of chromium-donating agent, activator, and infiltration agent in the infiltration agent can also increase the active chromium atoms and increase the infiltration rate, but some activators and infiltration agents are more expensive. Expensive, and some will produce side effects such as corrosion during the chromizing process, which will affect the surface quality and accelerate the failure of the infiltration box; generally, ferrochrome powder or chromium powder is used as the chromium supply agent, and the chromium layer is uniform, but the amount of ferrochrome powder or chromium powder Large, the content of ferrochrome powder in the infiltration agent is generally as high as 55%, and the content of chromium powder is generally as high as 50%, and the utilization rate is not high
Therefore, when the current technology is chromizing the inner surface of tubular metal parts, there are disadvantages such as high processing temperature, long processing time, high energy consumption, low utilization rate of the infiltration agent, high cost, and large deformation of the workpiece after chromizing.

Method used

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  • Direct current electric field enhanced powder chromizing method for inner surface of tubular part, and apparatus thereof
  • Direct current electric field enhanced powder chromizing method for inner surface of tubular part, and apparatus thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0021] Material to be infiltrated: seamless steel pipe made of 08Cr2AlMo steel, with an outer diameter of 25mm, an inner diameter of 20mm, and a length of 30mm; 2%; potassium fluoroborate, 5%), loosening agent (charcoal, 1%), filler (silicon carbide, balance).

[0022] Fill the solid powder chromizing agent 8 composed of the above materials into the steel pipe sample 6 to be chromized on the inner wall, place the cylindrical electrode 4 in the infiltrating agent, the distance between the cylindrical electrode 4 and the inner wall of the steel pipe 6 to be infiltrated is 8mm, and the two ends of the steel pipe 6 Install sealing cover 5 and insulating cover 3 at both ends of cylindrical electrode 4, and seal with refractory mud sealing material 10 again. The cylindrical electrode 4 is used as the positive pole, and the steel pipe 6 is used as the negative pole. The two poles are respectively connected to the positive and negative poles of a DC power supply system 7 with a contin...

Embodiment 2

[0025] Material to be infiltrated: seamless steel pipe made of 08Cr2AlMo steel, the outer diameter of the steel pipe is 25mm, the inner diameter is 20mm, and the length is 30mm. 5%; ammonium chloride, 1%), loosening agent (charcoal, 1%), filler (silicon carbide, balance).

[0026] The chromizing method and device are the same as in Example 1, the chromizing temperature: 750° C., the chromizing holding time is 4 hours, the distance between the cylindrical positive electrode and the infiltrated steel pipe sample (negative electrode) is 8 mm, and the A DC electric field with a current strength of 6 amps. Test results: The inner wall of the 08Cr2AlMo steel pipe obtained a chromizing layer of nearly 55 μm; while using the same infiltrating agent formula, using the existing conventional powder chromizing process, the same chromizing process at 750 ° C for 4 hours, the thickness of the chromizing layer on the inner wall of the 08Cr2AlMo steel pipe less than 10 μm.

Embodiment 3

[0028] Material to be infiltrated: welded steel pipe of 20 steel material, the outer diameter of the steel pipe is 30mm, the inner diameter is 24mm, and the length is 30mm; the composition of the chromizing agent: chromium donor (ferrochromium, content 40%), activator and infiltration agent (potassium fluoroborate, 5%; ammonium chloride; 1%), loosening agent (charcoal, 5%), filler (silicon carbide, balance).

[0029] The chromizing method and device are the same as in Example 1, the chromizing temperature: 800° C., the chromizing time of 4 hours, the distance between the cylindrical positive electrode and the infiltrated steel pipe sample (negative electrode) is 8 mm, and the distance between the cylindrical positive electrode and the infiltrated steel pipe sample is A DC electric field with a current strength of 6 amperes was applied. Test results: A chromizing layer of about 70 μm was obtained on the inner wall of the 20 steel pipe, and the same formula of the infiltrating a...

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Abstract

The present invention relates to a direct current electric field enhanced powder chromizing method for an inner surface of a tubular part, and an apparatus thereof. According to the method, a power chromizing agent is filled in the inner of a tubular part requiring treatment; a columnar electrode is placed in the middle of the power chromizing agent; both ends of the tubular part are sealed and insulated; the columnar electrode is adopted as the positive electrode, and the tubular part is adopted as the negative electrode, wherein the positive electrode is parallel to the negative electrode; the tubular part (including the columnar electrode) and an oxidation resistance filler are sealed in a chromizing box; the chromizing box is placed in a box type furnace to carry out heating; a direct current electric field is applied between the tubular part and the positive electrode when the temperature is achieved, such that the rapid chromizing on the inner surface of the tubular part can be achieved. Compared to the chromizing rate of the existing method, the chromizing rate of the method of the present invention can be improved at least 0.5-4 times (depending on the concrete process parameters) at the different temperature of the temperature range of 700-1000 DEG C. In addition, with the method and the apparatus, the powder chromizing rate on the inner surface of the tubular part can be improved, the chromizing temperature can be reduced, and the utilization rate of the chromizing agent can be improved.

Description

technical field [0001] The invention belongs to a method and device for chemical heat treatment on the surface of metal parts, in particular to a DC electric field enhanced powder infiltration method for modifying the inner surface of tubular metal parts and improving the inner surface's corrosion resistance, high temperature oxidation resistance and wear resistance. Chromium methods and apparatus. Background technique [0002] When the inner surface of some tubular metal parts is in contact with normal temperature, high temperature corrosive medium or fluid containing hard particles, the failure is mainly caused by surface corrosion, oxidation and wear. Using high-alloy materials with overall good corrosion resistance, high temperature oxidation resistance and wear resistance to make these parts will greatly increase the product cost. The inner surface is modified by chromizing to improve the corrosion resistance, high temperature oxidation resistance and wear resistance o...

Claims

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Application Information

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IPC IPC(8): C23C10/38
Inventor 谢飞潘建伟
Owner CHANGZHOU UNIV
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