Surface treatment process of seamless aluminum alloy cold drawn pipe

Abstract

The invention provides a surface treatment process of a seamless aluminum alloy cold drawn pipe. The surface treatment process comprises the following steps: step 1, preparing a pickling solution; step 2, acid pickling of the aluminum alloy blank pipe; 3, the aluminum alloy pipe is washed after acid pickling; 4, phosphating the aluminum alloy pipe; 5, flushing the aluminum alloy pipe after phosphorization; step 6, saponifying the aluminum alloy pipe; step 7, saponification effect judgment: after saponification is completed, the saponification effect is judged, whether a saponification layer meets the requirement or not is specifically judged, and if the thickness of the saponification layer is not enough, saponification treatment in the step 6 is repeated; and 8, surface treatment of the aluminum alloy pipe is completed. A saponification layer can be attached to the surface of the aluminum pipe subjected to surface treatment through the technology, and the lubricating requirement in the cold drawn pipe production process is met.

Description

Technical Field

[0001] The invention belongs to the field of aluminum tube surface treatment technology, and specifically relates to a surface treatment technology for a seamless aluminum alloy cold-drawn tube. Background Art

[0002] In the pre-production treatment of seamless aluminum alloy cold-drawn tubes, surface treatment is a key step and even determines the direction of the process route. The purpose of surface treatment is the same as that of seamless carbon steel cold-drawn tubes (hereinafter referred to as steel tubes), which is to remove oil, dust, etc., and also need to add surface lubrication.

[0003] The surface of aluminum alloy has an aluminum oxide film, which isolates the matrix from the external environment and prevents the formation of a stable lubricating layer on its surface. Therefore, the surface is often lubricated by oiling. If a chemical reaction is used, fluorine element needs to be used to react with it to form fluorine aluminum salt. However, the phosphating film generated by this method is very sensitive to the composition, temperature, pH value, etc. of the phosphating solution, and is difficult to control in the actual production process. Based on this, the physical and chemical properties of aluminum alloy tubes determine that the existing surface treatment process of steel pipes cannot be used to achieve subsequent cold drawing operations.

[0004] At present, in the cold drawing process of seamless aluminum alloy cold drawn tubes (hereinafter referred to as aluminum tubes), lubricating oil is often applied to the surface as a lubricant, and lubricating oil spraying is also used during the cold drawing process. Moreover, if lubricating oil is used for surface lubrication, lubricating oil will be introduced into the production equipment and each process, which is difficult to clean; in addition, this method has high requirements for lubricating oil, and special equipment is required to filter the lubricating oil, which increases the processing cost. Summary of the invention

[0005] The purpose of the present invention is to provide a surface treatment process for a seamless aluminum alloy cold-drawn tube, by treating the surface of the aluminum alloy tube so as to form a lubricating layer on its outer surface, thereby facilitating its subsequent cold drawing process, and well replacing the traditional oiling process, solving the problems of inconvenient cleaning of the lubricating oil and high filtering cost.

[0006] In order to realize the above technical features, the object of the present invention is achieved as follows: a surface treatment process of a seamless aluminum alloy cold-drawn tube comprises the following steps: Step 1, preparation of pickling solution: Put new industrial hydrochloric acid into the pickling tank, and continue to add iron filings into the pickling tank until the pickling liquid changes from yellow-green to cyan, so that a certain concentration of ferrous ions is formed in the pickling liquid, thereby preparing the pickling liquid; Step 2, pickling of aluminum alloy blank tube: The aluminum alloy blank tube is placed in a pickling tank, and then pickled for a certain time, so that a metal iron layer of a certain thickness is replaced on the outer surface of the aluminum alloy blank tube; Step 3, flushing of aluminum alloy tube after pickling: Pick up the aluminum alloy tube after pickling, and then rinse the residual acid on the surface of the aluminum alloy tube; Step 4, phosphating of aluminum alloy tube: The aluminum alloy tube is placed in a phosphating bath for phosphating treatment; Step 5, flushing of aluminum alloy tube after phosphating: Pick up the aluminum alloy tube after phosphating, and then rinse off the residual phosphating liquid on the surface of the aluminum alloy tube; Step 6, saponification of aluminum alloy tube: The aluminum alloy tube is placed in a saponification tank for saponification; Step 7, determination of saponification effect: After the saponification is completed, the saponification effect is judged, specifically whether the saponification layer meets the requirements. If the thickness of the saponification layer is not enough, the saponification process is repeated in step 6; Step 8: Surface treatment of aluminum alloy tube is completed.

[0007] The concentration of industrial hydrochloric acid in the pickling tank in step 1 is 18%±3%.

[0008] The concentration of ferrous ions formed in step 1 is 4.5-6.3 g / L.

[0009] The pickling solution prepared in step 1 can be reused. Before use, the color of the pickling solution is evaluated or the concentration of ferrous ions is measured. After pickling 1,000 tons of products, it is evaluated whether it can continue to be used. After pickling 500 tons, it is evaluated again until it can no longer meet the use requirements.

[0010] In the step 2, the pickling time is 5 to 8 minutes, or when a large number of bubbles are generated on the surface of the aluminum alloy blank tube, the pickling is completed after another 1 to 3 minutes.

[0011] In the phosphating process in step 4, the phosphating solution used is phosphoric acid and zinc ions, the specific phosphating time is 30 minutes, and the phosphating temperature is 70°C.

[0012] During the saponification process in step 6, the saponification time used is 30 minutes and the saponification temperature is 70°C.

[0013] During the phosphating process in step 4, a phosphating film will be formed on the outer surface of the aluminum alloy tube.

[0014] During the saponification process in step 6, a saponification layer will be formed on the outer surface of the aluminum alloy tube, and it will play a lubricating role during the cold drawing process of the aluminum alloy tube.

[0015] The present invention has the following beneficial effects: 1. The present invention provides a surface treatment process for a seamless aluminum alloy cold-drawn tube without introducing special equipment or updating the production line, which can simultaneously complete the cleaning and lubrication of the aluminum tube, so that the aluminum tube meets the cold-drawn production requirements.

[0016] 2. The process in the present invention is highly consistent with the surface treatment process of steel pipes. If the factory already has a steel pipe production line, the production cost of aluminum pipes can be greatly reduced.

[0017] 3. The surface saponification layer of the aluminum tube treated by the process of the present invention is slightly better than that of the steel tube. At the same time, the process of the present invention does not introduce fluorine into the production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0019] Figure 1 It is a process flow chart of the present invention.

[0020] Figure 2 This is the pickling reaction process of the present invention.

[0021] Figure 3 This is the phosphating reaction process of the present invention.

[0022] Figure 4 This is the saponification reaction process of the present invention.

[0023] Figure 5 It is a comparison diagram of phosphating and saponifying after pickling with hydrofluoric acid + hydrochloric acid (top) and pickling and phosphating and saponifying according to the scheme of the present invention (bottom). DETAILED DESCRIPTION

[0024] The embodiments of the present invention are further described below in conjunction with the accompanying drawings.

[0025] Embodiment 1: See also Figure 1 The present invention provides a surface treatment process for a seamless aluminum alloy cold-drawn tube, comprising the following steps: Step 1, preparation of pickling solution: Put new industrial hydrochloric acid into the pickling tank, and continue to add iron filings into the pickling tank until the pickling liquid changes from yellow-green to cyan, so that a certain concentration of ferrous ions is formed in the pickling liquid, thereby preparing the pickling liquid; Step 2, pickling of aluminum alloy blank tube: The aluminum alloy blank tube is placed in a pickling tank, and then pickled for a certain time, so that a metal iron layer of a certain thickness is replaced on the outer surface of the aluminum alloy blank tube; Step 3, flushing of aluminum alloy tube after pickling: Pick up the aluminum alloy tube after pickling, and then rinse the residual acid on the surface of the aluminum alloy tube; Step 4, phosphating of aluminum alloy tube: The aluminum alloy tube is placed in a phosphating bath for phosphating treatment; Step 5, flushing of aluminum alloy tube after phosphating: Pick up the aluminum alloy tube after phosphating, and then rinse off the residual phosphating liquid on the surface of the aluminum alloy tube; Step 6, saponification of aluminum alloy tube: The aluminum alloy tube is placed in a saponification tank for saponification; Step 7, determination of saponification effect: After the saponification is completed, the saponification effect is judged, specifically whether the saponification layer meets the requirements. If the thickness of the saponification layer is not enough, the saponification process is repeated in step 6; Step 8: Surface treatment of aluminum alloy tube is completed.

[0026] Furthermore, the concentration of industrial hydrochloric acid in the pickling tank in step 1 is 18%±3%.

[0027] Furthermore, the concentration of ferrous ions formed in step 1 is 4.5-6.3 g / L.

[0028] Furthermore, the pickling solution prepared in step 1 can be reused. The color of the pickling solution is evaluated or the concentration of ferrous ions is measured before use. After pickling 1,000 tons of products, it is evaluated whether it can continue to be used. After pickling 500 tons, it is evaluated again until it can no longer meet the use requirements.

[0029] Furthermore, in step 2, the pickling time is 5 to 8 minutes, or when a large number of bubbles are generated on the surface of the aluminum alloy blank tube, the pickling is completed after another 1 to 3 minutes.

[0030] Furthermore, in the phosphating process in step 4, the phosphating solution used is phosphoric acid and zinc ions, the specific phosphating time is 30 minutes, and the phosphating temperature is 70°C.

[0031] Furthermore, in the saponification process in step 6, the saponification time used is 30 minutes and the saponification temperature is 70°C.

[0032] Furthermore, during the phosphating process in step 4, a phosphating film will be formed on the outer surface of the aluminum alloy tube.

[0033] Furthermore, during the saponification process in step 6, a saponification layer will be formed on the outer surface of the aluminum alloy tube, and it will play a lubricating role during the cold drawing process of the aluminum alloy tube.

[0034] Embodiment 2: Step 1: Put new industrial hydrochloric acid into the pickling tank. The acid concentration in the pickling solution is 18%±3%. Add a small amount of iron filings and wait until the pickling solution changes from yellow-green to turquoise. The reference ferrous ion concentration is 4.5-6.3g / L. The pickling solution can be reused. Evaluate the color of the pickling solution or measure the ferrous ion concentration before use. After pickling 1,000 tons of products, evaluate whether it can continue to be used. After pickling 500 tons, evaluate again until it can no longer meet the use requirements; Step 2: Put the aluminum tube into the pickling tank for a reference of 5 minutes. Or when a large number of bubbles appear on the surface of the aluminum tube, the pickling should be completed in about 1 minute; Step 3: Rinse. Rinse the residual pickling liquid on the surface of the aluminum tube; Step 4: Phosphating. Put the aluminum tube into the phosphating tank for phosphating. The main components of the phosphating tank are phosphoric acid and zinc ions. The phosphating time and temperature of the steel tube can be referred to for phosphating. The phosphating time can also be appropriately extended. Step 5: Rinse. Rinse the residual phosphating solution on the surface of the aluminum tube; Step 6: Saponification. Place the aluminum tube into the saponification tank for saponification. The saponification tank can refer to the saponification time and temperature of the steel tube for saponification. Step 7: After drying, evaluate the thickness of the surface saponification layer. If the saponification effect is not satisfactory, repeat the saponification.

[0035] Reaction principle of the present invention: During the pickling process of the aluminum tube, in addition to using acid to wash away the oil stains, it also undergoes a replacement reaction with ferrous ions to form a layer of iron on the surface. The iron crystal grows on the surface of the aluminum tube, and theoretically there are a large number of nanopores inside. In the next step of phosphating, it reacts with the phosphating solution to produce an iron phosphating film. The reaction is more complete than the phosphating process of the steel tube, and more and more pores are generated. In the final saponification, a thicker saponification layer can be generated, which plays a lubricating role in the cold drawing process of the aluminum tube.

Claims

1. A surface treatment process for a seamless aluminum alloy cold-drawn tube, characterized in that: The following steps are involved: Step 1, preparation of pickling solution: Put new industrial hydrochloric acid into the pickling tank, and continue to add iron filings into the pickling tank until the pickling liquid changes from yellow-green to cyan, so that a certain concentration of ferrous ions is formed in the pickling liquid, thereby preparing the pickling liquid; Step 2, pickling of aluminum alloy blank tube: The aluminum alloy blank tube is placed in a pickling tank, and then pickled for a certain time, so that a metal iron layer of a certain thickness is replaced on the outer surface of the aluminum alloy blank tube; Step 3, flushing of aluminum alloy tube after pickling: Pick up the aluminum alloy tube after pickling, and then rinse the residual acid on the surface of the aluminum alloy tube; Step 4, phosphating of aluminum alloy tube: The aluminum alloy tube is placed in a phosphating bath for phosphating treatment; Step 5, flushing of aluminum alloy tube after phosphating: Pick up the aluminum alloy tube after phosphating, and then rinse off the residual phosphating liquid on the surface of the aluminum alloy tube; Step 6, saponification of aluminum alloy tube: The aluminum alloy tube is placed in a saponification tank for saponification; Step 7, determination of saponification effect: After the saponification is completed, the saponification effect is judged, specifically whether the saponification layer meets the requirements. If the thickness of the saponification layer is not enough, the saponification process is repeated in step 6; Step 8: Surface treatment of aluminum alloy tube is completed.

2. The surface treatment process of a seamless aluminum alloy cold-drawn tube according to claim 1 is characterized in that: The concentration of industrial hydrochloric acid in the pickling tank in step 1 is 18%±3%.

3. The surface treatment process of a seamless aluminum alloy cold-drawn tube according to claim 2 is characterized in that: The concentration of ferrous ions formed in step 1 is 4.5-6.3 g / L.

4. The surface treatment process of a seamless aluminum alloy cold-drawn tube according to claim 2 is characterized in that: The pickling solution prepared in step 1 can be reused. Before use, the color of the pickling solution is evaluated or the concentration of ferrous ions is measured. After pickling 1,000 tons of products, it is evaluated whether it can continue to be used. After pickling 500 tons, it is evaluated again until it can no longer meet the use requirements.

5. The surface treatment process of a seamless aluminum alloy cold-drawn tube according to claim 4 is characterized in that: In the step 2, the pickling time is 5 to 8 minutes, or when a large number of bubbles are generated on the surface of the aluminum alloy blank tube, the pickling is completed after another 1 to 3 minutes.

6. The surface treatment process of a seamless aluminum alloy cold-drawn tube according to claim 4, characterized in that: In the phosphating process in step 4, the phosphating solution used is phosphoric acid and zinc ions, the specific phosphating time is 30 minutes, and the phosphating temperature is 70°C.

7. The surface treatment process of a seamless aluminum alloy cold-drawn tube according to claim 4, characterized in that: During the saponification process in step 6, the saponification time used is 30 minutes and the saponification temperature is 70°C.

8. The surface treatment process of a seamless aluminum alloy cold-drawn tube according to claim 6, characterized in that: During the phosphating process in step 4, a phosphating film will be formed on the outer surface of the aluminum alloy tube.

9. The surface treatment process of a seamless aluminum alloy cold-drawn tube according to claim 7, characterized in that: During the saponification process in step 6, a saponification layer will be formed on the outer surface of the aluminum alloy tube, and it will play a lubricating role during the cold drawing process of the aluminum alloy tube.

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