Annealing and pickling method for titanium plate strip

Abstract

The invention discloses a method for annealing and pickling a titanium plate strip, and belongs to the field of annealing and pickling of hot rolled strips. According to the method, a titanium plate strip is subjected to annealing heat treatment through a heating furnace, is bent, withdrawn and straightened through a scale breaker to obtain a good model, is subjected to surface scale polishing and mechanical dephosphorization through steel shots of a shot blasting machine, and is subjected to hydrochloric acid, secondary brushing and mixed acid pickling to obtain the titanium plate which is free of scale on the surface and uniform in color. According to the method, efficient annealing and acid pickling of the hot-rolled strip are achieved, and meanwhile the titanium plate of a good model is obtained through the straightening effect of the scale breaker; the hot-rolled titanium plate passes through the hot-rolling annealing pickling line, so that grains of the hot-rolled titanium plate are recovered and recrystallized, and iron oxide scales on the surface are cleaned; the pickled titanium plate is good in surface quality, free of iron scale residues, flat and straight in strip steel model, and free of edge waves and big belly plate defects.

Description

Technical Field

[0001] The invention relates to a method for annealing and pickling a titanium plate strip, and belongs to the field of annealing and pickling a hot-rolled strip. Background Art

[0002] Titanium plate (pure titanium strip) is a finished product obtained by hot rolling a cast billet into a titanium coil of a certain thickness, then annealing and heat treatment of the hot rolled titanium material through an annealing and pickling line, and removing the surface oxide scale through descaling, shot blasting and pickling. The oxide scale on the surface of the hot rolled titanium plate is mainly due to oxidation caused by contact between the plate surface and the control during the hot rolling process. The oxide scale will affect the quality of the subsequent rolled titanium plate surface, reduce the surface finish, increase the corrosion rate, and affect the surface coating effect. Therefore, the surface of the titanium plate with high surface quality and high thickness accuracy needs to be treated before cold rolling. Summary of the invention

[0003] The invention aims to provide a method for annealing and pickling titanium plate and strip, which can effectively remove the oxide scale on the surface of hot-rolled pure titanium strip and obtain titanium plate and strip with uniform surface color, no oxide scale and good shape.

[0004] The invention provides a method for annealing and pickling of titanium plates and strips. The titanium plates and strips are subjected to annealing and heat treatment in a heating furnace, bent and straightened by a phosphorus-breaking machine to obtain a good version, and the surface oxide scale is blasted and dephosphorized by steel shots of a shot blasting machine. The titanium plates are then pickled with hydrochloric acid, brushed twice, and pickled with mixed acid (nitric acid + hydrofluoric acid) to obtain titanium plates without oxide scale on the surface and with uniform color.

[0005] Furthermore, pickling uses high-concentration acid pickling and precise pickling temperature, and precise control of plate temperature makes annealing more uniform.

[0006] Furthermore, the production speed of the titanium plate and strip through the furnace and pickling section is 9-15 m / min.

[0007] The above method is further described as follows: Main technical parameters for annealing and pickling of titanium plates and strips: 1. Fixed annealing temperature: Divide the heating furnace into 7 furnace zones, and set the temperature of each furnace zone as follows: Zone 1: 830℃±15℃; Zone 2: 830±15℃; Zone 3: 840±15℃; Zone 4: 840±10℃; Zone 5: 850±10℃; Zone 6: 850±5℃; Zone 7: 850±5℃; Ensure that the steel strip is annealed evenly without overburning or underburning.

[0008] 2. Process parameters of solidification and phosphorus breaking machine For products whose finished products are hot-rolled plates, in order to ensure the straightness of the product surface, descaling and straightening must be carried out during the process, and the elongation is set to: 0.5%~3%; the descaling machine is a five-roller BWG straightening machine (2# and 4# rollers are fixed rollers, and the following 1#, 3#, and 5# rollers are adjustable rollers), and the descaling roller pressure is set as follows:

[0009] 3. The shot blasting machine should ensure the removal effect of steel plate scale. The process parameters are as follows: Shot blasting speed: 1650 rpm ~ 1850 rpm Throwing current: 85A~115A; 4. Pickling process parameters are required to ensure that the steel plate is clean of iron scales, has uniform color, and has no under-acid or over-acid phenomenon. The specific requirements for pickling are as follows: Hydrochloric acid section: Hydrochloric acid concentration: 120g / l~180g / l, hydrochloric acid iron ion concentration ≤60g / l Hydrochloric acid temperature: 60℃~75℃ Mixed acid section: Nitric acid concentration: 100g / l~150g / l Hydrofluoric acid concentration: 15g / l~25g / l Mixed acid iron ion: ≤60g / l Mixed acid section temperature: 40~55℃.

[0010] The present invention is applied to the hot line of a cold rolling mill, and can continuously and stably pickle titanium plate coils. The production specifications have a thickness range of 2.0 mm to 6.0 mm and a width range of 1000 mm to 1300 mm. The produced titanium plates can be used as raw materials to continue cold rolling to thinner specifications, and can also be directly used as finished products.

[0011] Beneficial effects of the present invention: (1) The hot-rolled titanium plate according to the present invention can be subjected to a hot-rolling annealing and pickling line to recover the grains of the hot-rolled titanium plate and clean the surface iron oxide scale; (2) Highly efficient annealing and pickling of hot-rolled strips are achieved, and at the same time, a titanium plate with good shape is obtained through the straightening effect of the descaling machine; (3) After pickling, the surface quality of the titanium plate is good, with no iron scale residue, the strip steel plate is straight, and there are no edge waves or big belly plate defects. DETAILED DESCRIPTION

[0012] The present invention is further illustrated by the following examples, but is not limited to the following examples.

[0013] The No. 1 hot line of the cold rolling mill produces titanium plates with thicknesses of 3.0 mm, 4.0 mm, 5.0 mm, and 6.0 mm and a width of 1000 mm, and pickling 240 tons. Specific examples are provided below to illustrate the method of the present invention. Example 1

[0014] Take 3.0mm thickness as an example.

[0015] Take specific process parameters: 1. Fixed annealing temperature:

[0016] The above temperature setting ensures uniform annealing of the steel strip.

[0017] 2. Process parameters of solidification and phosphorus breaking machine For hot-rolled plates, in order to ensure the straightness of the product surface, the scale breaking and straightening process must be carried out, and the elongation is set to 2.0%; The scale-breaking machine is a five-roller BWG tension leveler, and the scale-breaking roll pressure setting is:

[0018] 3. Shot blasting machine process parameters to ensure the removal of steel scale Shot blasting speed: 1750 rpm Polishing head current: 103A; 4. Pickling process parameters are required to ensure that the steel plate is clean of iron scales, has uniform color, and has no under-acid or over-acid phenomenon. The specific requirements for pickling are as follows: Hydrochloric acid section: Hydrochloric acid concentration: 146g / l, hydrochloric acid iron ion concentration: 51g / l Hydrochloric acid temperature: 67°C Mixed acid section: Nitric acid concentration: 120g / l Hydrofluoric acid concentration: 20g / l Mixed acid iron ion: 36g / l Mixed acid section temperature: 45°C; 5. The production speed is 12~15m / min; 40 tons of pickling, the pickling surface quality is good, no iron scale residue, the strip shape is straight, no edge waves, big belly plate defects. Example 2

[0019] Take 4.0mm thickness as an example.

[0020] Take specific process parameters: 1. Fixed annealing temperature:

[0021] The above temperature setting ensures uniform annealing of the steel strip.

[0022] 2. Process parameters of solidification and phosphorus breaking machine For hot-rolled plates, in order to ensure the straightness of the product surface, the scale breaking and straightening process must be carried out, and the elongation is set at 1.5%; The scale-breaking machine is a five-roller BWG tension leveler, and the scale-breaking roll pressure setting is:

[0023] 3. Shot blasting machine process parameters to ensure the removal of steel scale Shot blasting speed: 1750 rpm Throwing current: 106A; 4. Pickling process parameters are required to ensure that the steel plate is clean of iron scales, has uniform color, and has no under-acid or over-acid phenomenon. The specific requirements for pickling are as follows: Hydrochloric acid section: Hydrochloric acid concentration: 146g / l, hydrochloric acid iron ion concentration: 51g / l Hydrochloric acid temperature: 68°C Mixed acid section: Nitric acid concentration: 120g / l Hydrofluoric acid concentration: 20g / l Mixed acid iron ion: 36g / l Mixed acid section temperature: 46°C; 5. Production speed is 10~13m / min; 52 tons of pickling was carried out, and the surface quality of the pickling was good, with no iron scale residue, the strip shape was straight, and there were no edge waves or big belly defects. Example 3

[0024] Take 5.0mm thickness as an example.

[0025] Take specific process parameters: 1. Fixed annealing temperature:

[0026] The above temperature setting ensures uniform annealing of the steel strip.

[0027] 2. Process parameters of solidification and phosphorus breaking machine For hot-rolled plates, in order to ensure the straightness of the product surface, the scale breaking and straightening process must be carried out, and the elongation is set to 1%; The scale-breaking machine is a five-roller BWG tension leveler, and the scale-breaking roll pressure setting is:

[0028] 3. Shot blasting machine process parameters to ensure the removal of steel scale Shot blasting speed: 1750 rpm Polishing head current: 108A; 4. Pickling process parameters are required to ensure that the steel plate is clean of iron scales, has uniform color, and has no under-acid or over-acid phenomenon. The specific requirements for pickling are as follows: Hydrochloric acid section: Hydrochloric acid concentration: 146g / l, hydrochloric acid iron ion concentration: 51g / l Hydrochloric acid temperature: 68°C Mixed acid section: Nitric acid concentration: 120g / l Hydrofluoric acid concentration: 20g / l Mixed acid iron ion: 36g / l Mixed acid section temperature: 47°C; 5. Production speed is 9~10m / min; 47 tons of pickling was carried out, and the surface quality of the pickling was good, with no iron scale residue, the strip shape was straight, and there were no edge waves or big belly defects. Example 4

[0029] Take 6.0mm thickness as an example.

[0030] Take specific process parameters: 1. Fixed annealing temperature:

[0031] The above temperature setting ensures uniform annealing of the steel strip.

[0032] 2. Process parameters of solidification and phosphorus breaking machine For hot-rolled plates, in order to ensure the straightness of the product surface, the scale breaking and straightening process must be carried out, and the elongation is set to 0.8%; The scale-breaking machine is a five-roller BWG tension leveler, and the scale-breaking roll pressure setting is:

[0033] 3. Shot blasting machine process parameters to ensure the removal of steel scale Shot blasting speed: 1750 rpm Throwing current: 106A; 4. Pickling process parameters are required to ensure that the steel plate is clean of iron scales, has uniform color, and has no under-acid or over-acid phenomenon. The specific requirements for pickling are as follows: Hydrochloric acid section: Hydrochloric acid concentration: 146g / l, hydrochloric acid iron ion concentration: 51g / l Hydrochloric acid temperature: 67°C Mixed acid section: Nitric acid concentration: 120g / l Hydrofluoric acid concentration: 20g / l Mixed acid iron ion: 36g / l Mixed acid section temperature: 44°C; 5. Production speed is 9~10m / min; 101 tons of pickling was carried out, and the pickling surface quality was good, with no iron scale residue, the strip shape was straight, and there were no edge waves or big belly defects.

Claims

1. A method for annealing and pickling titanium plate and strip, characterized in that: The titanium plate and strip are annealed in a heating furnace, bent and straightened in a phosphorus-breaking machine to obtain a good version, and the surface oxide scale is mechanically dephosphorized by shot blasting with steel shots in a shot blasting machine. Then, it is pickled with hydrochloric acid, heavily brushed, and pickled with mixed acid to obtain a titanium plate with no oxide scale on the surface and uniform color.

2. The method for annealing and pickling titanium plate and strip according to claim 1, characterized in that: Pickling uses high-concentration acid pickling and precise pickling temperature, and accurately controls the plate temperature to make annealing more uniform; the mixed acid includes nitric acid and hydrofluoric acid.

3. The method for annealing and pickling titanium plate and strip according to claim 1, characterized in that: The production speed of titanium plate and strip passing through the furnace and pickling section is 9~15m / min.

4. The method for annealing and pickling titanium plate and strip according to claim 1, characterized in that: During the annealing heat treatment process in the heating furnace, the heating furnace is divided into 7 furnace zones, and the annealing temperature of each furnace zone is set as follows: Zone 1: 830℃±15℃; Zone 2: 830±15℃; Zone 3: 840±15℃; Zone 4: 840±10℃; Zone 5: 850±10℃; Zone 6: 850±5℃; Zone 7: 850±5℃; Ensure that the steel strip is annealed evenly without overburning or underburning.

5. The method for annealing and pickling titanium plate and strip according to claim 1, characterized in that: The process parameters of the dephosphorization machine are: the elongation is set to 0.5%~3%; the dephosphorization machine is a five-roller straightening machine, among which the 1#, 3#, and 5# rollers are adjustable rollers, and the descaling roller pressure is set as follows: 。 6. The method for annealing and pickling titanium plate and strip according to claim 1, characterized in that: During the mechanical phosphorus removal process of the shot blasting machine, the process parameters are as follows: shot blasting speed: 1650 rpm~1850 rpm; shot blasting head current: 85A~115A.

7. The method for annealing and pickling titanium plate and strip according to claim 1, characterized in that: The process parameter requirements for hydrochloric acid pickling and mixed acid pickling are as follows: Hydrochloric acid section: Hydrochloric acid concentration: 120g / l~180g / l, hydrochloric acid iron ion concentration ≤60g / l; Hydrochloric acid temperature: 60℃~75℃; Mixed acid section: Nitric acid concentration: 100g / l~150g / l; Hydrofluoric acid concentration: 15g / l~25g / l; Mixed acid iron ion: ≤60g / l; Mixed acid section temperature: 40~55℃.

8. The method for annealing and pickling titanium plate and strip according to claim 1, characterized in that: The titanium plate and strip have a thickness range of 2.0 mm to 6.0 mm and a width range of 1000 mm to 1300 mm. The produced titanium plate is used as a raw material and further cold-rolled to a thinner specification or directly used as a finished product.

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