Stainless steel is actually iron with high purity. The principle of this refining process is simple, but the actual operation is difficult. Stainless steel plate, hot rolling refers to the first heating of the rough embryo and then rolling into a thin plate, because after heating the metal becomes soft, easy to shape, but high temperature will lead to material changes and expansion and contraction deformation, accuracy can not reach. Cold rolling is direct rolling, not heating, but requires high equipment, the accuracy of the plate is also high, a few millimeters can be zero.
Here is the content:
General requirements
The manufacture of stainless steel plate should have the conditions of ventilation, cleaning and civilized production. Stainless steel materials and parts shall be protected from long-term open storage and mixed storage. It requires timely feeding, centralized use, timely recovery and storage in designated areas. A special floor or rubber plate for preventing iron ion pollution shall be laid on the storage and manufacturing site of workpieces. The roller frame is equipped with rubber wheels. Prevent stepping on the surface of stainless steel plate. If it's unavoidable, you should wear soft soled shoes without nails and foot covers, and then wipe the surface clean. Use tools, such as copper hammer, wood hammer, stainless steel shovel or quenching tool steel shovel, etc. to keep the workpiece out of contact with iron as far as possible. The grinding wheel is made of pure oxide. The ink or marking pen for material marking shall not contain metal pigment, and the content of sulfur and chlorine shall be ≤ 25ppm. Prevent bumps and scratches. In the process of lifting and manufacturing stainless steel plate or parts, the surface of the steel plate, equipment and mould shall be kept clean to prevent welding beans, slag and oxide scale from pressing into the surface of workpiece. The spreader should be equipped with a copper pad. Nylon sling is preferred and is used for stainless steel parts. It is not allowed to be confused with other carbon steel. If steel wire rope is used, rubber hose or hemp rope must be used. Wood or rubber board shall be laid on the sawing machine for steel pipe cutting, and a special saw blade shall be used. Except for the cutting line, other marking lines shall not be crossed with "scriber" and punched with "punch". A hard color pen or marker pen can be used. It can also be marked with ink without metallic pigment and with sulfur and chlorine content less than 25ppm. Stainless steel parts should be cold formed as far as possible. When hot forming is adopted, the material shall not contact the coke in the coke oven. The heating temperature is 510 ~ 1150 ℃, and the heating times in the hot forming process is more than twice. The plate shall be cut by shearing or plasma cutting, and the slag after plasma cutting shall be removed. The bumps and scratches on the surface should be repaired. The grinding depth of plate thickness ＜ 10mm shall not exceed 0.3mm; the grinding depth of plate thickness ＞ 10mm shall not exceed 0.5mm, and shall not exceed the negative deviation of the plate. Stainless steel head procurement requires the supplier to supply after pickling and passivation, and the surface quality meets the requirements of article 7.4.
Welding
Preparation and welding environment of stainless steel plate before welding. The storehouse of welding rod, flux and other welding materials shall be kept dry, and the relative humidity shall not exceed 60%.
When any of the following conditions occur in the welding environment and there are no effective protective measures, welding is prohibited:
a) The wind speed of manual welding is more than 10m / s,
b) When gas shielded welding, the wind speed is greater than 2m / s,
c) The relative humidity is more than 90%,
d) Rain and snow environment.
The welding temperature of stainless steel plate shall not be lower than 5 ℃. When the ambient temperature is lower than 5 ℃, the weldment heated at room temperature shall be heated to 15 ℃ within 100 mm of the weld joint. It can be preheated by oxygen acetylene flame. Check the preheating temperature with a surface thermometer or a temperature tester.
Weld cleaning: stainless steel wire brush or grinding wheel shall be used to clean the plasma cutting surface. Before welding, alcohol shall be used to wipe off the oil stain in the groove and within the range of 20 mm nearby.
Welding process: The welding seam welded with pressure parts must pass the welding procedure qualification. In the welding process of stainless steel plate, the welder must follow the welding procedure specification. Welding requirements for temporary auxiliary parts on stainless steel plate parts: temporary auxiliary parts shall be avoided as far as possible, and materials similar to the original stainless steel plate shall be used for welding if necessary; positioning welding, spot welding and welding of temporary auxiliary parts shall be carried out according to the product welding process regulations. When welding stainless steel parts or containers, it is strictly forbidden to put the grounding wire directly on the stainless steel workpiece. The grounding wire must be firmly connected with the workpiece through clips made of the same or similar materials to prevent ignition. It is strictly forbidden to remove the temporary auxiliary parts and arc striking and extinguishing plate by positioning welding, spot welding and welding. Instead, it should be removed by mechanical methods such as air shovel or high-speed grinding wheel.
Heat treatment
Overall or partial heat treatment shall be carried out according to the drawing, and the heat treatment shall be outsourced according to the process requirements. After cold forming, if the deformation rate exceeds 15%, heat treatment should be carried out to eliminate the processing stress and improve the ductility.
Unidirectional tension (e.g. rolled steel plate)
ε=(δ/2Rf)×(1－Rf /Ro) ×100%
Biaxial tension (such as cylinder flanging and cold pressed head)
ε=(1.5δ/2Rf)×(1－Rf /Ro) ×100%
Where:
ε - deformation rate of steel plate,%,
δ - nominal thickness of steel plate, mm,
RF - center radius of steel plate after bending, mm,
Ro --- center radius of steel plate before bending, for flat plate, RO is infinite, mm.
Cold formed stainless steel head can not be heat treated, and hot formed parts must be heat treated. The heating temperature is 1000 ~ 1150 ℃, and the end temperature of hot work is greater than or equal to 750 ℃. Pressure test and compactness test. The medium for pressure test is generally water with chloride ion content ≤ 25ppm. Carry out density test or ammonia penetration test according to the drawing requirements. The required method is in accordance with the process specification for pressure test and compactness test.
Surface treatment
According to the drawing requirements, pickling and passivation treatment shall be carried out on the surface of stainless steel plate.
The surface quality requirements of stainless steel plate to be pickled. The oil, welding slag and spatter on the weld surface and both sides must be cleaned. When the oil pollution is serious, use 3-5% alkali solution or cleaning solvent to remove the oil pollution, and wash it with clean water. For the surface to be pickled and passivated, the weld undercut, scratch, scratch, splash damage and other defects shall be polished smooth, and the weld bead shall be removed or ground. It is forbidden to clean stainless steel surface with carbon steel brush. The paint on the surface shall be removed by chemical method (such as banana water). The oxide scale of stainless steel hot working parts can be removed by mechanical sand blasting. The sand must be pure silicon or alumina. Overheating (tempering) should be avoided when grinding the surface with grinding wheel. After cleaning, clean it with clean water (the content of chloride ion in the water is not more than 25mg / L). The surface and weld of stainless steel plate shall be cleaned with cotton yarn. For pickling and passivation treatment, the first operation should be carried out on the local surface of small parts or similar materials.
Effective measures shall be taken to prevent corrosion of stainless steel plate or steel parts after manufacturing. Acid pickling and passivation pretreatment can only be carried out after the specified items are inspected as qualified according to the requirements of drawings and process documents. Formulate safety measures for pickling and passivation, and determine necessary tools and labor protection articles.
Pickling and passivation operation.
Only pretreated stainless steel plates or parts can be pickled and passivated. The passivation paste is evenly applied on the stainless steel surface and welding seam, the coating thickness is 1-2mm, and the coating thickness of welding spot is slightly thick. It can be cleaned after 1-3 hours at room temperature. When cleaning the welding place, the seriously heat affected area can be cleaned with stainless steel wire brush. After cleaning, clean with water to ensure that the surface of stainless steel plate is clean without residual traces. For the oxide surface of hot pressed head or heat treatment parts, the coating is about 2mm. After staying for 5-10 hours, generally brush it once with steel wire brush, and then wipe it repeatedly with return wire or cotton yarn. After all cleaning, clean it with water to ensure that the surface of stainless steel plate is clean without residual traces. In the process of acid pickling, operators must observe carefully and timely to prevent excessive corrosion on the surface of the container.
Pickling and passivation quality inspection:After pickling and passivation, the surface of stainless steel plate shall be free of obvious corrosion traces, uneven color stripes, and oxidation color on the weld and hot working surface. The passivation film is complete and uniform, showing gray metal color.
Surface residual acidity test: The surface of the stainless steel plate after surface treatment shall be free of residual acid. During the inspection, the pH test paper can be dipped in water and pasted on the surface of the workpiece. If the color of the test paper does not change to red, it is qualified. The qualified stainless steel plate parts or containers should be wiped dry or blown dry with compressed air. Stainless steel plate containers and parts after pickling and passivation are not allowed to scratch the passivation film during handling, lifting and storage.
Precautions
Pickling passivation paste operation must be carried out outdoors or indoors with good ventilation.
For pickling and passivation treatment, the first operation should be carried out on the local surface of small parts of stainless steel plate or similar materials.
In the process of pickling, operators must observe carefully and timely to prevent the surface of the stainless steel plate containers from being corroded too much. Effective measures should be taken for carbon steel parts to prevent corrosion.
After pickling, the surface of stainless steel plate shall be free of obvious corrosion traces, uneven color stripes, and oxidation color on the weld and hot working surface.
During operation, operators must wear acid resistant clothing, gloves, masks and eye protection. Pickling in containers must be carried out with qualified gas masks under the supervision of special personnel.
Austenitic stainless steel plate parts with heat treatment requirements shall be subject to pickling and passivation treatment after heat treatment according to the drawing requirements.
The pickling passivation paste should be kept away from heat sources by special personnel. The residue and waste water after treatment should be neutralized with lime milk or calcium carbide paste in time to prevent environmental pollution.
Do not operate in strong sunlight to prevent stainless steel plate pickling passivation paste drying, affecting the passivation effect.
If you want to know the production process of stainless steel plate, Jiangsu C.J.M Stainless Steel Group will provide relevant step information. Our process steps are in good order, each step has quality control, unqualified products will be destroyed internally. You can rest assured to buy our stainless steel products. Tel. + 86-18092577236, post office postmaster@ssplatechina.com.
