What are the production characteristics of stainless steel se

What are the production characteristics of stainless steel seamless pipe? 
 

Stainless steel Seamless pipe production methods are mainly hot-rolled, hot extrusion, cold rolling and cold drawing of these four kinds. Their production characteristics from the plastic, deformation resistance, spread, the application of sensitivity and thermal conductivity, antioxidant properties of these aspects observed.

 

Detailed below.

 

Stainless steel Seamless pipe

Plastic Martensitic stainless steels are easy to perforate at elevated temperatures when they are single austenite, although perforation performance can be significantly reduced if the two-phase tissue is included. Stainless steel tube Billet Heating temperature is usually 1130-1160 ℃, the furnace tail temperature is lower than 900 ℃, the final rolling temperature is greater than the critical point transition temperature, low carbon is higher than 850 ℃, high carbon can not be greater than 925 ℃.

Martensitic stainless steel with the increase in carbon content, the strength and hardness of stainless steel will also be significantly enhanced, but the plasticity will be weakened, so cold drawing is best to use the core of the rod to pull, because after the air is easy to burst. The high temperature plasticity of austenitic stainless steels is related to the residual α. Usually the plasticity decreases as the alpha phase increases. In addition to the alpha phase, in austenitic stainless steel There will be other residues, such as various types of carbide, intermetallic compounds. The excess ductility of the stainless steel is affected, and the degree of influence depends on the quantity and state. When the excess phase is in the net distribution on the grain boundary, the plasticity of the stainless steel material can be greatly deteriorated.

 

Austenitic stainless steel under high temperature plasticity, deformation resistance will become larger, the use of oblique rolling perforation should pay particular attention to the selection of reasonable deformation parameters and temperature parameters. Because ferritic stainless steel is a single phase, there is no phase change, so the length of heating time and temperature is high when the grain grow seriously, will significantly weaken the plasticity of stainless steel. The maximum heating temperature of stainless steel tube billet is 1000-1060 ℃. In this temperature range of stainless steel will have excellent plasticity. Cold drawn hammer before the heating temperature is 700-850 ℃, in heating to avoid carburizing, hammer after water quenching. Because ferrite chromium stainless steel will have room temperature brittleness, cold processing performance is relatively weak, cold drawing is easy to crack and pull off, so it is best to have a certain temperature conditions under the drawing system, the speed of pulling is not too large. When cold rolled ferritic stainless steel tube, the deformation degree of stainless steel pipe material is not higher than 40%-48%. According to the grain refinement degree, the degree of deformation can be increased to 55%-65% in the subsequent passage.

 

In order to prevent the stainless steel pipe from forming crack during rolling, the temperature rise of the stainless steel pipe is advantageous when rolling, so it is not necessary to use emulsion cooling tool and metal when rolling the stainless steel tube in most cases.

 

Deformation resistance Austenitic and martensitic stainless steel have greater deformation resistance, the processing hardening tendency is also relatively large, and high temperature recrystallization at a slower rate, so cold-rolled this type of stainless steel needs to pay special attention to equipment and motor capacity.

 

Both ferrite and semi ferrite low carbon stainless steels have similar deformation resistance to ordinary carbon steels.

 

Spread The spread of stainless steel, martensite stainless steel is 1.3 times times the spread of carbon steel, austenitic stainless steel is 1.35-1.5 times times, ferritic stainless steel is 1.55-1.6 times times. Therefore, it is necessary to pay attention to the control of transverse deformation, to take a relatively small degree of ellipse.

 

Cold, hot-rolled pipe hole-type ellipse should be higher, and to take a small number of road deformation, so as to avoid defects such as Rzi, in the absence of tension to reduce the thickness of the stainless steel tube wall thickening, and reducing the hole of the machine to take a larger size.

 

Sensitivity to stress Ferrite stainless steel is brittle at room temperature, the sensitivity of cold processing to stress is high, the sensitivity of hot rolling is low, and the water quenching can be done after rolling. Martensite Stainless steel has a high sensitivity to crack, cooling should not be too fast after hot rolling, usually take a heap of cold.

 

The sensitivity of austenitic stainless steels to crack is low and can be quenched after hot rolling.

 

Thermal conductivity The low-temperature thermal conductivity of stainless steel is worse, but the linear expansion coefficient is larger than that of carbon steel.

 

To ensure the heating quality to choose low-temperature (<800℃) of slow heating.

 

Oxidation resistance Because stainless steel has a certain antioxidant, heating to the formation of iron oxide skin is lower. However, the iron oxide has chromium, nickel oxides and very dense, cold pickling is also more difficult.

 

Often use HF+HNO3 to do acid pickling or acid compound pickling.