What are the main characteristics of stainless steel?

What are the main characteristics of stainless steel?

Usage of different welding performance requirements also vary. A class of cutlery on the welding performance in general is not required, even including some pot enterprises. But the vast majority of products are required welding materials properties, like second-class cutlery, mug, steel pipes, water heaters, drinking fountains.

The vast majority of stainless steel products require good corrosion resistance, like a second class tableware, kitchen utensils, water heaters, drinking fountains, and some foreign businessmen corrosion products also do test: NACL solution heated to boiling, pour some time after out of solution, wash and drying, said weight loss, to determine the degree of corrosion (Note: When polishing products, emery cloth or sandpaper because the ingredients contained Fe, will lead to the surface rust test)

Polished performance

Today’s society is generally in the production of stainless steel products are polished this process, only a few products such as water heaters, drinking fountains, interior, etc. do not need polishing. Therefore, the performance of which requires a good polishing materials. Factors affecting the performance of polishing the following main points:
① material surface defects. Such as scratches, pitting, excessive pickling.
② raw material problem. Hardness is too low, it is not easy to throw light (BQ bad) when polished, and the hardness is too low, in the deep drawing surface prone to orange peel, thus affecting BQ sex. BQ relatively high hardness like.
③ after deep drawing products, deformation of the surface area will be a great little black spots and RIDGING, thus affecting BQ sex.

Heat resistance

Refers to a high temperature heat resistance stainless steel can maintain its excellent physical and mechanical properties.
The impact of carbon: carbon in austenitic stainless steel is strong and stable formation. Given austenite and the austenite region of the expansion element. Carbon formation of austenite capacity of about 30 times that of nickel, carbon is an interstitial element, solid solution strengthening can significantly improve the strength of austenitic stainless steel. Austenitic stainless steel carbon can also improve performance in high concentration of chloride (eg boiling 42% MgCl2 solution) resistance to stress corrosion.

However, in austenitic stainless steels, carbon is often regarded as harmful elements, mainly due to the corrosion of the stainless steel under some conditions of use (such as by welding or by 450 ~ 850 ℃ heating), the carbon steel may Cr23C6 type carbon chromium compounds leading to the formation of a local high chromium chromium depleted, especially the corrosion resistance of the steel is decreased resistance to intergranular corrosion. As such. Chromium-nickel austenitic stainless steel is mostly carbon content of new developments since the 1960s, less than 0.03% or 0.02% ultra-low carbon type, you can know with lower carbon content, intergranular corrosion susceptibility of steel decreases, when the carbon content of less than 0.02% that has the most significant effect, some experimental pearl also noted that carbon will increase the tendency of pitting points chromium austenitic stainless steel. Due to the harmful effects of carbon, not only in austenitic stainless steel smelting control over, and in accordance with the requirements as low carbon content, and in the subsequent heat, cold and heat treatment process also prevents the stainless steel surface by carbon and chromium-free carbide precipitation.


When the number of atoms of chromium content in the steel of not less than 12.5%, the electrode potential of steel can be mutated by the negative potential to rise to the positive electrode potential. Prevent galvanic corrosion.

Troubleshooting hydraulic tank have?

(1) serious tank tank temperature plays a “hot flywheel” effect, can prevent the absorption of heat in the short term, it can be prevented in the cold environment of the hydraulic system of short-term idling is excessive cooling, but the tank is still the main contradiction “warm l. ” The temperature rise will result in severe multiple hydraulic system failure. The causes serious tank temperature.

(2) severe fuel tank fuel tank temperature plays a “hot flywheel” effect, can prevent the absorption of heat in the short term, it can be prevented in the cold environment of the hydraulic system of short-term idling is excessive cooling, but the tank is still the main contradiction “warm l. ” The temperature rise will result in severe multiple hydraulic system failure. The causes serious tank temperature.

① Gao tank set up in the vicinity of radiation temperature, ambient temperature, Gao, and molten plastic injection molding machine. With a high-power heating means are provided in this environment

② various hydraulic system pressure loss, such as overflow losses, throttling losses, losses along the pipeline and local losses, caused by the oil temperature will be converted into heat

③ oil viscosity inappropriate choice, too Gao or too low.

④ tank design and inadequate cooling area. Way to solve the serious rise follows.

① try to avoid the heat, but the plastic machinery 〖such as injection molding machines, extruders, etc.) because they have to melt the plastic, there must be a “source.”

② proper design of the hydraulic system, such as system should uninstall the loop, using the pressure, flow and power matching circuits and other high hydraulic accumulator system, to reduce the overflow losses, throttling losses and pipeline losses, reduce heat rise

③ Select Gao efficient components, precision machining and assembly efforts to raise Gao precision hydraulic components, reducing leakage losses, the volume of losses and mechanical losses caused by heating phenomenon.

④ correct piping: reduce too small for too long, too much bending branches along with the bus improperly brought loss and partial loss.

⑤ Select the correct oil viscosity.

⑥ tank design should be considered when there is sufficient heat dissipation area A.

(3) the oxidative degradation of oil produces oil tank oxidative degradation and oil type, temperature, rest time and the presence of the oxidation catalyst related. When selecting seed oil according to the working conditions and working environment, select species and performance in line with the oil viscosity, temperature at 30 ~ 55 ℃ rest means: Do not break too short, otherwise it will accelerate the deterioration of oil oxidation.

(4) inside the fuel tank oil tank oil pollution contaminants from outside intrusion, there is internally generated, there are remnants of the assembly.

① assembly remaining pieces such as peeling paint, welding slag. Before cleaning the tank assembly must be strictly surface and go strictly to rust oil, and then paint the inner wall of the tank.

② from outside intrusion of dust seal should be noted that at this time the tank and install air filter and air at the top of the tank connected, so that the air is filtered before entering the tank. Often doubles as a fuel inlet air filter, now have been standard parts (EF type) for sale. Can be equipped with about 100 mesh copper mesh filter to filter added to the oil tank; also useful filter paper core, the better, but the atmosphere’s ability badly, so Zhixin larger capacity cartridges. In order to prevent outside intrusion of dirt inside the tank is sucked into the pump, the fuel tank to install partitions, to separate oil return area and absorbing areas. By partitions, extended back into the oil tank time to rest, to prevent oxidative degradation of oil, on the other hand is also conducive to the precipitation of dirt. Separator for oil level height of 3/4, as shown in Fig 3-88. Tank bottom should be tilted floor depending on the degree of tilt tank size and viscosity oil used, are generally set at the lowest part of the tank bottom drain plug at the bottom of the tank so that the accumulation of dirt to get cleared. Distance from the floor most of the suction pipe from Gao to be 150 plus 10 more, to prevent dirt being sucked people, as shown in Figure 3-89.

③ reduce contamination within the system generates a fuel tank to prevent condensation of moisture produced: it is necessary to select a sufficiently large capacity air cleaner, so that the heated air from the tank top as quickly as possible, does not condense into the cold water tank cover beads drop in the tank; the other large-capacity air cleaner or air vent, the top of the tank to eliminate the difference in space and atmospheric pressure, and prevent the top layer is lower than atmospheric pressure, from the outside into the dust. b. Use a good anti-rust performance lubricant reduces wear and rust generated material.

(5) oil tank air bubbles are difficult to separate oil return due to agitation in the tank, and easy to produce bubbles suspended in the oil folder, if they are with a person of the hydraulic system will generate a lot of it is chant (such as pump noise, cavitation and hydraulic cylinder crawling, etc.]. In order to prevent air bubbles in the fluid before it is sucked not eliminate the human pump. Set partition separated zone and back to the oil pump suction area, back to the oil separator was baffled, slow flow rates, which will help the bubble separation and the oil spill. But in this way is difficult to separate fine bubbles, the separation efficiency Gao.

Physical properties of stainless steel

Compared with steel

1. Density
Slightly higher than the density of steel ferritic and martensitic stainless steel, while slightly lower than austenitic stainless steel;

2, the resistivity
Resistivity by carbon steel, ferritic, martensitic and austenitic stainless steel Sort Ascending;

3, the size of the linear expansion coefficient of the sort similar, austenitic stainless steel and carbon steel up to minimum;

4, carbon steel, ferritic and martensitic stainless steel magnetic, non-magnetic austenitic stainless steel, but it will have to generate a magnetic work hardening, heat treatment method available martensitic transformation to eliminate this martensite organization and restore its non-magnetic.

Compared with austenitic stainless steel, has the following characteristics:
1) high resistivity, carbon steel is about 5 times.
2) a large linear expansion coefficient, 40% larger than that of carbon steel, and as the temperature rises, the value of the linear expansion coefficient is also increased accordingly.
3) low thermal conductivity, about 1/3 of carbon steel.

How to replace the hydraulic pump vane pump cartridge

First check 1. Install oil pump oil inlet flange seals and do have a pipeline is aging deformation (it is best to replace the new one), and should clean up the inner wall of dirt into the oil pipeline, oil pipeline inspection into each junction sealing performance.

2. Check that the motor shaft and bearing wear deformation, such as swing axle shaft deformation phenomenon should be confirmed or bearing wear, to prevent the motor due to issues affecting the life of the pump.

3. Check whether the coupling wear deformation, after installing the pump shaft is concentric with the motor shaft, the simplest way is to manually rotate the coupling (such as using the plug-in motor, the motor can be turned by hand rear cooling fan) Turn the intensity feeling homogeneous and flexible.

4. Before starting the motor to check the hydraulic oil tank is clean enough to clean the filter is deformed, it is recommended to thoroughly clean the tank, replace the standard new hydraulic oil and filter. To prevent burning pump phenomenon, before the start of the pump must be When you release the oil port of the pump discharge valve (if not vent the oil port of the pump slightly loosen joints) in order to exclude the pump and the air ducts and unloaded; the body is filled with hydraulic oil Jog style start, after operating normally (when no bubbles coming out) and then tighten the exhaust valve or the oil port connector.

5. In the process of working oil pump oil level should be noted, oil temperature, pressure, etc. use meets the requirements, the oil level after normal work generally higher than 50mm above the top of the filter, otherwise the pump easy to suck air and noise, oil best controlled at 60 degrees Celsius, the oil temperature is too high and prevent damage to the friction surface protection film formed on their own.

6. When replacing the pump core positioning holes in the pump housing to check whether the deformation, whether part of the inner shaft with external splines and spline wear pump core deformation, such as the positioning hole deformation or abrasion shaft key recommends that users replace the entire pump.

7. Check the seal (oil seal) is aging deformation, bearing wear loose (recommended replacement of the shaft seal and bearings), the replacement should be careful, consistent with the recommendations by the outside diameter of the seal (seal used) and outer diameter slightly larger than the bearing diameter, inside diameter slightly larger than the outside diameter of the shaft (bearing) flat hard objects to them to a fixed position to prevent deformation and damage bearing seal.

8. Check the old pump core models, the work is consistent direction, before installation to confirm the installation before the first clean the inner wall of the pump housing, together with lubricant and then loaded pump core, the installation is not very smooth as pump core in place to check pump stator core and is concentric with the oil pan, adjust the concentricity after the installation, the installation is to confirm whether the pump core positioning pins fixed to the positioning hole pump casing, check seals are complete and smooth. To prevent seal trimming, tightening the screw pump casing connection angle uniform response gradually tightened.

9. Adjust the pump out of the oil port direction, as long as the fixing screw screwed out of the pump casing, you can rotate the pump housing, the location rotating guide needed then tighten the screw; do not pull the pump core, in order to avoid pump core positioning pins and positioning hole pump housing dislocation or dislocation ring down the pump casing connection.

10. When the installation check oil pump oil inlet flange seals and do have a pipeline is aging deformation (it is best to replace the new one), and should clean up the inner wall of dirt into the oil pipeline, oil pipeline inspection into each junction sealing performance.

What are the common faults of the hydraulic pump eight?

A large pipeline pump output resistance


Whether an accurate output piping layout, pipe diameter can not be too small, the turning angle of the line ones

2 Check valves are flexible

3 appropriate outlet valve open until the operating point

Second, the water within the oil, gas more


4 oil inside the water, the bubbles control at about 100 ℃ -120 ℃ temperature, after slowly drained, can be gradually heated to operating point

Are five piping layout justice

6 Install three vent pipes and clog impeller


7 Clear the pipeline and road debris inside the impeller

8 Check whether the failure of four gate valves, inlet filter clogged


9 Regular cleaning filter

10 is not too dense mesh of five, pump inlet seal ring seal and impeller wear ring grim


11 to replace worn parts

12 caliber pump suction inlet that is less than or 100mm, mouth rings should be replaced when the gap is greater than 1.5mm; inhaling caliber or greater that is 125mm, while the mouth ring gap is greater than 2mm, should repair replacement

Six, speed and steering inaccurate


13 Check the speed value (measured by tachometer)

14 Check the line connection

15 is the reverse operation

Seven, the density of the fluid viscosity transport departing from the basic value


16 When ordering parameters deviate media failure should inquire eight factory, the device is too low NPSH S (steam energy margin is too low)


17 Check and adjust if necessary high level trough

18 pump inlet valve is fully open, and check the filter

19 When the high slot to the pump inlet piping resistance is too large, re-piping