Z6CND17.12 Powder Metallurgy Pressed Parts

Product Introduction

Product Description

• Mechanical properties

Hardness: annealed, ≤269HB; quenched and tempered, ≥55HV

• Heat treatment specification and metallographic structure

Heat treatment specifications: 1) Annealing, slow cooling at 800-920°C; 2) Quenching, oil cooling at 1050-1075°C; 3) Tempering, air cooling at 100-200°C.

Metallographic structure: The structure is characterized by martensitic type.

• Characteristics and scope of application

This stainless steel has good anti-rust ability. It is a high-quality stainless steel currently used in the high-end batch knife market. Its strength and sharpness are better than ATS-34.

The chromium content is as high as 16-18%. It is the second most commonly used stainless steel (after ATS-34), and it is also the first stainless steel accepted by swordsmiths.

And it has remained popular, especially since sub-zero treatments were developed, which strengthen the steel's toughness.

It has the disadvantage of being relatively viscous and heats up quickly when sanding, but it is easier to sand than any carbon steel and much easier to cut with a hand saw.

The annealing temperature of 440C is very low, and the hardness after quenching is high. The hardness usually reaches HRC56-58. It has good corrosion resistance (magnetic) and strong toughness. It is now more widely used in handmade knives and high-quality factory knives.

• Purpose

Knives, turbine blades, blades, nozzles, valves, board rulers, cutlery, scissors, bearings, etc.

Z6CND17.12 powder metallurgy pressed is used in the manufacture of stainless slices, mechanical cutting tools and shearing tools, surgical blades, high wear-resistant equipment parts, etc.

• Delivery status

Generally delivered in heat treatment state

Stainless steel

• Stainless steel effect

Stainless steel will not corrode, pit, rust, or wear. Stainless steel is also one of the strongest materials among architectural metal materials. Because stainless steel has good corrosion resistance, it allows structural components to permanently maintain the integrity of the engineering design. Chromium-containing stainless steel also combines mechanical strength and high elongation and is easy to process and manufacture parts, which can meet the needs of architects and structural designers.

• Typical uses of stainless steel

Most of the use requirements are to maintain the original appearance of the building for a long time. When determining the type of stainless steel to be selected, the main considerations are the required aesthetic standards, the corrosiveness of the local atmosphere, and the cleaning system to be adopted.

Increasingly, however, other applications simply seek structural integrity or impermeability. For example, roofs and side walls of industrial buildings. In these applications, the owner's cost of construction may be more important than aesthetics, and the surface is not very clean.

The effect of using 304 stainless steel in a dry indoor environment is quite good. However, to maintain its appearance outdoors in both the country and the city, frequent washing is required. In heavily polluted industrial areas and coastal areas, the surface will be very dirty and even rusted. However, to obtain the aesthetic effect in the outdoor environment, nickel-containing stainless steel is required. Therefore, 304 stainless steel is widely used in curtain walls, side walls, roofs and other construction purposes, but in severely corrosive industries or marine atmospheres, it is best to use 316 stainless steel.

• Stainless steel sliding door

The advantages of using stainless steel in structural applications are well recognized. There are several design criteria that include 304 and 316 stainless steel. Because "duplex" stainless steel 2205 has integrated good atmospheric corrosion resistance with high tensile strength and elastic limit strength, this steel is also included in the European standards.

• Product Shape

In fact, stainless steel is manufactured in all standard metal shapes and sizes, and there are many special shapes. The most commonly used products are made of sheet and strip steel, and special products are also produced from medium and thick plates, for example, the production of hot-rolled structural steel and extruded structural steel. There are also round, oval, square, rectangular, and hexagonal welded or seamless steel pipes and other forms of products, including profiles, bars, wires, and castings.

• The surface condition of stainless steel

As will be discussed later, various commercial finishes have been developed to meet the aesthetic requirements of architects. For example, the surface can be highly reflective or matte; it can be smooth, polished, or embossed; it can be colored, colored, electroplated, or etched with patterns on the surface of stainless steel, or brushed, etc., to meet the various requirements of designers for appearance.

Keeping the surface is easy. Dust can be removed with just occasional rinsing. Due to the good corrosion resistance, graffiti contamination or similar other surface contamination on the surface can also be easily removed.

The following methods are often used to prevent intergranular corrosion:

(1) Reduce the amount of carbon in the steel, so that the amount of carbon in the steel is lower than the saturation solubility in the austenite in the equilibrium state, that is, it fundamentally solves the problem of the precipitation of chromium carbide (Cr23C6) on the grain boundary. Usually, the amount of carbon in steel can be reduced to less than 0.03% to meet the requirements of intergranular corrosion resistance.

(2) Add Ti, Nb, and other elements that can form stable carbides (TiC or NbC) to avoid the precipitation of Cr23C6 on the grain boundary, which can prevent intergranular corrosion of upper austenitic stainless steel.

(3) By adjusting the ratio of austenite-forming elements and ferrite-forming elements in the steel, it has an austenite + ferrite dual-phase structure, of which ferrite accounts for 5% to 12%. This duplex structure is not prone to intergranular corrosion.

(4) Appropriate heat treatment process can prevent intergranular corrosion and obtain the best corrosion resistance.

• Stress Corrosion of Austenitic Stainless Steel

The cracking caused by the combined action of stress (mainly tensile stress) and corrosion is called stress corrosion cracking, or SCC (Stress Crack Corrosion) for short. Austenitic stainless steel is prone to stress corrosion in corrosive media containing chloride ions. When the Ni content reaches 8% to 10%, the austenitic stainless steel has the greatest stress corrosion tendency and continues to increase the Ni content to 45~50%, and the stress corrosion tendency gradually decreases until it disappears.

The most important way to prevent stress corrosion of austenitic stainless steel is to add Si2~4% and control the N content below 0.04% in smelting. In addition, the content of impurities such as P, Sb, Bi, and as should be reduced as much as possible. In addition, A-F dual-phase steel can be selected, which is not sensitive to stress corrosion in Cl- and OH-medium. When the initial fine cracks encounter the ferrite phase and no longer continue to expand, the ferrite content should be around 6%.

• Deformation strengthening of austenitic stainless steel

Single-phase austenitic stainless steel has good cold deformation properties, and can be cold drawn into very thin steel wires and cold rolled into very thin steel strips or steel pipes. After a large amount of deformation, the strength of the steel is greatly improved, especially when it is rolled in the sub-zero temperature zone, the effect is more significant. The tensile strength can reach more than 2000 MPa. This is because the deformation-induced M transformation is superimposed in addition to the cold work hardening effect.

Austenitic stainless steel can be used to make stainless springs, clock springs, and wire ropes in aviation structures after deformation strengthening. If welding is required after deformation, only the spot welding process can be used, and the deformation increases the tendency of stress corrosion. And due to the partial γ->M transformation, ferromagnetism should be considered when using it (such as in instrument parts).

The recrystallization temperature changes with the deformation amount. When the deformation amount is 60%, the recrystallization temperature drops to 650°C. The recrystallization annealing temperature of cold deformed austenitic stainless steel is 850~1050°C. At 850°C, it needs to be kept for 3 hours.

• Heat treatment of austenitic stainless steel

Commonly used heat treatment processes for austenitic stainless steel include solution treatment, stabilization treatment, and stress relief treatment.

(1) Solution treatment. The main purpose of heating the steel to 1050~1150°C and water quenching is to dissolve the carbides in the austenite and keep this state at room temperature so that the corrosion resistance of the steel will be greatly improved. As mentioned above, in order to prevent intergranular corrosion, solution treatment is usually used to dissolve Cr23C6 in austenite, and then rapidly cooled. Air cooling can be used for thin-walled parts, and water cooling is generally used.

(2) Stabilization treatment. Generally, it is carried out after solid solution treatment, which is often used for 18-8 steel containing Ti and Nb. After solid treatment, the steel is heated to 850~880°C and then air-cooled. At this time, the carbides of Cr are completely dissolved, and the carbides of titanium are not completely dissolved, and they are fully separated out during the cooling process, so that it is impossible for carbon to form chromium carbides, thus effectively eliminating intergranular corrosion.

(3) Stress relief treatment. Stress relief treatment is a heat treatment process to eliminate the residual stress of steel after cold working or welding. Generally, it is heated to 300~350°C for tempering. For steels that do not contain stabilizing elements Ti and Nb, the heating temperature should not exceed 450°C to avoid precipitation of chromium carbides and cause intergranular corrosion. For ultra-low carbon and cold-worked parts and welded parts of stainless steel containing Ti and Nb, it needs to be heated at 500~950 °C, and then slowly cooled to eliminate stress (the upper limit temperature for eliminating welding stress), which can reduce the tendency of intergranular corrosion and improve the stress corrosion resistance of steel.

• Austenitic-ferritic duplex stainless steel

On the basis of austenitic stainless steel, appropriately increase the Cr content and reduce the Ni content, and cooperate with the remelting treatment to obtain a stainless steel with a dual-phase structure of austenite and ferrite (containing 40~60% δ-ferrite). Typical steel grades are 0Cr21Ni5Ti, 1Cr21Ni5Ti, OCr21Ni6Mo2Ti, etc. Duplex stainless steel has good weldability, no heat treatment is required after welding, and its intergranular corrosion and stress corrosion tendencies are also small. However, due to the high content of Cr, it is easy to form σ phase, so attention should be paid when using it.

• Ferritic stainless steel

Its internal microstructure is ferrite, and its mass fraction of chromium is in the range of 11.5%~32.0%. With the increase of chromium content, its acid resistance is also improved. After adding molybdenum (Mo), it can improve the ability of acid corrosion resistance and stress corrosion resistance. The national standard grades of this type of stainless steel are 00Cr12, 1Cr17, 00Cr17Mo, 00Cr30Mo2, etc.

• Martensitic stainless steel

Its microstructure is martensite. The mass fraction of chromium in this type of steel is 11.5%~18.0%, but the mass fraction of carbon can reach up to 0.6%. The increase in carbon content increases the strength and hardness of steel. A small amount of nickel added to this type of steel can promote the formation of martensite and at the same time improve its corrosion resistance. This type of steel has poor weldability. The steel plates included in the national standard grades include 1Cr13, 2 Cr13, 3 Cr13, 1 Cr17Ni2, etc.

• Austenitic stainless steel

Its microstructure is austenitic. It is formed by adding appropriate nickel (the mass fraction of nickel is 8%~25%) to high-chromium stainless steel, and it is stainless steel with an austenitic structure. Austenitic stainless steel is based on Cr18Ni19 iron-based alloy, on this basis, with different uses, it has developed into the series of chromium-nickel austenitic stainless steel shown in Figure 1-2.

Austenitic stainless steel generally belongs to corrosion-resistant steel and is the most widely used type of steel. Among them, 18-8 stainless steel is the most representative. It has good mechanical properties and is convenient for machining, stamping, and welding. It has excellent corrosion resistance and good heat resistance in an oxidizing environment. However, it is particularly sensitive to the medium containing chloride ions (CL-) in the solution and is prone to stress corrosion. 18-8 stainless steel is divided into three grades according to the carbon content in its chemical composition: general carbon content (Wc≤0.15%) low carbon grade

(Wc≤0.08%) and ultra-low carbon grade (Wc≤0.03%). For example, the 1Cr18Ni9Ti, 0Cr18Ni9, and 00Cr17Ni14M02 steel plates in my country's national standards belong to the above three grades. Many countries in the world feel the shortage of nickel reserves. In order to save nickel, as early as the 1940s and 1950s, the world began to replace part of the nickel in 18-8 stainless steel with manganese and nitrogen. The grades of steel plates developed and included in national standards include 1Cr17Mn6Ni5N and 0Cr19Ni9N.

• Austenitic-ferritic stainless steel

Its microstructure is austenite plus ferrite. Stainless steel with a volume fraction of ferrite less than 10% is a steel grade developed on the basis of austenitic steel.

• Precipitation hardening stainless steel

According to its microstructure, it can be divided into three categories: precipitation-hardening semi-austenitic stainless steel, precipitation-hardening martensitic stainless steel, and precipitation-hardening austenitic stainless steel. There are 0Cr17Ni7A, 0Cr17Ni4Cu4Nb, and 0Cr15Ni7M02Al listed in my country's national standard steel plate grades, which belong to precipitation hardening semi-austenitic stainless steel. The microstructure of the steel is characterized by austenite plus ferrite with a volume fraction of 5% to 20% in the solid solution or annealed state. After a series of heat treatment or mechanical deformation treatments, the austenite transforms into martensite and then reaches the required high strength through aging precipitation hardening. This steel has good formability and good weldability and can be used as an ultra-high-strength material in the nuclear industry, aviation, and aerospace industries.

• The future of stainless steel

Because stainless steel already possesses many ideal properties required by building materials, it can be said to be unique among metals, and its development continues. Existing types are constantly being improved to make stainless steel perform better in traditional applications, and new stainless steels are being developed to meet the stringent requirements of advanced architectural applications. Due to increasing production efficiency and quality improvements, stainless steel has become one of the most cost-effective materials of choice for architects. Stainless steel combines performance, appearance, and use characteristics, so stainless steel will remain one of the best building materials in the world.

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